METHODS AND REAGENTS FOR MODULATING CHOLESTEROL LEVELS

Abstract: The invention features ABC1 nucleic acids and polypeptides for the diagnosis and treatment of abnormal cholesterol regulation. The invention also features methods for identifying compounds for modulating cholesterol levels in an animal (e.g., a human).

Description: METHODS AND REAGENTS FOR MODULATING CHOLESTEROL T ENET S Background of the Invention Low HDL cholesterol (HDL-C), or hypoalphalipoproteinemia, is a blood lipid abnormality which correlates with a high risk of cardiovascular disease (CND), in particular coronary artery disease (CAD), but also cerebrovascular disease, coronary restenosis, and peripheral vascular disease. HDL, or 'good cholesterol' levels are influenced by both environmental and genetic factors. Epidemiological studies have consistently demonstrated that plasma HDL-C concentration is inversely related to the incidence of CAD. HDL-C levels are a strong graded and independent cardiovascular risk factor. Protective effects of an elevated HDL-C persist until 80 years of age. A low HDL-C is associated with an increased CAD risk even with normal (<5.2 mmol/1) total plasma cholesterol levels. Coronary disease risk is increased by 2% in men and 3% in women for every 1 mg/dL (0.026 mmol/1) reduction in HDL-C and in the majority of studies this relationship is statistically significant even after adjustment for other lipid and non-lipid risk factors. Decreased HDL-C levels are the most common lipoprotein abnormality seen in patients with premature CAD. Four percent of patients with premature CAD with have an isolated form of decreased HDL-C levels with no other lipoprotein abnormalities while 25% have low HDL levels with accompanying hypertriglyceridemia. Even in the face of other dyslipidemias or secondary factors, HDL-C levels are important predictors of CAD. In a cohort of diabetics, those with isolated low HDL cholesterol had a 65% increased death rate compared to diabetics with normal HDL cholesterol levels (>0.9 mmol/1). Furthermore, it has been shown that even within high risk populations, such as those with familial hypercholesterolemia, HDL cholesterol level is an important predictor of CAD. Low HDL cholesterol levels thus constitute a major, independent, risk for CAD. These findings have led to increased attention to HDL cholesterol levels as a focus for treatment, following the recommendations of the National Cholesterol Education Program. These guidelines suggest that HDL cholesterol values below 0.9 mmol/1 confer a significant risk for men and women. As such, nearly half of patients with CAD would have low HDL cholesterol. It is therefore crucial that we obtain a better understanding of factors which contribute to this phenotype. In view of the fact that pharmacological intervention of low HDL cholesterol levels has so far proven unsatisfactory, it is also important to understand the factors that regulate these levels in the circulation as this understanding may reveal new therapeutic targets. Absolute levels of HDL cholesterol may not always predict risk of CAD. In the case of CETP deficiency, individuals display an increased risk of developing CAD, despite increased HDL cholesterol levels. What seems to be important in this case is the functional activity of the reverse cholesterol transport pathway, the process by which intracellular cholesterol is trafficked out of the cell to acceptor proteins such as ApoAI or HDL. Other important genetic determinants of HDL cholesterol levels, and its inverse relation with CAD, may reside in the processes leading to HDL formation and intracellular cholesterol trafficking and efflux. To date, this process is poorly understood, however, and clearly not all of the components of this pathway have been identified. Thus, defects preventing proper HDL-mediated cholesterol efflux may be important predictors of CAD. Therefore it is critical to identify and understand novel genes involved in the intracellular cholesterol trafficking and efflux pathways. HDL particles are central to the process of reverse cholesterol transport and thus to the maintenance of tissue cholesterol homeostasis. This process has multiple steps which include the binding of HDL to cell surface components, the acquisition of cholesterol by passive absorption, the esterification of this cholesterol by LCAT and the subsequent transfer of esterified cholesterol by CETP, to VLDL and chylomicron remnants for liver uptake. Each of these steps is known to impact the plasma concentration of HDL. Changes in genes for ApoAI-CIII, lipoprotein lipase, CETP, hepatic lipase, and LCAT all contribute to determination of HDL-C levels in humans. One rare form of genetic HDL deficiency is Tangier disease (TD), diagnosed in approximately 40 patients world- wide, and associated with almost complete absence of HDL cholesterol (HDL-C) levels (listed in OMIM as an autosomal recessive trait (OMIM 205400)). These patients have very low HDL cholesterol and ApoAI levels, which have been ascribed to hypercatabolism of nascent HDL and ApoAI, due to a delayed acquisition of lipid and resulting failure of conversion to mature HDL. TD patients accumulate cholesterol esters in several tissues, resulting in characteristic features, such as enlarged yellow tonsils, hepatosplenomegaly, peripheral neuropathy, and cholesterol ester deposition in the rectal mucosa. Defective removal of cellular cholesterol and phospholipids by ApoAI as well as a marked deficiency in HDL mediated efflux of intracellular cholesterol has been demonstrated in TD fibroblasts. Even though this is a rare disorder, defining its molecular basis could identify pathways relevant for cholesterol regulation in the general population. The decreased availability of free cholesterol for efflux in the surface membranes of cells in Tangier Disease patients appears to be due to a defect in cellular lipid metabolism or trafficking. Approximately 45% of Tangier patients have signs of premature CAD, suggesting a strong link between decreased cholesterol efflux, low HDL cholesterol and CAD. As increased cholesterol is observed in the rectal mucosa of persons with TD, the molecular mechanism responsible for TD may also regulate cholesterol adsorption from the gastrointestinal (GI) tract. A more common form of genetic HDL deficiency occurs in patients who have low plasma HDL cholesterol usually below the 5th percentile for age and sex (OMIM 10768), but an absence of clinical manifestations specific to Tangier disease (Marcil et al., Arterioscler. Thromb. Vase. Biol. 19:159-169, 1999; Marcil et al., Arterioscler. Thromb. Vase. Biol. 15:1015-1024, 1995). These patients have no obvious environmental factors associated with this lipid phenotype, and do not have severe hypertriglyceridemia nor have known causes of severe HDL deficiency (mutations in ApoAI, LCAT, or LPL deficiency) and are not diabetic. The pattern of inheritance of this condition is most consistent with a Mendelian dominant trait (OMIM 10768). The development of drugs that regulate cholesterol metabolism has so far progressed slowly. Thus, there is a need for a better understanding of the genetic components of the cholesterol efflux pathway. Newly-discovered components can then serve as targets for drug design. Low HDL levels are likely to be due to multiple genetic factors. The use of pharmacogenomics in the aid of designing treatment tailored to the patient makes it desirable to identify polymorphisms in components of the cholesterol efflux pathway. An understanding of the effect of these polymorphisms on protein function would allow for the design of a therapy that is optimal for the patient. Summary of the Invention In a first aspect, the invention features a substantially pure ABCl polypeptide having ABCl biological activity. Preferably, the ABCl polypeptide is human ABCl (e.g., one that includes amino acids 1 to 60 or amino acids 61 to 2261 of SEQ ID NO: 1). In one preferred embodiment, the ABCl polypeptide includes amino acids 1 to 2261 of SEQ ID NO: 1. Specifically excluded from the polypeptides of the invention are the polypeptide having the exact amino acid sequence as GenBank accession number CAA 10005.1 and the nucleic acid having the exact sequence as AJ012376.1. Also excluded is protein having the exact amino acid sequence as GenBank accession number X75926. In a related aspect, the invention features a substantially pure ABCl polypeptide that includes amino acids 1 to 2261 of SEQ ID NO: 1. In another aspect, the invention features a substantially pure nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity (e.g., a nucleic acid molecule that includes nucleotides 75 to 254 or nucleotides 255 to 6858 of SEQ ID NO: 2). In one preferred embodiment, the nucleic acid molecule includes nucleotides 75 to 6858 of SEQ ID NO: 2. In a related aspect, the invention features an expression vector, a cell, or a non- human mammal that includes the nucleic acid molecule of the invention. In yet another aspect, the invention features a substantially pure nucleic acid molecule that includes nucleotides 75 to 254 of SEQ ID NO: 2, nucleotides 255 to 6858 of SEQ ID NO: 2, or nucleotides 75 to 6858 of SEQ ID NO: 2. In still another aspect, the invention features a substantially pure nucleic acid molecule that includes at least fifteen nucleotides corresponding to the 5' or 3' untranslated region from a human ABCl gene. Preferably, the 3' untranslated region includes nucleotides 7015-7860 of SEQ ID NO: 2. In a related aspect, the invention features a substantially pure nucleic acid molecule that hybridizes at high stringency to a probe comprising nucleotides 7015- 7860 ofSEQ ID NO: 2. In another aspect, the invention features a method of treating a human having low HDL cholesterol or a cardiovascular disease, including administering to the human an ABCl polypeptide, or cholesterol-regulating fragment thereof, or a nucleic acid molecule encoding an ABCl polypeptide, or cholesterol-regulating fragment thereof. In a preferred embodiment, the human has a low HDL cholesterol level relative to normal. Preferably, the ABCl polypeptide is wild-type ABCl, or has a mutation increases its stability or its biological activity. A preferred biological activity is regulation of cholesterol. In a related aspect, the invention features a method of preventing or treating cardiovascular disease, including introducing into a human an expression vector comprising an ABCl nucleic acid molecule operably linked to a promoter and encoding an ABCl polypeptide having ABCl biological activity. In another related aspect, the invention features a method of preventing or ameliorating the effects of a disease-causing mutation in an ABCl gene, including introducing into a human an expression vector comprising an ABCl nucleic acid molecule operably linked to a promoter and encoding an ABCl polypeptide having ABCl biological activity. In still another aspect, the invention features a method of treating or preventing cardiovascular disease, including administering to an animal (e.g., a human) a compound that mimes the activity of wild-type ABCl or modulates the biological activity of ABCl. One preferred cardiovascular disease that can be treated using the methods of the invention is coronary artery disease. Others include cerebrovascular disease and peripheral vascular disease. The discovery that the ABCl gene and protein are involved in cholesterol transport that affects serum HDL levels allows the ABCl protein and gene to be used in a variety of diagnostic tests and assays for identification of HDL-increasing or CND-inhibiting drugs. In one family of such assays, the ability of domains of the ABCl protein to bind ATP is utilized; compounds that enhance this binding are potential HDL-increasing drugs. Similarly, the anion transport capabilities and membrane pore-forming functions in cell membranes can be used for drug screening. ABCl expression can also serve as a diagnostic tool for low HDL or CND; determination of the genetic subtyping of the ABCl gene sequence can be used to subtype low HDL individuals or families to determine whether the low HDL phenotype is related to ABCl function. This diagnostic process can lead to the tailoring of drug treatments according to patient genotype (referred to as pharmacogenomics), including prediction of the patient's response (e.g., increased or decreased efficacy or undesired side effects upon administration of a compound or drug. Antibodies to an ABCl polypeptide can be used both as therapeutics and diagnostics. Antibodies are produced by immunologically challenging a B-cell- containing biological system, e.g., an animal such as a mouse, with an ABCl polypeptide to stimulate production of anti-ABCl protein by the B-cells, followed by isolation of the antibody from the biological system. Such antibodies can be used to measure ABCl polypeptide in a biological sample such as serum, by contacting the sample with the antibody and then measuring immune complexes as a measure of the ABCl polypeptide in the sample. Antibodies to ABCl can also be used as therapeutics for the modulation of ABCl biological activity. Thus, in another aspect, the invention features a purified antibody that specifically binds to ABCl . In yet another aspect, the invention features a method for determining whether a candidate compound modulates ABCl biological activity, comprising: (a) providing an ABCl polypeptide; (b) contacting the ABCl polypeptide with the candidate compound; and (c) measuring ABCl biological activity, wherein altered ABCl biological activity, relative to an ABCl polypeptide not contacted with the compound, indicates that the candidate compound modulates ABCl biological activity. Preferably, the ABCl polypeptide is in a cell or is in a cell-free assay system. In still another aspect, the invention features a method for determining whether a candidate compound modulates ABCl expression. The method includes (a) providing a nucleic acid molecule comprising an ABCl promoter operably linked to a reporter gene; (b) contacting the nucleic acid molecule with the candidate compound; and (c) measuring reporter gene expression, wherein altered reporter gene expression, relative to a nucleic acid molecule not contacted with the compound, indicates that the candidate compound modulates ABCl expression. In another aspect, the invention features a method for determining whether candidate compound is useful for modulating cholesterol levels, the method including the steps of: (a) providing an ABCl polypeptide; (b) contacting the polypeptide with the candidate compound; and (c) measuring binding of the ABCl polypeptide, wherein binding of the ABCl polypeptide indicates that the candidate compound is useful for modulating cholesterol levels. In a related aspect, the invention features method for determining whether a candidate compound mimics ABCl biological activity. The method includes (a) providing a cell that is not expressing an ABCl polypeptide; (b) contacting the cell with the candidate compound; and (c) measuring ABCl biological activity of the cell, wherein altered ABCl biological activity, relative to a cell not contacted with the compound, indicates that the candidate compound modulates ABCl biological activity. Preferably, the cell has an ABCl null mutation. In one preferred embodiment, the cell is in a mouse or a chicken (e.g., a WHAM chicken) in which its ABCl gene has been mutated. In still another aspect, the invention features a method for determining whether a candidate compound is useful for the treatment of low HDL cholesterol. The method includes (a) providing an ABC transporter (e.g., ABCl); (b) contacting the transporter with the candidate compound; and (c) measuring ABC transporter biological activity, wherein increased ABC transporter biological activity, relative to a transporter not contacted with the compound, indicates that the candidate compound is useful for the treatment of low HDL cholesterol. Preferably the ABC transporter is in a cell or a cell free assay system. In yet another aspect, the invention features a method for determining whether candidate compound is useful for modulating cholesterol levels. The method includes (a) providing a nucleic acid molecule comprising an ABC transporter promoter operably linked to a reporter gene; (b) contacting the nucleic acid molecule with the candidate compound; and (c) measuring expression of the reporter gene, wherein increased expression of the reporter gene, relative to a nucleic acid molecule not contacted with the compound, indicates that the candidate compound is useful for modulating cholesterol levels. In still another aspect, the invention features a method for determining whether a candidate compound increases the stability or decreases the regulated catabolism of an ABC transporter polypeptide. The method includes (a) providing an ABC transporter polypeptide; (b) contacting the transporter with the candidate compound; and (c) measuring the half-life of the ABC transporter polypeptide, wherein an increase in the half- life, relative to a transporter not contacted with the compound, indicates that the candidate compound increases the stability or decreases the regulated catabolism of an ABC transporter polypeptide. Preferably the ABC transporter is in a cell or a cell free assay system. In a preferred embodiment of the screening methods of the present invention, the cell is in an animal. The preferred ABC transporters are ABCl, ABC2, ABCR, and ABC8, and the preferred biological activity is transport of cholesterol (e.g., HDL cholesterol or LDL cholesterol) or interleukin-1, or is binding or hydrolysis of ATP by the ABCl polypeptide. Preferably, the ABCl polypeptide used in the screening methods includes amino acids 1-60 of SEQ ID NO: 1. Alternatively, the ABCl polypeptide can include a region encoded by a nucleotide sequence that hybridizes under high stringency conditions to nucleotides 75 to 254 of SEQ ID NO: 2. In another aspect, the invention features a method for determining whether a patient has an increased risk for cardiovascular disease. The method includes determining whether an ABCl gene of the patient has a mutation, wherein a mutation indicates that the patient has an increased risk for cardiovascular disease. In related aspect, the invention features a method for determining whether a patient has an increased risk for cardiovascular disease. The method includes determining whether an ABCl gene of the patient has a polymorphism, wherein a polymorphism indicates that the patient has an increased risk for cardiovascular disease. In another aspect, the invention features a method for determining whether a patient has an increased risk for cardiovascular disease. The method includes measuring ABCl biological activity in the patient, wherein increased or decreased levels in the ABCl biological activity, relative to normal levels, indicates that the patient has an increased risk for cardiovascular disease. In still another aspect, the invention features a method for determining whether a patient has an increased risk for cardiovascular disease. The method includes measuring ABCl expression in the patient, wherein decreased levels in the ABCl expression relative to normal levels, indicates that the patient has an increased risk for cardiovascular disease. Preferably, the ABCl expression is determined by measuring levels of ABCl polypeptide or ABCl RNA. In another aspect, the invention features a non-human mammal having a transgene comprising a nucleic acid molecule encoding a mutated ABCl polypeptide. In one embodiment, the mutation is a dominant-negative mutation. In a related aspect, the invention features a non-human mammal, having a transgene that includes a nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity. In another related aspect, the invention features a cell from a non-human mammal having a transgene that includes a nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity. In still another aspect, the invention features a method for determining whether a candidate compound decreases the inhibition of a dominant-negative ABCl polypeptide. The method includes (a) providing a cell expressing a dominant- negative ABCl polypeptide; (b) contacting the cell with the candidate compound; and (c) measuring ABCl biological activity of the cell, wherein an increase in the ABCl biological activity, relative to a cell not contacted with the compound, indicates that the candidate compound decreases the inhibition of a dominant-negative ABCl polypeptide. By "polypeptide" is meant any chain of more than two amino acids, regardless of post-translational modification such as glycosylation or phosphorylation. By "substantially identical" is meant a polypeptide or nucleic acid exhibiting at least 50%, preferably 85%, more preferably 90%, and most preferably 95% identity to a reference amino acid or nucleic acid sequence. For polypeptides, the length of comparison sequences will generally be at least 16 amino acids, preferably at least 20 amino acids, more preferably at least 25 amino acids, and most preferably 35 amino acids. For nucleic acids, the length of comparison sequences will generally be at least 50 nucleotides, preferably at least 60 nucleotides, more preferably at least 75 nucleotides, and most preferably 110 nucleotides. Sequence identity is typically measured using sequence analysis software with the default parameters specified therein (e.g., Sequence Analysis Software Package of the Genetics Computer Group, University of Wisconsin Biotechnology Center, 1710 University Avenue, Madison, WI 53705). This software program matches similar sequences by assigning degrees of homology to various substitutions, deletions, and other modifications. Conservative substitutions typically include substitutions within the following groups: glycine, alanine, valine, isoleucine, leucine; aspartic acid, glutamic acid, asparagine, glutamine; serine, threonine; lysine, arginine; and phenylalanine, tyrosine. By "high stringency conditions" is meant hybridization in 2X SSC at 40 °C with a DNA probe length of at least 40 nucleotides. For other definitions of high stringency conditions, see F. Ausubel et al, Current Protocols in Molecular Biology, pp. 6.3.1-6.3.6, John Wiley & Sons, New York, NY, 1994, hereby incorporated by reference. By "substantially pure polypeptide" is meant a polypeptide that has been separated from the components that naturally accompany it. Typically, the polypeptide is substantially pure when it is at least 60%, by weight, free from the proteins and naturally-occurring organic molecules with which it is naturally associated. Preferably, the polypeptide is an ABCl polypeptide that is at least 75%, more preferably at least 90%, and most preferably at least 99%, by weight, pure. A substantially pure ABCl polypeptide may be obtained, for example, by extraction from a natural source (e.g., a pancreatic cell), by expression of a recombinant nucleic acid encoding a ABCl polypeptide, or by chemically synthesizing the protein. Purity can be measured by any appropriate method, e.g., by column chromatography, polyacrylamide gel electrophoresis, or HPLC analysis. A polypeptide is substantially free of naturally associated components when it is separated from those contaminants that accompany it in its natural state. Thus, a polypeptide which is chemically synthesized or produced in a cellular system different from the cell from which it naturally originates will be substantially free from its naturally associated components. Accordingly, substantially pure polypeptides include those which naturally occur in eukaryotic organisms but are synthesized in E. coli or other prokaryotes. By "substantially pure nucleic acid" is meant nucleic acid that is free of the genes which, in the naturally-occurring genome of the organism from which the nucleic acid of the invention is derived, flank the nucleic acid. The term therefore includes, for example, a recombinant nucleic acid that is incorporated into a vector; into an autonomously replicating plasmid or virus; into the genomic nucleic acid of a prokaryote or a eukaryote cell; or that exists as a separate molecule (e.g., a cDNA or a genomic or cDNA fragment produced by PCR or restriction endonuclease digestion) independent of other sequences. It also includes a recombinant nucleic acid that is part of a hybrid gene encoding additional polypeptide sequence. By "modulates" is meant increase or decrease. Preferably, a compound that modulates cholesterol levels (e.g., HDL-cholesterol levels, LDL-cholesterol levels, or total cholesterol levels), or ABCl biological activity, expression, stability, or degradation does so by at least 10%, more preferably by at least 25%, and most preferably by at least 50%. By "purified antibody" is meant antibody which is at least 60%, by weight, free from proteins and naturally occurring organic molecules with which it is naturally associated. Preferably, the preparation is at least 75%, more preferably 90%, and most preferably at least 99%, by weight, antibody. A purified antibody may be obtained, for example, by affinity chromatography using recombinantly-produced protein or conserved motif peptides and standard techniques. By "specifically binds" is meant an antibody that recognizes and binds to, for example, a human ABCl polypeptide but does not substantially recognize and bind to other non-ABCl molecules in a sample, e.g., a biological sample, that naturally includes protein. A preferred antibody binds to the ABCl polypeptide sequence of Fig. 9A (SEQ ID NO: 1). By "polymorphism" is meant that a nucleotide or nucleotide region is characterized as occurring in several different forms. A "mutation" is a form of a polymoφhism in which the expression level, stability, function, or biological activity of the encoded protein is substantially altered. By "ABC transporter" or "ABC polypeptide" is meant any transporter that hydrolyzes ATP and transports a substance across a membrane. Preferably, an ABC transporter polypeptide includes an ATP Binding Cassette and a transmembrane region. Examples of ABC transporters include, but are not limited to, ABCl, ABC2, ABCR, and ABC8. By "ABCl polypeptide" is meant a polypeptide having substantial identity to an ABCl polypeptide having the amino acid sequence of SEQ ID NO: 1. By "ABC biological activity" or "ABCl biological activity" is meant hydrolysis or binding of ATP, transport of a compound (e.g., cholesterol, interleukin- 1) or ion across a membrane, or regulation of cholesterol or phospholipid levels (e.g., either by increasing or decreasing HDL-cholesterol or LDL-cholesterol levels). The invention provides screening procedures for identifying therapeutic compounds (cholesterol-modulating or anti-CND pharmaceuticals) which can be used in human patients. Compounds that modulate ABC biological activity (e.g., ABCl biological activity) are considered useful in the invention, as are compounds that modulate ABC concentration, protein stability, regulated catabolism, or its ability to bind other proteins or factors. In general, the screening methods of the invention involve screening any number of compounds for therapeutically active agents by employing any number of in vitro or in vivo experimental systems. Exemplary methods useful for the identification of such compounds are detailed below. The methods of the invention simplify the evaluation, identification and development of active agents for the treatment and prevention of low HDL and CND. In general, the screening methods provide a facile means for selecting natural product extracts or compounds of interest from a large population which are further evaluated and condensed to a few active and selective materials. Constitutes of this pool are then purified and evaluated in the methods of the invention to determine their HDL- raising or anti-CND activities or both. Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims. Brief Description of the Drawings Figs. 1 A and IB are schematic illustrations showing two pedigrees with Tangier Disease, (TD-1 and TD-2). Square and circle symbols represent males and females, respectively. Diagonal lines are placed through the symbols of all deceased individuals. A shaded symbol on both alleles indicates the probands with Tangier Disease. Individuals with half shaded symbols have HDL-C levels at or below the 10th percentile for age and sex, while those with quarter shaded symbols have HDL-C between the 11th and 20th percentiles. Each individual's ID number, age at the time of lipid measurement, triglyceride level and HDL cholesterol level followed by their percentile ranking for age and sex are listed below the pedigree symbol. Markers spanning the 9q31.1 region are displayed to the left of the pedigree. The affected allele is represented by the darkened bars which illustrate the mapping of the limits of the shared haplotype region as seen in Fig. 3. Parentheses connote inferred marker data, questions marks indicate unknown genotypes, and large arrows show the probands. Fig. 1C shows ApoAI (10 μg/mL) -mediated cellular cholesterol efflux in control fibroblasts (n=5, normalized to 100%) and two subjects with Tangier disease (TD). Cells were 3 H-cholesterol (0.2 μCi/mL) labeled during growth and cholesterol (20 μg/mL) loaded in growth arrest. Cholesterol efflux is determined as 3 H medium/( 3 H cell + 3 H medium) Fig. 2A - 2D are schematic illustrations showing four French Canadian pedigrees with FHA (FHA-1 to -4). The notations are as in Fig. 1. Exclamation points on either side of a genotype (as noted in Families FHA-3 and FHA-4) are used when the marker data appears to be inconsistent due to potential microsatellite repeat expansions. A bar that becomes a single thin line suggests that the haplotype is indeterminate at that marker. Figs. 3A - 3E are a schematic illustration showing a genetic and physical map of 9q31 spanning 35 cM. Fig. 3A: YACs from the region of 9q22-34 were identified and a YAC contig spanning this region was constructed. Fig. 3B: A total of 22 polymorphic CA microsatellite markers were mapped to the contig and used in haplotype analysis in TD-1 and TD-2. Fig 3C: The mutant haplotypes for probands in TD-1 and -2 indicate a significant region of homozygosity in TD-2, while the proband in TD-1 has 2 different mutant haplotypes. The candidate region can be narrowed to the region of homozygosity for CA markers in proband 2. A critical crossover at D9S1690 in TD-1 (A)* also provides a centromeric boundary for the region containing the gene. Three candidate genes in this region (ABCl, LPA-R and RGS-3) are shown. Fig. 3D: Meiotic recombinations in the FHA families (A-H) refine the minimal critical region to 1.2 cM between D9S277 and D9S1866. The heterozygosity of the TD-2 proband at D9S127, which ends a continuous region of homozygosity in TD-2, further refines the region to less than 1 cM. This is the region to which ABCl has been mapped. Fig. 3E: Isolated YAC DNA and selected markers from the region were used to probe high-density BAC grid filters, selecting BACs which via STS-content mapping produced an 800 Kb contig. Four BACs containing ABCl were sequenced using high-throughput methods. Fig. 4A shows sequence of one mutation in family TD-1. Patient 111-01 is heterozygous for a T to C transition at nucleotide 4503 of the cDNA; the control is homozygous for T at this position. This mutation corresponds to a cysteine to arginine substitution in the ABCl protein (C1477R). Fig 4B shows the amino acid sequence conservation of residue 1477 in mouse and human, but not a related C. elegans gene. A change from cysteine to arginine likely has an important effect on the protein secondary and tertiary structure, as noted by its negative scores in most substitution matrices (Schuler et al., A Practical Guide to the Analysis of Genes and Proteins, eds. Baxevanis, A.D. & Ouellette, B.F.F. 145:171, 1998). The DNA sequences of the normal and mutant genes are shown above and below the amino acid sequences, respectively. Fig. 4C shows the segregation of the T4503C mutation in TD-1. The presence of the T4503C mutation (+) was assayed by restriction enzyme digestion with Hgal, which cuts only the mutant (C) allele (I). Thus, in the absence of the mutation, only the 194 bp PCR product (amplified between → and -) is observed, while in its presence the PCR product is cleaved into fragments of 134 bp and 60 bp. The proband (individual 111.01) was observed to be heterozygous for this mutation (as indicated by both the 194 bp and 134 bp bands), as were his daughter, father, and three paternal cousins. A fourth cousin and three of the father's siblings were not carriers of this mutation. Fig. 4D shows Northern blot analysis with probes spanning the complete ABCl gene reveal the expected ~8 Kb transcript and, in addition, a ~3.5 kb truncated transcript only seen in the proband TD-1 and not in TD-2 or control. This was detected by probes spanning exons 1-49 (a), 1-41 (b), 1-22 (c), and 23-29 (d), but not with probes spanning exons 30-41 (e) or 42-49 (f). Fig. 5 A shows the sequence of the mutation in family TD-2. Patient IV- 10 is homozygous for an A to G transition at nucleotide 1864 of the cDNA (SEQ ID NO: 2); the control is homozygous for A at this position. This mutation corresponds to a glutamine to arginine substitution in the ABCl protein (Q597R). Fig. 5B shows that the glutamine amino acid, which is mutated in the TD-2 proband, is conserved in human and mouse ABCl as well as in an ABC orthologue from C. elegans, revealing the specific importance of this residue in the structure/function of this ABC protein in both worms and mammals. The DNA sequences of the normal and mutant proteins are shown above and below the amino acid sequences, respectively. Fig. 5C shows the segregation of the A1864G mutation in TD-2. The presence of the Al 864G mutation (indicated by +) was assayed by restriction enzyme digestion with Acil. The 360 bp PCR product has one invariant Acil recognition site ( 1 ), and a second one is created by the Al 864G mutation. The wild-type allele is thus cleaved to fragments of 215 bp and 145 bp, while the mutant allele (G-allele) is cleaved to fragments of 185 bp, 145 bp and 30 bp. The proband (individual IV-10), the product of a consanguineous mating, was homozygous for the A1864G mutation (+/+), as evidenced by the presence of only the 185 bp and 145 bp bands, while four other family members for whom DNA was tested are heterozygous carriers of this mutation (both the 215 bp and 185 bp fragments were present). Two unaffected individuals (-/-), with only the 215 bp and 145 bp bands are shown for comparison. Fig. 6A shows a sequence of the mutation in family FHA-1. Patient 111-01 is heterozygous for a deletion of nucleotides 2151-2153 of the cDNA (SEQ ID NO: 2). This deletion was detected as a superimposed sequence starting at the first nucleotide after the deletion. This corresponds to deletion of leucine 693 in the ABCl protein (SEQ ID NO: 1). Fig. 6B is an alignment of the human and mouse wild-type amino acid sequences, showing that the human and mouse sequences are identical in the vicinity of ΔL693. L693 is also conserved in C. elegans. This highly conserved residue lies within a predicted transmembrane domain. The DNA sequences of the normal and mutant proteins are shown above and below the amino acid sequences, respectively. Fig. 6C shows segregation of the ΔL693 mutation in FHA-1, as assayed by Earl restriction digestion. Two invariant Eαrl restriction sites (indicated by I ) are present within the 297 bp PCR product located between the horizontal arrows (→-) while a third site is present in the wild-type allele only. The presence of the mutant allele is thus distinguished by the presence of a 210 bp fragment (+), while the normal allele produces a 151 bp fragment (-). The proband of this family (III.01) is heterozygous for this mutation, as indicated by the presence of both the 210 and 151 bp bands. Fig. 6D shows a sequence of the mutation in family FHA-3. Patient 111-01 is heterozygous for a deletion of nucleotides 5752-5757 of the cDNA (SΕQ ID NO: 2). This deletion was detected as a superimposed sequence starting at the first nucleotide after the deletion. This corresponds to deletion of glutamic acid 1893 and aspartic acid 1894 in the ABCl protein (SΕQ ID NO: 1). Fig. 6E is an alignment of the human and mouse wild-type amino acid sequences, showing that the human and mouse sequences are identical in the vicinity ofΔ5752-5757. This region is highly conserved in C. elegans. The DNA sequences of the normal and mutant proteins are shown above and below the amino acid sequences, respectively. Fig. 6F shows a sequence of the mutation in family FHA-2. Patient 111-01 is heterozygous for a for a C to T transition at nucleotide 6504 of the cDNA (SEQ ID NO: 2). This alteration converts an arginine at position 2144 of SEQ ID NO: 1 to a STOP codon, causing truncation of the last 118 amino acids of the ABCl protein. Figs. 7A and 7B show cholesterol efflux from human skin fibroblasts treated with ABCl antisense oligonucleotides. Fibroblasts from a control subject were labeled with 3 H cholesterol (0.2 μCi/mL) during growth for 48 hours and transfected with 500 nM ABCl antisense AN-1 (5'-GCA GAG GGC ATG GCT TTA TTT G-3'; SEQ ID NO: 3) with 7.5 μg lipofectin for 4 hours. Following fransfection, cells were cholesterol loaded (20 μg/mL) for 12 hours and allowed to equilibrate for 6 hours. Cells were either then harvested for total RNA and 10 μg was used for Northern blot analysis. Cholesterol efflux experiments were carried out as described herein. Fig. 7 A: AN-1 was the oligonucleotide that resulted in a predictable decrease in ABCl RNA transcript levels. Fig. 7B: A double antisense fransfection method was used. In this method, cells were labeled and transfected with AN-1 as above, allowed to recover for 20 hours, cholesterol loaded for 24 hours, and then re-transfected with AN-1. Twenty hours after the second fransfection, the cholesterol efflux as measured. A -50%) decrease in ABCl transcript levels was associated with a significant decrease in cholesterol efflux intermediate between that seen in wild-type and TD fibroblasts. Fig. 7C shows show cholesterol efflux from human skin fibroblasts treated with antisense oligonucleotides directed to the region encoding the amino-terminal 60 amino acids. Note that the antisense oligonucleotide AN-6, which is directed to the previously unrecognized translation start site, produces a substantial decrease in cellular cholesterol efflux. Fig. 8 is a schematic illustration showing predicted topology, mutations, and polymoφhisms of ABCl in Tangier disease and FHA. The two transmembrane and ATP binding domains are indicated. The locations of mutations are indicated by the arrows with the amino acid changes, which are predicted from the human ABCl cDNA sequence. These mutations occur in different regions of the ABCl protein. Fig. 9A shows the amino acid sequence of the human ABCl protein (SEQ ID NO: 1). Figs. 9B - 9E show the nucleotide sequence of the human ABCl cDNA (SEQ ID NO: 2). Fig. 10 shows the 5' and 3' nucleotide sequences suitable for use as 5' and 3' PCR primers, respectively, for the amplification of the indicated ABCl exon. Fig. 11 shows a summary of alterations found in ABCl, including sequencing errors, mutations, and polymoφhisms. Fig. 12 shows a series of genomic contigs (SEQ ID NOS. 14-29) containing the ABCl promoter (SEQ ID NO: 14), as well as exons 1-49 (and flanking intronic sequence) of ABCl. The exons (capitalized letters) are found in the contigs as follows: SEQ ID NO: 14--exon 1; SEQ ID NO: 15-exon 2; SEQ ID NO: 16-exon 3; SEQ ID NO: 17-exon 4; SEQ ID NO: 18-exon 5; SEQ ID NO: 19-exon 6; SEQ ID NO: 20-exons 7 and 8; SEQ ID NO: 21-exons 9 through 22; SEQ ID NO: 22-exons 23 through 28; SEQ ID NO: 23-exon 29; SEQ ID NO: 24-exons 30 and 31; SEQ ID NO: 25-exon 32; SEQ ID NO: 26-exons 33 through 36; SEQ ID NO: 27-exons 37 through 41; SEQ ID NO: 28-exons 42-45; SEQ ID NO: 29-exons 46-49. Fig. 13 is a series of illustrations showing that the amino-terminal 60 amino acid region of ABCl is protein-coding. Lysates of normal human fibroblasts were immunoblotted in parallel with a rabbit polyclonal antibody to amino acids 1-20 of human ABCl (1); a rabbit polyclonal antibody to amino acids 1430-1449 of human ABCl (2); and a mouse monoclonal antibody to amino acids 2236-2259 of human ABCl . The additional bands detected in lane 2 may be due to a lack of specificity of that antibody or the presence of degradation products of ABCl. Fig. 14 is a schematic illustration showing that the WHAM chicken contains a non-conservative substitution (G265A) resulting in an amino acid change (E89K). Fig. 15 is a schematic illustration showing that the mutation in the WHAM chicken is at an amino acid that is conserved among human, mouse, and chicken. Fig. 16 show a summary of locations of consensus transcription factor binding sites in the human ABCl promoter (nucleotides 1-8238 of SEQ ID NO: 14). The abbreviations are as follows: PPRE^peroxisome proliferator-activated receptor. SRE=steroid response element-binding protein site. ROR=RAR-related oφhan receptor. Detailed Description Genes play a significant role influencing HDL levels. Tangier disease (TD) was the first reported genetic HDL deficiency. The molecular basis for TD is unknown, but has been mapped to 9q31 in three families. We have identified two additional probands and their families, and confirmed linkage and refined the locus to a limited genomic region. Mutations in the ABCl gene accounting for all four alleles in these two families were detected. A more frequent cause of low HDL levels is a distinct disorder, familial HDL deficiency (FHA). On the basis of independent linkage, meiotic recombinants and disease associated haplotypes, FHA was localized to a small genomic region encompassing the ABCl gene. A mutation in a conserved residue in ABCl segregated with FHA. Antisense reduction of the ABCl transcript in fibroblasts was associated with a significant decrease in cholesterol efflux. Cholesterol is normally assembled with intracellular lipids and secreted, but in TD the process is diverted and cholesterol is degraded in lysosomes. This disturbance in intracellular trafficking of cholesterol results in an increase in intracellular cholesterol ester accumulation associated with moφhological changes of lysosomes and the Golgi apparatus and cholesteryl ester storage in histiocytes, Schwann cells, smooth muscle cells, mast cells and fibroblasts. The clinical and biochemical heterogeneity in patients with TD has led to the possibility that genetic heterogeneity may also underlie this disorder. Considering this, we initially performed linkage analysis on these two families of different ancestries (TD-1 is Dutch, TD-2 is British; Frohlich et al., Clin. Invest. Med. 10:377- 382, 1987) and confirmed that the genetic mutations underlying TD in these families were localized to the same 9q31 region, to which a large family with TD had been assigned (Rust et al., Nature Genetics 20:96-98, 1998). Detailed haplotype analysis, together with the construction of a physical map, refined the localization of this gene. Mutations in the ABCl gene were found in TD. FHA is much more common than TD, although its precise frequency is not known. While TD has been described to date in only 40 families, we have identified more than 40 FHA families in the Netherlands and Quebec alone. After initial suggestions of linkage to 9q31, thirteen polymoφhic markers spanning approximately 10 cM in this region were typed and demonstrated the highest LOD score at D9S277. Analysis of the homozygosity of markers in the TD-2 proband, who was expected to be homozygous for markers close to TD due to his parents' consanguinity, placed the TD gene distal to D95127. Combined genetic data from TD and FHA families pointed to the same genomic segment spanning approximately 1 ,000 kb between D9S 127 and D9S 1866. The ABCl transporter gene was contained within the minimal genomic region. RT-PCR analysis in one family demonstrated a deletion of leucine at residue 693 (Δ693) in the first transmembrane domain of ABCl, which segregated with the phenotype of HDL deficiency in this family. ABCl is part of the ATP -binding cassette (ABC transporter) superfamily, which is involved in energy-dependent transport of a wide variety of substrates across membranes (Dean et al, Curr. Opin. Gen. Dev. 5:779-785, 1995). These proteins have characteristic motifs conserved throughout evolution which distinguish this class of proteins from other ATP binding proteins. In humans these genes essentially encode two ATP binding segments and two transmembrane domains (Dean et al., Curr. Opin. Gen. Dev. 5:779-785, 1995). We have now shown that the ABCl transporter is crucial for intracellular cholesterol transport. We have demonstrated that reduction of the ABCl transcript using oligonucleotide antisense approaches results in decreased efflux, clearly demonstrating the link between alterations in this gene and its functional effects. TD and FHA now join the growing list of genetic diseases due to defects in the ABC group of proteins including cystic fibrosis (Zielenski, et al, Annu. Rev. Genet. 29:777-807, 1995), adrenoleukodystrophy (Mosser et al., Nature 361 : 726-730, 1993), Zellweger syndrome (Gartner et al., Nat. Genet. 1 :23, 1992), progressive familial intrahepatic cholestatis (Bull et al., Nat. Genet. 18:219-224, 1998), and different eye disorders including Stargardt disease (Allikmets et al., Nat. Genet.15:236-246, 1997), autosomal recessive retinitis pigmentosa (Allikmets et al., Science 277:1805-1807, 1997), and cone-rod dystrophy (Cremers et al., Hum. Mol. Genet. 7:355-362, 1998). Patients with TD have been distinguished from patients with FHA on the basis that Tangier disease was an autosomal recessive disorder (OMIM 20540) while FHA is inherited as an autosomal dominant trait (OMIM 10768). Furthermore, patients with TD have obvious evidence for intracellular cholesterol accumulation which is not seen in FHA patients. It is now evident that heterozygotes for TD do have reduced HDL levels and that the same mechanisms underlie the HDL deficiency and cholesterol efflux defects seen in heterozygotes for TD as well as FHA. Furthermore, the more severe phenotype in TD represents loss of function from both alleles of the ABCl gene. ABCl is activated by protein kinases, presumably via phosphorylation, which also provides one explanation for the essential role of activation of protein kinase C in promoting cholesterol efflux (Drobnick et al., Arterioscler. Thromb. Vase. Biol. 15: 1369-1377, 1995). Brefeldin, which inhibits trafficking between the endoplasmic reticulum and the Golgi, significantly inhibits cholesterol efflux, essentially reproducing the effect of mutations in ABCl, presumably through the inhibition of ABCl biological activity. This finding has significance for the understanding of mechanisms leading to premature atherosclerosis. TD homozygotes develop premature coronary artery disease, as seen in the proband of TD-1 (III-01) who had evidence for coronary artery disease at 38 years. This is particular noteworthy as TD patients, in addition to exhibiting significantly reduced HDL, also have low LDL cholesterol, and yet they develop atherosclerosis despite this. This highlights the importance of HDL intracellular transport as an important mechanism in atherogenesis. There is significant evidence that heterozygotes for TD are also at increased risk for premature vascular disease (Schaefer et al., Ann. Int. Med. 93:261- 266, 1980; Serfaty-Lacrosniere et al., Atherosclerosis 107:85-98, 1994). There is also preliminary evidence for premature atherosclerosis in some probands with FHA (Fig. 2B), e.g., the proband in FHA-2 (III-01) had a coronary artery bypass graft at 46 years while the proband in FHA-3 (Fig. 2C) had evidence for GAD around 50 years of age. The TD-1 proband had more severe efflux deficiency than the TD-2 proband (Fig. 1C). Interestingly, the TD-2 proband had no evidence for CAD by 62 when he died of unrelated causes, providing preliminary evidence for a relationship between the degree of cholesterol efflux (mediated in part by the nature of the mutation) and the likelihood of atherosclerosis. The ABCl gene plays a crucial role in cholesterol transport and, in particular, intracellular cholesterol trafficking in monocytes and fibroblasts. It also appears to play a significant role in other tissues such as the nervous system, GI tract, and the cornea. Completely defective intracellular cholesterol transport results in peripheral neuropathy, corneal opacities, and deposition of cholesterol esters in the rectal mucosa. HDL deficiency is heterogeneous in nature. The delineation of the genetic basis of TD and FHA underlies the importance of this particular pathway in intracellular cholesterol transport, and its role in the pathogenesis of atherosclerosis. Unraveling of the molecular basis for TD and FHA defines a key step in a poorly defined pathway of cholesterol efflux from cells and could lead to new approaches to treatment of patients with HDL deficiency in the general population. HDL has been implicated in numerous other biological processes, including but not limited to: prevention of lipoprotein oxidation; absoφtion of endotoxins; protection against Trypanosoma brucei infection; modulation of endothelial cells; and prevention of platelet aggregation (see Genest et al, J. Invest. Med. 47: 31-42, 1999, hereby incoφorated by reference). Any compound that modulates HDL levels may be useful in modulating one or more of the foregoing processes. The present discovery that ABCl functions to regulate HDL levels links, for the first time, ABCl with the foregoing processes. The following examples are to illustrate the invention. They are not meant to limit the invention in any way. Analysis of TD Families Studies of cholesterol efflux Both probands had evidence of marked deficiency of cholesterol efflux similar to that previously demonstrated in TD patients (Fig. 1C). TD-1 is of Dutch descent while TD-2 is of British descent. Linkage analysis and establishment of a physical map Multiple DNA markers were genotyped in the region of 9q31 to which linkage to TD had been described (Rust et al., Nat. Genet. 20, 96-98, 1998). Two point linkage analysis gave a maximal peak LOD score of 6.49 at D9S 1832 (Table 1) with significant evidence of linkage to all markers in a -10 cM interval. Recombination with the most proximal marker, D9S1690 was seen in 11-09 in Family TD-1 (A* in Fig. 3D) providing a centromeric boundary for the disease gene. Multipoint linkage analysis of these data did not increase the precision of the positioning of the disease trait locus. A physical map spanning approximately 10 cM in this region was established with the development of a YAC contig (Fig. 3 A). In addition, 22 other polymoφhic multi-allelic markers which spanned this particular region were mapped to the contig (Fig. 3B) and a subset of these were used in construction of a haplotype for further analysis (Figs. 1 A and IB; Table 2). While the family of Dutch decent did not demonstrate any consanguinity, the proband in TD-2 was the offspring of a first-cousin consanguineous marriage (Fig. IB). We postulated, therefore, that it was most likely that this proband would be homozygous for the mutation while the proband in the Dutch family was likely to be a compound heterozygote. The Dutch proband shows completely different mutation bearing haplotypes, supporting this hypothesis (Fig. 3C). The TD-2 proband was homozygous for all markers tested (Fig. IB) distal to D9S 127 but was heterozygous at D9S127 and DNA markers centromeric to it (Fig. 3C). This suggested that the gene for TD was likely located to the genomic region telomeric of D9S127 and encompassed by the markers demonstrating homozygosity (Fig. 3B). TABLE 1 Two Point Linkage Analysis of TD-1 and TD-2 etween t e sease ocus and a marker locus for specified values of the rsco t nbinaiion fraction. TABLE 2. Microsatellite markers used in this studv Genetic Marker- Type Hetero- Number Allele frequency zygocity of alleles size.br (proportion) D9S233 CA o.so 10 179 ( 0.0 4 ): 181(0.34); 183(0.1*1; 1-3(0.--* 1-9(0.0-): 193(0.04); 197(0.07): l« ( O θV~ 201(0.04): 203(0.04) D9S I76 CA 0.32 9 129 ( 0.03); 131(0.16); 133(0.-.!: 135(0.1:*: 137(0.23): 139(0.03): I(O.Ol): l-<t005V 147(0.05) ' • D9S 1690 CA 0.79 5 223(0JS): 227(0.14); 229(0.C-!: 13 K0.1-Ϊ -3 (0.03): 233(0.16): 237(0.03): -39(0.03) D9S277 CA 0.S9 15 167(0.07); 171(0.02); 173(0.13): 173(0.1 iy. 177(0.07): 179(0.04): 131(0.17); l-ΗO 06)- 183(0.02): 187(0.02); 189(0.13i: 191(0.13): 193(0.02): 197(0.00); 199(0.00) D9S 127 CA 0.72 6 9 ( 0.l 1): 131(0.07): 133(0--!): 133(0.031: 137(0.43): 139(0.06) D95306 CA 0.87 13 102(0.06); 104(0.01): I lOtO.C},: 1 12(0.0S!: 1 1-1(0.16): 116(0.13): 1 18(0 1 1)- 1*0(0 23)- 122 ( 0.06): 124(0.06); 126(0X3!: 134(0.0:_ 136(0.01) D9S I S66 CA 0.62 1 1 2 4 8(0.06): 232(0.04); 254(0.0!): 236(58): --5(0.03); 260(0.06); 262(00">)- ->6-<0 PV 266(0.06): 268(0.03): 270(0.01) D9S I7S4 CA 0.86 15 17 4 (0.10): 176(0.02): 178(0.CC): 1 S0(0.0S'-. 132(0.1 1): I8-K0.22): 186(0.13): 1-3(0.06)- 190(0.0 4 ): 192(0.07): 194(0.C.i: 196(0.07): 198(0.01): 200(0.01): 202 ( 0.01) AFMal07xf9 CA n.a. n.a. n.a. D9S 170 C. n.a. n.a- n.a. D9S 1 1 CA n.a. n.a. n.a. D9S2107 CA 0.63 5 n.a. D9S 172 CA 0-54 5 291(0.00); 297(0.03); 299(0--:): 303(0.6:): 305(0.02) D9S2109 CA 0.51 3 1(0.42); 2(0.36); 3(0.02) D9S 1832 CA 0.88 12 161(0.04): 163(0.02): 167(0X2): 169(0.0-): 171(0.10): 173(0.09): 175(0.13): 177(0.28): 179(0.19): 181(0.04); 183(0.01): 183(0.01) D9S1835 CA 0.48 4 110(0.02): 112(0-23): 116<0-£3): 118(0.07) • D9S 1801 CA 0.77 10 1 -6(0.10); 172(0.04); 174(0.02); 1S2(0.02):1-4(0.19); 186(0.40); 188(0.15): 150(0.04); 192(0.02); l94(0_-2) D9S261 CA 0.63 7 90 ( 0.02): 92(0-52): 94(0.02): 58(0.02): 100(0.29): 102(0.04); 104(0.08) D9S160 CA 0.62 6 136(0.25); 138(0.33); 140(0.01): 142(0.12): 14-1(0.00): 146(0.07) D9S1677 CA 0.81 10 251(0.27); 257(0_-7): 239(0.07); 261(0.09): 263(0.27); 263(0.14); 267(0.02): 269(0.02); 271(0.04); 273(0.02) D9S279 CA 0.78 6 2 4 4(0.09); 246(0.18): 2481.0-S): 230(0.29): 232(0.07); 234(0.09) D9S275 CA 0.62 4 190(0-51); 196(0.07): 198(0-!2): 200(0.09) I population of French Canadian or French descent (J. eissenbach. P-rsonnal Communication 1993). n.a i These polymoφhic microsatellite markers were used for DNA typing in the region of 9q31 seen in Fig.3. The majority come from the last version of the Gcnethon human linkage map ". The frequency of heierozygosity. the number of alleles as well as the allele frequency of each marker are presented. Mutation detection Based on the defect in intracellular cholesterol transport in patients with TD, we reviewed the EST database for genes in this region which might be relevant to playing a role in this process. One gene that we reviewed as a candidate was the lysophosphatidic acid (LP A) receptor (EDG2) which mapped near D9S 1801 (Fig. 3C). This receptor binds LPA and stimulates phospholipase-C (PLC), and is expressed in fibroblasts. It has previously been shown that the coordinate regulation of PLC that is necessary for normal HDL3 mediated cholesterol efflux is impaired in TD (Walter et al., J. Clin. Invest. 98:2315-2323, 1996). Therefore this gene represented an excellent candidate for the TD gene. Detailed assessment of this gene, using Northern blot and RT-PCR and sequencing analysis, revealed no changes segregating with the mutant phenotype in this family, in all likelihood excluding this gene as the cause for TD. Polymoφhisms were detected, however, in the RT-PCR product, indicating expression of transcripts from both alleles. The second candidate gene (RGS3) encodes a member of a family regulating G protein signaling which could also be involved in influencing cholesterol efflux (Mendez et al., Trans. Assoc. Amer. Phys. 104:48-53, 1991). This gene mapped 0.7 cM telomeric to the LPA-receptor (Fig. 3C), and is expressed in fibroblasts. It was assessed by exon-specific amplification, as its genomic organization was published (Chatterjee et al., Genomics 45:429-433, 1997). No significant sequence changes were detected. The ABCl transporter gene had previously been mapped to 9q31, but its precise physical location had not been determined (Luciani et al., Genomics 21 : 150- 159, 1994). The ABCl gene is a member of the ATP binding cassette transporters which represents a super family of highly conserved proteins involved in membrane transport of diverse substrates including amino acids, peptides, vitamins and steroid hormones (Luciani et al., Genomics 21 : 150-159, 1994; Dean et al., Curr. Opin. Gen. Dev. 5:779-785, 1995). Primers to the 3' UTR of this gene mapped to YACs spanning D9S306 (887-B2 and 930-D3) compatible with it being a strong candidate for TD. We initiated large scale genomic sequencing of BACs spanning approximately 800 kb around marker D9S306 (BACs 269, 274, 279 and 291) (Fig 3E). The ABCl gene was revealed encompassing 49 exons and a minimum of 75 Kb of genomic sequence. In view of the potential function of a gene in this family as a cholesterol transporter, its expression in fibroblasts and localization to the minimal genomic segment underlying TD, we formally assessed ABCl as a candidate. Patient and control total fibroblast RNA was used in Northern blot analysis and RT-PCR and sequence analyses. RT-PCR and sequence analysis of TD-1 revealed a heterozygous T to C substitution (Fig. 4A) in the TD-1 proband, which would result in a substitution of arginine for cysteine at a conserved residue between mouse and man (Fig. 4B). This mutation, confirmed by sequencing exon 30 of the ABCl gene, exhibited complete segregation with the phenotype on one side of this family (Fig. 4C). This substitution creates a Hgal site, allowing for RFLP analysis of amplified genomic DNA and confirmation of the mutation (Fig. 4C). The point mutation in exon 30 was not seen on over 200 normal chromosomes from unaffected persons of Dutch decent, and 250 chromosomes of Western European decent, indicating it is unlikely to be a polymoφhism. Northern blot analysis of fibroblast RNA from this patient, using a cDNA encompassing exons 1 to 49 of the gene, revealed a normal sized ~8 Kb transcript and a truncated mutant transcript which was not visible in control RNA or in RNA from other patients with HDL deficiency (Fig. 4D). Additionally, Northern blot analysis using clones encompassing discrete regions of the cDNA revealed that the mutant transcript was detected with a cDNA compassing exons 1 to 49 (a), 1 to 41 (b), 1 to 22 (c), much more faintly with a probe spanning exon 23 to 29 (d) and not seen with probes encompassing exons 30 to 42 (e), but not seen with cDNA fragment spanning exons 30 to 49 (f). This was repeated on multiple filters with control RNA, RNA from other patients with HDL deficiency and the other TD proband, and only in TD-1 was the truncated transcript observed. Sequence analysis of the coding region did not reveal an alteration in sequence that could account for this finding. Furthermore, DNA analysis by Southern blot did not reveal any major rearrangements. Completion of exon sequencing in genomic DNA showed that this mutation was a G to C transversion at position (+1) of intron 24, (Fig. 11) affecting a splice donor site and causing aberrant splicing. RT-PCR analysis of fibroblast RNA encoding the ABCl gene from the proband in TD-2 (Fig. IB) revealed a homozygous nucleotide change of A to G at nucleotide 1864 of SEQ ID NO: 2 in exon 13 (Fig. 5 A), resulting in a substitution of arginine for glutamine at residue 597 of SEQ ID NO: 1 (Fig. 5B), occurring just proximal to the first predicted transmembrane domain of ABCl (Fig. 8) at a residue conserved in mouse and as well as a C. elegans homolog. This mutation creates a second Acil site within exon 13. Segregation analysis of the mutation in this family revealed complete concordance between the mutation and the low HDL phenotype as predicted (Fig 5C). The proband in TD-2 is homozygous for this mutation, consistent with our expectation of a disease causing mutation in this consanguineous family. Analysis of FHA families Linkage analysis and refinement of the minimal genomic region containing the gene for FHA Data from microsatellite typing of individual family members from the four pedigrees of French Canadian origin were analyzed (Fig. 2). A maximum LOD score of 9.67 at a recombination fraction of 0.0 was detected at D9S277 on chromosome 9q31 (Fig. 3; Table 3). Thereafter, 22 markers were typed in a region spanning 10 cM around this locus in these families (Figs. 2 and 3). The frequency for these markers were estimated from a sample of unrelated and unaffected subjects of French ancestry (Table 2). TD and FHA have thus far been deemed distinct with separate clinical and biochemical characteristics. Even though the genes for these disorders mapped to the same region, it was uncertain whether FHA and TD were due to mutations in the same gene or, alternatively, due to mutations in genes in a similar region. Refinement of the region containing the gene for FHA was possible by examining haplotype sharing and identification of critical recombination events (Fig. 2). Seven separate meiotic recombination events were seen in these families ("A" through "G" in Figs. 2 and 3), clearly indicating that the minimal genomic region containing the potential disease gene was a region of approximately 4.4 cM genomic DNA spanned by marker D9S1690 and D9S1866 (Figs. 2 and 3). This region is consistent with the results of two point linkage analysis which revealed maximal LOD scores with markers TABLE 3 Two Point Linkage Analysis in FHA between the disease locus and a marker locus for specified values cf the recom i nat i on ract i on. D9S277 and D9S306 and essentially excluded the region centromeric to D9S1690 or telomeric to D9S1866. An 8 th meiotic recombination event ("H" in Fig. 3) further refined the FHA region to distal to D9S277. As described herein, the ABCl gene mapped within this interval. The overlapping genetic data strongly suggested that FHA may in fact be allelic to TD. Utilization of sets of genetic data from FHA and TD provided a telomeric boundary at D9S1866 (meiotic recombinant) (Fig. 3D) and a centromeric marker at D9S127 based on the homozygosity data of TD-2. This refined the locus to approximately 1 Mb between D9S127 and D9S1866. The ABCl gene mapped within this minimal region (Fig. 3E). Mutation detection in FHA Mutation assessment of the ABCl gene was undertaken in FHA-1 (Fig. 2A). Using primers that spanned overlapping segments of the mRNA we performed RT- PCR analysis and subjected these fragments to mutational analysis. A deletion of three nucleotides is evident in the RT-PCR sequence of FHA-1 III.01 (Fig. 6A), resulting in a loss of nucleotides 2151-2153 of SEQ ID NO: 2 and deletion of a leucine (ΔL693) at amino acid position 693 of SEQ ID NO: 1 (Fig. 6A). This leucine is conserved in mouse and C. elegans (Fig. 6B). The alteration was detected in the RT-PCR products as well as in genomic sequence from exon 14 specific amplification. This mutation results in a loss of an E rl restriction site. Analysis of genomic DNA from the family indicated that the mutation segregated completely with the phenotype of HDL deficiency. The loss of the Eαrl site results in a larger fragment being remaining in persons heterozygous for this mutation (Fig. 6C). This mutation maps to the first putative transmembrane domain of ABCl (Fig. 8) and was not seen in 130 chromosomes from persons of French Canadian descent nor seen in over 400 chromosomes from persons of other Western European ancestry. A mutation has also been found in patient genomic DNA in pedigree FHA-3 from Quebec. The alteration, a 6 bp deletion of nucleotides 5752-5757 of SEQ ID NO: 2 within exon 41, results in a deletion of amino acids 1893 (Glu) and 1894 (Asp) of SEQ ID NO: 1. The deletion was detected as a double, superimposed, sequence starting from the point of the deletion (Fig. 6D), and was detected in sequence reads in both directions. The deletion can be detected on 3% agarose or 10% polyacrylamide gels, and segregates with disease in FHA-3. It was not seen in 128 normal chromosomes of French-Canadian origin or in 434 other control chromosomes. Amino acids 1893 and 1894 are in a region of the ABCl protein that is conserved between human, mouse, and C. elegans (Fig. 6E), implying that it is of functional importance. An additional mutation has been found in patient genomic DNA in pedigree FHA-2 from Quebec (Fig. 6F). The alteration, a C to T transition at position 6504 of SEQ ID NO: 2, converts an arginine at position 2144 of SEQ ID NO: 1 to a STOP codon, causing truncation of the last 118 amino acids of the ABCl protein. This alteration segregates with disease in family FHA-2. A summary of all mutations and polymoφhisms found in ABCl is shown in Fig. 11. Each variant indicated as a mutation segregates with low HDL in its family, and was not seen in several hundred control chromosomes. Functional relationship between changes in ABCl transcript levels and cholesterol efflux Antisense approaches were undertaken to decrease the ABCl transcript and assess the effect of alteration of the transcript on intracellular cholesterol transport. The use of antisense primers to the 5' end of ABCl clearly resulted in a decrease to approximately 50% of normal RNA levels (Fig. 7A). This would be expected to mimic in part the loss of function due to mutations on one allele, similar to that seen in heterozygotes for TD and patients with FHA. Importantly, reduction in the mRNA for the ABCl gene resulted in a significant reduction in cellular cholesterol efflux (Fig. 7B), further establishing the role of this protein in reverse cholesterol transport and providing evidence that the mutations detected are likely to constitute loss of function mutations. Furthermore, these data support the functional importance of the first 60 amino acids of the protein. Antisense oligonucleotide AN-6 is directed to the novel start codon 5' to the one indicated in AJ012376.1; this antisense oligonucleotide effectively suppresses efflux. The above-described results were obtained using the following materials and methods. Patient selection The probands in TD families had previously been diagnosed as suffering from TD based on clinical and biochemical data. Study subjects with FHA were selected from the Cardiology Clinic of the Clinical Research Institute of Montreal. The main criterion was an HDL-C level <5th percentile for age and gender, with a plasma concentration of triglycerides <95th percentile in the proband and a first-degree relative with the same lipid abnormality. In addition, the patients did not have diabetes. Biochemical studies Blood was withdrawn in EDTA-containing tubes for plasma lipid, lipoprotein cholesterol, ApoAI, and triglyceride analyses, as well as storage at -80°C. Leukocytes were isolated from the buffy coat for DNA extraction. Lipoprotein measurement was performed on fresh plasma as described elsewhere (Rogler et al., Arterioscler. Thromb. Vase. Biol. 15:683-690, 1995). The laboratory participates and meets the criteria of the Lipid Research Program Standardization Program. Lipids, cholesterol and triglyceride levels were determined in total plasma and plasma at density d< 1.006 g/mL (obtained after preparative ultracentrifugation) before and after precipitation with dextran manganese. Apolipoprotein measurement was performed by nephelometry for ApoB and ApoAI. Linkage analysis Linkage between the trait locus and microsatellite loci was analyzed using the FASTLINK version (4.0 P). FASTLINK/MLiNK was used for two-point linkage analysis assuming an autosomal dominant trait with complete penetrance. In FHA and TD heterozygotes, the phenotype was HDL deficiency <5th percentile for age and sex. The disease allele frequency was estimated to be 0.005. Marker allele frequencies were estimated from the genotypes of the founders in the pedigrees using NEWPREP. Multipoint linkage analysis was carried out using FASTLESfK/LINKMAP. Genomic clone assembly and physical map construction of the 9q31 region Using the Whitehead Institute/MIT Center for Genome Research map as a reference, the genetic markers of interest at 9q31 were identified within YAC contigs. Additional markers that mapped to the approximate 9q31 interval from public databases and the literature were then assayed against the YAC clones by PCR and hybridization analysis. The order of markers was based on their presence or absence in the anchored YAC contigs and later in the BAC contig. Based on the haplotype analysis, the region between D9S277 and D9S306 was targeted for higher resolution physical mapping studies using bacterial artificial chromosomes (BACs). BACs within the region of interest were isolated by hybridization of DNA marker probes and whole YACs to high-density filters containing clones from the RPCI-11 human BAC library (Fig. 3). Sequence retrieval and alignment The human ABCl mRNA sequence was retrieved from GenBank using the Entrez nucleotide query (Baxevanis et al., A Practical Guide to the Analysis of Genes and Proteins, eds. Baxevanis, A.D. & Ouellette, B.F.F. 98:120, 1998) as GenBank accession number AJ012376.1. The version of the protein sequence we used as wild- type (normal) was CAA 10005.1. We identified an additional 60 amino acids in- frame with the previously- believed start methionine (Fig. 9A). Bioinformatic analysis of the additional amino acids indicates the presence of a short stretch of basic amino acid residues, followed by a hydrophobic stretch, then several polar residues. This may represent a leader sequence, or another transmembrane or membrane-associated region of the ABCl protein. In order to differentiate among the foregoing possibilities, antibodies directed to the region of amino acids 1 -60 are raised against and used to determine the physical relationship of amino acids 1-60 in relation to the cell membrane. Other standard methods can also be employed, including, for example, expression of fusion proteins and cell fractionation. We also identified six errors in the previously-reported nucleotide sequence (at positions 839, 4738, 5017, 5995, 6557, and 6899 of SEQ ID NO: 2; Fig. 11). Hence, the sequence of the ABCl polypeptide of Fig. 9A differs from CAA10005.1 as follows: Thr Ile at position 1554; Pro=_>Leu at position 1642; Arg=- Lys at position 1973; and Pro^Leu at position 2167. We also identified 5' and 3' UTR sequence (Figs. 9B - 9E). The mouse ABCl sequence used has accession number X75926. It is very likely that this mouse sequence is incomplete, as it lacks the additional 60 amino acids described herein for human ABC 1. Version 1.7 of ClustalW was used for multiple sequence alignments with BOXSHADE for graphical enhancement (http://www.isrec.isb-sib.ch:8080/ software/BOX_form.html) with the default parameter. A Caenorhabditis elegans ABCl orthologue was identified with BLAST (version 2.08) using CAA1005.1 (see above) as a query, with the default parameter except for doing an organism filter for C. elegans. The selected protein sequence has accession version number AAC69223.1 with a score of 375, and an E value of 103. Genomic DNA sequencing BAC DNA was extracted from bacterial cultures using NucleoBond Plasmid Maxi Kits (Clontech, Palo Alto, CA). For DNA sequencing, a sublibrary was first constructed from each of the BAC DNAs (Rowen et al., Automated DNA Sequencing and Analysis, eds. Adams, M.D., Fields, C. & Venter, J.C., 1994). In brief, the BAC DNA was isolated and randomly sheared by nebulization. The sheared DNA was then size fractionated by agarose gel electrophoresis and fragments above 2 kb were collected, treated with Mung Bean nuclease followed by T4 DNA polymerase and klenow enzyme to ensure blunt-ends, and cloned into Smal-cvit M13mpl9. Random clones were sequenced with an ABI373 or 377 sequencer and fluorescently labeled primers (Applied BioSystems, Foster City, CA). DNAStar software was used for gel trace analysis and contig assembly. All DNA sequences were examined against available public databases primarily using BLASTn with RepeatMasker (University of Washington). Reverse transcription (RT)-PCR amplification and sequence analysis Total RNA was isolated from the cultured fibroblasts of TD and FHA patients, and reverse transcribed with a CDS primer containing oligo d(T)18 using 250 units of Superscript II reverse transcriptase (Life Technologies, Inc., Rockville, MD) as described (Zhang et al., J. Biol. Chem. 27:1776-1783, 1996). cDNA was amplified with Taq DNA polymerase using primers derived from the published human ABCl cDNA sequence (Luciani et al., Genomics 21:150-159, 1994). Six sets of primer pairs were designed to amplify each cDNA sample, generating six DNA fragments which are sequentially overlapped covering 135 to 7014 bp of the full-length human ABCl cDNA. The nucleotides are numbered according to the order of the published human cDNA sequence (AJ012376.1). Primer pairs (1): 135-158 (f) and 1183-1199 (r); (2): 1080-1107 (f) and 2247-2273 (r); (3): 2171-2197 (f) and 3376-3404 (r); (4): 3323- 3353 (f) and 4587-4617 (r); (5) 4515-4539 (f) and 5782-5811 (r); (6): 5742-5769 (f) and 6985-7014 (r). RT-PCR products were purified by Qiagen spin columns. Sequencing was carried out in a Model 373A Automated DNA sequencer (Applied Biosystems) using Taq di-deoxy terminator cycle sequencing and Big Dye Kits according to the manufacturer's protocol. Northern blot analysis Northern transfer and hybridizations were performed essentially as described (Zhang et al, J. Biol. Chem. 27:1776-1783, 1996). Briefly, 20 μg of total fibroblast RNA samples were resolved by electrophoresis in a denaturing agarose (1.2%; w/v) gel in the presence of 7% formaldehyde, and transferred to nylon membranes. The filters were probed with 32 P-labeled human ABCl cDNA as indicated. Pre- hybridization and hybridizations were carried out in an ExpressHyb solution (ClonTech) at 68°C according to the manufacturer's protocol. Detection of the mutations in TD Genotyping for the T4503C and A1864G variants was performed by PCR amplification of exon 30 followed by restriction digestion with Hgal and amplification of exon 13 followed by digestion with Acil, respectively. PCR was carried out in a total volume of 50 μL with 1.5 mM MgCl 2 , 187.5 nM of each dNTP, 2.5U Taq polymerase and 15 pmol of each primer (forward primer in exon 30: 5'- CTG CCA GGC AGG GGA GGA AGA GTG-3 ' (SEQ ID NO: 4); reverse primer spanning the junction of exon 30 and intron 30: 5'-GAA AGT GAC TCA CTT GTG GAG GA-3' (SEQ ID NO: 5); forward primer in intron 12: 5'-AAA GGG GCT TGG TAA GGG TA-3' (SEQ ID NO: 6); reverse in intron 13: 5 '-CAT GCA CAT GCA CAC AC A TA -3' (SEQ ID NO: 7)). Following an initial denaturation of 3 minutes at 95°C, 35 cycles consisting of 95°C 10 seconds, 58°C 30 seconds, 72°C 30 seconds were performed, with a final extension of 10 minutes at 72°C. For detection of the T4503C mutation, 15 μL of exon 30 PCR product was incubated with 4 U Hgal in a total volume of 25 μL, for 2 hours at 37°C, and the resulting fragments were separated on a 1.5% agarose gel. The presence of the T4503C mutation creates a restriction site for H l, and thus the 194 bp PCR product will be cut into fragments of 134 and 60 bp in the presence of the T4503C variant, but not in its absence. For detection of the A1864G mutation, 15 μL of exon 13 PCR products were digested with 8 U Acil for three hours at 37°C. Products were separated on 2% agarose gels. The presence of the Al 864G mutation creates a second Acil site within the PCR product. Thus, the 360 bp PCR product is cleaved into fragments of 215 bp and 145 bp on the wild-type allele, but 185 bp, 145 bp and 30 bp on the mutant allele. Detection of mutation in FHA Genotyping for the Δ693 variant was performed by PCR amplification of exon 14 followed by restriction enzyme digestion with Earl. PCR was carried out in a total volume of 80 μL with 1.5 mM MgCl 2 , 187.5 nM of each dNTP, 2.5 U Taq polymerase and 20 pmol of each primer (forward primer in exon 14: 5'- CTT TCT GCG GGT GAT GAG CCG GTC AAT-3' (SEQ ID NO: 8); reverse primer in intron 14: 5'-CCT TAG CCC GTG TTG AGC TA-3' (SEQ ID NO: 9)). Following an initial denaturation of 3 minutes at 95°C, 35 cycles consisting of 95°C 10 seconds, 55°C 30 seconds, 72°C 30 seconds were performed, with a final extension of 10 minutes at 72°C. Twenty microliters of PCR product was incubated with 4 U Eαrl in a total volume of 25 μL, for two hours at 37°C, and the fragments were separated on a 2 % agarose gel. The presence of the Δ693 mutation destroys a restriction site for Eαrl, and thus the 297 bp PCR product will be cut into fragments of 151 bp, 59 bp, 48 bp and 39 bp in the presence of a wild- type allele, but only fragments of 210 bp, 48 bp and 39 bp in the presence of the deletion. A 6 bp deletion encompassing nucleotides 5752-5757 (inclusive), was detected in exon 41 in the proband of family FHA-3 by genomic sequencing using primers located within the introns flanking this exon. Genotyping of this mutation in family FHA-3 and controls was carried out by PCR with forward (5 ' -CCT GTA AAT GCA AAG CTA TCT CCT CT- 3' (SΕQ ID NO: 10)) and reverse primers (5'-CGT CAA CTC CTT GAT TTC TAA GAT GT (SΕQ ID NO: 11)) located near the 5' and 3' ends of exon 41, respectively. Each PCR was carried out as for the genotyping of the 693 variant, but with annealing temperature of 58°C. Twenty microliters of PCR product was resolved on 3% agarose or 10% acrylamide gels. The wild type allele was detected as a 117 bp band and the mutant allele as a 111 bp band upon staining with ethidium bromide. A C to T transition was detected at nucleotide 6504 in genomic DNA of the proband of family FHA-2. It was detectable as a double C and T peak in the genomic sequence of exon 48 of this individual, who is heterozygous for the alteration. This mutation, which creates a STOP codon that results in truncation of the last 118 amino acids of the ABCl protein, also destroys an Rsal restriction site that is present in the wild type sequence. Genotyping of this mutation in family FHA-2 and controls was carried out by PCR with forward (5'-GGG TTC CCA GGG TTC AGT AT-3') (SEQ ID NO: 12)) and reverse (5'-GAT CAG GAA TTC AAG CAC CAA-3') (SEQ ID NO: 13)) primers directed to the intronic sequences flanking exon 48. PCR was done as for the 693 variant. Fifteen microliters of PCR product was digested with 5 Units of Rsa at 37°C for two hours and the digestion products resolved on 1.5% agarose gels. The mutant allele is detected as an uncut 436 bp band. The normal sequence is cut by Rsal to produce 332 and 104 bp bands. Cell culture Skin fibroblast cultures were established from 3.0 mm punch biopsies of the forearm of FHD patients and healthy control subjects as described (Marcil et al., Arterioscler. Thromb. Vase. Biol. 19:159-169, 1999). Cellular cholesterol labeling and loading The protocol for cellular cholesterol efflux experiments was described in detail elsewhere (Marcil et al., Arterioscler. Thromb. Vase. Biol. 19:159-169, 1999). The cells were 3 H-cholesterol labeled during growth and free cholesterol loaded in growth arrest. Cholesterol efflux studies Efflux studies were carried out from 0 to 24 hours in the presence of purified ApoAI (10 μg protein/mL medium). Efflux was determined as a percent of free cholesterol in the medium after the cells were incubated for specified periods of time. All experiments were performed in triplicate, in the presence of cells from one control subject and the cells from the study subjects to be examined. All results showing an efflux defect were confirmed at least three times. Oligonucleotide synthesis Eight phosphorothioate deoxyoligonucleotides complementary to various regions of the human ABCl cDNA sequence were obtained from GIBCO BRL. The oligonucleotides were purified by HPLC. The sequences of the antisense oligonucleotides and their location are listed. One skilled in the art will recognize that other ABCl antisense sequences can also be produced and tested for their ability to decrease ABCl -mediated cholesterol regulation. Name Sequence (5'- ') mRNA target % control AN-1 GCAGAGGGCATGGCTTTATTTG (SEQ ID NO: 3) AUG codon 46 AN-2 GTGTTCCTGCAGAGGGCATG (SEQ ID NO: 30) AUG codon 50 AN-3 CACTTCCAGTAACAGCTGAC (SEQ ID NO: 31) 5 '-Untranslated 79 AN-4 CTTTGCGCATGTCCTTCATGC (SEQ ID NO: 32) Coding 80 AN-5 GACATCAGCCCTCAGCATCTT (SEQ ID NO: 33) Coding 120 AN-6 CAACAAGCCATGTTCCCTC (SEQ ID NO: 34) Coding AN-7 CATGTTCCCTCAGCCAGC (SEQ ID NO: 35) Coding AN-8: CAGAGCTCACAGCAGGGA C (SEQ ID NO: 36) Coding Cell transfection with antisense oligonucleotides Cells were grown in 35 mm culture dishes until 80 % confluent, then washed once with DMEM medium (serum and antibiotics free). One milliliter of DMEM (serum and antibiotics free) containing 500 nM antisense oligonucleotides and 5 μg/ml or 7.5 μg/ml of lipofectin (GIBCO BRL) were added to each well according to the manufacturer's protocol. The cells were incubated at 37°C for 4 hours, and then the medium was replaced by DMEM containing 10% FCS. Twenty- four hours after the transfection, the total cell RNA was isolated. Ten micrograms of total RNA was resolved on a 1% of agarose- formaldehyde gel and transferred to nylon membrane. The blot was hybridized with α- 32 P dCTP labeled human ABCl cDNA overnight at 68°C. The membrane was subsequently exposed to x-ray film. The hybridizing bands were scanned by optical densitometry and standard to 28S ribosome RNA. Cholesterol efflux with anti-ABCl oligonucleotides Human skin fibroblasts were plated in 6-well plates. The cells were labeled with 3 H-cholesterol (0.2 μCi /ml) in DMEM with 10% FBS for two days when the cell reached 50% confluence. The cells were then transfected with the antisense ABCl oligonucleotides at 500nM in DMEM (serum and antibiotic free) with 7.5 μg/ml Lipofectin (GIBCO BRL) according to the manufacturer's protocol. Following the transfection, and the cells were loaded with nonlipoprotein (20 μg/ml) for 12 hours in DMEM containing 2 mg/ml BSA without serum. The cellular cholesterol pools were then allowed to equilibrate for 6 hours in DMEM-BSA. The cholesterol efflux mediated by ApoAI (lOμg /ml, in DMEM-BSA) were then carried out which is 48 hours after transfection. Radiolabeled cholesterol released into the medium is expressed as a percentage of total 3 H-cholesterol per well (medium + cell ). Results are the mean +/- SD of triplicate dishes. Determination of genomic structure of the ABCl gene Most splice junction sequences were determined from genomic sequence generated from BAC clones spanning the ABCl gene. More than 160 kb of genomic sequence were generated. Genomic sequences were aligned with cDNA sequences to identify intron/exon boundaries. In some cases, long distance PCR between adjacent exons was used to amplify intron/exon boundary sequences using amplification primers designed according to the cDNA sequence. Functionality of the newly-discovered 60 amino acids at the N-terminus Antisense experiments Phosphorothioate antisentisense oligonucleotides were designed to be complementary to the regions of the cDNA near newly discovered translation start site. AN-6 and AN-7 both overlap the initiator methionine codon; this site is in the middle of oligonucleotide AN-6. AN-8 is complementary to the very 5' end of the ABCl cDNA. Antisense oligonucleotide AN-1 is complementary to the region of the ABCl cDNA corresponding to the site identified as the ABCl initiator methionine in AJ012376. Fig. 7C shows that antisense oligonucleotide AN-6 interferes with cellular cholesterol efflux in normal fibroblasts to the same extent as does antisense oligonucleotide AN-1. Transfection with either of these antisense oligonucleotides results in a decrease in cellular cholesterol efflux almost as severe as that seen in FHA cells. In general, antisense oligonucleotides complementary to coding sequences, especially near the 5' end of a gene's coding sequence, are expected to be more effective in decreasing the effective amount of transcript than are oligonucleotides directed to more 3' sequences or to non-coding sequences. The observation that AN-6 depresses cellular cholesterol efflux as effectively as AN-1 implies that both of these oligonucleotides are complementary to ABCl coding sequences, and that the amino terminal 60 amino acids are likely to be contained in ABCl protein. In contrast, the ineffectiveness of AN-8 shows that it is likely to be outside the protein coding region of the transcript, as predicted by presence of an in-frame stop codon between the initiator methionine and the region targeted by AN-8. Antibody experiments Polyclonal and monoclonal antibodies have been generated using peptides corresponding to discrete portions of the ABCl amino acid sequence. One of these, 20-amino acid peptide #2 (Pep2: CSVRLSYPPYEQHECHFPNKA (SEQ ID NO: 37), in which the N-terminal cysteine was added to facilitate conjugation of the peptide) corresponds to a protein sequence within the 60 amino-terminal amino acids of the newly-discovered ABCl protein sequence. The peptide was coupled to the KLH carrier protein and 300 μg injected at three intervals into two Balb/c mice over a four week period. The spleen was harvested from the mouse with the highest ELISA-determined immune response to free peptide, and the cells fused to NS-1 myeloma cells by standard monoclonal antibody generation methods. Positive hybridomas were selected first by ELISA and then further characterized by western blotting using cultured primary human fibroblasts. Monoclonal cell lines producing a high antibody titre and specifically recognizing the 245 kD human ABCl protein were saved. The same size ABCl protein product was detected by antibodies directed to four other discrete regions of the same protein. The 245 kD band could be eliminated in competition experiments with appropriate free peptide, indicating that it represents ABCl protein (Fig. 13). The foregoing experiments indicate that ABCl protein is detected not only by antibodies corresponding to amino acid sequences within the previously-described ABCl amino acid sequence, but also by the Pep2 monoclonal antibody that recognizes an epitope within the newly-discovered N-terminal 60 amino acids. The N-terminal 60 amino acid region is therefore coding, and is part of the ABCl protein. The epitope recognized by the Pep2 monoclonal antibody is also conserved among human, mouse, and chicken. Liver tissues from these three species employed in a Western blot produced an ABCl band of 245 kD when probed with the Pep2 monoclonal antibody. This indicates that the 60 amino acid N-terminal sequence is part of the ABCl coding sequence in humans, mice, and chickens. Presence of this region is therefore evolutionarily conserved and likely to be of important functional significance for the ABCl protein. Bioinformatic analyses of ABCl protein sequences Transmembrane prediction programs indicate 13 transmembrane (TM) regions, the first one being between amino acids 26 and 42 (http://psort.nibb.ac.jp:8800/psort/helpwww2.html#ealom). The tentative number of TM regions for the threshold 0.5 is 13. (INTEGRAL Likelihood = -7.75 Transmembrane 26-42). The other 12 TM range in value between -0.64 and -12 (full results below). It is therefore very likely that the newly-discovered 60 amino acids contain a TM domain, and that the amino end of ABCl may be on the opposite side of the membrane than originally thought. ALOM: TM region allocation Init position for calculation: 1 Tentative number of TMs for the threshold 0.5: 13 INTEGRAL Likelihood = -7.75 Transmembrane 26 - 42 INTEGRAL Likelihood = -3.98 Transmembrane 640 - 656 INTEGRAL Likelihood = -8.70 Transmembrane 690 - 706 INTEGRAL Likelihood = -9.61 Transmembrane 717 - 733 INTEGRAL Likelihood = -1.44 Transmembrane 749 - 765 INTEGRAL Likelihood = -0.64 Transmembrane 771 - 787 INTEGRAL Likelihood = -1.28 Transmembrane 1041 ■1057 INTEGRAL Likelihood =-12.79 Transmembrane 1351 -1367 INTEGRAL Likelihood = -8.60 Transmembrane 1661 1677 INTEGRAL Likelihood = -6.79 Transmembrane 1708 1724 INTEGRAL Likelihood = -3.40 Transmembrane 1737 ■1753 INTEGRAL Likelihood = - 1.49 Transmembrane 1775 1791 INTEGRAL Likelihood = -8.39 Transmembrane 1854 ■1870 PERIPHERAL Likelihood = 0.69 (at 1643) ALOM score: -12.79 (number of TMSs: 13) There does not appear to be an obvious cleaved peptide, so this first 60 amino acid residues are not likely to be cleaved, and are therefore not specifically a signal/targeting sequence. No other signals (e.g., for targeting to specific organelles) are apparent. Agonists and Antagonists Useful therapeutic compounds include those which modulate the expression, activity, or stability of ABCl . To isolate such compounds, ABCl expression, biological activity, or regulated catabolism is measured following the addition of candidate compounds to a culture medium of ABCl -expressing cells. Alternatively, the candidate compounds may be directly administered to animals (for example mice, pigs, or chickens) and used to screen for their effects on ABCl expression. In addition its role in the regulation of cholesterol, ABCl also participates in other biological processes for which the development of ABCl modulators would be useful. In one example, ABCl transports interleukin-lβ (IL-lβ) across the cell membrane and out of cells. IL-lβ is a precursor of the inflammatory response and, as such, inhibitors or antagonists of ABCl expression or biological activity may be useful in the treatment of any inflammatory disorders, including but not limited to rheumatoid arthritis, systemic lupus erythematosis (SLE), hypo- or hyper- thyroidism, inflammatory bowel disease, and diabetes mellitus. In another example, ABCl expressed in macrophages has been shown to be engaged in the engulfment and clearance of dead cells. The ability of macrophages to ingest these apoptotic bodies is impaired after antibody-mediated blockade of ABCl. Accordingly, compounds that modulate ABCl expression, stability, or biological activity would be useful for the treatment of these disorders. ABCl expression is measured, for example, by standard Northern blot analysis using an ABCl nucleic acid sequence (or fragment thereof) as a hybridization probe, or by Western blot using an anti-ABCl antibody and standard techniques. The level of ABCl expression in the presence of the candidate molecule is compared to the level measured for the same cells, in the same culture medium, or in a parallel set of test animals, but in the absence of the candidate molecule. ABCl activity can also be measured using the cholesterol efflux assay. Transcriptional Regulation of ABCl Expression ABCl mRNA is increased approximately 8-fold upon cholesterol loading. This increase is likely controlled at the transcriptional level. Using the promoter sequence described herein, one can identify transcription factors that bind to the promoter by performing, for example, gel shift assays, DNAse protection assays, or in vitro or in vivo reporter gene-based assays. The identified transcription factors are themselves drug targets. In the case of ABCl, drug compounds that act through modulation of transcription of ABCl could be used for HDL modulation, atherosclerosis prevention, and the treatment of cardiovascular disease. For example, using a compound to inhibit a transcription factor that represses ABCl would be expected to result in up-regulation of ABCl and, therefore, HDL levels. In another example, a compound that increases transcription factor expression or activity would also increase ABCl expression and HDL levels. Transcription factors known to regulate other genes in the regulation of apolipoprotein genes or other cholesterol- or lipid-regulating genes are of particular relevance. Such factors include, but are not limited to, the steroid response element binding proteins (SREBP-1 and SREBP-2), the PPAR (peroxisomal proliferation-activated receptor) transcription factors. Several consensus sites for certain elements are present in the sequenced region 5' to the ABCl gene (Fig. 16) and are likely to modulate ABCl expression. For example, PPARs may alter transcription of ABCl by mechanisms including heterodimerization with retinoid X receptors (RXRs) and then binding to specific proliferator response elements (PPREs). Examples of such PPARs include PPARα, β, γ and δ. These distinct PPARs have been shown to have transcriptional regulatory effects on different genes. PPARα is expressed mainly in liver, whereas PPARγ is expressed in predominantly in adipocytes. Both PPARα and PPARγ are found in coronary and carotid artery atherosclerotic plaques and in endothelial cells, smooth muscle cells, monocytes and monocyte-derived macrophages. Activation of PPARα results in altered lipoprotein metabolism through PPARα's effect on genes such as lipoprotein lipase (LPL), apolipoprotein CIII (apo CHI) and apolipoprotein Al (apo Al) and All (apo All). PPARα activation results in overexpression of LPL and apoA-I and apoA-II, but inhibits the expression of apo CIII. PPARα activation also inhibits inflammation, stimulates lipid oxidation and increases the hepatic uptake and esterification of free fatty acids (FFA's). PPARα and PPARγ activation may inhibit nitric oxide (NO) synthase in macrophages and prevent interleukin-1 (IL-1) induced expression of IL-6 and cyclo-oxygenase-2 (COX-2) and thrombin induced endothelin-1 expression secondary to negative transcriptional regulation of NF-KB and activation of protein- 1 signaling pathway. It has also been shown that PPARα induces apoptosis in monocyte-derived macrophages through the inhibition of NF-KB activity. Activation of PPARα can be achieved by compounds such as fibrates, β-estradiol, arachidonic acid derivatives, WY- 14,643 and LTB4 or 8(s)HETE. PPARγ activation can be achieved through compounds such as thiozolidinedione antidiabetic drugs, 9-HODE and 13-HODE. Additional compounds such as nicotinic acid or HMG Co A reductase inhibitors may also alter the activity of PPARs. Compounds which alter activity of any of the PPARs (e.g., PPARα or PPARγ) may have an effect on ABCl expression and thereby could affect HDL levels, atherosclerosis and risk of CAD. PPARs are also regulated by fatty acids (including modified fatty acids such as 3 thia fatty acids), leukotrienes such as leukotriene B4 and prostaglandin J2, which is a natural activator/ligand for PPARγ. Drugs that modulate PPARs may therefore have an important effect on modulating lipid levels (including HDL and triglyceride levels) and altering CAD risk. This effect could be achieved through the modulation of ABCl gene expression. Drugs may also effect ABCl gene expression and thereby HDL levels, by an indirect effect on PPARs via other transcriptional factors such as adipocyte differentiation and determination factor- 1 (ADD-1) and sterol regulatory element binding protein- 1 and 2 (SREBP-1 and 2). Drugs with combined PPARα and PPARγ agonist activity or PPARα and PPARγ agonists given in combination for example, may increase HDL levels even more. A PPAR binding site (PPRE element) is found 5' to the ABCl gene (nucleotides 2150 to 2169 of SEQ ID NO: 14). Like the PPRE elements found in the C-ACS, HD, CYP4A6 and ApoA-I genes, this PPRE site is a trimer related to the PPRE consensus sequence. Partly because of its similarity in the number and arrangement of repeats in this PPAR binding site, this element in particular is very likely to be of physiological relevance to the regulation of the ABCl gene. Additional transcription factors which may also have an effect in modulating ABCl gene expression and thereby HDL levels, atherosclerosis and CAD risk include; REV-ERBα, SREBP-1 & 2, ADD-1 , EBPα, CREB binding protein, P300, HNF 4, RAR, LXR, and RORα. Additional degenerate binding sites for these factors can be found through examination of the sequence in SEQ ID NO: 14. Additional utility of ABCl polypeptides, nucleic acids, and modulators ABCl may act as a transporter of toxic proteins or protein fragments (e.g., APP) out of cells. Thus, ABCl agonists/upregulators may be useful in the treatment of other disease areas, including Alzheimer's disease, Niemann-Pick disease, and Huntington's disease. ABC transporters have been shown to increase the uptake of long chain fatty acids from the cytosol to peroxisomes and, moreover, to play a role in β-oxidation of very long chain fatty acids. Importantly, in x-linked adrenoleukodystrophy (ALD), fatty acid metabolism is abnormal, due to defects in the peroxisomal ABC transporter. Any agent that upregulates ABC transporter expression or biological activity may therefor be useful for the treatment of ALD or any other lipid disorder. ABCl is expressed in macrophages and is required for engulfment of cells undergoing programmed cell death. The apoptotic process itself, and its regulation, have important implications for disorders such as cancer, one mechanism of which is failure of cells to undergo cell death appropriately. ABCl may facilitate apoptosis, and as such may represent an intervention point for cancer treatment. Increasing ABCl expression or activity or otherwise up-regulating ABCl by any method may constitute a treatment for cancer by increasing apoptosis and thus potentially decreasing the aberrant cellular proliferation characterized by this disease. Conversely, down-regulation of ABCl by any method may provide opportunity for decreasing apoptosis and allowing increased proliferation of cells in conditions where cell growth is limited. Such disorders include but are not limited to neurodeficiencies and neurodegeneration, and growth disorders. ABCl could, therefore, potentially be used as a method for identification of compounds for use in the treatment of cancer, or in the treatment of degenerative disorders. Agents that have been shown to inhibit ABCl include, for example, the antidiabetic agents glibenclamide and glyburide, flufenamic acid, diphenylamine-2- carbonic acid, sulfobromophthalein, and DIDS. Agents that upregulate ABCl expression or biological activity include but are not limited to protein kinase A, protein kinase C, vanadate, okadaic acid, and IBMXl . Those in the art will recognize that other compounds can also modulate ABCl biological activity, and these compounds are also in the spirit of the invention. Drug screens based on the ABCl gene or protein The ABCl protein and gene can be used in screening assays for identification of compounds which modulate its activity and may be potential drugs to regulate cholesterol levels. Useful ABCl proteins include wild-type and mutant ABCl proteins or protein fragments, in a recombinant form or endogenously expressed. Drug screens to identify compounds acting on the ABCl expression product may employ any functional feature of the protein. In one example, the phosphorylation state or other post-translational modification is monitored as a measure of ABCl biological activity. ABCl has ATP binding sites, and thus assays may wholly or in part test the ability of ABCl to bind ATP or to exhibit ATPase activity. ABCl, by analogy to similar proteins, is thought to be able to form a channel-like structure; drug screening assays could be based upon assaying for the ability of the protein to form a channel, or upon the ability to transport cholesterol or another molecule, or based upon the ability of other proteins bound by or regulated by ABCl to form a channel. Alternatively, phospho lipid or lipid transport can also be used as measures of ABCl biological activity. There is evidence that, in addition to its role as a regulator of cholesterol levels, ABCl also transports anions. Functional assays could be based upon this property, and could employ drug screening technology such as (but not limited to) the ability of various dyes to change color in response to changes in specific ion concentrations in such assays can be performed in vesicles such as liposomes, or adapted to use whole cells. Drug screening assays can also be based upon the ability of ABCl or other ABC transporters to interact with other proteins. Such interacting proteins can be identified by a variety of methods known in the art, including, for example, radioimmunoprecipitation, co-immunoprecipitation, co-purification, and yeast two- hybrid screening. Such interactions can be further assayed by means including but not limited to fluorescence polarization or scintillation proximity methods. Drug screens can also be based upon functions of the ABCl protein deduced upon X-ray crystallography of the protein and comparison of its 3-D structure to that of proteins with known functions. Such a crystal structure has been determined for the prokaryotic ABC family member HisP, histidine permease. Drug screens can be based upon a function or feature apparent upon creation of a transgenic or knockout mouse, or upon overexpression of the protein or protein fragment in mammalian cells in vitro. Moreover, expression of mammalian (e.g., human) ABCl in yeast or C. elegans allows for screening of candidate compounds in wild-type and mutant backgrounds, as well as screens for mutations that enhance or suppress an ABC1- dependent phenotype. Modifier screens can also be performed in ABCl transgenic or knock-out mice. Additionally, drug screening assays can also be based upon ABCl functions deduced upon antisense interference with the gene function. Intracellular localization of ABC 1 , or effects which occur upon a change in intracellular localization of the protein, can also be used as an assay for drag screening. Immunocytochemical methods will be used to determine the exact location of the ABCl protein. Human and rodent ABCl protein can be used as an antigen to raise antibodies, including monoclonal antibodies. Such antibodies will be useful for a wide variety of puφoses, including but not limited to functional studies and the development of drug screening assays and diagnostics. Monitoring the influence of agents (e.g., drugs, compounds) on the expression or biological activity of ABCl can be applied not only in basic drug screening, but also in clinical trials. For example, the effectiveness of an agent determined by a screening assay as described herein to increase ABCl gene expression, protein levels, or biological activity can be monitored in clinical trails of subjects exhibiting altered ABCl gene expression, protein levels, or biological activity. Alternatively, the effectiveness of an agent determined by a screening assay to modulate ABCl gene expression, protein levels, or biological activity can be monitored in clinical trails of subjects exhibiting decreased altered gene expression, protein levels, or biological activity. In such clinical trials, the expression or activity of ABCl and, preferably, other genes that have been implicated in, for example, cardiovascular disease can be used to ascertain the effectiveness of a particular drug. For example, and not by way of limitation, genes, including ABCl, that are modulated in cells by treatment with an agent (e.g., compound, drag or small molecule) that modulates ABCl biological activity (e.g., identified in a screening assay as described herein) can be identified. Thus, to study the effect of agents on cholesterol levels or cardiovascular disease, for example, in a clinical trial, cells can be isolated and RNA prepared and analyzed for the levels of expression of ABCl and other genes implicated in the disorder. The levels of gene expression can be quantified by Northern blot analysis or RT-PCR, or, alternatively, by measuring the amount of protein produced, by one of a number of methods known in the art, or by measuring the levels of biological activity of ABCl or other genes. In this way, the gene expression can serve as a marker, indicative of the physiological response of the cells to the agent. Accordingly, this response state may be determined before, and at various points during, treatment of the individual with the agent. In a preferred embodiment, the present invention provides a method for monitoring the effectiveness of treatment of a subject with an agent (e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drag candidate identified by the screening assays described herein) including the steps of (i) obtaining a pre-administration sample from a subject prior to administration of the agent; (ii) detecting the level of expression of an ABCl protein, mRNA, or genomic DNA in the preadministration sample; (iii) obtaining one or more post-administration samples from the subject; (iv) detecting the level of expression or activity of the ABCl protein, mRNA, or genomic DNA in the post-administration samples; (v) comparing the level of expression or activity of the ABCl protein, mRNA, or genomic DNA in the pre-administration sample with the ABCl protein, mRNA, or genomic DNA in the post administration sample or samples; and (vi) altering the administration of the agent to the subject accordingly. For example, increased administration of the agent may be desirable to increase the expression or activity of ABCl to higher levels than detected, i.e., to increase the effectiveness of the agent. Alternatively, decreased administration of the agent may be desirable to decrease expression or activity of ABCl to lower levels than detected. The ABCl gene or a fragment thereof can be used as a tool to express the protein in an appropriate cell in vitro or in vivo (gene therapy), or can be cloned into expression vectors which can be used to produce large enough amounts of ABCl protein to use in in vitro assays for drag screening. Expression systems which may be employed include baculovirus, heφes virus, adenovirus, adeno-associated virus, bacterial systems, and eucaryotic systems such as CHO cells. Naked DNA and DNA- liposome complexes can also be used. Assays of ABCl activity includes binding to intracellular interacting proteins; interaction with a protein that up-regulates ABCl activity; interaction with HDL particles or constituents; interaction with other proteins which facilitate interaction with HDL or its constituents; and measurement of cholesterol efflux. Furthermore, assays may be based upon the molecular dynamics of macromolecules, metabolites and ions by means of fluorescent-protein biosensors. Alternatively, the effect of candidate modulators on expression or activity may be measured at the level of ABCl protein production using the same general approach in combination with standard immunological detection techniques, such as Western blotting or immunoprecipitation with an ABCl -specific antibody. Again, useful cholesterol-regulating or anti-CVD therapeutic modulators are identified as those which produce an change in ABCl polypeptide production. Agonists may also affect ABCl activity without any effect on expression level. Candidate modulators may be purified (or substantially purified) molecules or may be one component of a mixture of compounds (e.g., an extract or supernatant obtained from cells). In a mixed compound assay, ABCl expression is tested against progressively smaller subsets of the candidate compound pool (e.g., produced by standard purification techniques, e.g., HPLC or FPLC; Ausubel et al.) until a single compound or minimal compound mixture is demonstrated to modulate ABCl expression. Agonists, antagonists, or mimetics found to be effective at modulating the level of cellular ABCl expression or activity may be confirmed as useful in animal models (for example, mice, pigs, rabbits, or chickens). For example, the compound may ameliorate the low HDL levels of mouse or chicken hypoalphalipoproteinemias. A compound that promotes an increase in ABCl expression or activity is considered particularly useful in the invention; such a molecule may be used, for example, as a therapeutic to increase the level or activity of native, cellular ABCl and thereby treat a low HDL condition in an animal (for example, a human). One method for increasing ABC biological activity is to increase the stabilization of the ABC protein or to prevent its degradation. Thus, it would be useful to identify mutations in an ABC polypeptide (e.g., ABCl) that lead to increased protein stability. These mutations can be incoφorated into any protein therapy or gene therapy undertaken for the treatment of low HDL-C or any other condition resulting from loss of ABCl biological activity. Similarly, compounds that increase the stability of a wild-type ABC polypeptide or decrease its catabolism may also be useful for the treatment of low HDL-C or any other condition resulting from loss of ABCl biological activity. Such mutations and compounds can be identified using the methods described herein. In one example, cells expressing an ABC polypeptide having a mutation are transiently metabolically labeled during translation and the half- life of the ABC polypeptide is determined using standard techniques. Mutations that increase the half-life of an ABC polypeptide are ones that increase ABC protein stability. These mutations can then be assessed for ABC biological activity. They can also be used to identify proteins that affect the stability of ABCl mRNA or protein. One can then assay for compounds that act on these factors or on the ability of these factors to bind ABCl. In another example, cells expressing wild-type ABC polypeptide are transiently metabolically labeled during translation, contacted with a candidate compounds, and the half- life of the ABC polypeptide is determined using standard techniques. Compounds that increase the half-life of an ABC polypeptide are useful compounds in the present invention. If desired, treatment with an agonist of the invention may be combined with any other HDL-raising or anti-CVD therapies. It is understood that, while ABCl is the preferred ABC transporter for the drag screens described herein, other ABC transporters can also be used. The replacement of ABCl with another ABC transporter is possible because it is likely that ABC transporter family members, such as ABC2, ABCR, or ABC8 will have a similar mechanism of regulation. Exemplary assays are described in greater detail below. Protein-based assays ABCl polypeptide (purified or unpurified) can be used in an assay to determine its ability to bind another protein (including, but not limited to, proteins found to specifically interact with ABCl). The effect of a compound on that binding is then determined. Protein Interaction Assays ABCl protein (or a polypeptide fragment thereof or an epitope-tagged form or fragment thereof) is harvested from a suitable source (e.g., from a prokaryotic expression system, eukaryotic cells, a cell-free system, or by immunoprecipitation from ABCl -expressing cells). The ABCl polypeptide is then bound to a suitable support (e.g., nitrocellulose or an antibody or a metal agarose column in the case of, for example, a his-tagged form of ABCl). Binding to the support is preferably done under conditions that allow proteins associated with ABCl polypeptide to remain associated with it. Such conditions may include use of buffers that minimize interference with protein-protein interactions. The binding step can be done in the presence and absence of compounds being tested for their ability to interfere with interactions between ABCl and other molecules. If desired, other proteins (e.g., a cell lysate) are added, and allowed time to associate with the ABC polypeptide. The immobilized ABCl polypeptide is then washed to remove proteins or other cell constituents that may be non-specifically associated with it the polypeptide or the support. The immobilized ABCl polypeptide is then dissociated from its support, and so that proteins bound to it are released (for example, by heating), or, alternatively, associated proteins are released from ABCl without releasing the ABCl polypeptide from the support. The released proteins and other cell constituents can be analyzed, for example, by SDS-PAGE gel electrophoresis, Western blotting and detection with specific antibodies, phosphoamino acid analysis, protease digestion, protein sequencing, or isoelectric focusing. Normal and mutant forms of ABCl can be employed in these assays to gain additional information about which part of ABCl a given factor is binding to. In addition, when incompletely purified polypeptide is employed, comparison of the normal and muatant forms of the protein can be used to help distinguish true binding proteins. The foregoing assay can be performed using a purified or semipurified protein or other molecule that is known to interact with ABC 1. This assay may include the following steps. 1. Harvest ABCl protein and couple a suitable fluorescent label to it; 2. Label an interacting protein (or other molecule) with a second, different fluorescent label. Use dyes that will produce different quenching patterns when they are in close proximity to each other vs. when they are physically separate (i.e., dyes that quench each other when they are close together but fluoresce when they are not in close proximity); 3. Expose the interacting molecule to the immobilized ABCl in the presence or absence of a compound being tested for its ability to interfere with an interaction between the two; and 4. Collect fluorescent readout data. Another assay is includes Fluorescent Resonance Energy Transfer (FRET) assay. This assay can be performed as follows. 1. Provide ABCl protein or a suitable polypeptide fragment thereof and couple a suitable FRET donor (e.g.,. nitro-benzoxadiazole (NBD)) to it; 2. Label an interacting protein (or other molecule) with a FRET acceptor (e.g., rhodamine); 3. Expose the acceptor-labeled interacting molecule to the donor-labeled ABCl in the presence or absence of a compound being tested for its ability to interfere with an interaction between the two; and 4. Measure fluorescence resonance energy transfer. Quenching and FRET assays are related. Either one can be applied in a given case, depending on which pair of fluorophores is used in the assay. Membrane permeability assay The ABCl protein can also be tested for its effects on membrane permeability. For example, beyond its putative ability to translocate lipids, ABCl might affect the permeability of membranes to ions. Other related membrane proteins, most notably the cystic fibrosis transmembrane conductance regulator and the sulfonylurea receptor, are associated with and regulate ion channels. ABCl or a fragment of ABCl is incoφorated into a synthetic vesicle, or, alternatively, is expressed in a cell and vesicles or other cell sub-stractures containing ABCl are isolated. The ABCl -containing vesicles or cells are loaded with a reporter molecule (such as a fluorescent ion indicator whose fluorescent properties change when it binds a particular ion) that can detect ions (to observe outward movement), or alternatively, the external medium is loaded with such a molecule (to observe inward movement). A molecule which exhibits differential properties when it is inside the vesicle compared to when it is outside the vesicle is preferred. For example, a molecule that has quenching properties when it is at high concentration but not when it is at another low concentration would be suitable. The movement of the charged molecule (either its ability to move or the kinetics of its movement) in the presence or absence of a compound being tested for its ability to affect this process can be determined. In another assay, membrane permeability is determined electro- physiologically by measuring ionic influx or efflux mediated by or modulated by ABCl by standard electrophysiological techniques. A suitable control (e.g., TD cells or a cell line with very low endogenous ABCl expression) can be used as a control in the assay to determine if the effect observed is specific to cells expressing ABCl. In still another assay, uptake of radioactive isotopes into or out of a vesicle can be measured. The vesicles are separated from the extravesicular medium and the radioactivity in the vesicles and in the medium is quantitated and compared. Nucleic acid-based assays ABCl nucleic acid may be used in an assay based on the binding of factors necessary for ABCl gene transcription. The association between the ABCl DNA and the binding factor may be assessed by means of any system that discriminates between protein-bound and non-protein-bound DNA (e.g., a gel retardation assay). The effect of a compound on the binding of a factor to ABCl DNA is assessed by means of such an assay. In addition to in vitro binding assays, in vivo assays in which the regulatory regions of the-4RC/ gene are linked to reporter genes can also be performed. \Assays measuring ABC1 stability A cell-based or cell-free system can be used to screen for compounds based on their effect on the half-life of ABCl mRNA or ABCl protein. The assay may employ labeled mRNA or protein. Alternatively, ABCl mRNA may be detected by means of specifically hybridizing probes or a quantitative PCR assay. Protein can be quantitated, for example, by fluorescent antibody-based methods. In vitro mRNA stability assay 1. Isolate or produce, by in vitro transcription, a suitable quantity of ABCl mRNA; 2. Label the ABCl mRNA; 3. Expose aliquots of the mRNA to a cell lysate in the presence or absence of a compound being tested for its ability to modulate ABCl mRNA stability; 4. Assess intactness of the remaining mRNA at suitable time points. In vitro protein stability assay 1. Express a suitable amount of ABCl protein; 2. Label the protein; 3. Expose aliquots of the labeled protein to a cell lysate in the presence or absence of a compound being tested for its ability to modulate ABCl protein stability; 4. Assess intactness of the remaining protein at suitable time points In vivo mRNA or protein stability assay 1. Incubate cells expressing ABCl mRNA or protein with a tracer (radiolabeled ribonucleotide or radiolabeled amino acid, respectively) for a very brief time period (e.g., five minutes) in the presence or absence of a compound being tested for its effect on mRNA or protein stability; 2. Incubate with unlabeled ribonucleotide or amino acid; and 3. Quantitate the ABCl mRNA or protein radioactivity at time intervals beginning with the start of step 2 and extending to the time when the radioactivity in ABCl mRNA or protein has declined by approximately 80%. It is preferable to separate the intact or mostly intact mRNA or protein from its radioactive breakdown products by a means such as gel electrophoresis in order to quantitate the mRNA or protein. Assays measuring inhibition of dominant negative activity Mutant ABCl polypeptides are likely to have dominant negative activity (i.e., activity that interferes with wild-type ABCl function). An assay for a compound that can interfere with such a mutant may be based on any method of quantitating normal ABCl activity in the presence of the mutant. For example, normal ABCl facilitates cholesterol efflux, and a dominant negative mutant would interfere with this effect. The ability of a compound to counteract the effect of a dominant negative mutant may be based on cellular cholesterol efflux, or on any other normal activity of the wild- type ABCl that was inhibitable by the mutant. Assays measuring phosphorylation The effect of a compound on ABCl phosphorylation can be assayed by methods that quantitate phosphates on proteins or that assess the phosphorylation state of a specific residue of a ABC 1. Such methods include but are not limited to 32 P labelling and immunoprecipitation, detection with antiphosphoamino acid antibodies (e.g., antiphosphoserine antibodies), phosphoamino acid analysis on 2-dimensional TLC plates, and protease digestion fmgeφrinting of proteins followed by detection of 32 P-labeled fragments. Assays measuring other post-translational modifications The effect of a compound on the post-translational modification of ABCl is based on any method capable of quantitating that particular modification. For example, effects of compounds on glycosylation may be assayed by treating ABCl with glycosylase and quantitating the amount and nature of carbohydrate released. Assays measuring ATP binding The ability of ABCl to bind ATP provides another assay to screen for compounds that affect ABCl. ATP binding can be quantitated as follows. 1. Provide ABCl protein at an appropriate level of purity and reconsititute it in a lipid vesicle; 2. Expose the vesicle to a labeled but non-hydrolyzable ATP analog (such as gamma 35 S-ATP) in the presence or absence of compounds being tested for their effect on ATP binding. Note that azido-ATP analogs can be used to allow covalent attachment of the azido-ATP to protein (by means of UN. light), and permit easier quantitation of the amount of ATP bound to the protein. 3. Quantitate the amount of ATP analog associated with ABCl Assays measuring ATPase activity Quantitation of the ATPase activity of ABCl can also be assayed for the effect of compounds on ABCl . This is preferably performed in a cell-free assay so as to separate ABCl from the many other ATPases in the cell. An ATPase assay may be performed in the presence or absence of membranes, and with or without integration of ABCl protein into a membrane. If performed in a vesicle-based assay, the ATP hydrolysis products produced or the ATP hydrolyzed may be measured within or outside of the vesicles, or both. Such an assay may be based on disappearance of ATP or appearance of ATP hydrolysis products. For high-throughput screening, a coupled ATPase assay is preferable. For example, a reaction mixture containing pyravate kinase and lactate dehydrogenase can be used. The mixture includes phosphoenolpyravate (PEP), nicotinamide adenine dinucleotide (ΝAD+), and ATP. The ATPase activity of ABCl generates ADP from ATP. The ADP is then converted back to ATP as part of the pyravate kinase reaction. The product, pyravate, is then converted to lactate. The latter reaction generates a colored quinone (NADH) from a colorless substrate (NAD+), and the entire reaction can be monitored by detection of the color change upon formation of NADH. Since ADP is limiting for the pyravate kinase reaction, this coupled system precisely monitors the ATPase activity of ABCl . Assays measuring cholesterol efflux A transport-based assay can be performed in vivo or in vitro. For example, the assay may be based on any part of the reverse cholesterol transport process that is readily re-created in culture, such as cholesterol or phospholipid efflux. Alternatively, the assay may be based on net cholesterol transport in a whole organism, as assessed by means of a labeled substance (such as cholesterol). For high throughput, fluorescent lipids can be used to measure ABCl -catalyzed lipid efflux. For phospho lipids, a fluorescent precursor, C6-NBD-phosphatidic acid, can be used. This lipid is taken up by cells and dephosphorylated by phosphatidic acid phosphohydrolase. The product, NBD-diglyceride, is then a precursor for synthesis of glycerophospho lipids like phosphatidylcholine. The efflux of NBD-phosphatidylcholine can be monitored by detecting fluorescence resonance energy transfer (FRET) of the NBD to a suitable acceptor in the cell culture medium. This acceptor can be rhodamine-labeled phosphatidylethanolamine, a phospholipid that is not readily taken up by cells. The use of short-chain precursors obviates the requirement for the phospholipid transfer protein in the media. For cholesterol, NBD-cholesterol ester can be reconstituted into LDL. The LDL can efficiently deliver this lipid to cells via the LDL receptor pathway. The NBD-cholesterol esters are hydrolyzed in the lysosomes, resulting in NBD-cholesterol that can now be transported back to the plasma membrane and efflux from the cell. The efflux can be monitored by the aforementioned FRET assay in which NBD transfers its fluorescence resonance energy to the rhodamine-phosphatidylethanoline acceptor. Animal Model Systems Compounds identified as having activity in any of the above-described assays are subsequently screened in any available animal model system, including, but not limited to, pigs, rabbits, and WHAM chickens. Test compounds are administered to these animals according to standard methods. Test compounds may also be tested in mice bearing mutations in the ABCl gene. Additionally, compounds may be screened for their ability to enhance an interaction between ABCl and any HDL particle constituent such as ApoAI, ApoAII, or ApoE. The cholesterol efflux assay as a drag screen The cholesterol efflux assay measures the ability of cells to transfer cholesterol to an extracellular acceptor molecule and is dependent on ABCl function. In this procedure, cells are loaded with radiolabeled cholesterol by any of several biochemical pathways (Marcil et al., Arterioscler. Thromb. Vase. Biol. 19:159-169, 1999). Cholesterol efflux is then measured after incubation for various times (typically 0 to 24 hours) in the presence of HDL3 or purified ApoAI. Cholesterol efflux is determined as the percentage of total cholesterol in the culture medium after various times of incubation. ABCl expression levels and/or biological activity are associated with increased efflux while decreased levels of ABCl are associated with decreased cholesterol efflux. This assay can be readily adapted to the format used for drug screening, which may consist of a multi-well (e.g., 96-well) format. Modification of the assay to optimize it for drug screening would include scaling down and streamlining the procedure, modifying the labeling method, using a different cholesterol acceptor, altering the incubation time, and changing the method of calculating cholesterol efflux. In all these cases, the cholesterol efflux assay remains conceptually the same, though experimental modifications may be made. A transgenic mouse overexpressing ABCl would be expected to have higher than normal HDL levels. Knock-out mouse model An animal, such as a mouse, that has had one or both ABCl alleles inactivated (e.g., by homologous recombination) is likely to have low HDL-C levels, and thus is a preferred animal model for screening for compounds that raise HDL-C levels. Such an animal can be produced using standard techniques. In addition to the initial screening of test compounds, the animals having mutant ABCl genes are useful for further testing of efficacy and safety of drugs or agents first identified using one of the other screening methods described herein. Cells taken from the animal and placed in culture can also be exposed to test compounds. HDL-C levels can be measured using standard techniques, such as those described herein. WHAM chickens: an animal model for low HDL cholesterol Wisconsin Hypo- Alpha Mutant (WHAM) chickens arose by spontaneous mutation in a closed flock. Mutant chickens came to attention through their a Z- linked white shank and white beak phenotype referred to as 'recessive white skin' (McGibbon, 1981) and were subsequently found to have a profound deficiency of HDL (Poernama et al., 1990). This chicken low HDL locus (Y) is Z-linked, or sex-linked. (In birds, females are ZW and males are ZZ). Genetic mapping placed the Y locus on the long arm of the Z chromosome (Bitgood, 1985), proximal to the ID locus (Bitgood, 1988). Examination of current public mapping data for the chicken genome mapping project, ChickMap (maintained by the Roslin Institute; http://www.ri.bbsrc.ac.uk/ chickmap/ChickMapHomePage.html) showed that a region of synteny with human chromosome 9 lies on the long arm of the chicken Z chromosome (Zq) proximal to the ID locus. Evidence for this region of synteny is the location of the chicken aldolase B locus (ALDOB) within this region. The human ALDOB locus maps to chromosome 9q22.3 (The Genome Database, http://gdbwww.gdb.org/), not far from the location of human ABCl. This comparison of maps showed that the chicken Zq region near chicken ALDOB and the human 9q region near human ALDOB represent a region of synteny between human and chicken. Since a low HDL locus maps to the 9q location in humans and to the Zq region in chickens, these low HDL loci are most probably located within the syntenic region. Thus we predicted that ABCl is mutated in WHAM chickens. In support of this, we have identified an E < K mutation at a position that corresponds to amino acid 89 of human ABCl (Figs. 14 and 15). This non-conservative substitution is at a position that is conserved among human, mouse, and chicken, indicating that it is in a region of the protein likely to be of functional importance. Discovery of the WHAM mutation in the amino-terminal portion of the ABCl protein also establishes the importance of the amino-terminal region. This region may be critical because of association with other proteins required to carry out cholesterol efflux or related tasks. It may be an important regulatory region (there is a phosphorylation site for casein kinase near the mutated residue), or it may help to dictate a precise topological relationship with cellular membranes (the N-terminal 60 amino acid region contains a putative membrane-spanning or membrane-associated segment). The amino-terminal region of the protein (up to the first 6-TM region at approximately amino acid 639) is an ideal tool for screening factors that affect ABCl activity. It can be expressed as a truncated protein in ABCl wild type cells in order to test for interference of the normal ABCl function by the truncated protein. If the fragment acts in a dominant negative way, it could be used in immunoprecipitations to identify proteins that it may be competing away from the normal endogenous protein. The C-terminus also lends itself to such experiments, as do the intracellular portions of the molecule, expressed as fragments or tagged or fusion proteins, in the absence of transmembrane regions. Since it is possible that there are several genes in the human genome which affect cholesterol efflux, it is important to establish that any animal model to be used for a human genetic disease represents the homologous locus in that animal, and not a different locus with a similar function. The evidence above establishes that the chicken Y locus and the human chromosome 9 low HDL locus are homologous. WHAM chickens are therefore an important animal model for the identification of drags that modulate cholesterol efflux. The WHAM chickens' HDL deficiency syndrome is not, however, associated with an increased susceptibility to atherosclerosis in chickens. This probably reflects the shorter lifespan of the chicken rather than an inherent difference in the function of the chicken ABCl gene compared to the human gene. Wo propose the WHAM chicken as a model for human low HDL for the development and testing of drags to raise HDL in humans. Such a model could be employed in several forms, through the use of cells or other derivatives of these chickens, or by the use of the chickens themselves in tests of drag effectiveness, toxicity, and other drug development puφoses. Therapy Compounds of the invention, including but not limited to, ABCl polypeptides, ABCl nucleic acids, other ABC transporters, and any therapeutic agent that modulates biological activity or expression of ABCl identified using any of the methods disclosed herein, may be administered with a pharmaceutically-acceptable diluent, carrier, or excipient, in unit dosage form. Conventional pharmaceutical practice may be employed to provide suitable formulations or compositions to administer such compositions to patients. Although intravenous administration is preferred, any appropriate route of administration may be employed, for example, perenteral, subcutaneous, intramuscular, intracranial, intraorbital, ophthalmic, intraventricular, intracapsular, intraspinal, intracisternal, intraperitoneal, intranasal, aerosol, or oral administration. Therapeutic formulations may be in the form of liquid solutions or suspension; for oral administration, formulations may be in the form of tablets or capsules; and for intranasal formulations, in the form of powders, nasal drops, or aerosols. Methods well known in the art for making formulations are found in, for example, Remington: The Science and Practice of Pharmacy, (19th ed.) ed. A.R. Gennaro AR., 1995, Mack Publishing Company, Easton, PA. Formulations for parenteral administration may, for example, contain excipients, sterile water, or saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylene-polyoxypropylene copolymers may be used to control the release of the compounds. Other potentially useful parenteral delivery systems for agonists of the invention include ethylenevinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. Formulations for inhalation may contain excipients, or example, lactose, or may be aqueous solutions containing, for example, polyoxyethylene-9-lauryl ether, glycocholate and deoxycholate, or may be oily solutions for administration in the form of nasal drops, or as a gel. Compounds In general, novel drugs for the treatment of aberrant cholesterol levels and/or CVD are identified from large libraries of both natural product or synthetic (or semi- synthetic) extracts or chemical libraries according to methods known in the art. Those skilled in the field or drug discovery and development will understand that the precise source of test extracts or compounds is not critical to the screening procedure(s) of the invention. Accordingly, virtually any number of chemical extracts or compounds can be screened using the exemplary methods described herein. Examples of such extracts or compounds include, but are not limited to, plant-, fungal-, prokaryotic- or animal-based extracts, fermentation broths, and synthetic compounds, as well as modification of existing compounds. Numerous methods are also available for generating random or directed synthesis (e.g. , semi-synthesis or total synthesis) of any number of chemical compounds, including, but not limited to, saccharide-, lipid-, peptide-, and nucleic acid-based compounds. Synthetic compound libraries are commercially available from Brandon Associates (Merrimack, NH) and Aldrich Chemical (Milwaukee, WI). Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant, and animal extracts are commercially available from a number of sources, including Biotics (Sussex, UK), Xenova (Slough, UK), Harbor Branch Oceangraphics Institute (Ft. Pierce, FL), and PharmaMar, U.S.A. (Cambridge, MA). In addition, natural and synthetically produced libraries are produced, if desired, according to methods known in the art, e.g., by standard extraction and fractionation methods. Furthermore, if desired, any library or compound is readily modified using standard chemical, physical, or biochemical methods. In addition, those skilled in the art of drug discovery and development readily understand that methods for dereplication (e.g. , taxonomic dereplication, biological dereplication, and chemical dereplication, or any combination thereof) or the elimination of replicates or repeats of materials already known for their HDL-raising and anti-CVD activities should be employed whenever possible. When a crude extract is found to have cholesterol-modulating or anti-CVD activities or both, further fractionation of the positive lead extract is necessary to isolate chemical constituent responsible for the observed effect. Thus, the goal of the extraction, fractionation, and purification process is the careful characterization and identification of a chemical entity within the crude extract having cholesterol- modulating or anti-CVD activities. The same in vivo and in vitro assays described herein for the detection of activities in mixtures of compounds can be used to purify the active component and to test derivatives thereof. Methods of fractionation and purification of such heterogeneous extracts are known in the art. If desired, compounds shown to be useful agents for the treatment of pathogenicity are chemically modified according to methods known in the art. Compounds identified as being of therapeutic value are subsequently analyzed using any standard animal model of diabetes or obesity known in the art. It is understood that compounds that modulate activity of proteins that modulate or are modulated by ABCl are useful compounds for modulating cholesterol levels. Exemplary compounds are provided herein; others are known in the art. Compounds that are structurally related to cholesterol, or that mimic ApoAI or a related apolipoprotein, and increase ABCl biological activity are particularly useful compounds in the invention. Other compounds, known to act on the MDR protein, can also be used or derivatized and assayed for their ability to increase ABCl biological activity. Exemplary MDR modulators are PSC833, bromocriptine, and cyclosporin A. Screening patients having low HDL-C ABCl expression, biological activity, and mutational analysis can each serve as a diagnostic tool for low HDL; thus determination of the genetic subtyping of the ABCl gene sequence can be used to subtype low HDL individuals or families to determine whether the low HDL phenotype is related to ABCl function. This diagnostic process can lead to the tailoring of drug treatments according to patient genotype, including prediction of side effects upon administration of HDL increasing drugs (referced to herein as pharmacogenomics). Pharmacogenomics allows for the selection of agents (e.g., drags) for therapeutic or prophylactic treatment of an individual based on the genotype of the individual (e.g., the genotype of the individual is examined to determine the ability of the individual to respond to a particular agent). Agents, or modulators which have a stimulatory or inhibitory effect on ABCl biological activity or gene expression can be administered to individuals to treat disorders (e.g., cardiovascular disease or low HDL cholesterol) associated with abenant ABCl activity. In conjunction with such treatment, the pharmacogenomics (i.e., the study of the relationship between an individual's genotype and that individual's response to a foreign compound or drug) of the individual may be considered. Differences in efficacy of therapeutics can lead to severe toxicity or therapeutic failure by altering the relation between dose and blood concentration of the pharmacologically active drag. Thus, the pharmacogenomics of the individual permits the selection of effective agents (e.g., drags) for prophylactic or therapeutic treatments based on a consideration of the individual's genotype. Such pharmacogenomics can further be used to determine appropriate dosages and therapeutic regimens. Accordingly, the activity of ABCl protein, expression of ABCl nucleic acid, or mutation content of ABCl genes in an individual can be determined to thereby select appropriate agent(s) for therapeutic or prophylactic treatment of the individual. Pharmacogenomics deals with clinically significant hereditary variations in the response to drugs due to altered drag disposition and abnormal action in affected persons (Eichelbaum, M., Clin. Exp. Pharmacol. Physiol., 23:983-985, 1996; Linder, M. W., Clin. Chem., 43:254-266, 1997). In general, two types of pharmaco genetic conditions can be differentiated. Genetic conditions transmitted as a single factor altering the way drags act on the body (altered drug action) or genetic conditions transmitted as single factors altering the way the body acts on drags (altered drug metabolism). Altered drug action may occur in a patient having a polymoφhism (e.g., an single nucleotide polymoφhism or SNP) in promoter, intronic, or exonic sequences of ABCl . Thus by determining the presence and prevalence of polymoφhisms allow for prediction of a patient's response to a particular therapeutic agent. In particular, polymoφhisms in the promoter region may be critical in determining the risk of HDL deficiency and CVD. In addition to the mutations in the ABCl gene described herein, we have detected polymoφhisms in the human ABCl gene (Fig. 11). These polymoφhisms are located in promoter, intronic, and exonic sequence of ABCl. Using standard methods, such as direct sequencing, PCR, SSCP, or any other polymoφhism- detection system, one could easily ascertain whether these polymoφhisms are present in a patient prior to the establishment of a drug treatment regimen for a patient having low HDL, cardiovascular disease, or any other ABCl -mediated condition. It is possible that some these polymoφhisms are, in fact, weak mutations. Individuals harboring such mutations may have an increased risk for cardiovascular disease; thus, these polymoφhisms may also be useful in diagnostic assays. Association Studies of ABCl Gene Variants and HDL Levels or Cardiovascular Disease The following polymoφhisms have been examined for their effect on cholesterol regulation and the predisposition for the development of cardiovascular disease. Substitution of G for A at nucleotide -1045 [G(-1045)A]. This variant is in complete linkage disequilibrium with the variant at -738 in the individuals we have sequenced, and thus any potential phenotypic effects currently attributed to the variant at -738 may at least in part be due to changes at this site. Substitution of G for A at nucleotide -738 [G(-738)Aj. This variant has been found at very high frequencies in populations selected for low HDL cholesterol or premature coronary artery disease. Insertion of a G nucleotide at position -4 [G ins (-4)]. This variant has been associated with less coronary artery disease in its carriers than in non-carriers. Substitution of a Cfor G at nucleotide -57 [G(-57)C]. This variant is in complete linkage disequilibrium with the variant at -4 in the individuals we have sequenced, and thus the phenotypic effects currently attributed to the variant at -4 may at least in part be due to changes at this site. Substitution of A for G at nucleotide 730 (R219K). We have found carriers to have significantly less cardiovascular disease. Substitution of C for Tat nucleotide 1270 (V399A). Within the French Canadian population, this variant has only been found in individuals from the low HDL population. It has also been seen in individuals with low HDL or premature coronary artery disease in individuals of Dutch ancestry. Substitution of A for G at nucleotide 2385 (V771M). This variant has been found at an increased frequency in a Dutch population selected for low HDL and at an increased frequency in a population selected for premature coronary artery disease compared to a control Dutch population, indicating carriers of this variant may have reduced HDL and an increased susceptibility to coronary artery disease. Substitution of C for A at nucleotide 2394 (T774P). This variant has been seen at lower frequencies in populations with coronary artery disease or low HDL than in individuals without. Substitution of C for G at nucleotide 2402 (K776N). This variant has been found at a significantly lower frequency (0.56% vs. 2.91%, p=0.02) in a coronary artery disease population vs. a control population of similar Dutch background. Substitution of C for G at nucleotide 3590 (E1172D). This variant is seen at lower frequencies in individuals with low HDL and in some populations with premature coronary artery disease. Substitution of Afar G at nucleotide 4384 (R1587K). This variant has been found at decreased frequencies in the 1/3 of individuals with the highest HDL levels in our large Dutch coronary artery disease population (p=0.036), at increased frequencies in those with HDL cholesterol <0.9 mmol/L (pθ.0001) and at decreased frequencies in the cohorts with HDL cholesterol >1.4 mmol/L in both this population (p=0.02) and the Dutch control population (p=0.003). Substitution of G for C at nucleotide 5266 (SI 731C). Two FHA individuals who have this variant on the other allele have much lower HDL cholesterol (0.155±0.025) than the FHA individuals in the family who do not have this variant on the other allele (0.64±0.14, p=0.0009). This variant has also been found in one general population French Canadian control with HDL at the 8th percentile (0.92) and one French Canadian individual from a population selected for low HDL and coronary disease (0.72). Substitution of G for A at nucleotide -1113 [A(-1113)G]. This variant has been seen at varying frequencies in populations distinguished by their HDL levels. Additional polymoφhisms that may be associated with altered risk for cardiovascular disease or altered cholesterol levels are as follows: Substitution of G for A at nucleotide 2723 (I883M). This variant has been seen at a much higher frequency in individuals of Dutch ancestry with premature coronary artery disease. Insertion of 4 nucleotides (CCCT) at position -1181. Substitution of C for A at nucleotide -479 (linkage disequilibrium with -518). Substitution of G for A at nucleotide -380. Other Embodiments All publications mentioned in this specification are herein incoφorated by reference to the same extent as if each independent publication was specifically and individually indicated to be incoφorated by reference. While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses, or adaptations following, in general, the principles of the invention and including such departures from the present disclosure within known or customary practice within the art to which the invention pertains and may be applied to the essential features hereinbefore set forth.

Claims: What we claim is: 1. A substantially pure ABCl polypeptide having ABCl biological activity. 2. The substantially pure ABCl polypeptide of claim 1, wherein said ABCl polypeptide is human ABCl . 3. The substantially pure ABCl polypeptide of claim 1, wherein said polypeptide comprises amino acids 1 to 60 of SEQ ID NO: 1. 4. The substantially pure ABCl polypeptide of claim 1, wherein said polypeptide comprises amino acids 61 to 2261 of SEQ ID NO: 1. 5. The substantially pure ABCl polypeptide of claim 1, wherein said polypeptide comprises amino acids 1 to 2261 of SEQ ID NO: 1. 6. A substantially pure ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1. 7. A substantially pure ABCl polypeptide comprising amino acids 61 to 2261 of SEQ ID NO: 1. 8. A substantially pure ABCl polypeptide comprising amino acids 1 to 2261 of SEQ ID NO: 1. 9. A substantially pure nucleic acid molecule that hybridizes at high stringency conditions to nucleotides 75 to 254 of SEQ ID NO: 2 and encodes a polypeptide having ABCl biological activity. 10. A substantially pure nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity. 11. The substantially pure nucleic acid molecule of claim 9 or 10, wherein said nucleic acid molecule comprises nucleotides 75 to 254 of SEQ ID NO: 2. 12. The substantially pure nucleic acid molecule of claim 9 or 10, wherein said nucleic acid molecule comprises nucleotides 255 to 6857 of SEQ ID NO: 2. 13. The substantially pure nucleic acid molecule of claim 9 or 10, wherein said nucleic acid molecule comprises nucleotides 75 to 6857 of SEQ ID NO: 2. 14. An expression vector comprising the nucleic acid molecule of claim 9. 15. A cell expressing the nucleic acid molecule of claim 9. 16. A non-human mammal expressing the nucleic acid molecule of claim 9. 17. A substantially pure nucleic acid molecule comprising nucleotides 75 to 254 of SEQ ID NO: 2. 18. A substantially pure nucleic acid molecule comprising nucleotides 255 to 6857 of SEQ ID NO: 2. 19. A substantially pure nucleic acid molecule comprising nucleotides 75 to 6857 of SEQ ID NO: 2. 20. A substantially pure nucleic acid molecule comprising at least thirty consecutive nucleotides corresponding to nucleotides 7015-7860 of SEQ ID NO: 2. 21. The substantially pure nucleic acid molecule of claim 20, wherein said nucleic acid molecule comprises nucleotides 7015-7860 of SEQ ID NO: 2. 22. A substantially pure nucleic acid molecule that hybridizes at high stringency to a probe comprising nucleotides 7015-7860 of SEQ TD NO: 2. 23. A method of treating a human having low HDL cholesterol or cardiovascular disease, said method comprising administering to said human an ABCl polypeptide, or cholesterol-regulating fragment thereof. 24. The method of claim 23, wherein said ABCl polypeptide has the sequence of SEQ ID NO: 1. 25. The method of claim 23, wherein said ABCl polypeptide comprises a mutation that increases its stability. 26. The method of claim 23, wherein said ABCl polypeptide comprises a mutation that increases its biological activity. 27. A method of treating a human having low HDL cholesterol or cardiovascular disease, said method comprising administering to said human a nucleic acid molecule encoding an ABCl polypeptide or a cholesterol-regulating fragment thereof. 28. The method of claim 27, wherein said ABCl polypeptide has the amino acid sequence of SEQ ID NO: 1. 29. The method of claim 27, wherein said ABCl polypeptide comprises a mutation that increases its stability. 30. The method of claim 27, wherein said ABCl polypeptide comprises a mutation that increases its biological activity. 31. The method of claim 30, wherein said biological activity is regulation of cholesterol. 32. The method of claim 27, wherein said human has low HDL cholesterol levels relative to normal. 33. A method of increasing ABCl biological activity in a human, said method comprising administering to said human a nucleic acid molecule that hybridizes at high stringency conditions to nucleotides 75 to 254 of SEQ ID NO: 2 and encodes a polypeptide having ABCl biological activity. 34. The method of claim 33, wherein said human has a disease selected from the group consisting of Alzheimer's disease, Niemann-Pick disease, Huntington's disease, x-linked adrenoleukodystrophy, and cancer. 35. A method of increasing ABCl biological activity in a human, said method comprising administering to said human a compound that increases ABCl biological activity. 36. The method of claim 35, wherein said human has a disease selected from the group consisting of Alzheimer's disease, Niemann-Pick disease, Huntington's disease, x-linked adrenoleukodystrophy, and cancer. 37. A method of preventing cardiovascular disease in a human, said method comprising administering to said human an expression vector comprising an ABCl nucleic acid molecule operably linked to a promoter, said ABCl nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity. 38. A method of preventing or ameliorating the effects of a disease-causing mutation in an ABCl gene in a human, said method comprising introducing into said human an expression vector comprising a promoter operably linked to an ABCl nucleic acid molecule encoding an ABCl polypeptide having ABCl biological activity. 39. A method of treating or preventing cardiovascular disease in an animal, said method comprising administering to said animal a compound that mimics the activity of wild-type ABCl. 40. The method of claim 39, wherein said animal is a human. 41. A method of treating or preventing cardiovascular disease in an animal, said method comprising administering to said animal a compound that modulates the biological activity of ABC 1. 42. The method of claim 41, wherein said animal is a human. 43. The method of claim 41, wherein said compound is selected from a group consisting of protein kinase A, protein kinase C, vanadate, okadaic acid, IBMXl, fibrates, β-estradiol, arachidonic acid derivatives, WY- 14,643, LTB4, 8(s)HETE, thiozolidinedione antidiabetic drugs, 9-HODE, 13-HODE, nicotinic acid, HMG CoA reductase inhibitors, and compounds that increase PPAR-mediated ABCl expression. 44. The method of claim 23, 27, 39, or 41, wherein said cardiovascular disease is coronary artery disease, cerebrovascular disease, coronary restenosis, or peripheral vascular disease. 45. A method for determining whether a candidate compound is useful for modulating cholesterol levels, said method comprising the steps of: (a) providing a chicken comprising a mutation in an ABCl gene; (b) administering said candidate compound to said chicken; and (c) measuring ABCl biological activity in said chicken, wherein altered ABCl biological activity, relative to a WHAM chicken not contacted with said compound, indicates that said candidate compound modulates cholesterol levels. 46. The method of claim 45, wherein said ABCl biological activity is transport of cholesterol. 47. A method for determining whether a candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing a cell expressing an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1; (b) contacting said cell with said candidate compound; and (c) measuring ABCl biological activity of said cell, wherein altered ABCl biological activity, relative to a cell not contacted with said compound, indicates that said candidate compound modulates ABCl biological activity. 48. A method for determining whether a candidate compound modulates ABCl expression, said method comprising the steps of: (a) providing a cell expressing an ABCl gene comprising nucleotides 75 to 254 of SEQ ID NO: 2; (b) contacting said cell with said candidate compound; and (c) measuring ABCl expression of said cell, wherein altered ABCl expression, relative to a cell not contacted with said compound, indicates that said candidate compound modulates ABCl expression. 49. A method for determining whether a candidate compound modulates ABCl expression, said method comprising the steps of: (a) providing a nucleic acid molecule comprising an ABCl promoter operably linked to a reporter gene; (b) contacting said nucleic acid molecule with said candidate compound; and (c) measuring expression of said reporter gene, wherein altered reporter gene expression, relative to a control not contacted with said compound, indicates that said candidate compound modulates ABCl expression. 50. The method of claim 49, wherein said promoter comprises 50 consecutive nucleotides selected from nucleotides 1 to 8238 of SEQ ID NO: 14. 51. The method of claim 50, wherein said promoter comprises a binding site for a transcription factor selected from a group consisting of steroid response element binding proteins, peroxisomal proliferation-activated receptors, retinoid X receptors, and RAR-related oφhan receptors. 52. A method for determining whether a candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1 ; (b) contacting said polypeptide with said candidate compound; and (c) measuring ABCl biological activity, wherein a change in ABCl biological activity, relative to a control not contacted with said compound, indicates that said candidate compound modulates ABCl biological activity. 53. A method for determining whether a candidate compound modulates ABCl expression, said method comprising the steps of: (a) providing an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1; (b) contacting said polypeptide with said candidate compound; and (c) measuring expression of said ABCl polypeptide, wherein a change in expression of said ABCl polypeptide, relative to a control not contacted with said compound, indicates that said candidate compound modulates ABCl expression. 54. A method for determining whether candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1; (b) contacting said polypeptide with said candidate compound; and (c) measuring binding of said ABCl polypeptide to said candidate compound, wherein binding of said ABCl polypeptide to said compound indicates that said candidate compound modulates ABCl biological activity. 55. A method for determining whether candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing (i) an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1, and (ii) a second polypeptide that interacts with said ABCl polypeptide; (b) contacting said polypeptides with said candidate compound; and (c) measuring interaction of said ABCl polypeptide with said second polypeptide, wherein an alteration in the interaction of said ABCl polypeptide with said second polypeptide indicates that said candidate compound modulates ABCl biological activity. 56. A method for determining whether a candidate compound increases the stability or decreases the regulated catabolism of an ABCl polypeptide, said method comprising the steps of: (a) providing a cell comprising an ABCl polypeptide comprising amino acids 1 to 60 of SEQ ID NO: 1; (b) contacting said cell with said candidate compound; and (c) measuring the half-life of said ABCl polypeptide, wherein an increase in said half-life, relative to a control not contacted with said compound, indicates that said candidate compound increases the stability or decreases the regulated catabolism of an ABC 1 polypeptide. 57. A method for determining whether a candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing an ABCl polypeptide in a lipid membrane; (b) contacting said polypeptide with said candidate compound; and (c) measuring ABCl -mediated lipid transport across said lipid membrane, wherein a change in lipid transport, relative to a control not contacted with said compound, indicates that said candidate compound modulates ABCl biological activity. 58. The method of claim 49, 52, 53, 54, 55, or 57, wherein said ABCl polypeptide is in a cell-free system. 59. The method of claim 49, 52, 53, 54, 55, or 57, wherein said ABCl polypeptide is in a cell. 60. The method of claim 59, wherein said cell is from a WHAM chicken. 61. The method of claim 59, wherein said cell is in a human or in a non- human mammal. 62. The method of claim 61, wherein said animaHs a WHAM chicken. 63. The method of claim 52, wherein said biological activity is transport of lipid or interleukin-1. 64. The method of claim 62, wherein said lipid is cholesterol. 65. The method of claim 64, wherein said cholesterol is HDL-cholesterol. 66. The method of claim 52, wherein said biological activity is binding or hydrolysis of ATP by the ABCl polypeptide. 67. A method for determining whether a patient has an increased risk for cardiovascular disease, said method comprising determining whether an ABCl gene of said patient has a mutation, wherein a mutation indicates that said patient has an increased risk for cardiovascular disease. 68. A method for determining whether a patient has an increased risk for cardiovascular disease, said method comprising measuring ABCl biological activity in said patient or in a cell from said patient, wherein increased or decreased levels in said ABCl biological activity, relative to normal levels, indicates that said patient has an increased risk for cardiovascular disease. 69. A method for determining whether a patient has an increased risk for cardiovascular disease, said method comprising measuring ABCl expression in said patient or in a cell from said patient, wherein decreased levels in said ABCl expression relative to normal levels, indicates that said patient has an increased risk for cardiovascular disease. 70. The method of claim 69, wherein said ABCl expression is determined by measuring levels of ABCl polypeptide. 71. The method of claim 69, wherein said ABCl expression is determined by measuring levels of ABCl RNA. 72. A non-human mammal comprising a transgene comprising a nucleic acid molecule encoding a dominant-negative ABCl polypeptide. 73. A cell isolated from a non-human mammal comprising a transgene comprising a nucleic acid molecule encoding an ABCl polypeptide having biological activity. 74. A method for determining whether a candidate compound decreases the inhibition of a dominant-negative ABCl polypeptide, said method comprising the steps of: (a) providing a cell expressing a dominant-negative ABCl polypeptide; (b) contacting said cell with said candidate compound; and (c) measuring ABCl biological activity of said cell, wherein an increase in said ABCl biological activity, relative to a cell not contacted with said compound, indicates that said candidate compound decreases the inhibition of a dominant-negative ABCl polypeptide. 75. A method for determining whether a person has an altered risk for developing cardiovascular disease, comprising examining the person's ABCl gene for polymoφhisms, wherein the presence of a polymoφhism associated with cardiovascular disease indicates the person has an altered risk for developing cardiovascular disease. 76. A method for predicting a person's response to a drug, comprising determining whether the person has a polymoφhism in an ABCl gene that alters the person's response to said drug. 77. A method for predicting a person's response to a drug, comprising determining whether the person has a polymoφhism in an ABCl promoter that alters the person's response to said drug. 78. A method for altering ABCl expression in a cell, said method comprising contacting said cell with a compound selected from a group consisting of fibrates, β-estradiol, arachidonic acid derivatives, WY-14,643, LTB4, 8(s)HETE, thiozolidinedione antidiabetic drags, 9-HODE, 13-HODE, nicotinic acid, HMG CoA reductase inhibitors, and compounds that increase PPAR-mediated ABCl expression. 79. A pharmaceutical composition comprising (i) a nucleic acid molecule that hybridizes under high stringency conditions to nucleotides 75 to 254 of SEQ ID NO: 2 and encodes a polypeptide having ABCl biological activity; and (ii) a pharmaceutically acceptable carrier. 80. A nucleic acid that hybridizes under high stringency conditions to nucleotides 1 to 8236 of SEQ ID NO: 14. 81. A nucleic acid comprising a region that is 80% identical to at least thirty contiguous nucleotides of nucleotides 1 to 8236 of SEQ ID NO: 14. 82. A method for determining whether candidate compound modulates ABCl biological activity, said method comprising the steps of: (a) providing an ABCl polypeptide; (b) contacting said polypeptide with cholesterol and said candidate compound; and (c) measuring binding of said cholesterol to said ABCl polypeptide, wherein binding of said cholesterol to said ABCl polypeptide indicates that said candidate compound modulates ABCl biological activity. 83. The method of claim 82, wherein said cholesterol is HDL cholesterol. 84. The method of claim 82, wherein said method is performed in a cell free assay. 85. The method of claim 82, wherein said ABCl polypeptide comprises amino acids 1 to 60 of SEQ ID NO: 1. 86. the method of claim 82, wherein said cholesterol or said ABCl polypeptide is detectably labeled.

Inventors: HAYDEN MICHAEL R, PIMSTONE SIMON N, WILSON ANGELA R, HAYDEN, MICHAEL, R., PIMSTONE, SIMON, N., WILSON, ANGELA, R.
Applicants: UNIV BRITISH COLUMBIA, XENON BIORESEARCH INC, UNIVERSITY OF BRITISH COLUMBIA, XENON BIORESEARCH, INC.
Application year: 2000
Main classification: C12N15
IPC codes: A01K67, A61K35, A61K38, A61K45, A61K48, A61P3, A61P9, A61P25, A61P35, C07K14, C12N5, C12N15, C12Q1, G01N33