Abstract:
The present invention relates to a novel α-catenin with a new, specific expression pattern in mainly heart and testis. The invention further relates to the use of this α-catenin in the prediction, diagnosis, and/or treatment of cadherin-catenin related diseases, in particular cardiomyopathies and male infertility.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of PCT International Application Number PCT/EP01/07392 filed Jun. 28, 2001, designating the United States of America (which itself claimed priority, inter alia, from U.S. Provisional Patent Application 60/218,309 filed Jul. 14, 2000), and published, in English, as PCT International Publication Number WO 02/04636 A1 on Jan. 17, 2002, the contents of the entirety of which is incorporated by this reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to the field of biotechnology, and specifically to a novel α-catenin with a new, specific expression pattern in mainly heart and testis. The invention further relates to the use of the α-catenin in prediction, diagnosis or treatment of cadherin-catenin related diseases, such as cardiomyopathies and male infertility. 
     BACKGROUND 
     The αE-catenin protein, a component of the epithelial cadherin-catenin adhesion complex, is a well-known invasion suppressor. To reach full functionality of the cadherin-catenin cell-cell adhesion complex, it is necessary to link the complex to the actin cytoskeleton. AlphaE-catenin provides this link by binding to β-catenin or plakoglobin through its amino terminal side, and by binding actin or the actin-binding molecule α-actinin through its carboxy-terminus (reviewed in Rudiger, 1998). It has been shown that loss of αE-catenin affects cell-cell adhesion and promotes tumorigenicity (Ewing et al., 1995). In many cases of invasive cells, αE-catenin defects are seen, and introduction of exogenous α-catenin can restore cell-cell aggregation and counteract invasiveness (Hirano et-al., 1992; van Hengel et al., 1997; Watabe et al., 1994). 
     The family of α-catenins contains so far four known members. The αE-catenin protein is ubiquitously expressed, mainly in epithelial tissues. AlphaN-catenin protein has about 75% identity to αE-catenin, but is restricted in its expression to neural tissues (Hirano et al., 1992). In analogy with αE-catenin, it can also bind to β-catenin and plakoglobin and is supposed to bind α-actinin and actin. Although the vinculin protein shows much less identity (20%) to αE- and αN-catenin, it shares some similar characteristics. This protein is mainly found in focal adhesions where it forms the link to the actin cytoskeleton and binds the integrin-binding molecule talin. Vinculin is sometimes found in cell-cell contacts as well, and it may even be able to take over the function of αE-catenin, by binding to β-catenin (Hazan et al., 1997). On the other hand, vinculin has been reported to bind to a central region of αE-catenin and to be essential for apical junctional organization (Watabe-Uchida et al., 1998). Moreover, vinculin has a unique proline-rich hinge domain, which is absent in the other family members and which allows the vinculin tail to bind to the head, thus masking some “cryptic” binding sites (Johnson &amp; Craig, 1995). For the recently reported α-catulin (Janssens et al., 1999; Zhang et al., 1998), the identity to other family members is about 25% at the amino acid level, but no functional evidence for adhesive properties was found yet. In addition to their structural role, it is becoming clear that α-catenins and vinculin also have a regulatory function in the coordination of assembly and disassembly of junctions (Rudiger, 1998), and that αN-catenin can locate to the nucleus where it inhibits β-catenin/Tcf signaling (Giannini et al., 2000). 
     DISCLOSURE OF THE INVENTION 
     The present invention relates to a novel α-catenin with about 55% identity and 70% similarity to other α-catenins. Surprisingly, the novel catenin shows a specific expression in mainly heart and testis. Moreover, it interacts more strongly with β-catenin than the known α-catenins. 
     In one aspect, the invention provides an isolated novel α-catenin polypeptide comprising the sequence as presented in SEQ ID NO:2 for the human molecule, or variants thereof, which variants have at least 70% identity, preferably at least 80% identity, more preferably at least 90% identity with such sequences, as measured by a BLAST search (Altschul et al. 1997). A specific embodiment of a variant is the mouse molecule of which the sequence comprises the sequence presented in SEQ ID NO:5. Preferably, the variant consists essentially of SEQ ID NO:5. 
     In another aspect, the invention provides a nucleic acid sequence encoding the polypeptide. A preferred embodiment is a nucleic acid sequence, comprising the sequence presented in SEQ ID NO:1 for the human molecule and SEQ ID NO:4 for the mouse molecule. Such novel α-catenin polypeptide is expressed selected tissues or organs such as heart and/or testis, possibly combined with expression in brain, kidney, liver, lung, ovary, tongue, uterus and skeletal muscle. 
     It is another aspect of the invention to provide the genomic organization of the gene, encoding the novel human α-catenin polypeptide. Human exon-intron boundaries have been determined and the exons have been allocated to different bacterial and P1 derived artificial chromosomes (BACs and PACs). The determination of the intronic sequences is a routine technique known to the person skilled in the art. 
     Still another aspect of the invention is a nucleic acid comprising the promoter region of a gene, encoding a polypeptide according to the invention. A preferred embodiment is the nucleic acid comprising the human sequence presented in SEQ ID NO:3 and the mouse sequence presented in SEQ ID NO:6. The sequences were found to contain several putative binding sites for muscle-specific transcription factors such as Nkx2.5, MEF-2 and MEF-3. By modifying this promoter sequence, or by modulating the correspondingly binding transcription factors the transcription of the novel α-catenin can be influenced. 
     Another aspect of the invention is the use of the novel α-catenin, or variants thereof, to modulate the cadherin-catenin related pathway. Alpha-catenin-like molecules can interact with the cadherin-catenin adhesion complex and are influencing as such the cell-cell adhesion and the β-catenin mediated signaling that is influencing the transcription of, as a non-limiting example, genes as c-myc, cyclin-D1, matrilysin, and c-jun. As the novel α-catenin of the invention is more strongly interacting with β-catenin than any other of the known α-catenin like molecules, it can be useful to use this molecule, or its β-catenin binding domain, or a polypeptide comprising this β-catenin binding domain either to block the α-catenin/β-catenin interaction, or to restore a deficient interaction. In a preferred embodiment, the cadherin-catenin related pathway is specifically modulated in selected tissues or organs such as heart and/or testis, eventually combined with modulation of the pathway in brain, kidney, liver, skeletal muscle. 
     Still another aspect of the invention is the use of the novel α-catenin, or variants thereof, to treat cadherin-catenin related diseases. Such diseases include, but are not limited to cancer, cardiomyopathies including dilated cardiomyopathy, and male infertility. 
     Still another aspect of the invention is the use of the nucleic acid sequence encoding the novel α-catenin, or fragments thereof, or the gene encoding the novel α-catenin or fragments thereof for the diagnosis of cadherin-catenin related diseases, or for predicting the likelihood of developing the cadherin-catenin related diseases. A preferred embodiment is the use of the nucleic acid or the gene for predicting the likelihood and/or diagnosis of cancer. Another preferred embodiment is the use of the nucleic acid or the gene for predicting the likelihood and/or diagnosis of cardiomyopathies including dilated cardiomyopathy, and male infertility. The nucleic acid sequence, gene, or fragments thereof can be used for detecting mutations and/or for quantifying messenger RNA expression levels, by techniques know to the person skilled in the art, such as but not limited to PCR, DNA-DNA hybridization, DNA-RNA hybridization or fluorescent in situ hybridization (“FISH”). 
     Still another aspect of the invention is the use of the nucleic acid sequence encoding the novel α-catenin, or functional fragments thereof, for the treatment of cadherin-catenin related diseases. Indeed, the nucleic acid sequence can be incorporated in a vector suitable for gene therapy. Such vectors are known to the person skilled in the art and do include, but are not limited to retroviral vectors, adenoviral vectors, adenovirus-associated viral vectors and lentiviral vectors. 
     Another aspect of the invention is antibodies against a novel α-catenin according to the invention. Preferably, the antibodies are monoclonal antibodies. One embodiment is a monoclonal antibody deposited at BCCM under the number LMBP 5537CB. Another embodiment is a monoclonal antibody deposited at BCCM under the number LMBP 5728CB. 
     Still another aspect of the invention is the use of the antibodies to treat cadherin-catenin related diseases. A preferred embodiment is the use of the antibodies whereby the disease is cancer. Another preferred embodiment is the use of the antibodies whereby the disease is a cardiomyopathy including dilated cardiomyopathy. Still another preferred embodiment is male infertility. 
     Still another aspect of the invention is the use of the antibody for the diagnosis of cadherin-catenin related diseases, or for predicting the likelihood of developing the cadherin-catenin related diseases. A preferred embodiment is the use of the antibodies for predicting the likelihood and/or diagnosis of cancer. Another preferred embodiment is the use of the antibodies for predicting the likelihood and/or diagnosis of cardiomyopathies including dilated cardiomyopathy, and male infertility. Antibodies can be used in tests such as a Western blot or an ELISA test, known to the person skilled in the art, to compare expression levels of the protein. 
     Definitions 
     Fragment of a nucleic acid or gene, as used here means any fragment that can be used as specific probe in hybridization reaction or specific primer in PCR reaction. 
     Functional fragment of the novel α-catenin means a fragment encoding a polypeptide that comprises a functional β-catenin binding domain. 
     Promoter region of a gene as used here means a region that is sufficient to obtain transcription of the normally transcribed regions of the gene. Promoter region of a gene, encoding a polypeptide according to the invention means a promoter region that is in a natural, non-recombinant situation linked to a gene encoding a polypeptide comprising the sequence presented in SEQ ID NO:2, or a variant thereof, which variant has at least 70% identity, preferably at least 80% identity, more preferably at least 90% identity with the sequence. 
     Cadherin-catenin related disease is a disease that is caused by overexpression, underexpression or dysfunction of one or more compounds of the cadherin-catenin cell adhesion complex and the related β-catenin mediated signaling pathway and includes, but is not limited to cancer, cardiomyopathies including dilated cardiomyopathy, and male infertility. 
     β-catenin mediated signaling pathway as used here means the pathway that is influenced by protein complexes in which β-catenin takes part. 
     Gene as used here, means the genomic structure of the gene, including the promoter, the terminator and the complete transcribed sequence, which includes both exonic and intronic sequences. 
    
    
     
       BRIEF DESCRIPTION OF THE TABLES AND FIGURES 
       Table 1: List of genomic Genbank submissions containing CTNNA3-specific sequences, complemented with proprietary data on BAC 162A20 and PAC 320B7. 
       Table 2: Sequences of CTNNA3 exon-intron and intron-exon boundaries. Coding sequences are shown in capital letters. The open reading frame is indicated, with translation to amino acids on top of the sequence. Position of exon boundaries in the cDNA sequence is annotated under the sequence. All introns start with gt and end with ag, conform to the rules for exon boundaries (Mount, 1982). Intron sizes are indicated as minimum size, based on the length of intronic sequences obtained so far. 
       Table 3: Overview of CTNNA3 exon-specific primers. For each exon, primer sequences in flanking intronic sequences are given, with the length of the PCR product (in bp), the optimum MgCl 2  concentration and the recommended annealing temperature (A.T.) to be used for genomic PCR. 
         FIG. 1 : Isolation of the novel human αT-catenin cDNA by two consecutive 5′-RACE experiments. (A) On the basis of one single EST sequence (IMAGE clone #728263), primers for 5′-RACE were designed and used to obtain a product of 1,011 bp. As this fragment was still lacking a suitable start codon, a second 5′-RACE was performed, which yielded a product of 1,306 bp containing the start codon. By aligning sequences from these clones, a full-length cDNA sequence of 3,024 bp wa amino acid residues (boxed). Percentage identity (B) and similarity (C) by MegAlign sequence comparison (DNAStar, Madison, Wis.) after alignment of the protein sequences by the CLUSTALW method (Higgins &amp; Sharp, 1989) and distance calculation with GCG software (www.BEN.ac.be). GenBank accession numbers of the used human sequences are M33308 (vinculin), U97067 (α-catulin), AF091606 (αT-catenin), D14705 (αE-catenin) and M94151 (αN2-catenin). 
         FIG. 2 : Amino acid sequence alignment of the human α-catenins. MegAlign sequence comparison (DNAStar, Madison, Wis.) after alignment of the protein sequences by the CLUSTALW method (Higgins &amp; Sharp, 1989), shaded by the Boxshade server (http://ulrec3.unil.ch/softward/BOX_form.html). Partial 3-dimensional structure as, determined for αE-catenin (Pokutta &amp; Weis, 2000) is shown by the location of the respective α-helices. Two characteristic proline residues, inducing a kink in the α-helices, are marked with “P”. Annotated domains are: the β-catenin binding domain as determined by Pokutta &amp; Weis (2000) and by Huber et a/. (1997), the α-actinin binding domain (Nieset et al., 1997), the amphiphatic helices possibly responsible for actin binding (Rudiger, 1998) and the position of the alternatively spliced insert (Claverie et al., 1993), which is generally found for αN-catenin, but rarely for αE-catenin. GenBank accession numbers of the used sequences are AF091606 (αT-catenin), D14705 (αE-catenin) and M94151 (αN2-catenin). 
         FIG. 3 : Chromosomal localization of the CTNNA3 gene, encoding human αT-catenin. (A) Fluorescence in situ hybridization with a specific PAC clone; arrows point at the positive signal; (B) G-banding by DAPI staining of the same chromosomes as shown in (A); (C) Fine mapping by Genebridge4 PCR analysis reveals the CTNNA3 location between the markers as shown; the obtained PCR pattern was: 000000001000000000000010120000110010100011000001000000000000000010010001010000 001110000000100, and was used as such for analysis on Webpage http://www.hgmp.mrc.ac.uk/cgi-bin/contig/rhmapper.pl. 
         FIG. 4 : Positioning of exon-exon boundaries (boxed) in the protein sequences of human αT-catenin and αE-catenin. Three boundaries in the αT-catenin sequence that do not coincide with αE-catenin are shown in bold. Indicated numbers refer to exons of αT-catenin (see also Table 1, Table 2 and  FIG. 5 ). 
         FIG. 5 : Overview of BAC and PAC clones covering the human CTNNA3 gene. Clones 162A20 and 320B7 are, respectively, a BAC and PAC clone isolated by us. All other sequences were obtained from GenBank and are annotated with their respective Accession Numbers. Lengths of contig sequences, in which a match is found with one or more CTNNA3 exons (indicated by “Ex” followed by the appropriate exon number), are mentioned in kilobase pairs (kb) or base pairs (bp). BAC or PAC clone lengths are mentioned between brackets and refer to the number of sequenced bp of the respective clones (GenBank including HTGS database, sequence versions as indicated). 
         FIG. 6 : (A) The human αT-catenin promoter sequence as determined from a human genomic BAC clone (clone 162A20). The sequence-listed comprises 1,237 bp of the upstream sequences, the sequence of exon-1 (bp 1238-1433) and part of intron-1 (bp 1434-1740). Several transcription factor binding sites as predicted by the Matinspector transcription factor binding site search program (Quandt et al., 1995), are indicated in bold and underlined. (B) Alignment of human and mouse αT-catenin promoter sequences, as determined from the human genomic BAC clone 162A20 and mouse genomic BAC clone 164N16. Transcription factor binding sites are indicated. The sequence conservation of the MEF2C site and two GATA-binding sites is striking. The arrow indicates the transcription initiation site. 
         FIG. 7 : Interaction between αT-catenin and β-catenin/plakoglobin in the yeast two-hybrid system. (A) Introduction in the two-hybrid system by cotransformation of the respective fusion constructs. Plasmids used for cotransformation were pGBT9-ATCTN(179-2860), pGBT9-αctl(50-2264), pGBT9-αECTN, pGBT9-αNCTN, pGAD424-ATβctn and pGAD424-Plakoglobin(227-2340), followed by XGAL staining of colonies on SD plates lacking leucine, tryptophan and histidine; pVA3 and pTD1 are control bait and prey plasmids (Clontech): they code for interacting fusion proteins derived of murine p53 and SV40 large T-antigen, respectively. (B) Quantification of interaction strength between β-catenin and either αE- or αT-catenin in the yeast two-hybrid system. β-Galactosidase activity was measured using CPRG as a substrate. Two different yeast strains and corresponding bait plasmids were used: the L40 yeast strain which was cotransformed with either pLexMG-αEctn (1) or pLexMG-αTctn (2) plus in each case pGAD424-βctn, and the Y190 yeast strain cotransformed with either pGBT9-αEctn (3) or pGBKT7-αTctn (4) plus in each case pGAD424-ATβctn. In both systems, the interaction between αT-catenin and β-catenin was found to be about 4 times stronger than the one between αE-catenin and β-catenin. (C) Confirmation of αT-catenin/β-catenin interactions by co-immunoprecipitation (IP) from HEK-293 cells transfected with plasmid pEF6MH-ATCTN(1-2860), encoding Myc-tagged αT-catenin. In the Western blots at the left, which serve as controls for efficient transfection, αT-catenin was detected by monoclonal antibody 892 — 24D2S and β-catenin by a polyclonal antibody (Sigma). The IP results at the right were obtained either with monoclonal anti-β-catenin antibody (Transduction) or with monoclonal anti-Myc antibody 9E10 (Oncogene, Cambridge, Mass.). SDS-PAGE was followed by Western blotting. A mixture of both antibodies was then used to probe this blot. In mock transfected cells, only β-catenin was detected as expected (data not shown). (D) Confirmation of αT-catenin/β-catenin interactions by co-immunoprecipitation (IP) from mouse tissues. IP from mouse testis and heart was performed with polyclonal antibody #952, specific for αT-catenin, and with a polyclonal antibody specific for β-catenin (Sigma). After Western blotting of total lysates (at the left) and coimmunoprecipitates (at the right), αT-catenin and β-catenin were detected by use of the same antibodies. 
         FIG. 8 : Tissue-specific expression patterns of αT-catenin. (A) Rapid-scan RT-PCR expression analysis of human αT-catenin and αE-catenin mRNAs. The specific 743-bp product of the first reaction was visible in heart, testis and skeletal muscle (not shown). After nested PCR, this first product of 743 bp is still visible, whereas the nested PCR product of 630 bp is detectable in the same three samples and a few more (brain, kidney, liver, fetal liver). PCR with αE-catenin-specific primers (yielding a 747-bp product) reveals expression in most tissues. PBL, peripheral blood lymphocytes. (B) RT-PCR analysis of αE-catenin, αT-catenin and αN-catenin mRNAs in mouse organs. GAPDH mRNA analysis served as a positive control. (C) Western blot analysis of αT-catenin, αE-catenin and β-catenin protein expression in various mouse organs. For detection of αT-catenin, polyclonal serum #952 was applied. In brain tissue, the 104-kDa band revealed by anti-αE-catenin corresponds to cross-reacting αN2-catenin protein. 
         FIG. 9 : Immunolocalization of αT-catenin in human tissues. (A) Frozen section of human heart stained with 892 — 24D2S monoclonal antibodies, showing localization of αT-catenin protein at intercalated discs of cardiac myocytes. (B) Enlarged detail of (A). (C) Frozen cross-section of human testis seminiferous tubules stained with 892 — 24D2S monoclonal antibodies, showing localization of αT-catenin protein in presumptive peritubular myoid cells at the basement membrane of seminiferous tubules. (D) Enlarged view of human testis staining with arrowhead pointing to a peritubular myoid cell. 
         FIG. 10 : Immunolocalization of αT-catenin in cryosections of human heart. (A) Double immunofluorescent staining of αT-catenin (monoclonal antibody 892 — 24D2S) and αE-catenin (polyclonal antibody) shows colocalization of the α-catenin proteins at intercalated discs of cardiomyocytes. (B) Double immunofluorescent staining of αT-catenin (polyclonal antibody #952) and N-cadherin (monoclonal antibody) shows colocalization at intercalated discs of cardiomyocytes. (C) Immunohistochemical staining for αT-catenin (monoclonal antibody 892 — 24D2) or desmin (monoclonal antibody 33) shows that αT-catenin is localized at the intercalated discs of cardiomyocytes, while desmin is present also at Z-discs. In the negative control (neg), only secondary antibody was used. 
         FIG. 11 : Immunolocalization of αT-catenin in cryosections of human testis. (A) Double immunofluorescent staining of αT-catenin (monoclonal antibody 892 — 24D2) and αE-catenin (polyclonal antibody) shows differential localization of these two related proteins. The αT-catenin is present in peritubular cells, clearly separated from αE-catenin, which is present in cells within the seminiferous tubules. (B) Immunohistochemical staining of consecutive sections for αT-catenin (monoclonal antibody 892 — 24D2) and desmin (monoclonal antibody 33) demonstrates that αT-catenin is localized in desmin-expressing peritubular myoid cells. In the negative control (neg), only secondary antibody was used. 
         FIG. 12 : Transient overexpression of αT-catenin in α-catenin-negative HCT-8/R1 colon carcinoma cells restores cadherin/catenin-mediated cell-cell adhesion. At 10 h after transfection with pE/L-GFP-ATCTN plasmid and simultaneous infection with ΔA36R vaccinia virus, opposing cells expressing GFP-αT-catenin show increased fluorescence at their common cell-cell contacts (A). This results in recruitment of β-catenin and E-cadherin to the same sites (B). 
         FIG. 13 : Relocalization of multiple cell-cell adhesion components in stably transfected colon cancer cells, expressing Myc-tagged αT-catenin. The α-catenin-negative parental HCT-8/R1 cells (left panels) were compared to the cloned transfectant HCT-8/R1/T31 (right panels). Cells were stained for the Myc tag (exogenous αT-catenin), for E-cadherin, desmoglein-2 or ZO-1 antigens. 
         FIG. 14 : Fast aggregation of α-catenin-negative HCT-8/R1 colon cancer cells is restored upon stable transfection with αT-catenin cDNA. After preparation of single-cell suspensions, cell aggregation was measured by determination of the volume % distribution in function of the particle diameter at the starting point (t0) and after 30 min (t30). HCT-8/R1, HCT-8/E11R1 and HCT-8/E8 cells were all obtained by subcloning HCT-8 cells, but only HCT-8/E8 cells express endogenous αE-catenin. HRpCαN2 is a cloned transfectant of HCT-8/E11R1 cells expressing exogenous αN-catenin (van Hengel et al., 1997); HCT-8/R1/T31 is a cloned transfectant of HCT-8/R1 cells expressing exogenous αT-catenin. MB2 is a monoclonal E-cadherin blocking antibody. 
         FIG. 15 : Slow aggregation and compaction of HCT-8 colon cancer cells on semi-solid agar. Images of two representative cultures were taken 24 h after seeding single-cell suspensions of the indicated cell lines. No aggregation is seen in cultures of either the untransfected α-catenin-negative HCT-8/R1 cells, or the control transfectant HCT-8/R1/1743 (also α-catenin-negative). Cells expressing either endogenous αE-catenin or exogenous αN-catenin (see, also, legend to  FIG. 8 ) form small aggregates, whereas cells expressing exogenous αT-catenin form compacted large aggregates. 
         FIG. 16 : Isolation of the novel mouse αT-catenin cDNA by consecutive 5′-RACE and RT-PCR experiments. (A) On the basis of one single EST sequence (GenBank Accession No. AW556211), primers for 5′-RACE were designed and used to obtain a product of 1,177 bp. As this fragment was still lacking a suitable start codon, an RT-PCR was performed using primers MCB2335 and MCB2567. This yielded a product of 684 bp of which 668 bp were new sequences. A second 5′-RACE was performed to obtain a 696-bp fragment containing the start codon. By aligning sequences from these clones, a full-length cDNA sequence of 2,979 bp was obtained, containing an open reading frame of 895 amino acid residues (boxed). (B) Percentages of identity (and similarities) between mouse αT-catenin, human αT-catenin and other mouse α-catenins, after alignment of the protein sequences by the CLUSTALW method (Higgins &amp; Sharp, 1989) and distance calculation with GCG software (www.BEN.ac.be). GenBank accession numbers of the used sequences are AF091606 (human αT-catenin), AF344871 (mouse αT-catenin), NM — 009818 (mouse αE-catenin) and NM — 009819 (mouse αN-catenin). 
         FIG. 17 : The full-length mouse αT-catenin clone pGEMTeasy-maTctn(1-2979) was expressed in an in vitro coupled transcription and translation reaction, using the TNT® Coupled Reticulocyte Lysate System (Promega). The in vitro synthesized proteins were analyzed by Western blotting and compared with endogenous αT-catenin protein in mouse heart and testis. (A) For detection of αT-catenin, polyclonal serum #952 was applied. As a negative control we used the TNT product of human cDNA encoding p120 ctn  isoform 3B (Keirsebilck et al., 1998). (B) TNT products of human and mouse αT-catenin were compared with endogenous αT-catenin protein in lysates of human and mouse heart. The αT-catenin proteins were analyzed by Western blotting and detected with either the polyclonal serum #952 (at the left) or with the monoclonal antibody 893 — 32C6S (at the right). 
         FIG. 18 : Amino acid sequence alignment of the human and mouse αT-catenin. The sequences were aligned using the CLUSTALW program (Higgins &amp; Sharp, 1989). Alignments were shaded using the Boxshade server. GenBank accession numbers of the used sequences are AF091606 (human αT-catenin) and AF344871 (mouse αT-catenin). Arrows indicate the amino-terminal β-catenin binding domains (Pokutta and Weis, 2000). 
         FIG. 19 : Amino acid sequence alignment of the mouse α-catenins. The sequences were aligned using the CLUSTALW program (Higgins &amp; Sharp, 1989). Alignments were shaded using the Boxshade server. GenBank accession numbers of the used sequences are NM — 009818 (mouse αE-catenin), NM — 009819 (mouse αN-catenin) and AF344871 (mouse αT-catenin). 
         FIG. 20 : Northern blot analysis of mouse αT-catenin. RNAs of 10 different mouse tissues were separated by gel electrophoresis, blotted on a membrane and hybridized with a mouse αT-catenin-specific probe, consisting of 296 bp of the 3′ end of the mouse αT-catenin cDNA. The sizes of the mRNAs were determined by sequential hybridizations of the Northern blot with a mouse GAPDH probe, with a mouse αE-catenin probe and finally staining of ribosomal RNA with methylene blue. 
         FIG. 21 : Western blot analysis of αT-catenin protein expression in various mouse tissues. (A) Detection of αT-catenin with polyclonal serum #952; (B) Detection of αT-catenin with polyclonal serum #952 after pre-incubation with the specific peptide #893, which blocks detection not only of the 100-kDa band (full-length mouse αT-catenin) but also the 86-kDa band, the 66-kDa band and the 43-kDa band in heart and testis lysates. 
         FIG. 22 : Influence of MEF2C transcription factor on the αT-catenin promoter activity. AlphaT-catenin promoter luciferase constructs were cotransfected with a MEF2C encoding plasmid in P19 cells (mouse embryonal carcinoma cells). Cells were lysed 48 h after transfection and luciferase activity was measured. A β-galactosidase encoding plasmid was cotransfected to normalize for transfection efficiency. A luciferase construct without αT-catenin promoter serves as negative control and is insensitive to MEF2C. A construct with luciferase under the control of the αT-catenin promoter sequence shows background activity unless cotransfected with MEF2C. This leads to a 10-fold upregulation of the αT-catenin promoter activity. Deletion or mutation of the consensus MEF2C binding site abolishes this effect as illustrated. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     EXAMPLES 
     Materials and Methods to the Examples 
     Cell Cultures 
     Most of the cell lines used were purchased from the American Cell Type Culture Collection (ATCC, Rockville, Md.). HCT-8/E8, HCT-8/E11R1 and HCT-8/R1 cell lines were obtained by subcloning of the human ileocecal adenocarcinoma cell line HCT-8 (CCL-224), where E stands for epithelioid and R for round-cell variants lacking αE-catenin (VAN Hengel et al., 1997). PC-3 (CRL-1435) is a human prostate carcinoma cell line and HEK-293 (CRL-1573) is a human embryonic kidney fibroblast cell line. 
     Cloning and cDNA Isolation of Human and Mouse αT-catenin 
     A human αT-catenin-specific EST clone (IMAGE #728263) was identified by BLAST analysis (Altschul et al., 1990) and requested from the IMAGE consortium UK-HGMP Resource Center (Hinxton, UK). Expression of the corresponding transcript was confirmed by RT-PCR on mRNA from the prostate cancer cell line PC3 with primers MCB967 (5′-TGAGGCAGAAAAAGAAAAGA-3′ (SEQ ID NO:87)) and MCB968 (5′-AGTGTGGTTAGGCAGGATT-3′ (SEQ ID NO:88)). In order to complete the cDNA sequence we performed two consecutive 5′ Marathon™ RACE experiments on a human testis Marathon cDNA library (Clontech, Palo Alto, Calif.). For the first 5′ RACE, the gene-specific primer was MCB1027 (5′-AATCTGCCGAGCAAGGACATCCA-3′ (SEQ ID NO:90)) and the nested primer was MCB1028 (5′-TCAGGCAGTTGAGTCATCTTAGC-3′ (SEQ ID NO:91)). RACE-PCR was performed on a Perkin Elmer 2400 thermal cycler (Perkin Elmer, Foster City, Calif.) following the supplied protocol (touchdown PCR). Obtained RACE fragments were purified from agarose gel on QIAquick™ columns (Qiagen, Chatsworth, Calif.) and cloned in the pGEMT® vector (Promega Corp., Madison, Wis.). The cloned fragment was called pGEMT-ATCTN-RACE1. As the obtained clone appeared to be incomplete, a second 5′-RACE experiment was performed with gene-specific primer MCB1254 (5′-ACCCGTGACGATGTGAGCAACTC-3′ (SEQ ID NO:92)) and nested primer MCB1255 (5′-GAGCTGTCTGCGAAGGTCTCTTG-3′ (SEQ ID NO:93)). The obtained fragment was cloned in the pGEMT®-easy vector (Promega Corp), and called pGEMTeasy-ATCTN-RACE2. 
     A mouse αT-catenin-specific expression tag (EST) clone sequence (GenBank Accession No. AW556211) of 624 bp was identified by BLAST analysis (Altschul et al., 1990). In order to complete the mouse cDNA sequence, we performed a 5′ RACE reaction (Life Technologies, Paisley, UK) on mouse cDNA. This cDNA was prepared with a gene-specific primer, MCB2461 (5′-CCCCAATGTTTTATGTTAT-3′ (SEQ ID NO:114)) from RNA that was isolated with the RNeasy method (Qiagen, Chatsworth, Calif.) from mouse testis and heart tissues. For the 5′ RACE reaction, we used primer MCB2481 (5′-CTTGGTGGAGGCAATGTATGAC-3′ (SEQ ID NO:118)) and nested primer MCB2482 (5′-TCTGCCGAGCAAGAACATCCAT-3′ (SEQ ID NO:119)). The obtained RACE fragments were purified from agarose gel using the CONCERT™ Rapid Gel Extraction System (Life Technologies) and cloned into the pGEMT®-easy vector (Promega, Madison, Wis.). The resulting plasmid was called pGEMTeasy-maTctn(RACE 1 )cDNA. 
     As the cloned cDNA was incomplete, we performed a PCR using human primer MCB2335 (5′-CCTCTTGCAACATGTGTC-3′ (SEQ ID NO:110)) and mouse gene-specific primer MCB2567 (5′-GCGGAGGTCTCTTGTCTTCTT-3′ (SEQ ID NO:120)), yielding a product of 684 bp. The obtained fragment was cloned into the pGEMT®-easy vector (Promega), and called pGEMTeasy-maTctn(PCR2567+2335). 
     As the cloned cDNA was still incomplete we performed another 5′ RACE reaction using the GeneRacer™ Kit, version B (Invitrogen, San Diego, Calif.) on RNA isolated from mouse heart tissue. For this 5′ RACE reaction, primer MCB2569 (5′-CGCAGTCAGAGAGTTCTTGCTT-3′ (SEQ ID NO:121)) was used to prepare gene-specific mouse cDNA. For the touchdown PCR we used primer MCB2711 (5′-CTTCCCGAGCTTCTGGTAGGTTCT-3′ (SEQ ID NO:124)). The obtained RACE fragments were purified from agarose gel using the CONCERTT Rapid Gel Extraction system (Life Technologies) and cloned into the pGEMT®-easy vector (Promega). The resulting plasmid was called pGEMTeasy-maTctn(RACE3)cDNA. 
     On the basis of the consensus mouse αT-catenin sequence, primers MCB2818 (5′-AACGCCTAGAAGCCATCATC-3′ (SEQ ID NO:125)) and MCB2819 (5′-TGGCAAGAACAATGATGTCA-3′ (SEQ ID NO:126)) were designed to amplify the full-length cDNA. The predicted 2979-bp product was obtained by PCR on heart cDNA, using the TaqPlus® Precision PCR System (Stratagene Cloning Systems, La Jolla, Calif.). The PCR-fragment was purified from agarose gel using the CO (Life Technologies) and cloned into the pGEMT®-easy vector (Promega). The resulting plasmid was called pGEMTeasy-maTctn(1-2979). This full-length mouse αT-catenin clone was expressed in an in vitro coupled transcription and translation reaction, using the TNT® Coupled Reticulocyte Lysate System (Promega). The in vitro synthesized proteins were analyzed by Western blotting. 
     All DNA sequences were obtained by the dideoxy chain termination method (Sanger et al., 1977), using fluorescent dye terminators in a 373ABI automated DNA sequencer (Applied Biosystems, Foster City, Calif.). Sequences were assembled and compared by the DNAstar (DNASTAR Inc, Madison, Wis.), and Staden gap4 software packages (Bonfield et al., 1995). Amino acid similarities alignments were obtained using the CLUSTALW program (Higgins &amp; Sharp, 1989; Thompson et al., 1994) and GCG software. Alignments were shaded using the WWW-BOXSHADE server (http://ulrec3.unil.ch/softward/BOX-form.html). 
     PAC and BAC Human and Mouse Genomic Library Screening 
     For the isolation of a human genomic clone of αT-catenin, the PAC genomic library RPCI1 constructed by Ioannou and de Jong (1996), and obtained from HGMP (UK), was screened by PCR with the 3′ located primers MCB1260 (5′-GAAAAAGAAAAGATTGCTGAG-3′ (SEQ. ID NO:94)) and MCB1261 (5′-CCCTAGTGAAGTCTGTCATCT-3′ (SEQ ID NO:95)), yielding a product of 157 bp. The PCR reaction was optimized on total human genomic DNA and performed with 2.5 mM MgCl 2  at an annealing temperature of 56° C. Clone 320B7 (#1487) was found to be specific by DNA sequencing using primers MCB1260 and MCB1261. However, this PAC clone was found to contain only the last exon of the CTNNA3 gene (exon 18 in  FIGS. 4 and 5 ). 
     A BAC (Bacterial Artificial Chromosome) human genomic library (Genome Systems, St. Louis, Mo.) was screened with primers located in the first protein encoding exon, i.e., primers MCB2099 (5′-TGTCATCTGCCTCTCAATTTG-3′ (SEQ ID NO:104)) and MCB2100 (5′-ATGCTGCCTTTCTGTTTCTTC-3′ (SEQ ID NO:105)), yielding a product of 149 bp at an annealing temperature of 52° C. and 2 mM MgCl 2 . Clone 162A20 was found to comprise this exon, as confirmed by direct sequencing and fragment subcloning. To clone the  αT-catenin promoter region, the BAC162A20 clone was digested with the 6-bp cutters BamHI, BglII, EcoRI, HindIII, MluI, SstI, SalI, XbaI and XhoI. Fragments containing exon 1 of the αT-catenin gene were identified by Southern blot hybridization with a primer located in this first exon, i.e. MCB2099. An 8-kb BamHI fragment was cloned in the pGEM11 vector and positive clones were identified by colony hybridization with primer MCB2099. The promoter region in this clone was sequenced by primer walking using primers MCB2217 (5′-CAGATGACAGTGGGGCAGTC-3′ (SEQ ID NO:106)), MCB2287 (5′-AACTTGTTACTGAAAATACT-3′ (SEQ ID NO:109)), and MCB2350 (5′-CATTACCATTTTTCCGACTT-3′ (SEQ ID NO:111)). 
     A BAC mouse genomic library (Genome Systems) was screened by PCR with primers located in either exon 1 (primers MCB2820 and MCB2837), in exon 2 (primers MCB2840 and MCB2841) and in exon 3 of the mouse αT-catenin gene (primers MCB2838 and MCB2839). Sequences of these primers are: 
     
       
         
               
               
               
             
           
               
                 MCB2820: 
                   
                   
               
               
                 5′-CCCCTTTCTCTCTTATCCTGAG-3′ 
                 (SEQ ID NO:127) 
               
               
                   
               
               
                 MCB2837: 
               
               
                 5′-CTTTCTGATGCTTCCTACAAGTAAA-3′ 
                 (SEQ ID NO:128) 
               
               
                   
               
               
                 MCB2840: 
               
               
                 5′-GTCGGCAGAAACGCCAATA-3′ 
                 (SEQ ID NO:131) 
               
               
                   
               
               
                 MCB2841: 
               
               
                 5′-GAGGCTCCAGCAGTTTCTCC-3′ 
                 (SEQ ID NO:132) 
               
               
                   
               
               
                 MCB2838: 
               
               
                 5′-CCGCAGAATCCTTCCAACA-3′ 
                 (SEQ ID NO:129) 
               
               
                   
               
               
                 MCB2839: 
               
               
                 5′-GCTGCCAGCTCTTCCTTTAAA-3′. 
                 (SEQ ID NO:130) 
               
             
          
         
       
     
     Clone 164N16 was found to comprise these first three exons, as confirmed by Southern blot analysis. 
     Fluorescence In Situ Hybridization (FISH) 
     PAC clone 320B7 (#1487) was used for fluorescence in situ hybridization (Kievits et al., 1990). PAC DNA was prepared with Kb-Magnum purification columns (Genome Systems, St. Louis, Mo.) and nick-translated using a BioNick kit (Gibco-BRL). Denaturation of labeled probe and human chromosomes, hybridization and fluorescent detection were performed as described previously (van Hengel et al., 1995). The chromosomes were stained with DAPI to reproduce G-banding. The slides were observed using a Zeiss Axiophot fluorescent microscope (Zeiss, Jena, Germany) and images captured with a Photometrics Image Point CCD camera (Photometrics, Munich, Germany). Results were analyzed with the MacProbe software of PSI (Perceptive Scientific International, League City, Tex.). At least 20 metaphase spreads of normal human lymphocytes were analyzed. 
     Confirmation of Human Chromosomal Localization by PCR-based Hybrid Mapping 
     Genomic PCR was performed with primers 
                         MCB2056           (5′-GAAATGCCATGGAGCTCTAAC-3′ (SEQ ID NO:102)) and               MCB2057       (5′-ATGGGAAGGCAAACCAGTCAC-3′ (SEQ ID NO:103)).            
These primers correspond to intronic sequences and are flanking an exon, as deduced from the sequence of a genomic clone (GenBank No AQ163827) (Table 1;  FIG. 5 ). A product of 274 bp was expected. As a positive control, genomic DNA from human placenta was used to optimize the annealing temperature of 52° C. and a concentration of 2 mM MgCl 2 . The PCR was performed on samples of the Genebridge 4 radiation hybrid mapping panel (HGMP-RC, UK), which allows construction of high-resolution contiguous maps of human chromosomes. Analysis was performed on the Web page http://www.hgmp.mrc.ac.uk/cgi-bin/contig/rhmapper.pl.
 
     PCR with the same primer set was also performed on a monochromosomal hybrid mapping panel (NIGMS Human/Rodent Somatic Cell Hybrid Mapping Panel #2, Coriell Cell Repositories, Camden, N.J.). All cell hybrid templates were diluted to a final DNA concentration of 100 ng/μl, using 1 μl as PCR templates. 
     Cloning of Two Hybrid Prey and Bait Plasmids 
     After completion of plasmid constructs, as described below, all clones were checked by DNA sequencing. For all PCRs, Pfu polymerase (Stratagene, La Jolla, Calif.) with proofreading activity was used. 
     αT-catenin 
     For cloning of the full-length hαT-catenin cDNA in the pGBT9 vector (Clontech), in fusion with the GAL4 binding domain, four consecutive constructs were made. A PCR product of 1,134 bp was synthesized with primers MCB1607 (5′-AGAATTCTCAGCTGAAACACCAATCAC-3′ (SEQ ID NO:96)) and MCB1609 (5′-AGGATCCTGCGAAGGTCTCTTGTCT-3′ (SEQ ID NO:98)) using the pGEMTeasy-ATCTN-RACE2 clone as a template. This product was restricted with EcoRI plus BamHI and ligated to the EcoRI and BamHI sites of the pGBT9 vector, thus yielding pGBT9-ATCTN(179-949). This construct was opened with PstI, and the PstI insert of 1,111 bp from clone pGEMT-ATCTN-RACE2 was ligated to obtain pGBT9-ATCTN(179-1306). From this construct, the EcoRI-SspI insert of 1,082 bp was isolated and ligated together with fragment SspI-SalI from pGEMTeasy-ATCTN-RACE1 in the pGBT9 vector, restricted with EcoRI-SalI. In this way pGBT9-ATCTN(179-2176) was obtained. In order to have an overlapping 3′ clone, a PCR product of 890 bp was synthesized with primers MCB1610 (5′-GGATGATAATCAATTTGTGGACATCTC-3′ (SEQ ID NO:99)) and MCB 1608 (5′-GGGATCCGTAGATTTGTCTTCCTCTAA-3′ (SEQ ID NO:97)). For this PCR, template cDNA was synthesized from RNA prepared with the RNeasy kit (Qiagen) from the PC-3 prostate cancer cell line (American Type Culture Collection, Rockville, Md., U.S.A.). The PCR product was cut with BglII and SalI, and inserted in the BglII-SalI opened construct pGBT9-ATCTN(179-2176) to finally achieve the construct pGBT9-ATCTN(179-2860). 
     From pGBT9-ATCTN(179-2860), the EcoRI-SacI insert was ligated together with the SacI-NotI fragment from the original EST clone pT3T7-EST728263, in the EcoRI-NotI digested pGBKT7 vector (Clontech). The obtained construct was designated pGBKT7-ATCTN(179-3024). Further, the EcoRI-SalI insert from pGBT9-ATCTN(179-2860) was cloned into the EcoRI-SalI sites of the LexA bait vector pLexMG (pGBT9 in which the GAL4 binding domain has been exchanged with the LexA binding domain by Mathias Gautel, EMBL, Heidelberg). In this way, pLexMG-ATCTN(179-2860) was obtained. 
     α-catulin 
     The full-length α-catulin cDNA sequence (GenBank Accession number U97067) was isolated by us in 3 steps (Janssens et al., 1999): The full-length sequence was compiled from 2 EST sequences (clones 36498 and 67201) and one 5′-RACE clone. In order to obtain a clone with the full-length sequence, these 3 clones were assembled in the pGEM11 vector (Clontech). First, the insert of EST clone 67201 was isolated by a SmaI-MunI digest and ligated to the SmaI-MunI opened vector pGEMT-αctlRACE. In that way the construct pGEMT-αctl(1-1369) was obtained. Part of the EST #36498 sequence (1,003 bp) was obtained by a BglII restriction digest, yielding a fragment comprising the complete 3′ part of the open reading frame (ORF) but only part of the 3′ untranslated region. This fragment was inserted in the plasmid pGEMT-αctl(1-1369) opened with BglII. This resulted in a clone containing the complete open reading frame of α-catulin, i.e. pGEMT-αctl(1-2264). 
     This clone was used as a template to generate a PCR product with primer MCB725 (5′-TATTAGATATCGCCTCTCCCGGACCCGCC-3′ (SEQ ID NO:86) comprising an EcoRV site) and primer MCB711 (5′-AGGGGGCAGTGGCTGAAGAAAGAAGTAATC-3′(SEQ ID NO:85)). In a 3-point ligation this PCR product, cut with EcoRV +MunI, was ligated together with a MunI-SalI fragment of pGEMT-αctl(1-2264) into the BamHI(blunted)-SalI restricted pGBT9 two-hybrid vector (Clontech), in frame with the ORF encoding the GAL4 DNA binding domain. The obtained constructed was called pGBT9-αctl(50-2264). 
     αE-catenin 
     Screening of a human fetal kidney 5′ Stretch cDNA library in vector λDR2 (Clontech, Calif.) resulted in isolation of the pDR2αECTN plasmid, containing full-length αE-catenin cDNA. From this plasmid, Eco47III-SphI and SphI-SalI fragments were ligated in the SmaI-SalI digested pGBT9 vector, yielding pGBT9-αECTN, in which the full-length αE-catenin ORF is fused in frame with the OF encoding the GAL4 DNA binding domain. 
     From pGBT9-αECTN, the EcoRI-SalI fragment was cloned into the pLexMG vector restricted with EcoRI and SalI. In this way pLexMG-αECTN was obtained in which the full-length αE-catenin ORF is fused in frame with the ORF encoding the LexA DNA binding domain. 
     αN-catenin 
     The cDNA for human αN-catenin was kindly provided as plasmid pPN-hANCTN by Dr. C. Petit (Claverie et al., 1993). Nearly full-length αN-catenin was amplified from pPN-hANCTN with primers MCB137 (5′-ACCCCCCGGGGGCAACTTCACCTATCATTC-3′ (SEQ ID NO:83)) containing an XmaI site), and MCB138 (5′-GCCGCCGCCTTCCTTTTCATTTCCGCTCTT-3′(SEQ ID NO:84)). The PCR fragment was digested with XmaI and BanI and ligated together with a BanI-HindIII fragment of pPN-hANCTN in the XmaI-HindIII digested pAS2 vector (Clontech). Thus the pAS2-αNCTN plasmid was obtained, in which codons 4 to 906 of αN-catenin are fused in frame with the ORF encoding the GAL4 DNA binding domain. From this construct, the XmaI-HindIII insert was transferred to the XmaI-HindIII opened pGBT9 vector, yielding pGBT9-αNCTN. 
     β-catenin 
     The full-length β-catenin cDNA was kindly provided as plasmid pBAT-βCAT (from Dr. J. Behrens, Berlin, Germany). The amino terminal fragment 239-717 was obtained as an NcoI-PstI restriction fragment, of which the NcoI cut end was filled in with Pfu polymerase. This fragment was cloned into the SmaI-PstI opened pGAD424 vector, by which the construct pGAD424-ATβctn was obtained. 
     Plakoglobin 
     Plasmid pHPGCa2.1 with the full-length human plakoglobin cDNA was kindly provided by Dr. W. Franke. PCR was performed on this plasmid, with primer MCB133 (5′-GGTGAATTCGTCAGCAGCAAGGGCATCAT-3′(SEQ ID NO:81)), containing an EcoRI site) and primer MCB134 (5′-GGTTTGATGCAGGGTCCACAGGCAGTTCT-3′(SEQ ID NO:82)). The obtained PCR product (encoding plakoglobin residues 227-1228) was digested with EcoRI and SacI (residues 227-559) and ligated together with the fragments SacI-BglII (residues 560-1856) and BglII-PstI (residues 1857-2340) from pHPGCa2.1, into the EcoRI-PstI opened pGAD424 vector (Clontech). Thus, the plasmid pGAD424-Plakoglobin(227-2340) was obtained. 
     Yeast Two-hybrid Transformation 
     The yeast strain Y190 (Matchmaker, Clontech, CA), which contains GAL4 promoter driven His and β-galactosidase reporters, was used for cotransformation of pGBT9 bait and pGAD424 prey plasmids, comprising the cloned inserts of interest. The yeast strain L40, which contains LexA promoter driven His and β-galactosidase reporters, was used for cotransformation of pLexMG bait with pGAD424 prey plasmids, comprising the cloned inserts of interest. 
     The yeast cells were grown in YPD medium until a log-phase culture with an O.D. 600  of about 0.8 was obtained, and transformed by the lithium acetate procedure (Gietz et al., 1992). Cotransformants were selected by plating the transformation mix on SD minimal medium plates lacking leucine and tryptophan. After three days, colonies were picked and grown overnight in SD without leucine and tryptophan, but containing 0.07 M potassium phosphate. Replica plates selecting for interaction were made on SD lacking leucine, tryptophan and histidine, but containing 0.07 M potassium phosphate, 40 mM 3-amino-triazol to suppress leaky His expression, and 80 mg/ml X-β-GAL (Duchefa, Haarlem, The Netherlands). 
     CPRG Yeast Two-hybrid Quantification of β-galactosidase 
     To assay the strength of interaction between α-catenins and β-catenin, β-galactosidase activity was assayed using chlorophenol red-β-D-galactopyranoside (CPRG, Boehringer Mannheim, Del.) as a substrate, according to the provided protocol (Clontech Yeast Protocols Handbook). Briefly, transformed yeasts are grown until OD 600  of about 0.6, concentrated in three different dilutions (1.25, 2.5 and 5 times concentrated, respectively) and allowed to develop red color after addition of CPRG substrate (measured at that time point, at OD 578 ). One β-galactosidase unit is defined as the amount which hydrolyzes 1 μmol of CPRG to chlorophenol red and D-galactose per minute per cell (Miller et al., 1972). The amount of units is calculated as 10,000×OD 578 /(time×concentration factor×OD 600 ). 
     Cloning of Expression Plasmids 
     The full-length human αT-catenin cDNA was excised from the construct pGBT9-ATCTN(179-2860) with restriction enzymes EcoRI-SalI and inserted in the EcoRI-SalI digested pEGFPC2 vector (Clontech), in order to obtain an in-frame amino-terminal fusion with the GFP protein. The resulting plasmid was called pEGFPC2-ATCTN(179-2860). The EcoRI-NotI insert from pGBT9-ATCTN(179-2860) was ligated into the EcoRI-NotI digested vector pEF6MycHisA (Invitrogen), providing a C-terminal fusion between αT-catenin and the Myc and His epitopes in the construct pEF6MH-ATCTN(179-2860). In this construct, no in-frame start codon is present at the very 5′ side, but there is a start codon present at position 596. The full-length fusion construct, named pEF6MH-ATCTN(1-2860), was obtained by introducing the 5′ part of the αT-catenin cDNA from clone pGEMT-RACE2, cut with EcoRI-BstEII, into the EcoRI-BstEII opened vector pEF6MH-ATCTN(179-2860). 
     Transfection Methods 
     For vaccinia virus-mediated transient overexpression, α-catenins were cloned in the pE/L-GFP vector (Frischknecht et al., 1999). Cells were transfected with Lipofectin (Life Technologies) and simultaneously co-infected with vaccinia virus strain ΔA36R, which does not make actin tails (Parkinson and Smith, 1994). At 4 to 30 h after transfection, high levels of expression under control of the vaccinia virus early/late promoter (E/L) (Chakrabarti et al., 1997) were obtained of the cloned cDNA, amino-terminally fused to GFP. Human αT-catenin was amplified with Taq+Precision polymerase (Stratagene) using primers containing a 5′ NotI site and a 3′ EcoRI site (MCB2386, 5′-GGGGGCGGCCGCGGAGGGTCAGCTGAAACACCAATCACATTG-3′ (SEQ ID NO:112) and MCB2387, 5 ′-CCCCGAATTCGCCGTGTGGTTAGGCAGGATTTTGTCATATAG-3′ (SEQ ID NO:113)) and cloned into the NotI-EcoRI sites of the pE/L-GFP vector. 
     For stable transfection of HCT-8/R1 carcinoma cells, 4×10 6  cells were electroporated (Easyject; Eurogentec, Seraing, Belgium) with 10 μg of plasmid pEF6MH-ATCTN(179-2860). Cells were plated and cultured in the presence of 6 μg/ml blasticidin (Invitrogen) to select for stable transfectants. Colonies of blasticidin-resistant cells were isolated and tested by immunofluorescence and Western blotting for expression of αT-catenin. One stable clone was isolated and called HCT-8/R1/T31. As a negative control we transfected HCT-8/R1 cells with the empty pEF6MH vector, resulting in stable clones called HCT-8/R1/1743. A clone of HCT-8/E11R1 cells, stably transfected with αN-catenin cDNA and designated HRpCαN2 (van Hengel et al., 1997), was used in comparison. Likewise, HCT-8/E11R1 carcinoma cells were transfected with plasmid pEGFPC2-ATCTN(179-2860). After selection with G418 (800 μg/ml), one stable αT-catenin expressing clone was isolated and called HCT-8/E11R1/T14. 
     Expression Analysis by RT-PCR 
     Expression analysis using the human Rapid-Scan panel (OriGene Technologies Inc, Rockville, Md.) was performed on 100-times diluted template, followed by a nested PCR ( 1/10 of the end volume of the first reaction was used). The end-point determination method used does not allow a reliable determination of expression levels to be deduced from the amount of PCR product visualized on gel. Therefore, visual presence of a signal (even weak) was scored as positive, and complete absence was scored as negative. Primers MCB967 (5′-TGAGGCAGAAAAAGAAAAGA-3′ (SEQ ID NO:87)) and MCB968 (5′-AGTGTGGTTAGGCAGGATT-3′(SEQ ID NO:88)) were used for the first PCR, yielding a product of 743 bp. For nested PCR, primers MCB967 (5′-TGAGGCAGAAAAAGAAAAGA-3′(SEQ ID NO:87)) and MCB1010 (5′-GCTGAGCCTCGTCTGAC-3′(SEQ ID NO:89)) were combined, yielding a smaller product of 630 bp. Amplified products were checked for specificity by sequence analysis, showing that the double bands observed after nested RT-PCR of heart and testis samples in particular are indeed the larger primary product and the smaller nested product. 
     As a control, an αE-catenin-specific product of 747 bp was amplified with primers MCB53 (5′-CTTCGGGCCTCTGGAATTTA-3′(SEQ ID NO:79)) and MCB73 (5′-CGACATCAGGGTGCTGTAGG-3′(SEQ ID NO:80)). 
     For RT-PCR analysis of mouse tissues, RNA was prepared from different tissues with the RNAeasy method (Qiagen) and cDNA was prepared using a commercial kit (Life Technologies, Ghent, Belgium). For mouse αT-catenin, primers MCB2461 (5′-CCCCAATGTTTTATGTTAT-3′ (SEQ ID NO:114)) and MCB2463 (5′-GGGGAGAACTCATCGTAT-3′ (SEQ ID NO:115)) were designed on the sequence of an EST clone (GenBank Accession No. AW556211), resulting in amplification of a 442-bp product. For mouse αE-catenin (GenBank Accession No. NM — 009818), a 733-bp product was amplified with primers MCB2636 (5′-GAAGGCCCCTGAGAAGAA-3′ (SEQ ID NO:122)) and MCB2637 (5′-CCCGAATAAAGCAACTCCAT-3′ (SEQ ID NO:123)). For mouse αN-catenin (GenBank Accession No. NM — 009819), a 858-bp product was amplified with primers MCB2479 (5′-GCCCTGATTGAGTTTGATAA-3′ (SEQ ID NO:116)) and MCB2480 (5′-CCCAGCTTCATAGTTCTCC-3′ (SEQ ID NO:117)). As a control, a 452-bp fragment of mouse GAPDH was amplified with primers MCB2219 (5′-ACCACAGTCCATGCCATCAC-3′ (SEQ ID NO:107)) and MCB2220 (5′-TCCACCACCCTGTTGCTG TA-3′ (SEQ ID NO:108)). 
     Expression Analysis by Northern Blotting 
     RNA was prepared from different mouse tissues, using the RNeasy method (Qiagen). For each tissue sample, 25 μg RNA was separated on a 1% agarose gel. RNA was transferred by Northern blotting on a Hybond™-N +  membrane (Amersham Pharmacia Biotech, Rainham, UK). 
     A mouse αT-catenin-specific probe of 296 bp was generated by PCR with primer MCB2043 (5′-TCGAGGATGAAGGCTCTG-3′ (SEQ ID NO:100)) and primer MCB2044 (5′-TGTTTAACCCCAATGTTT-3′ (SEQ ID NO:101)). The PCR product was labeled with α[ 32 P]-dCTP using the Radprime DNA labeling System (Life Technologies). After hybridization according to standard procedures, the blot was washed at high stringency. For detection, a Phosphor Imager cassette (Molecular Dynamics, Sunnyvale, Calif.) was exposed for 4 days and scanned with a Molecular Imager® FX using the Quantity One software (BioRad, Richmond, Calif.). 
     Antibodies 
     Peptides corresponding to, respectively, the amino-terminus (MSAETPITLNIDPQDLQ-C (SEQ ID NO:133)) and the carboxy-terminus (C-KIHPLQVMSEFRGRQIY (SEQ ID NO:134)) of the human αT-ctn protein were synthesized and coupled to keyhole-limpet hemocyanin via the additional cysteine residue at either the carboxyterminal or the amino terminal end of the peptides. 200 μg of peptide was injected in each of three rabbits using Titermax (Sigma, St Louis, Mo.) as adjuvant. Boosts were given with intervals of minimum two weeks. Sera were tested by ELISA on the peptide used for injection, using the non-relevant peptide as a negative control. The sera #952 (specific for the carboxy-terminal peptide) and #954 (specific for the amino-terminal peptide) were affinity purified on hydroxymercuribenzoate-agarose (Sigma, St Louis, Mo.), coupled to the respective immunizing peptides. Crude and purified sera were tested on lysates of HEK cells transfected with plasmids pEGFPC2-ATCTN(179-2860) and pEF6MH-ATCTN(1-2860), encoding respectively full-length Myc-tagged and GFP-tagged αT-catenin. For Western blotting, a dilution of 1:1,000 was used for the crude polyclonal sera and a dilution of 1:250 for the affinity purified sera. Recognition of αT-catenin was inhibited by incubation of the polyclonal antibody with the antigenic peptide for one hour prior to use. Serum #952, but not serum #954, turned out to cross-react with mouse αT-catenin. 
     Monoclonal antibodies were generated by injection of the N-terminal peptide (MSAETPITLNIDPQDLQ-C (SEQ ID NO:133)) or the C-terminal peptide (C-KIHPLQVMSEFRGRQIY (SEQ ID NO:134)) in C57B1/6 mice. Boosts were given with intervals of 2 weeks, and sera were tested by ELISA until a titer of 1:10,000 without loss of reactivity was obtained after 6 weeks. Hybridomas were generated by fusion of spleen cells with Sp20_Ag14 myeloma cells. Supernatants of hybridoma cell lines were tested by ELISA. 
     For the N-terminal peptide, up to 72 strongly reacting clones were tested on Western blots for recognition of αT-catenin, fused at its amino terminus to GFP. From the 17 positive hybridomas identified in this way, 4 were also able to recognize native αT-catenin protein in MCF-7 cells transfected with plasmid pEGFPC2-ATCTN(179-2860). A subclone of hybridoma 892 — 24D2, 892 — 24D2S (deposited at BCCM under the number LMBP 5537CB), was used for further analysis. 
     For the C-terminal peptide, 30 out of 96 ELISA-positive clones recognized GFP-αT-catenin by Western Blotting, from which 3 were able to recognize native αT-catenin protein by immunofluorescence. A subclone, called hybridoma 893 — 32C6S, was deposited at BCCM under the number LMBP 5728CB. 
     Neither monoclonal antibody was found to cross-react with mouse αT-catenin. 
     SDS-PAGE and Western Blot Analysis 
     Protein lysates from various mouse tissues were prepared by isolating the tissues from normal BALB/c mice and mixing them in Laemmli buffer (Laemmli, 1970). Debris was removed by centrifugation and protein concentration was measured by the BioRad DC kit (BioRad, Richmond, Calif.). Lysates from subconfluent cultures of cell lines were also prepared in Laemmli buffer, followed by sonication and centrifugation. Of each protein lysate, 40 μg was diluted with 6× sample buffer (0.35 M Tris-HCl, pH 6.8, 10.28% SDS, 36% glycerol, 5% β-mercaptoethanol, 0.012% bromophenol blue), boiled for 5 min and subjected to separation on 10% polyacrylamide gels. Proteins were transferred onto Immobilon-P membranes (Millipore, Bredford, Mass.) and blocked with 5% nonfat dry milk, 0.1% Tween-20 in Tris-buffered saline buffer (100 mM Tris-HCl, pH 7.4, 1.4 M NaCl) prior to incubation with the primary antibody. Detection was carried out by phosphatase-coupled secondary antibodies (Sigma) and nitroblue tetrazolium/5-bromo-4-chloro-3-indolyl phosphate (NBT/BCIP) as a substrate. 
     Co-immunoprecipitation was performed on lysates of transfected HEK cells, prepared in PBS containing 1% NP-40 and a protease inhibitor cocktail (Boehringer). Lysate (800 μg) was incubated overnight with 4 μg of the respective antibody, after which 100 μl of 50% protein-G (Amersham Pharmacia Biotech, Rainham, UK) was added to monoclonal antibodies, whereas protein-A Sepharose (Amersham Pharmacia Biotech) was added to polyclonal antibodies. After 2 h of incubation, the Sepharose beads were washed three times with PBS containing 0.1% NP-40, followed by boiling for 5 min in Laemmli buffer, before being subjected to SDS-PAGE and Western blotting. On these Western blots, protein was detected by the ECL detection system using secondary antibodies coupled to horseradish peroxidase (Amersham Pharmacia Biotech). 
     Tissue Staining 
     Frozen sections of human heart and testis tissue were treated for 20 min with 0.3% H 2 O 2  diluted in methanol, then washed in water and PBS, and pretreated for 10 min with goat serum diluted 1:10. The sections were then incubated for 30 min with crude monoclonal 892 — 24D2S hybridoma supernatans, which was diluted 1:5 in PBS containing 1% bovine serum albumin. The secondary antibody used was biotin-labeled goat-anti-mouse Ig (DAKO, Denmark), which was subsequently linked to the streptavidin-ABC complex coupled to horseradish peroxidase. Detection was carried out by a 5 min incubation with the chromogenic peroxidase substrate diaminobenzidine (Sigma). Cell nuclei were counterstained for 5 min with haematoxylin (Sigma), after which the slides were dehydrated by washing in 70%, 90% and two times 100% ethanol. Finally the slides were cleared in toluol and mounted. 
     For double immunofluorescent staining, frozen sections were air dried, fixed in acetone at 4° C. for 10 min, washed in PBS and preincubated with 10% goat serum for 10 min. The slides were then incubated for 45 min with mixtures of primary antibodies diluted in PBS: either 1:5 monoclonal antibody 892 — 24D2S plus 1:500 polyclonal anti-αE-catenin, or 1:500 polyclonal antibody #952 plus 1:500 monoclonal anti-N-cadherin. The secondary goat anti-mouse IgG and goat anti-rabbit IgG antibodies used were labeled with FITC or TRITC (Santa Cruz, Santa Cruz, Calif.), or with Alexa 488 or Alexa 594 (Molecular Probes, Eugene, Oreg.). 
     Immunocytochemistry of Cell Cultures 
     Cells were grown on glass coverslips until confluency, rinsed briefly with PBS and fixed with either ice-cold methanol for 1 min, or with 3% paraformaldehyde (Merck, Darmstadt, Germany) for 10 min at room temperature, followed by permeabilization in 0.2% Triton X-100 (Sigma) for 2 min. Cells were then incubated for 30 min with primary antibody diluted in blocking solution (20 mM Tris/HCl pH 7.5, 154 mM NaCl, 2 mM EDTA, 2 mM MgCl 2 , with 1% BSA and 1% goat serum), washed in PBS, and incubated for 30 min with secondary antibodies diluted in blocking solution. Secondary anti-mouse IgG or anti-rabbit IgG antibodies were coupled to either Alexa 594 or Alexa 488 (Molecular Probes) and used at dilution 1:300. Finally, cells were treated for 10 sec with a 4′-6-diamidine-2-phenylindole-dihydrochloride so DNA, followed by mounting in Vectashield (Vector Laboratories, Burlingame, Calif.) to prevent photobleaching. Samples were examined with a Zeiss Axiophot microscope and images were recorded with a high-performance charge-coupled digital camera (Cohu, San Diego, Calif.) and NIH image software (version 1.62), or with a MicroMAX camera (Princeton, Trenton, N.J.) and MetaMorph software (Image Universal Corporation, New York, N.Y.). 
     Fast Aggregation Assay 
     Cell-cell adhesion was numerically evaluated in an aggregation assay as described before (Bracke et al., 1993). In brief, cultures were dissociated into single-cell suspensions under E-cadherin-saving conditions using collagenase. They were incubated under Gyrotory shaking (New Brunswick Scientific, New Brunswick, N.J.) at 80 rpm for 30 min in an isotonic buffer containing either 1 mM EGTA or 1.25 mM Ca 2+ . E-cadherin could be functionally blocked by treatment with MB2 anti-cadherin monoclonal antibody, starting 30 min before aggregation at 4° C. and continued throughout aggregation at 37° C. The volume % distribution in function of the particle diameter was measured by an LS200 particle size analyzer (Coulter Electronics Ltd., Luton, UK), at the start of the incubation at 37° C. (t0) and after 30 min (t30). 
     Slow Aggregation Assay 
     Slow aggregation was performed as described (Boterberg et al., 2000). Briefly, single-cell suspensions were seeded onto a semi-solid agar medium. After 24 h, aggregate formation was evaluated subjectively by phase contrast microscopy at 40 times magnification. 
     Example 1 
     Isolation of Novel α-catenin cDNAs 
     By performing BLAST analyses (Altschul et al., 1990) with αE-catenin sequences as a query, human EST sequences with GenBank Accession Nos. AA393647 and AA400832 (both originating from IMAGE clone-#728263) were found to be, similar but not identical to αE- or αN-catenin. By RT-PCR, we confirmed faint expression of this novel transcript in the PC3 prostate carcinoma cell line. Two consecutive 5′ RACE experiments provided us with a full-length cDNA sequence ( FIG. 1A ), which was deposited with GenBank under the Accession No AF091606. The 3024-bp sequence (SEQ ID NO:1) contains a Kozak-consensus start codon (Kozak, 1991) at position 176, preceded by a stop codon at position 137. A stop codon terminating the long open reading frame (ORF) is located at position 2861, and a putative poly-adenylation signal is seen at the 3′ untranslated region at 38 bp before the end of the sequence. The ORF encodes a protein of 895 amino acid residues (SEQ ID NO:2), with a predicted molecular weight of 100 kDa and an overall identity to αE-catenin (102 kDa) and αN-catenin (104 kD) of respectively 58 and 56% ( FIG. 1B ). The overall homology is higher, as similarities were calculated of 74 and 70% with respectively αE- and αN-catenin. This novel protein is therefore to be considered a true α-catenin family member, and was called αT-catenin because its transcript was discovered in testis-derived mRNA. When the three main homology domains, as proposed by Herrenknecht (Herrenknecht et al., 1991), are aligned separately, we noticed that sequence conservation is elevated up to 71.5% identity in the carboxy-terminal domains. In the alignment of the three full-length α-catenin proteins, high sequence conservation in previously described functional domains was observed, but also in other regions ( FIG. 2 ). 
     5′ RACE and RT-PCR experiments provided us with a full-length mouse αT-catenin cDNA sequence of 2979 bp ( FIG. 16 ; SEQ ID NO:4), which we cloned in the pGEMT®-easy vector. The obtained sequence is deposited with GenBank under the Accession No AF344871. This 2979-bp sequence contains a start codon at position 160, preceded by a stop codon at position 114. The stop codon terminating the ORF is located at position 2846. The ORF encodes a protein of 895 amino acid residues (SEQ ID NO:5), with a predicted molecular weight of 100 kDa. Indeed, after in vitro transcription/translation of plasmid pGEMTeasy-maTctn(1-2979), encoding the full-length mouse αT-catenin cDNA, a protein of approximately 100 kDa was detected ( FIG. 17A ). 
     The overall identity of the mouse αT-catenin to the human αT-catenin protein ( FIGS. 16B and 18 ) is about 95%, whereas the overall identity to mouse αE- and αN-catenin is about 66% and 67%. Hence, we can conclude that the cloned sequence is the mouse orthologue of human αT-catenin. 
     Example 2 
     Analysis of Human and Mouse αT-catenin Genes 
     By PCR screening, we isolated a human genomic PAC clone, called clone 320B7 (#1487). This clone was used to perform fluorescence in situ hybridization (FISH), which revealed the localization of the αT-catenin gene CTNNA3 on chromosome band 10q21 ( FIGS. 3A and 3B ). This localization was confirmed by monochromosomal hybrid mapping and by Genebridge4™ PCR screening. The obtained pattern of PCR products indeed pointed to localization on 10q21, close to marker D10S1461 ( FIG. 3C ). The region 10q21-23 has been identified as a candidate region for autosomal dominant dilated cardiomyopathy (Bowles et al., 1996). However, up to now, there was no indication of a candidate gene in that region. Partial sequencing of PAC clone #1487 revealed that the clone contains only the last exon of CTNNA3 (exon 18 in  FIGS. 4 and 5 ) besides intronic sequences preceding this exon. Upon database mining by BLAST algorithms, it was found that several genomic sequences (listed in Table 1 and 2) comprise boundaries of different exons of the CTNNA3 gene ( FIGS. 4 and 5 ). 
     In order to obtain a human genomic clone containing the 5′ end of CTNNA3, a human BAC library was screened by PCR with 5′ located primers. Clone 162A20 indeed contains the upstream genomic region but comprises only exons 1 and 2 with flanking intronic sequences, besides the upstream gene-regulatory 5′ sequences of the CTNNA3 gene. Indeed, from this genomic BAC clone about 1.2 kb of αT-catenin promoter region was sequenced ( FIG. 6A  and SEQ ID NO:3). This promoter sequence was found to bear several putative binding sites for muscle specific transcription factors as predicted by the “Matinspector-Transcription-Factor-binding-site search program” (Quandt et al., 1995). The functional relevance of such sites is suggested by the conservation across species ( FIG. 6B ) and indeed demonstrated for the MEF2C binding site ( FIG. 22 ). 
     All genomic data were deposited with GenBank under accession numbers AF282678 to AF282692 and AF391792 to AF391794. Primers were designed on intronic sequences flanking each exon in order to amplify each of the 18 CTNNA3 exons for applications such as analysis of mutations and polymorphisms by SSCP or denaturing HPLC (Table 3). At the amino acid level, most exon-exon boundaries (boxed in  FIG. 4 ) coincide with the boundaries determined for the αE-catenin CTNNA1 gene (Furukawa et al., 1994) and the CTNNAL1 gene (Janssens et al., 1999), pointing towards a common ancestor for all α-catenin genes. Interestingly, divergence in the genomic structure is observed for the CTNNA3 region covering exons 13 to 15. This domain corresponds to a region where the a-catulin gene CTNNAL1 also shows a divergent genomic organization, besides a “gap” in the open reading frame. 
     In order to obtain a mouse genomic clone containing the 5′ end of the Ctnna3 gene, a mouse BAC library was screened by PCR with primers located in the first three exons of the mouse Ctnna3 gene. Genomic clone 164N 16 was found to contain these three exons. Part of the mouse promoter sequence was determined (SEQ ID NO:6). 
     Example 3 
     αT-catenin Interacts Stronger with β-catenin than Other α-catenins Do 
     The colocalization of αT-catenin and β-catenin suggested interaction between these two proteins. We confirmed this interaction in the two-hybrid system, by cotransformation of full-length αT-catenin, αE-catenin, αN-catenin and α-catulin bait fusions with prey fusions containing an amino terminal part of β-catenin and nearly full-length plakoglobin ( FIG. 7A ). In this way, we confirmed the reported interaction between αE-catenin and β-catenin (Aberle et al., 1994; Funayama et al., 1995; Hulsken et al., 1994; Jou et al., 1995), and between αN-catenin and β-catenin (Sehgal et al., 1997). Interestingly, α-catulin does not interact with β-catenin. On the other hand, we demonstrated the presumptive interaction between αT-catenin and β-catenin, and noticed strong blue staining as compared to other positive interactions ( FIG. 7A ), suggesting that α-catenins bind to β-catenin with the following decreasing strength: αT-catenin &gt;αN-catenin &gt;αE-catenin. 
     When the interaction with β-catenin was quantified in the two-hybrid system, by using CPRG as a substrate for β-galactosidase, the values found for interaction with αT-catenin were about four times higher than these found for interaction with αE-catenin ( FIG. 7B ). This confirms that αT-catenin is able to interact in a stronger way to β-catenin than other α-catenins do. The interaction between αT-catenin and β-catenin could be confirmed by coimmunoprecipitation from lysates of HEK-293 cells overexpressing Myc-tagged αT-catenin ( FIG. 7C ), and also by coimmunoprecipitation from lysates of mouse heart and testis tissues ( FIG. 7D ). Thus, the interaction between αT-catenin and β-catenin occurs also in vivo. 
     Example 4 
     The αT-catenin Protein is Preferentially Expressed in Heart and Testis Tissues 
     A human cDNA Rapid Scan panel (OriGene Technologies, Rockville, Md.) was screened by PCR for αT-catenin expression. A first PCR reaction revealed expression in heart and testis tissues only, whereas a second, nested PCR amplified low amounts in some other tissues (brain, kidney, liver, skeletal muscle, fetal liver) ( FIG. 8A ). In comparison to the ubiquitously expressed αE-catenin ( FIG. 8A ), the novel αT-catenin shows a very restricted expression pattern. Besides the original testis-derived EST clone (Accession Nos. AA393647 and AA400832), one additional αT-catenin-specific EST sequence, derived from kidney, was identified recently (Accession No AW444927). Weak amplification of the αT-catenin transcript is indeed seen by us in kidney tissue ( FIG. 8A ). 
     These findings were confirmed by RT-PCR analysis ( FIG. 8B ) of several mouse tissues. The brain-specific expression of mouse αN-catenin mRNA is in line with the literature (Hirano et al., 1992). 
     We generated αT-catenin-specific polyclonal antibodies #952, specific for a carboxyterminal peptide of human αT-catenin with sequence C-KIHPLQVMSEFRGRQIY (SEQ ID NO:134). Using serum #952 on several mouse tissue protein lysates, we observed strong expression of αT-catenin in heart, lower levels in testis but hardly any αT-catenin protein in kidney, ovary, spleen or colon tissue, whereas these same tissues contain αE-catenin and β-catenin protein ( FIG. 8C ). This confirms the observed tissue-specificity of the αT-catenin mRNA ( FIG. 8B ) at the protein level. Monoclonal antibody 893 — 32C6S, generated against the same antigenic peptide as serum #952, is specific for human αT-catenin but does not cross-react with mouse αT-catenin ( FIG. 17B ). 
     Northern blot analysis confirmed the strong expression of mouse αT-catenin in heart and testis. Different strong signals, which appear smaller (±2000 nt and ±2500 nt) than the full-length mouse αT-catenin mRNA (2,979 nt) on agarose gel, suggest the expression of alternative transcripts of mouse αT-catenin in both organs ( FIG. 20 ). Also in Western blot analysis, some bands with smaller apparent molecular weights (of about 43 kDa, 66 kDa and 86 kDa) were detected in heart and testis lysates ( FIG. 21A ). Immunodetection of all these bands is competed out by addition of the αT-catenin-specific immunogenic peptide ( FIG. 21B ). Importantly, the smallest mRNA transcript is very abundant in testis. Correspondingly, the 66-kDa band on Western blot also appears to be stronger than the full-length mouse αT-catenin protein in lysates of testis. As the probes and antibody used are specific for respectively the 3′-end of the αT-catenin transcript or the C-terminal end of the αT-catenin protein, the alternative variants may be N-terminally truncated and possibly deficient for β-catenin binding. 
     Example 5 
     Human αT-catenin Can be Detected in Cardiomyocytes and Testis Tissue 
     Frozen sections of human heart and testis tissue were stained with the monoclonal 892 — 24D2S antibodies, shown to be specific for αT-catenin. Human αT-catenin protein can be detected in high amounts at intercalated discs, which are the specific heart cell-cell junctions to which actin microfilaments anchor ( FIG. 9A and 9B ). In testis, weaker but specific staining can be seen in interstitial elongated cells nearby the basement membrane of seminiferous tubules, which are probably peritubular myoid cells ( FIG. 11A and 11B ). These results suggest that αT-catenin protein is expressed in specific contractile cells of heart and testis tissues. 
     In double labeling experiments, it co-localizes with αE-catenin ( FIG. 10A ) as well as N-cadherin ( FIG. 10B ). The muscle marker desmin can be detected at both intercalated discs and sarcomeric Z-lines, whereas αT-catenin expression is confined to intercalated discs ( FIG. 10C ). In human testis, αT-catenin protein was detected mainly in spindle-shaped cells surrounding testicular tubuli ( FIG. 11 ). Interestingly, αT-catenin did not co-localize here with αE-catenin, as the latter showed an abundant intratubular expression pattern ( FIG. 11A ). The αT-catenin expressing cells in testis correspond to desmin-positive cells, and therefore could be identified as peritubular myoid cells ( FIG. 11B ). These stainings strongly suggest that αT-catenin expression is confined to specific muscle cell types 
     Example 6 
     αT-catenin Functionally Restores Cell Aggregation in α-catenin-Negative Cancer Cells 
     To assess whether αT-catenin binding to β-catenin has functional implications for the formation of cell-cell contacts, we carried out rescue experiments by overexpression of αT-catenin in round HCT-8/R1 cells lacking α-catenins (Vermeulen et al., 1995; Vermeulen et al., 1999). Vaccinia virus-mediated expression was used to obtain high transient transfection efficiencies (between 30 and 70%). Cell-cell adhesion was found to be restored if neighboring cells were expressing the ectopic protein that became enriched at the cell-cell contacts, whereas solitary expressing cells remained round with diffuse expression of the ectopic protein ( FIG. 12A ). Moreover, when GFP-tagged αT-catenin was overexpressed in neighboring cells, its enrichment in cell-cell contacts recruited both β-catenin and E-cadherin to these sites ( FIG. 12B ). However, when αT-catenin was overexpressed for longer time periods, it tended to form cytoplasmic rod-like aggregates. 
     In order to quantify the restoration of cell-cell adhesion by αT-catenin expression in HCT-8/R1 cells, these cells were transfected with a plasmid encoding Myc-tagged αT-catenin. A stable transfectant was cloned and called HCT-8/R1/T31. Western blotting with polyclonal antiserum #952 showed high expression of αT-catenin protein in this cell line. Immunofluorescent analysis of HCT-8/R1/T31 cells with anti-Myc antibodies showed that the αT-catenin-Myc protein was localized at restored cell-cell contacts ( FIG. 13 ). Components of the adherens junctions (E-cadherin, β-catenin and plakoglobin) were recruited to such αT-catenin positive sites (illustrated in  FIG. 13 ), but also desmosomes (desmoglein-2) and tight junctions (ZO-1, occludin) showed reassembly (illustrated in  FIG. 13 ). 
     By using the fast aggregation assay, we were able to show that HCT-8/RI/T31 cells are strongly aggregating in contrast to nonaggregating parental HCT-8/R1 cells ( FIG. 14 ). HCT-8/R1/T31 cells aggregated to similar extent as αE-catenin-positive HCT-8/E8 cells and αN-catenin-transfected HRpCαN2 cells, thus showing that αT-catenin is able to functionally restore aggregation. These findings were confirmed using another transfected cell line, HCT-8/E11R1/T14, stably expressing a GFP-αT-catenin fusion protein. 
     In a slow aggregation assay, αT-catenin-transfected HCT-8/R1/T31 cells were compacting even better than αE-catenin-positive HCT-8/E8 cells or αN-catenin-transfected HRpCαN2 cells ( FIG. 15 ). 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Corresponding 
                   
                   
                   
               
               
                   
                 Genomic Clone 
                 BAC 
                 Size (bp) 
               
               
                 CTNNA 
                 (Name or 
                 size (bp) 
                 of exon- 
                 position of 
               
               
                 3 exon 
                 GenBank 
                 as far as 
                 containing 
                 exon 
               
               
                 # 
                 Acc. No.) 
                 sequenced 
                 contig 
                 in contig 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 BAC 162A20 
                 &gt;9,000 
                 8,000 
                 2,500-2,600 
               
               
                 2 
                 BAC 162A20 
                 &gt;9,000 
                 1,000 
               
               
                   
                 AC009037.6 
                 30,769 
                 30,769 
                 7,602-7,499 
               
               
                 3 
                 AC026394.9 
                 180,805 
                 54,182 
                 25,892-26,084 
               
               
                   
                 AC027668.2 
                 32,000 
                 9,167 
                 91,612-91,804 
               
               
                 4 
                 AC026394.9 
                 180,805 
                 23,941 
                 17,471-17,637 
               
               
                 5 
                 AC026394.9 
                 180,805 
                 11,415 
                 541-660 
               
               
                 6 
                 AC022534.7 
                 185,679 
                 185,679 
                 56,887-56621  
               
               
                   
                 AC022401.3 
                 172,591 
                 172,591 
                 163,589-163,323 
               
               
                 7 
                 AC024602.5 
                 175,504 
                 175,504 
                 48,365-48,559 
               
               
                   
                 AC022534.7 
                 185,679 
                 185,679 
                 17,533-17,330 
               
               
                   
                 AQ163827.1 
                 396 
                 396 
                  16-289 
               
               
                   
                 AC022401.3 
                 172,591 
                 172,591 
                 124,236-124,033 
               
               
                 8 
                 n.a. 
                 n.a. 
                 n.a. 
                 n.a. 
               
               
                 9 
                 n.a. 
                 n.a. 
                 n.a. 
                 n.a. 
               
               
                 10 
                 AQ351427.1 
                 476 
                 476 
                 151-243 
               
               
                   
                 AC020642.6 
                 145,695 
                 145,695 
                 110,853-110,945 
               
               
                   
                 AQ355080.1 
                 677 
                 677 
                 151-243 
               
               
                 11 
                 AC023847.2 
                 80,449 
                 8,532 
                 7,255-7,411 
               
               
                   
                 AC027668.3 
                 200,268 
                 140,908 
                 93,854-93,699 
               
               
                 12 
                 AC016819.4 
                 136,685 
                 17,473 
                 4,170-4,370 
               
               
                   
                 AC027675.5 
                 160,439 
                 1,919 
                 561-761 
               
               
                 13 
                 AC027675.5 
                 160,439 
                 2,474 
                 208-359 
               
               
                 14 
                 AC021888.3 
                 174,470 
                 7,744 
                 6,707-6799 
               
               
                   
                 AC022017.5 
                 183,665 
                 141,718 
                 46,258-46,350 
               
               
                   
                 AC022024.2 
                 369,279 
                 2,919 
                 2,863-2,919 
               
               
                   
                 AL592075 
                 173,925 
                 7,743 
                 6,705-6,797 
               
               
                 15 
                 AC022017.5 
                 183,665 
                 141,718 
                 80,018-80,400 
               
               
                   
                 AC022024.2 
                 369,279 
                 8,442 
                 3,097-3,278 
               
               
                   
                 AP001355.2 
                 186,290 
                 15,133 
                 1,474-1,655 
               
               
                   
                 AL513126.4 
                 163,341 
                 77,255 
                 61,704-561,522 
               
               
                 16 
                 AC022024.2 
                 369,279 
                 2,571 
                 549-654 
               
               
                   
                 AP001355.2 
                 186,290 
                 11,104 
                 1,303-1,408 
               
               
                   
                 AC022017.5 
                 183,665 
                 21,147 
                 1,709-1,818 
               
               
                   
                 AL513126.4 
                 163,341 
                 68,244 
                 66,959-66,854 
               
               
                 17 
                 AP001355.2 
                 186,290 
                 6,741 
                 5,376-5,510 
               
               
                   
                 AL513126.4 
                 163,341 
                 68,244 
                 44,908-44,774 
               
               
                 18 
                 AP001355.2 
                 186,290 
                 46,144 
                 31,409-31,852 
               
               
                   
                 PAC 320B7 
                 &gt;1,000 
                 1,000 
               
               
                   
                 AC018979.6 
                 356,758 
                 3,084 
                 2,111-2,557 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 EXON 
                 exon size 
                 slice donor 
                 intron size 
                 slice acceptor 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   
                   
                   
                 &gt;0.5 
                 kb 
                 axxctgggtgaa  CAACGCTCA- 
                   
               
               
                   
                   
                   
                   
                   
                   
                               1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                                        M 
               
               
                 1 
                 170 
                 bp 
                 AAC-AGA-A AG    gt aagaatcaag 
                 &gt;23.2 
                 kb 
                 tttgtgcagc ag   -GC-AGC-ATG- 
               
               
                   
                   
                   
                         170 
                   
                   
                                171 
               
               
                   
               
               
                   
                   
                   
                  I   I   Q 
                   
                   
                                V   T   T 
               
               
                 2 
                 104 
                 bp 
                 ATA-ATC-C AG    gt attaatacca 
                 &gt;8.6 
                 kb 
                 ttccaatttt ag    GT T-ACC-ACA- 
               
               
                   
                   
                   
                         274 
                   
                   
                               275 
               
               
                   
               
               
                   
                   
                   
                  K   E 
                   
                   
                                S   E   A 
               
               
                 3 
                 193 
                 bp 
                 AAA-GAA-A--   gt gagtactcca 
                 67 
                 kb 
                 tgtatttttc ag   - GT -GAA-GCT- 
               
               
                   
                   
                   
                         467 
                   
                   
                                468 
               
               
                   
               
               
                   
                   
                   
                  V   S   A 
                   
                   
                                F   Q   R 
               
               
                 4 
                 167 
                 bp 
                 GTG-TCA-GCT   gt aagtaaaga. 
                 17.5 
                 kb 
                 tttcaatttc ag   TTT-CAA-AGG- 
               
               
                   
                   
                   
                         634 
                   
                   
                               635 
               
               
                   
               
               
                   
                   
                   
                  R   Q   Q 
                   
                   
                                D   L   K 
               
               
                 5 
                 120 
                 bp 
                 CGT-CAG-C AG    gt aggagtcaga. 
                 &gt;100 
                 kb 
                 ttaccttctc ag   GAC-TTA-AAA- 
               
               
                   
                   
                   
                         754 
                   
                   
                               755 
               
               
                   
               
               
                   
                   
                   
                  E   L   E 
                   
                   
                                N   L   I 
               
               
                 6 
                 264 
                 bp 
                 GAG-CTG-G AG    gt aagtcgggag. 
                 39.5 
                 kb 
                 ttcttctctt ag   AAT-TTA-ATT- 
               
               
                   
                   
                   
                        1018 
                   
                   
                               1019 
               
               
                   
               
               
                   
                   
                   
                  M   N   N 
                   
                   
                                 A   G   K 
               
               
                 7 
                 204 
                 bp 
                 ATG-AAC-AAC   gt aagtatagtt. 
                 &gt;50 
                 kb 
                 tcttcctttgc ag   GCT-GGA-AAA- 
               
               
                   
                   
                   
                        1222 
                   
                   
                                1223 
               
               
                   
               
               
                   
                   
                   
                  R   R   Q 
                   
                   
                                L   R   K 
               
               
                 8 
                 81 
                 bp 
                 CGC-AGA-C AG    gt gagggaagag. 
                 9 
                 kb 
                 atttcttctc ag   CTC-CGC-AAG- 
               
               
                   
                   
                   
                        1303 
                   
                   
                               1304 
               
               
                   
               
               
                   
                   
                   
                  L   V   E 
                   
                   
                                V   A   N 
               
               
                 9 
                 153 
                 bp 
                 CTT-GTA-G AG    gt aagcatgcta. 
                 &gt;150 
                 kb 
                 attgtattta ag    GT G-GCA-AAT- 
               
               
                   
                   
                   
                        1456 
                   
                   
                               1457 
               
               
                   
               
               
                   
                   
                   
                  C   P   Q 
                   
                   
                                I   I   N 
               
               
                 10 
                 93 
                 bp 
                 TGT-CCA-C AG    gt atgacaacta. 
                 100 
                 kb 
                 ttatctttat ag   ATT-ATT-AAT- 
               
               
                   
                   
                   
                        1549 
                   
                   
                               1550 
               
               
                   
               
               
                   
                   
                   
                  V   S 
                   
                   
                                E   S   H 
               
               
                 11 
                 157 
                 bp 
                 GTA-TCT-G--   gt atgtttttat. 
                 &gt;2.5 
                 kb 
                 atttacttac ag   -AA-AGC-CAT- 
               
               
                   
                   
                   
                      1706 
                   
                   
                                1707 
               
               
                   
               
               
                   
                   
                   
                  S   T 
                   
                   
                                V   I   P 
               
               
                 12 
                 201 
                 bp 
                 AGT-ACT-G--   gt aagtcagttg. 
                 &gt;7.2 
                 kb 
                 ttattttaac ag   -TA-ATT-CCT- 
               
               
                   
                   
                   
                      1907 
                   
                   
                                1908 
               
               
                   
               
               
                   
                   
                   
                  M   I   R 
                   
                   
                                    T   P 
               
               
                 13 
                 151 
                 bp 
                 ATG-ATT-CG-   gt aagtttgctt. 
                 &gt;6.7 
                 kb 
                 ttctttttat ag   --G-ACC-CCA- 
               
               
                   
                   
                   
                       2058 
                   
                   
                                 2059 
               
               
                   
               
               
                   
                   
                   
                  T   D   R 
                   
                   
                                A   K   M 
               
               
                 14 
                 94 
                 bp 
                 ACT-GAT-AGG   gt atgtcacttc. 
                 34 
                 kb 
                 cacatgtttt ag   GCT-AAG-ATG- 
               
               
                   
                   
                   
                        2152 
                   
                   
                               2153 
               
               
                   
               
               
                   
                   
                   
                  F   T   R 
                   
                   
                                    G   K 
               
               
                 15 
                 182 
                 bp 
                 TTC-ACT- AG -   gt aattatgtgg 
                 81 
                 kb 
                 atttttttcc ag   --G-GGC-AAA- 
               
               
                   
                   
                   
                       2334 
                   
                   
                                 2335 
               
               
                   
               
               
                   
                   
                   
                  A   N   Q 
                   
                   
                                C   P   D 
               
               
                 16 
                 106 
                 bp 
                 GCT-AAT-C AG    gt gagttactta. 
                 22 
                 kb 
                 atgcatattt ag   TGC-CCA-GAT- 
               
               
                   
                   
                   
                        2440 
                   
                   
                               2441 
               
               
                   
               
               
                   
                   
                   
                  M   S   A 
                   
                   
                                L   D   S 
               
               
                 17 
                 135 
                 bp 
                 ATG-TCA-GCT   gt gagtactgcc. 
                 46 
                 kb 
                 ttttccctac ag   TTG-GAC-AGT- 
               
               
                   
                   
                   
                        2575 
                   
                   
                               2576 
               
               
                   
               
               
                 18 
                 445 
                 bp 
                 ATA-TAT-A--  tttgggatcatt 
                 &gt;200 
                 kb 
               
               
                   
                   
                   
                      3019 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Overview of CTNNA3 exon-specific PCRs 
                   
               
             
          
           
               
                   
                   
                   
                 [MgC12] 
                 Product 
                 A.T. 
                   
               
               
                 Exon 
                 Upper Primer 
                 Lower Primer 
                 (mM) 
                 (bp) 
                 (° C.) 
               
               
                   
               
             
          
           
               
                 1 
                 FVR 2513 (SEQ ID NO:43) 
                 FVR 2514 (SEQ ID NO:44) 
                 2 
                 395 
                 61 
                   
               
               
                   
                 5′ TTGCTTGTAACCTCCCCTTT 3′ 
                 5′ GCGTGAAAGCCTACGTTTCT 3′ 
               
               
                   
               
               
                 2 
                 FVR 2515 (SEQ ID NO:45) 
                 FVR 2516 (SEQ ID NO:46) 
                 2 
                 407 
                 55.8 
               
               
                   
                 5′ TAATTTGTTACAGGACCTAAGC 3′ 
                 5′ TCTTCATTATTCATTTTTCCCAC 3′ 
               
               
                   
               
               
                 3 
                 FVR 2517 (SEQ ID NO:47) 
                 FVR 2518 (SEQ ID NO:48) 
                 2 
                 353 
                 59.6 
               
               
                   
                 5′ TATCCCAGGACTGTGTTCTC 3′ 
                 5′ TGGAGCCAAAAACAAAACA 3′ 
               
               
                   
               
               
                 4 
                 FVR 2519 (SEQ ID NO:49) 
                 FVR 2520 (SEQ ID NO:50) 
                 2 
                 252 
                 56.7 
               
               
                   
                 5′ TGGGGTTGTATTTTTCAGGTG 3′ 
                 5′ GCCAGGTTCAGAGAATGAAAT 3′ 
               
               
                   
               
               
                 5 
                 FVR 2521 (SEQ ID NO:51) 
                 FVR 2522 (SEQ ID NO:52) 
                 2 
                 406 
                 59.3 
               
               
                   
                 5′ GGACTGAACAGGCTTCTCAT 3′ 
                 5′ GCAGGAAGCCTAAAGTGTTC 3′ 
               
               
                   
               
               
                 6 
                 FVR 2523 (SEQ ID NO:53) 
                 FVR 2524 (SEQ ID NO:54) 
                 2 
                 404 
                 59.3 
               
               
                   
                 5′ GTCTTTCTCCCATAACCCATT 3′ 
                 5′ CGCCAACATGTGGATCTTCT 3′ 
               
               
                   
               
               
                 7 
                 FVR 2525 (SEQ ID NO:55) 
                 FVR 2526 (SEQ ID NO:56) 
                 2 
                 326 
                 57.8 
               
               
                   
                 5′ TGAAATGCCATGGAGCTCTAA 3′ 
                 5′ ACGGAAAGTATCTCAGCCTAT 3′ 
               
               
                   
               
               
                 8 
                 FVR 2958 (SEQ ID NO:57) 
                 FVR 2959 (SEQ ID NO:58) 
                 2 
                 156 
                 57.8 
               
               
                   
                 5′ CCATTGCTTATGTCGTTTTTTC 3′ 
                 5′ TTAGCCCCTATGTTTCTGACT 3′ 
               
               
                   
               
               
                 9 
                 FVR 2960 (SEQ ID NO:59) 
                 FVR 2961 (SEQ ID NO:60) 
                 2 
                 259 
                 56.5 
               
               
                   
                 5′ AGAAAAGGAAACACAGTGAACT 3′ 
                 5′ TTCTCCTGGACTTTAGTGAGTT 3′ 
               
               
                   
               
               
                 10 
                 FVR 2527 (SEQ ID NO:61) 
                 FVR 2528 (SEQ ID NO:62) 
                 2 
                 267 
                 62.4 
               
               
                   
                 5′ TGTTGCTGCATTTCCTTGCTA 3′ 
                 5′ GCGAGACCTGGTCTCAAAAA 3′ 
               
               
                   
               
               
                 11 
                 FVR 2529 (SEQ ID NO:63) 
                 FVR 2530 (SEQ ID NO:64) 
                 2 
                 300 
                 62.4 
               
               
                   
                 5′ GTGCCCATCACCCAAATAGT 3′ 
                 5′ CCATGCCTGTCCCAGTATTA 3′ 
               
               
                   
               
               
                 12 
                 FVR 2531 (SEQ ID NO:65) 
                 FVR 2532 (SEQ ID NO:66) 
                 2 
                 350 
                 61.0 
               
               
                   
                 5′ CCATTTCCAATGTGCACTCTA 3′ 
                 5′ AATTGTGCAGCTGTTATTGGC 3′ 
               
               
                   
               
               
                 13 
                 FVR 2956 (SEQ ID NO:67) 
                 FVR 2957 (SEQ ID NO:68) 
                 2 
                 217 
                 60.8 
               
               
                   
                 5′ ACAAAGAGGACAATCTTCTCC 3′ 
                 5′ TCAATGGAAGGAAAAGCAAAC 3′ 
               
               
                   
               
               
                 14 
                 FVR 2533 (SEQ ID NO:69) 
                 FVR 2534 (SEQ ID NO:70) 
                 2 
                 301 
                 64.3 
               
               
                   
                 5′ TGGGAGTGAAATTGCTGGGT 3′ 
                 5′ TAGAGGCTGCCTAGATTGAC 3′ 
               
               
                   
               
               
                 15 
                 FVR 2535 (SEQ ID NO:71) 
                 FVR 2536 (SEQ ID NO:72) 
                 2 
                 326 
                 56.7 
               
               
                   
                 5′ TGCTTTTGACATAGTGGAATGA 3′ 
                 5′ TGGCACTTGACACTCAGAGA 3′ 
               
               
                   
               
               
                 16 
                 FVR 2537 (SEQ ID NO:73) 
                 FVR 2538 (SEQ ID NO:74) 
                 2 
                 295 
                 56.7 
               
               
                   
                 5′ CCGTTCTTTGGGATGCGAAT 3′ 
                 5′ GGCAAAGAGCAATTAGCATGA 3′ 
               
               
                   
               
               
                 17 
                 FVR 2539 (SEQ ID NO:75) 
                 FVR 2540 (SEQ ID NO:76) 
                 2 
                 313 
                 59.3 
               
               
                   
                 5′ AAGGTACCTGCCATGTGAATA 3′ 
                 5′AGATTTGGTCATGTAAACAAGG 3′ 
               
               
                   
               
               
                 18 
                 FVR 2541 (SEQ ID NO:77) 
                 FVR 2542 (SEQ ID NO:78) 
                 2 
                 552 
                 62.8 
               
               
                   
                 5′ CCACGCTTGGCAATAATTAAC 3′ 
                 5′TGCTGACCATACAGAAATGAC 3′ 
               
               
                   
               
             
          
         
       
     
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