bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical impact of the differentiation profile assessed by immunophenotyping in patients with diffuse large B-cell lymphoma
Authors: Colomo Lluı́s , López-Guillermo Armando , Perales Marı́a , Rives Susana , Martı́nez Antonio , Bosch Francesc , Colomer Dolors , Falini Brunangelo , Montserrat Emili , Campo Elı́as
Published: December 2002

To analyze the relationship between immunophenotyping profile and main clinicopathological features and outcome in diffuse large B-cell lymphoma (DLBCL), we studied 128 patients (59 men, 69 women; median age 65 years) consecutively diagnosed with de novo DLBCL in a single institution. Cells from each patient were immunostained with CD20, CD79a, CD5, CD10, bcl-6, MUM1, CD138, bcl-2, p53, p27, and Ki-67 antibodies. Four immunophenotyping profiles were distinguished according to the pattern of differentiation: germinal center–CD10+ (GC-CD10+; CD10+/Bcl-6+/MUM1−/CD138−), germinal center–CD10− (GC-CD10−; CD10−/Bcl-6+/ MUM1−/CD138−), post–germinal center (pGC; CD10−/bcl-6±/ MUM1+/CD138−), and plasmablastic (CD10−/bcl-6−/MUM1+/CD138+). Rearrangement of bcl-2 was studied by polymerase chain reaction (PCR) in 57 patients. Single-antigen expression was as follows: CD5, 2%; CD10, 21%; bcl-6, 72%; MUM1, 54%; CD138, 2%; bcl-2, 59%; p53, 28%; p27, 40%. Distribution according to differentiation profiles was as follows: GC-CD10+, 24 patients, GC-CD10-, 30 patients; pGC, 60 patients; plasmablastic, 2 patients; other patterns, 12 patients. The pGC profile was associated with primary nodal presentation and immunoblastic morphology, whereas GC-CD10+ tumors showed disseminated disease, centroblastic morphology, bcl-2 rearrangement, and lower Ki-67 proliferative index. GC-CD10− patients more often presented with primary extranodal origin, early stage, normal lactic acid dehydrogenase (LDH) levels, and low or low/intermediate International Prognostic Index (IPI) scores than the others. However, no significant difference was found in terms of response or overall survival (OS) according to these profiles. Expression of bcl-2 was associated with advanced stage, high or high-intermediate IPI, and poor OS. Expression of bcl-2 maintained predictive value in multivariate analysis, with stage and LDH. In conclusion, differentiation profile was associated with particular clinicopathological features but was not essential to predicting outcome in DLBCL patients.
The myeloid master regulator transcription factor PU.1 is inactivated by AML1-ETO in t(8;21) myeloid leukemia
Authors: Vangala Rajani K. , Heiss-Neumann Marion S. , Rangatia Janki S. , Singh Sheo M. , Schoch Claudia , Tenen Daniel G. , Hiddemann Wolfgang , Behre Gerhard
Published: December 2002

The transcription factor PU.1 plays a pivotal role in normal myeloid differentiation. PU.1−/− mice exhibit a complete block in myeloid differentiation. Heterozygous PU.1 mutations were reported in some patients with acute myeloid leukemia (AML), but not in AML with translocation t(8;21), which gives rise to the fusion geneAML1-ETO. Here we report a negative functional impact of AML1-ETO on the transcriptional activity of PU.1. AML1-ETO physically binds to PU.1 in t(8;21)+ Kasumi-1 cells. AML1-ETO binds to the β3β4 region in the DNA-binding domain of PU.1 and displaces the coactivator c-Jun from PU.1, thus down-regulating the transcriptional activity of PU.1. This physical interaction of AML1-ETO and PU.1 did not abolish the DNA-binding capacity of PU.1. AML1-ETO down-regulates the transactivation capacity of PU.1 in myeloid U937 cells, and the expression levels of PU.1 target genes in AML French-American-British (FAB) subtype M2 patients with t(8;21) were lower than in patients without t(8;21). Conditional expression of AML1-ETO causes proliferation in mouse bone marrow cells and inhibits antiproliferative function of PU.1. Overexpression of PU.1, however, differentiates AML1-ETO–expressing Kasumi-1 cells to the monocytic lineage. Thus, the function of PU.1 is down-regulated by AML1-ETO in t(8;21) myeloid leukemia, whereas overexpression of PU.1 restores normal differentiation.
Thrombogenicity of β2-glycoprotein I–dependent antiphospholipid antibodies in a photochemically induced thrombosis model in the hamster
Authors: Jankowski Milosz , Vreys Ingrid , Wittevrongel Christine , Boon Doris , Vermylen Jos , Hoylaerts Marc. F. , Arnout Jef
Published: December 2002

We previously showed that β2-glycoprotein I (β2GPI)–dependent lupus anticoagulants (LAs) form bivalent antigen-antibody complexes with high affinity for phospholipids; these complexes are responsible for their in vitro anticoagulant effect. We now studied the role of these bivalent complexes in arterial thrombosis in the hamster. Three monoclonal antibodies (mAbs) raised against human β2GPI were selected on the basis of their cross-reactivity with hamster β2GPI. Two of these, one with LA activity, 5H2, and one with only anticardiolipin properties, 11E8, were infused at 0 to 10 mg/kg prior to photochemically induced vessel damage. 5H2 promoted thrombus formation dose dependently, raising the thrombus size from 6.0 arbitrary units (AU) in controls (n = 9) to 65.0 AU in the high-dose group (10 mg/kg, n = 6, P = .007). The LA−mAb 11E8 and mAb 27A8, reactive with human β2GPI exclusively, did not significantly promote thrombus formation. In a second set of experiments, intact mAb 5H2 was compared to its fragments. Intact mAb 5H2 at 3.3 mg/kg and the equimolar dose of F(ab′)2 fragments (2.2 mg/kg) promoted thrombus formation equally well (55.8 AU, n = 8 and 62.5 AU, n = 7, respectively); mAb 5H2-derived Fab′ fragments were inactive. Immunohistochemical analysis showed platelet-rich thrombi, with 5H2 or its F(ab′)2fragments mainly bound to individual platelets. Our results indicate that bivalent immune complex formation plays an important role in the genesis of arterial thrombosis by certain antiphospholipid antibodies. Cellular activation via the Fc portion of these immune complexes, however, is not essential, because F(ab′)2 fragments of 5H2 still promote thrombus formation.
A novel rapid single nucleotide polymorphism (SNP)–based method for assessment of hematopoietic chimerism after allogeneic stem cell transplantation
Authors: Hochberg Ephraim P. , Miklos David B. , Neuberg Donna , Eichner Daniel A. , McLaughlin Stephen F. , Mattes-Ritz Alex , Alyea Edwin P. , Antin Joseph H. , Soiffer Robert J. , Ritz Jerome
Published: December 2002

A major end point of nonmyeloablative hematopoietic stem cell transplantation is the attainment of either mixed chimerism or full donor hematopoiesis. Because the majority of human genetic disparity is generated by single nucleotide polymorphisms (SNPs), direct measurement of SNPs should provide a robust tool for the detection and quantitation of chimerism. Using pyrosequencing, a rapid quantitative sequencing technology, we developed a SNP-based assay for hematopoietic chimerism. Based on 14 SNPs with high allele frequencies, we were able to identify at least 1 informative SNP locus in 55 patients with HLA-identical donors. The median number of informative SNPs in related pairs was 5 and in unrelated pairs was 8 (P < .0001). Assessment of hematopoietic chimerism in posttransplantation DNA was shown to be quantitative, accurate, and highly reproducible. The presence of 5% donor cells was reliably detected in replicate assays. Compared with current measures of engraftment based on identification of short tandem repeats (STRs), variable number of tandem repeats (VNTRs), or microsatellite polymorphisms, this SNP-based method provides a more rapid and quantitative assessment of chimerism. A large panel of SNPs enhances the ability to identify an informative marker in almost all patient/donor pairs and also facilitates the simultaneous use of multiple markers to improve the statistical validity of chimerism measurements. The inclusion of SNPs that encode minor histocompatibility antigens or other genetic polymorphisms that may influence graft-versus-host disease or other transplantation outcomes can provide additional clinically relevant data. SNP-based assessment of chimerism is a promising technique that will assist in the analysis of outcomes following transplantation.
Exogenous stress proteins enhance the immunogenicity of apoptotic tumor cells and stimulate antitumor immunity
Authors: Feng Hanping , Zeng Yi , Graner Michael W. , Likhacheva Anna , Katsanis Emmanuel
Published: December 2002

We have previously reported that apoptotic tumor cells can be either immunogenic or nonimmunogenic in vivo, depending on whether or not these cells are heat stressed before induction of apoptosis. Stressed apoptotic cells express heat shock proteins on their plasma membranes and dendritic cells are capable of distinguishing them from nonstressed apoptotic cells. Here we provide evidence that when purified heat shock protein 70 or chaperone-rich cell lysate (CRCL) from syngeneic normal tissue is used as an adjuvant with nonimmunogenic apoptotic tumor cells in vaccination, potent antitumor immunity can be generated. This antitumor immunity is mediated by T cells because antitumor effects are not observed in either severe combined immunodeficiency or T cell–depleted mice. We further demonstrate that vaccination of mice with apoptotic tumor cells mixed with liver-derived CRCL as adjuvant were capable of enhancing the production of TH1 cytokines, inducing specific cytotoxic T lymphocytes and eliciting long-lasting antitumor immunity. Stress proteins from autologous normal tissue components therefore can serve as danger signals to enhance the immunogenicity of apoptotic tumor cells and stimulate tumor-specific immunity
Relationship between hepatocellular injury and transfusional iron overload prior to and during iron chelation with desferrioxamine: a study in adult patients with acquired anemias
Authors: Jensen Peter D. , Jensen Finn T. , Christensen Thorkil , Nielsen Johan L. , Ellegaard Joergen
Published: December 2002

The role of iron overload as cause of liver dysfunction has never been studied in detail in patients without concomitant hepatotropic infections who receive multiple transfusions. We therefore investigated the relationship between the extent of hepatocellular injury as reflected by serum levels of aminotransferases (alanine aminotransferase [ALT] and aspartate aminotransferase [AST]) and several iron status indices in 39 anti–hepatitis C virus-negative (HCV−) nonthalassemic patients with transfusional iron overload owing to acquired anemias. In 12 patients, we monitored aminotransferase levels and indices of iron status during iron chelation treatment. Before treatment, elevated aminotransferase activity was seen only at liver iron concentrations more than 300 μM/g. During treatment all aminotransferase values were normal if the liver iron concentration returned below 350 μM/g. At the start of treatment, ALT (R2 = 0.64, P = .006) and AST activity (R2 = 0.57,P = .01) were closely related to urinary iron excretion, reflecting the size of the chelatable or the labile iron pool. During treatment, a comparable pattern was seen and the urinary iron excretion was also directly related to the liver iron concentration at concentrations above approximately 400 μM/g. All elevated ALT values were associated with a urinary iron excretion more than 15 mg/24 h. In conclusion, our data suggest the existence of a critical liver iron concentration range, above which hepatocellular injury is seen. The extent of the injury seems to be determined mainly by the size of the chelatable or labile iron pool, supporting the concept of the labile iron pool as the compartment directly involved in iron toxicity. Our findings may be helpful in establishing criteria for safety from complications of transfusional iron overload.
Noninvasive measurement of iron: report of an NIDDK workshop
Authors: Brittenham Gary M. , Badman David G.
Published: December 2002

An international workshop on the noninvasive measurement of iron was conducted by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) on April 17, 2001, to assess the current state of the science and to identify areas needing further investigation. The workshop concluded that a clear clinical need is evident for quantitative, noninvasive, safe, accurate, and readily available means of measuring body storage iron to improve the diagnosis and management of patients with iron overload from such disorders as hereditary hemochromatosis, thalassemia major, sickle cell disease, aplastic anemia, and myelodysplasia, among others. Magnetic resonance imaging (MRI) potentially provides the best available technique for examining the 3-dimensional distribution of excess iron in the body, but further research is needed to develop means of making measurements quantitative. Biomagnetic susceptometry provides the only noninvasive method to measure tissue iron stores that has been calibrated, validated, and used in clinical studies, but the complexity, cost, and technical demands of the liquid-helium–cooled superconducting instruments required at present have restricted clinical access to the method. The workshop identified basic and clinical research opportunities for deepening our understanding of the physical properties of iron and iron toxicity, for further investigation of MRI as a method for quantitative determinations of tissue iron, especially in liver, heart and brain, and for development of improved methods and more widely available instrumentation for biomagnetic susceptometry.
Recombinant PfEMP1 peptide inhibits and reverses cytoadherence of clinical Plasmodium falciparum isolates in vivo
Authors: Yipp Bryan G. , Baruch Dror I. , Brady Ciaran , Murray Allan G. , Looareesuwan Sornchai , Kubes Paul , Ho May
Published: December 2002

The parasite ligand Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) and host endothelial receptors represent potential targets for antiadhesive therapy for cytoadherence. In the present study, the major host receptor CD36 was targeted in vitro and in vivo with a recombinant peptide, PpMC-179, corresponding to the minimal CD36-binding domain from the cysteine-rich interdomain region 1 (CIDR1) within the MCvar1 PfEMP1. The in vitro inhibitory effect of PpMC-179 on human dermal microvascular endothelial cells (HDMECs) expressing multiple relevant adhesion molecules was investigated using a parallel-plate flow chamber. Pretreatment of endothelial monolayers with PpMC-179 (2 μM) inhibited the adhesion of infected erythrocytes (IRBCs) from all clinical isolates tested by 84.4% on resting and 62.8% on tumor necrosis factor α (TNF-α)–stimulated monolayers. Adhesion to stimulated cells was further inhibited (90.4%) when PpMC-179 was administered with an inhibitory anti–intercellular adhesion molecule 1 (ICAM-1) monoclonal antibody 84H10 (5 μg/mL). To determine the in vivo effectiveness of PpMC-179, we used a human/severe combined immunodeficiency (SCID) mouse chimeric model that allowed direct visualization of cytoadherence on intact human microvasculature. In unstimulated skin grafts, PpMC-179 inhibited adhesion by 86.3% and by 84.6% in TNF-α–stimulated skin grafts. More importantly, PpMC-179 administration resulted in the detachment of already adherent IRBCs by 80.7% and 83.3% on resting and stimulated skin grafts, respectively. The antiadhesive effect of PpMC-179 was rapid and sustained in vivo for at least 30 minutes. Our data indicate that targeting cytoadhesion in vivo is feasible and may offer a rapid antimalarial therapy.
A new locus on chromosome 18 that influences normal variation in activated protein C resistance phenotype and factor VIII activity and its relation to thrombosis susceptibility
Authors: Soria José Manuel , Almasy Laura , Souto Joan Carles , Buil Alfonso , Martı́nez-Sánchez Elisabeth , Mateo José , Borrell Montserrat , Stone William H. , Lathrop Mark , Fontcuberta Jordi , Blangero John
Published: December 2002

Activated protein C resistance (APCR) is the most prevalent risk factor for thrombosis, accounting for 20% to 60% of familial thrombophilia. A mutation in the F5 gene, factor V Leiden (FVL), is a major determinant of pathological APCR in some populations. However, APCR predicts risk for thrombosis independently of FVL. This suggests that other genetic factors may influence risk of thrombosis through quantitative variation in APCR. To search for these unknown loci, we conducted a genome-wide linkage screen for genes affecting normal variation in APCR in the 21 Spanish families from the Genetic Analysis of Idiopathic Thrombophilia (GAIT) project. Conditional on FVL, the strongest linkage signal for APCR was found on chromosome 18 near D18S53. Bivariate linkage analyses with a genetically correlated trait, levels of clotting factor VIII, strengthened evidence for the chromosome 18 quantitative trait locus (QTL; logarithm of the odds [LOD], 4.5; P = 3.08 × 10−5). However, the region on chromosome 1 that contains the F5structural gene showed little evidence of linkage to APCR (LOD, < 1). This indicates that apart from the FVL, the F5 locus itself plays a relatively minor role in normal variation in APCR, including the HR2 haplotype polymorphisms. A second bivariate analysis of APCR with thrombosis liability suggested that this QTL also influences the risk of thrombosis (P = .0016). These results indicate that a locus on chromosome 18 pleiotropically influences normal variation in the APCR phenotype and factor VIII (FVIII) levels as well as susceptibility to thrombosis. Importantly, there are no known thrombosis-related candidate genes in this region, implying that this QTL represents a completely novel thrombosis risk factor.
Acute sickle cell hepatopathy represents a potential contraindication for percutaneous liver biopsy
Authors: Zakaria Nada , Knisely Alex , Portmann Bernard , Mieli-Vergani Giorgina , Wendon Julia , Arya Roopen , Devlin John
Published: December 2002

After several complications following percutaneous liver biopsy in patients with sickle cell disease, we reviewed our experience. We examined 14 patients with sickle cell disease who underwent a percutaneous liver biopsy. Clinicopathologic findings were correlated with outcome. Of 14 patients, 5 (36%) suffered serious hemorrhage; 4 died (80%; 28% of all patients). None of the 9 patients without biopsy complications was in an acute sickling crisis at the time of biopsy; 4 of 5 patients with complications were in acute sickling crisis. Of the 5 patients with complications, 4 underwent biopsy for an emergency indication. Chronic venous outflow obstruction, marked hepatic sequestration of erythrocytes, and sinusoidal dilatation were strongly associated with complications. Data obtained by biopsy in group 1 were not of substantial value in clinical management, in contrast to group 2 (8/9; 89%). Acute hepatic disease complicating sickle cell anemia represents a newly identified contraindication to percutaneous liver biopsy.
Homeostasis of telomere length rather than telomere shortening after allogeneic peripheral blood stem cell transplantation
Authors: Roelofs Helene , de Pauw Elmar S. D. , Zwinderman Aeilko H. , Opdam Sonja M. , Willemze Roel , Tanke Hans J. , Fibbe Willem E.
Published: December 2002

Hematopoietic reconstitution after stem cell transplantation requires excessive replicative activity because of the limited number of stem cells that are used for transplantation. Telomere shortening has been detected in hematopoietic cells after bone marrow transplantation. This has been thought to result from excessive replication of the stem cells, with putative concomitant reduction of their replicative potential. Hematopoietic stem cells from cytokine-mobilized peripheral blood are increasingly used for stem cell transplantation. These grafts contain higher numbers of hematopoietic stem cells, resulting in a faster hematopoietic reconstitution. We have performed a combined prospective and cross-sectional study of hematologic recovery and telomere length dynamics in the immediate reconstitution period after allogeneic T-cell–depleted blood stem cell transplantation. We analyzed hematologic recovery and telomere length of granulocytes, monocytes, B cells, and T-cell subsets in 30 donor/recipient combinations. We found fast recovery in combination with transient telomere shortening in the myeloid lineages. This initial reduction of telomere length was followed by an increase in telomere length to such an extent that 1 year after transplantation the telomere length in recipient cells was similar to the telomere length in donor-derived cells. Therefore, our data indicate telomere length homeostasis after peripheral blood stem cell transplantation, implying no loss of replicative capacity of the stem cells. Our data indicate that fast expansion is accompanied by a reduction of telomere length and that telomere length homeostasis is achieved by de novo generation of hematopoietic cells from stem cells without transplantation-related telomere loss.
HK Utrecht: missense mutation in the active site of human hexokinase associated with hexokinase deficiency and severe nonspherocytic hemolytic anemia
Authors: van Wijk Richard , Rijksen Gert , Huizinga Eric G. , Nieuwenhuis Hendrik K. , van Solinge Wouter W.
Published: December 2002

Hexokinase deficiency is a rare autosomal recessive disease with a clinical phenotype of severe hemolysis. We report a novel homozygous missense mutation in exon 15 (c.2039C>G, HK [hexokinase] Utrecht) of HK1, the gene that encodes red blood cell–specific hexokinase-R, in a patient previously diagnosed with hexokinase deficiency. The Thr680Ser substitution predicted by this mutation affects a highly conserved residue in the enzyme's active site that interacts with phosphate moieties of adenosine diphosphate, adenosine triphosphate (ATP), and inhibitor glucose-6-phosphate. We correlated the molecular data to the severe clinical phenotype of the patient by means of altered enzymatic properties of partially purified hexokinase from the patient, notably with respect to Mg2+-ATP binding. These kinetic properties contradict those obtained from a recombinant mutant brain hexokinase-I with the same Thr680Ser substitution. This contradiction thereby stresses the valuable contribution of studying patients with hexokinase deficiency to achieve a better understanding of hexokinase's key role in glycolysis.
High-level expression of hemoglobin A in human thalassemic erythroid progenitor cells following lentiviral vector delivery of an antisense snRNA
Authors: Vacek Marla M. , Ma Hong , Gemignani Federica , Lacerra Giuseppina , Kafri Tal , Kole Ryszard
Published: December 2002

Mutations at nucleotides 654, 705, or 745 in intron 2 of the human β-globin gene activate aberrant 3′ and 5′ splice sites within the intron and prevent correct splicing of β-globin pre-mRNA, resulting in inhibition of β-globin synthesis and in consequence β-thalassemia. Transfection of HeLa cells expressing the 3 thalassemic mutants with modified U7 snRNA (U7.623), containing a sequence antisense to a region between the aberrant splice sites, reduced the incorrect splicing of pre-mRNA and led to increased levels of the correctly spliced β-globin mRNA and protein. A lentiviral vector carrying the U7.623 gene was effective in restoration of correct splicing in the model cell lines for at least 6 months. Importantly, the therapeutic value of this system was demonstrated in hematopoietic stem cells and erythroid progenitor cells from a patient with IVS2-745/IVS2-1 thalassemia. Twelve days after transduction of the patient cells with the U7.623 lentiviral vector, the levels of correctly spliced β-globin mRNA and hemoglobin A were approximately 25-fold over background. These results should be regarded as a proof of principle for lentiviral vector–based gene therapy for β-thalassemia.
Arg2074Cys missense mutation in the C2 domain of factor V causing moderately severe factor V deficiency: molecular characterization by expression of the recombinant protein
Authors: Duga Stefano , Montefusco Maria Claudia , Asselta Rosanna , Malcovati Massimo , Peyvandi Flora , Santagostino Elena , Mannucci Pier Mannuccio , Tenchini Maria Luisa
Published: December 2002

Factor V (FV) deficiency is a rare bleeding disorder whose genetic basis has been described in a relatively small number of cases. Among a total of 12 genetic defects reported in severely or moderately severe deficient patients, 3 were missense mutations and in no case was the mechanism underlying the deficiency explored at the molecular level. In this study, a homozygous missense mutation at cDNA position 6394 in exon 23 of the FV gene was identified in a 22-year-old Italian patient. This mutation causes the replacement of arginine 2074 with a cysteine residue (Arg2074Cys) in the C2 domain of the protein. The effect of the Arg2074Cys mutation on FV secretion, stability, and activity was investigated. Site-directed mutagenesis of FV cDNA was used to introduce the identified mutation, and wild-type as well as mutant FV proteins were expressed by transient transfection in COS-1 cells. An enzyme immunoassay detected low FV antigen levels both in the conditioned media of cells expressing the mutant protein and in cell lysates. Metabolic labeling and pulse-chase experiments confirmed that the mutation caused an impaired secretion of FV associated with rapid intracellular degradation. In addition, evaluation of wild-type and mutant coagulant activity demonstrated that the FV molecules carrying the Arg2074Cys mutation have reduced activity. These findings, beside confirming the structural and functional importance of the arginine 2074 residue, demonstrate that its substitution with a cysteine impairs both FV secretion and activity.
Mac-1 (CD11b/CD18) is crucial for effective Fc receptor–mediated immunity to melanoma
Authors: van Spriel Annemiek B. , van Ojik Heidi H. , Bakker Annie , Jansen Marco J. H. , van de Winkel Jan G. J.
Published: December 2002

Antibody-reliant destruction of tumor cells by immune effector cells is mediated by antibody-dependent cellular cytotoxicity, in which Fc receptor (FcR) engagement is crucial. This study documents an important role for the β2 integrin Mac-1 (CD11b/CD18) in FcR-mediated protection against melanoma. CD11b-deficient mice, those that lack Mac-1, were less protected by melanoma-specific monoclonal antibody TA99 than wild-type (WT) mice. Significantly more lung metastases and higher tumor loads were observed in Mac-1−/− mice. Histologic analyses revealed no differences in neutrophil infiltration of lung tumors between Mac-1−/− and WT mice. Importantly, Mac-1−/−phagocytes retained the capacity to bind tumor cells, implying that Mac-1 is essential during actual FcR-mediated cytotoxicity. In summary, this study documents Mac-1 to be required for FcR-mediated antimelanoma immunity in vivo and, furthermore, supports a role for neutrophils in melanoma rejection.
GA-binding protein (GABP) and Sp1 are required, along with retinoid receptors, to mediate retinoic acid responsiveness of CD18 (β2 leukocyte integrin): a novel mechanism of transcriptional regulation in myeloid cells
Authors: Bush Thomas S. , St. Coeur Michele , Resendes Karen K. , Rosmarin Alan G.
Published: December 2002

CD18 (β2 leukocyte integrin) is transcriptionally regulated in myeloid cells, but the mechanisms that increase its expression in response to retinoic acid (RA) have not been defined. The CD18 promoter was activated by RA treatment in stably transfected U937 myeloid cells. We identified a retinoic acid response element (RARE) that lies nearly 900 nucleotides upstream of the CD18 transcriptional start site that was bound by the RA receptors, retinoic acid receptor (RAR) and retinoic X receptor (RXR). This RARE accounted for one half of the RA responsiveness of CD18. However, unexpectedly, one half of the dynamic response to RA was mediated by the 96-nucleotide CD18 minimal promoter, which lacks a recognizable RARE. Binding sites for the ets transcription factor, GA-binding protein (GABP), and Sp1 were required for full RA responsiveness of both the CD18 minimal promoter and the full-length promoter. The ets sites conferred RA responsiveness on an otherwise unresponsive heterologous promoter, and RA responsiveness was directly related to the number of ets sites. The transcriptional coactivator p300/CBP physically interacted with GABP in vivo, and p300 increased the responsiveness of the CD18 promoter to RA. These studies demonstrate a novel role for non-RAR transcription factors in mediating RA activation in myeloid cells. They support the concept that transcription factors other than RARs are required for RA-activated gene expression. We hypothesize that a multiprotein complex—an enhanceosome—that includes GABP, other transcription factors, and coactivators, dynamically regulates CD18 expression in myeloid cells.
Induction and patterning of the telencephalon inXenopus laevis
Authors: Lupo Giuseppe , Harris William A. , Barsacchi Giuseppina , Vignali Robert
Published: December 2002

We report an analysis of the tissue and molecular interplay involved in the early specification of the forebrain, and in particular telencephalic, regions of the Xenopus embryo. In dissection/recombination experiments,different parts of the organizer region were explanted at gastrula stage and tested for their inducing/patterning activities on either naive ectoderm or on midgastrula stage dorsal ectoderm. We show that the anterior dorsal mesendoderm of the organizer region has a weak neural inducing activity compared with the presumptive anterior notochord, but is able to pattern either neuralized stage 10.5 dorsal ectoderm or animal caps injected with BMP inhibitors to a dorsal telencephalic fate. Furthermore, we found that a subset of this tissue, the anterior dorsal endoderm, still retains this patterning activity. At least part of the dorsal telencephalic inducing activities may be reproduced by the anterior endoderm secreted molecule cerberus, but not by simple BMP inhibition, and requires the N-terminal region of cerberus that includes its Wnt-binding domain. Furthermore, we show that FGF action is both necessary and sufficient for ventral forebrain marker expression in neuralized animal caps, and possibly also required for dorsal telencephalic specification. Therefore, integration of organizer secreted molecules and of FGF, may account for patterning of the more rostral part of XenopusCNS.
Control ofDrosophilaeye specification by Wingless signalling
Authors: Baonza Antonio , Freeman Matthew
Published: December 2002

Organ formation requires early specification of the groups of cells that will give rise to specific structures. The Wingless protein plays an important part in this regional specification of imaginal structures inDrosophila, including defining the region of the eye-antennal disc that will become retina. We show that Wingless signalling establishes the border between the retina and adjacent head structures by inhibiting the expression of the eye specification genes eyes absent, sine oculisand dachshund. Ectopic Wingless signalling leads to the repression of these genes and the loss of eyes, whereas loss of Wingless signalling has the opposite effects. Wingless expression in the anterior of wild-type discs is complementary to that of these eye specification genes. Contrary to previous reports, we find that under conditions of excess Wingless signalling, eye tissue is transformed not only into head cuticle but also into a variety of inappropriate structures.
Gene profiling during neural induction inXenopus laevis:regulation of BMP signaling by post-transcriptional mechanisms and TAB3, a novel TAK1-binding protein
Authors: Muñoz-Sanjuán Ignacio , Bell Esther , Altmann Curtis R. , Vonica Alin , Brivanlou Ali H.
Published: December 2002

The earliest decision in vertebrate neural development is the acquisition of a neural identity by embryonic ectodermal cells. The default model for neural induction postulates that neural fate specification in the vertebrate embryo occurs by inhibition of epidermal inducing signals in the gastrula ectoderm. Bone morphogenetic proteins (BMPs) act as epidermal inducers, and all identified direct neural inducers block BMP signaling either intra- or extracellularly. Although the mechanism of action of the secreted neural inducers has been elucidated, the relevance of intracellular BMP inhibitors in neural induction is not clear. In order to address this issue and to identify downstream targets after BMP inhibition, we have monitored the transcriptional changes in ectodermal explants neuralized by Smad7 using a Xenopus laevis 5000-clone gastrula-stage cDNA microarray. We report the identification and initial characterization of 142 genes whose transcriptional profiles change in the neuralized explants. In order to address the potential involvement during neural induction of genes identified in the array, we performed gain-of-function studies in ectodermal explants. This approach lead to the identification of four genes that can function as neural inducers inXenopus and three others that can synergize with known neural inducers in promoting neural fates. Based on these studies, we propose a role for post-transcriptional control of gene expression during neural induction in vertebrates and present a model whereby sustained BMP inhibition is promoted partly through the regulation of TGFβ activated kinase (TAK1) activity by a novel TAK1-binding protein (TAB3).
Expression of pair-rule gene homologues in a chelicerate: early patterning of the two-spotted spider miteTetranychus urticae
Authors: Dearden Peter K. , Donly Cameron , Grbić Miodrag
Published: December 2002

Embryo segmentation has been studied extensively in the fruit fly,Drosophila. These studies have demonstrated that a mechanism acting with dual segment periodicity is required for correct patterning of the body plan in this insect, but the evolutionary origin of the mechanism, the pair-rule system, is unclear. We have examined the expression of the homologues of two Drosophila pair-rule genes, runt andpaired (Pax Group III), in segmenting embryos of the two-spotted spider mite (Tetranychus urticae Koch). Spider mites are chelicerates, a group of arthropods that diverged from the lineage leading toDrosophila at least 520 million years ago. In T. urticae,the Pax Group III gene Tu-pax3/7 was expressed during patterning of the prosoma, but not the opisthosoma, in a series of stripes which appear first in even numbered segments, and then in odd numbered segments. The miterunt homologue (Tu-run) in contrast was expressed early in a circular domains that resolved into a segmental pattern. The expression patterns of both of these genes also indicated they are regulated very differently from their Drosophila homologues. The expression pattern of Tu-pax3/7 lends support to the possibility that a pair-rule patterning mechanism is active in the segmentation pathways of chelicerates.
Shh signaling within the dental epithelium is necessary for cell proliferation, growth and polarization
Authors: Gritli-Linde Amel , Bei Marianna , Maas Richard , Zhang Xiaoyan M. , Linde Anders , McMahon Andrew P.
Published: December 2002

Sonic hedgehog (Shh), a member of the mammalian Hedgehog(Hh) family, plays a key role during embryogenesis and organogenesis. Tooth development, odontogenesis, is governed by sequential and reciprocal epithelial-mesenchymal interactions. Genetic removal of Shh activity from the dental epithelium, the sole source of Shh during tooth development, alters tooth growth and cytological organization within both the dental epithelium and mesenchyme of the tooth. In this model it is not clear which aspects of the phenotype are the result of the direct action of Shh on a target tissue and which are indirect effects due to deficiencies in reciprocal signalings between the epithelial and mesenchymal components. To distinguish between these two alternatives and extend our understanding of Shh's actions in odontogenesis, we have used the Cre-loxP system to remove Smoothened(Smo) activity in the dental epithelium. Smo, a seven-pass membrane protein is essential for the transduction of all Hh signals. Hence, removal of Smo activity from the dental epithelium should block Shh signaling within dental epithelial derivatives while preserving normal mesenchymal signaling. Here we show that Shh-dependent interactions occur within the dental epithelium itself. The dental mesenchyme develops normally up until birth. In contrast,dental epithelial derivatives show altered proliferation, growth,differentiation and polarization. Our approach uncovers roles for Shh in controlling epithelial cell size, organelle development and polarization. Furthermore, we provide evidence that Shh signaling between ameloblasts and the overlying stratum intermedium may involve subcellular localization ofPatched 2 and Gli1 mRNAs, both of which are targets of Shh signaling in these cells.
Recruitment of cell groups through Delta/Notch signalling during spider neurogenesis
Authors: Stollewerk Angelika
Published: December 2002

Early neurogenesis in the spider is characterised by a stereotyped pattern of sequential recruitment of neural cells from the neuroectoderm, comparable with neuroblast formation in Drosophila. However, in contrast toDrosophila, where single cells delaminate from the neuroectoderm,groups of cells adopt the neural fate and invaginate into the spider embryo. This raises the question of whether Delta/Notch signalling is involved in this process, as this system normally leads to a singling out of individual cells through lateral inhibition. I have therefore cloned homologues ofDelta and Notch from the spider Cupiennius saleiand studied their expression and function. The genes are indeed expressed during the formation of neural cells in the ventral neuroectoderm. Loss of function of either gene leads to an upregulation of the proneural genes and an altered morphology of the neuroectoderm that is comparable with Deltaand Notch mutant phenotypes in Drosophila. Thus, although Delta/Notch signalling appears to be used in the same way as inDrosophila, the lateral inhibition process produces clusters of invaginating cells, rather than single cells. Intriguingly, neuroectodermal cells that are not invaginating seem to become neural cells at a later stage,while the epidermal cells are derived from lateral regions that overgrow the neuroectoderm. In this respect, the neuroectodermal region of the spider is more similar to the neural plate of vertebrates, than to the neuroectoderm ofDrosophila.
Role of a positive regulator of root hair development,CAPRICE,inArabidopsisroot epidermal cell differentiation
Authors: Wada Takuji , Kurata Tetsuya , Tominaga Rumi , Koshino-Kimura Yoshihiro , Tachibana Tatsuhiko , Goto Koji , Marks M. David , Shimura Yoshiro , Okada Kiyotaka
Published: December 2002

In Arabidopsis, root hairs are formed only from a set of epidermal cells named trichoblasts or hair-forming cells. Previous studies showedCAPRICE (CPC) promotes differentiation of hair-forming cells by controlling a negative regulator, GLABRA2 (GL2), which is preferentially expressed in hairless cells. Here, we show that CPC is also predominantly expressed in the hairless cells, but not in the neighboring hair-forming cells, and that CPC protein moves to the hair-forming cells and represses the GL2 expression. We also show that the N terminus of bHLH protein interacts with CPC and is responsible for the GL2expression. We propose a model in which CPC plays a key role in the fate-determination of hair-forming cells.
Restoration of synapse formation inMuskmutant mice expressing a Musk/Trk chimeric receptor
Authors: Herbst Ruth , Avetisova Ekaterina , Burden Steven J.
Published: December 2002

Mice lacking Musk, a muscle-specific receptor tyrosine kinase that is activated by agrin, fail to form neuromuscular synapses and consequently die at birth because of their failure to move or breathe. We produced mice that express a chimeric receptor, containing the juxtamembrane region of Musk and the kinase domain of TrkA, selectively in muscle, and we crossed this transgene into Musk mutant mice. Expression of this chimeric receptor restores presynaptic and postsynaptic differentiation, including the formation of nerve terminal arbors, synapse-specific transcription, and clustering of postsynaptic proteins, allowing Musk mutant mice to move, breathe and survive as adults. These results show that the juxtamembrane region of Musk,including a single phosphotyrosine docking site, even in the context of a different kinase domain, is sufficient to activate the multiple pathways leading to presynaptic and postsynaptic differentiation in vivo. In addition,we find that Musk protein can be clustered at synaptic sites, even ifMusk mRNA is expressed uniformly in muscle. Moreover, acetylcholine receptor clustering and motor terminal branching are restored in parallel,indicating that the extent of presynaptic differentiation is matched to the extent of postsynaptic differentiation.
early in short days 4, a mutation inArabidopsisthat causes early flowering and reduces the mRNA abundance of the floral repressorFLC
Authors: Reeves Paul H. , Murtas Giovanni , Dash Sudhansu , Coupland George
Published: December 2002

The plant shoot is derived from the apical meristem, a group of stem cells formed during embryogenesis. Lateral organs form on the shoot of an adult plant from primordia that arise on the flanks of the shoot apical meristem. Environmental stimuli such as light, temperature and nutrient availability often influence the shape and identity of the organs that develop from these primordia. In particular, the transition from forming vegetative lateral organs to producing flowers often occurs in response to environmental cues. This transition requires increased expression in primordia of genes that confer floral identity, such as the Arabidopsis gene LEAFY. We describe a novel mutant, early in short days 4 (esd4),that dramatically accelerates the transition from vegetative growth to flowering in Arabidopsis. The effect of the mutation is strongest under short photoperiods, which delay flowering of Arabidopsis. The mutant has additional phenotypes, including premature termination of the shoot and an alteration of phyllotaxy along the stem, suggesting that ESD4has a broader role in plant development. Genetic analysis indicates thatESD4 is most closely associated with the autonomous floral promotion pathway, one of the well-characterized pathways proposed to promote flowering of Arabidopsis. Furthermore, mRNA levels of a floral repressor(FLC), which acts within this pathway, are reduced by esd4,and the expression of flowering-time genes repressed by FLC is increased in the presence of the esd4 mutation. Although the reduction inFLC mRNA abundance is likely to contribute to the esd4phenotype, our data suggest that esd4 also promotes flowering independently of FLC. The role of ESD4 in the regulation of flowering is discussed with reference to current models on the regulation of flowering in Arabidopsis.
The chickenRaxLgene plays a role in the initiation of photoreceptor differentiation
Authors: Chen C.-M. Amy , Cepko Constance L.
Published: December 2002

The paired type homeodomain gene, Rax, was previously identified as a key molecule in early eye formation in mice and humans. We report the expression patterns of two Rax family members from chicken, Rax andRaxL, and on the function of RaxL in photoreceptor development. Both Rax and RaxL are expressed in early retinal progenitor cells, with Rax being expressed at a significantly higher level than RaxL. At the time that photoreceptors begin to form, RaxL appears at a relatively high level in a subset of cells within the zone of proliferating progenitor cells. Subsequently, it is expressed in cells migrating to the photoreceptor layer, where it is highly expressed during the initial, but not late, stages of photoreceptor differentiation. To test the function of RaxL, a putative dominant-negative allele of RaxL comprising a fusion of theengrailed repressor domain and a region of RaxL(EnRaxLΔC) was introduced in vivo into the early chick eye using a retroviral vector. EnRaxLΔC, but not the dominant negative Rax(EnRaxΔC), caused a significant reduction in expression of early markers of photoreceptor cells. Examination of the transactivation activity of RaxL on a reporter construct bearing a canonical photoreceptor-specific enhancer element showed that RaxL exhibited significant activation activity, and that this activity was severely diminished in the presence of EnRaxLΔC. The effect on photoreceptor gene expression in vivo was specific in that other cell types were unaffected, as was general proliferation in the retina. The reduction in numbers of cells expressing photoreceptor markers was probably due to decreased survival of developing photoreceptor cells, as there was increased apoptosis among cells of the retina expressing dominant-negativeRaxL. We propose that RaxL plays a role in the initiation of differentiation, and also possibly commitment, of photoreceptor cells in the chicken retina.
Eyes Absent, a key repressor of polar cell fate duringDrosophilaoogenesis
Authors: Bai Jianwu , Montell Denise
Published: December 2002

Throughout Drosophila oogenesis, specialized somatic follicle cells perform crucial functions in egg chamber formation and in signaling between somatic and germline cells. In the ovary, at least three types of somatic follicle cells, polar cells, stalk cells and main body epithelial follicle cells, can be distinguished when egg chambers bud from the germarium. Although specification of these three somatic cell types is important for normal oogenesis and subsequent embryogenesis, the molecular basis for establishment of their cell fates is not completely understood. Our studies reveal the gene eyes absent (eya) to be a key repressor of polar cell fate. EYA is a nuclear protein that is normally excluded from polar and stalk cells, and the absence of EYA is sufficient to cause epithelial follicle cells to develop as polar cells. Furthermore, ectopic expression of EYA is capable of suppressing normal polar cell fate and compromising the normal functions of polar cells, such as promotion of border cell migration. Finally, we show that ectopic Hedgehog signaling, which is known to cause ectopic polar cell formation, does so by repressing eya expression in epithelial follicle cells.