title: Wnt target genes identified by DNA microarrays in immature CD34+ thymocytes regulate proliferation and cell adhesion.
abstract: The thymus is seeded by very small numbers of progenitor cells that undergo massive proliferation before differentiation and rearrangement of TCR genes occurs. Various signals mediate proliferation and differentiation of these cells, including Wnt signals. Wnt signals induce the interaction of the cytoplasmic cofactor beta-catenin with nuclear T cell factor (TCF) transcription factors. We identified target genes of the Wnt/beta-catenin/TCF pathway in the most immature (CD4-CD8-CD34+) thymocytes using Affymetrix DNA microarrays in combination with three different functional assays for in vitro induction of Wnt signaling. A relatively small number (approximately 30) of genes changed expression, including several proliferation-inducing transcription factors such as c-fos and c-jun, protein phosphatases, and adhesion molecules, but no genes involved in differentiation to mature T cell stages. The adhesion molecules likely confine the proliferating immature thymocytes to the appropriate anatomical sites in the thymus. For several of these target genes, we validated that they are true Wnt/beta-catenin/TCF target genes using real-time quantitative PCR and reporter gene assays. The same core set of genes was repressed in Tcf-1-null mice, explaining the block in early thymocyte development in these mice. In conclusion, Wnt signals mediate proliferation and cell adhesion, but not differentiation of the immature thymic progenitor pool.
authors.affiliation: Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.
authors.forename: Frank J T
authors.initials: FJ
authors.lastname: Staal
authors.forename: Floor
authors.initials: F
authors.lastname: Weerkamp
authors.forename: Miranda R M
authors.initials: MR
authors.lastname: Baert
authors.forename: Caroline M M
authors.initials: CM
authors.lastname: van den Burg
authors.forename: Mascha
authors.initials: M
authors.lastname: van Noort
authors.forename: Edwin F E
authors.initials: EF
authors.lastname: de Haas
authors.forename: Jacques J M
authors.initials: JJ
authors.lastname: van Dongen
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000096:biosynthesis*; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D002474:Cell-Free System / Q000502:physiology; D002648:Child; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter; D051538:Hepatocyte Nuclear Factor 1-alpha; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology; D051821:Lymphoid Enhancer-Binding Factor 1; D051379:Mice; D008810:Mice, Inbred C57BL; D020411:Oligonucleotide Array Sequence Analysis; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D051822:T Cell Transcription Factor 1; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology; D014161:Transduction, Genetic; D014162:Transfection; D051153:Wnt Proteins; D060508:Wnt3 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: D018952:Antigens, CD34; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; C496488:Hnf1a protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051822:T Cell Transcription Factor 1; C497576:TCF7 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D060508:Wnt3 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin; D018021:Lithium Chloride