title: Activated Ras signals differentiation and expansion of CD4+8+ thymocytes.
abstract: We describe a novel approach to assay the ability of particular gene products to signal transitions in lymphocyte differentiation in vivo. The method involves transfection of test expression constructs into RAG-1-deficient embryonic stem cells, which are subsequently assayed by the RAG-2-deficient blastocyst complementation approach. We have used this method to demonstrate that expression of activated Ras in CD4-8- (double negative, DN) prothymocytes in vivo induces their differentiation into small CD4+8+ (double positive, DP) cortical thymocytes with accompanying expansion to normal thymocyte numbers. However, activated Ras expression in DP cells does not cause proliferation or maturation to CD4+8- or CD4-8+ (single positive) thymocytes. Therefore, signaling through Ras is sufficient for promoting differentiation of DN to DP cells, but further differentiation requires the activity of additional signaling pathways.
authors.affiliation: Howard Hughes Medical Institute, The Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: W
authors.initials: W
authors.lastname: Swat
authors.forename: Y
authors.initials: Y
authors.lastname: Shinkai
authors.forename: H L
authors.initials: HL
authors.lastname: Cheng
authors.forename: L
authors.initials: L
authors.lastname: Davidson
authors.forename: F W
authors.initials: FW
authors.lastname: Alt
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D011905:Genes, ras; D018398:Homeodomain Proteins; D051379:Mice; D008822:Mice, Transgenic; D011506:Proteins / Q000235:genetics; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D018631:ras Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D011506:Proteins; C499308:Rag2 protein, mouse; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D018631:ras Proteins