title: Transgenic expression of RasGRP1 induces the maturation of double-negative thymocytes and enhances the production of CD8 single-positive thymocytes.
abstract: RasGRP1 is a guanine nucleotide exchange factor for Ras that is required for the efficient production of both CD4 and CD8 single-positive thymocytes. We found that RasGRP1 expression is rapidly up-regulated in double-negative thymocytes following pre-TCR ligation. Transgenic overexpression of RasGRP1 compensated for deficient pre-TCR signaling in vivo, enabling recombinase-activating gene 2(-/-) double-negative thymocytes to mature to the double-positive stage. RasGRP1 transgenic mice had a 4-fold increase in CD8 single-positive thymocytes, most of which had atypically low levels of CD3. The RasGRP1 transgene lowered the threshold of TCR signaling needed to initiate proliferation of single-positive thymocytes, with this effect being particularly evident among CD8 single-positive cells. In 3-day cultures, TCR stimulation via anti-CD3 caused a 10-fold increase in the ratio of CD8 to CD4 thymocytes among RasGRP1 transgenic vs nontransgenic thymocytes. These results demonstrate that in addition to driving the double-negative to double-positive transition, increased expression of RasGRP1 selectively increases CD8 single-positive thymocyte numbers and enhances their responsiveness to TCR signaling.
authors.affiliation: Department of Immunology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Norment
authors.forename: Lisa Y
authors.initials: LY
authors.lastname: Bogatzki
authors.forename: Mark
authors.initials: M
authors.lastname: Klinger
authors.forename: Ethan W
authors.initials: EW
authors.lastname: Ojala
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bevan
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kay
mesh_terms: D000276:Adjuvants, Immunologic / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D016827:CD8 Antigens / Q000096:biosynthesis* / Q000235:genetics; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D003433:Crosses, Genetic; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D018655:Lymphocyte Count; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D019076:Transgenes / Q000276:immunology; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology; D018631:ras Proteins / Q000502:physiology
chemical_list: D000276:Adjuvants, Immunologic; D016827:CD8 Antigens; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C499311:RAG2 protein, human; C491790:RASGRP1 protein, human; C499308:Rag2 protein, mouse; C112278:Rasgrp1 protein, mouse; D011948:Receptors, Antigen, T-Cell; C064655:V(D)J recombination activating protein 2; D018631:ras Proteins