title: Differential regulation of proximal and distal Vbeta segments upstream of a functional VDJbeta1 rearrangement upon beta-selection.
abstract: Developmental stage-specific regulation of transcriptional accessibility helps control V(D)J recombination. Vβ segments on unrearranged TCRβ alleles are accessible in CD4(-)/CD8(-) (double-negative [DN]) thymocytes, when they recombine, and inaccessible in CD4(+)/CD8(+) (double-positive [DP]) thymocytes, when they do not rearrange. Downregulation of Vβ accessibility on unrearranged alleles is linked with Lat-dependent β-selection signals that inhibit Vβ rearrangement, stimulate Ccnd3-driven proliferation, and promote DN-to-DP differentiation. Transcription and recombination of Vβs on VDJβ-rearranged alleles in DN cells has not been studied; Vβs upstream of functional VDJβ rearrangements have been found to remain accessible, yet not recombine, in DP cells. To elucidate contributions of β-selection signals in regulating Vβ transcription and recombination on VDJβ-rearranged alleles, we analyzed wild-type, Ccnd3(-/-), and Lat(-/-) mice containing a preassembled functional Vβ1DJCβ1 (Vβ1(NT)) gene. Vβ10 segments located just upstream of this VDJCβ1 gene were the predominant germline Vβs that rearranged in Vβ1(NT/NT) and Vβ1(NT/NT)Ccnd3(-/-) thymocytes, whereas Vβ4 and Vβ16 segments located further upstream rearranged at similar levels as Vβ10 in Vβ1(NT/NT)Lat(-/-) DN cells. We previously showed that Vβ4 and Vβ16, but not Vβ10, are transcribed on Vβ1(NT) alleles in DP thymocytes; we now demonstrate that Vβ4, Vβ16, and Vβ10 are transcribed at similar levels in Vβ1(NT/NT)Lat(-/-) DN cells. These observations indicate that suppression of Vβ rearrangements is not dependent on Ccnd3-driven proliferation, and DN residence can influence the repertoire of Vβs that recombine on alleles containing an assembled VDJCβ1 gene. Our findings also reveal that β-selection can differentially silence rearrangement of germline Vβ segments located proximal and distal to functional VDJβ genes.
authors.affiliation: Immunology Graduate Group, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Brenna L
authors.initials: BL
authors.lastname: Brady
authors.forename: Craig H
authors.initials: CH
authors.lastname: Bassing
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002469:Cell Separation; D005434:Flow Cytometry; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor / Q000235:genetics* / Q000276:immunology; D019674:Genes, T-Cell Receptor beta / Q000235:genetics* / Q000276:immunology; D038041:Lymphopoiesis / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta