title: The interleukin 7 receptor is required for T cell receptor gamma locus accessibility to the V(D)J recombinase.
abstract: Defects in the interleukin (IL)-7 signal transduction pathway lead to severe immunodeficiency in humans and in mice. In IL-7 receptor-deficient (IL-7R-/-) mice, lymphoid precursors show a reduced survival rate and variable/diversity/joining region V(D)J recombination is variously affected in different loci, being arrested in the T cell receptor (TCR)-gamma locus, aberrant in the immunoglobulin heavy chain (IgH) locus, and delayed in the TCR-beta locus. Here, we analyze the recombination defect of the TCR-gamma locus. Using ligation-mediated polymerase chain reaction, we sought intermediates of the recombination process. In the absence of the IL-7 signal, no initiation of recombination of the TCR-gamma locus was observed, whereas recombination intermediates at the TCR-beta locus could be detected. Thus, the failure to rearrange the TCR-gamma locus is due to a failure to initiate cleavage rather than a failure to religate broken DNA ends. V(D)J recombination was previously thought to begin at the pro-T2 stage of T cell development after the arrest of IL-7R-/- thymocytes at the pro-T1 stage. However, here we show that both TCR-gamma and -beta recombination intermediates are readily detectable in normal T1 cells, but only TCR-beta intermediates were detected in IL-7R-/- T1 cells, supporting a mechanistic role for IL-7 in TCR-gamma locus rearrangement. Since reduced recombination activating gene (rag) expression has been reported in the absence of the IL-7 signal, we directly tested whether the TCR-gamma locus is accessible to cleavage by recombinant Rag proteins in vitro. We found a reduction in chromatin accessibility for Rag-mediated cleavage in IL-7R-/- thymocytes compared with wild-type. Thus, IL-7 controls recombination at the TCR-gamma locus by regulating locus accessibility.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Schlissel
authors.forename: S D
authors.initials: SD
authors.lastname: Durum
authors.forename: K
authors.initials: K
authors.lastname: Muegge
mesh_terms: D000818:Animals; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D019426:Integrases; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D005810:Multigene Family; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000378:metabolism; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000235:genetics* / Q000378:metabolism*; D020395:Receptors, Interleukin-7 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D045522:Recombinases; D011995:Recombination, Genetic; D016176:T-Lymphocyte Subsets / Q000201:enzymology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology / Q000276:immunology / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D020395:Receptors, Interleukin-7; D045522:Recombinases; C064658:RAG-1 protein; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C115006:integron integrase IntI1