title: Germ-line transcription and methylation status of the TCR-J alpha locus in its accessible configuration.
abstract: We have generated two in vivo mouse models to study the regulation of DNA accessibility to the V(D)J recombinase machinery in the T cell receptor (TCR)-J alpha locus. In recombination activating gene (RAG)-deficient mice, both injection of a TCR-beta chain transgene (RTB mice) or anti-CD3-epsilon treatment in vivo (RT3 mice) lead to the same phenotype with homogeneous thymocyte populations blocked at the CD4+ CD8+ double positive (DP) stage. At this developmental stage, the TCR-alpha rearrangements are about to start, and the TCR-J alpha locus is frozen in an accessible but yet unrearranged configuration in these mice. We show high level of TCR-alpha germ-line transcription in thymocytes from RTB and RT3 mice. Transcripts are skewed towards the 5' end of the TCR-J alpha locus, and the T early alpha (TEA) sterile transcript is predominant and therefore provides a useful marker for the TCR-J alpha locus opening. Analysis of the DNA methylation status reveals a global surmethylation of the TCR-J alpha locus in the thymus in comparison with non-lymphoid cells in these mice. We propose that hypermethylation of the locus could precede a progressive demethylation, providing a specific protective and regulatory role in the rearrangement events.
authors.affiliation: INSERM U429, Hôpital Necker-enfants malades, Paris, France.
authors.forename: I
authors.initials: I
authors.lastname: Villey
authors.forename: P
authors.initials: P
authors.lastname: Quartier
authors.forename: F
authors.initials: F
authors.lastname: Selz
authors.forename: J P
authors.initials: JP
authors.lastname: de Villartay
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology; D019175:DNA Methylation; D015329:Gene Rearrangement, T-Lymphocyte / Q000276:immunology*; D005854:Germ Cells / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008954:Models, Biological; D011401:Promoter Regions, Genetic / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D013950:Thymus Gland / Q000276:immunology / Q000378:metabolism; D014158:Transcription, Genetic / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D016693:Receptors, Antigen, T-Cell, alpha-beta