Restriction of Endogenous T Cell Antigen Receptor β Rearrangements to Vβ14 through Selective Recombination Signal Sequence Modifications

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 10; pp. 4002 - 4007
• Main Authors: Wu, Cherry, Ranganath, Sheila, Gleason, Megan, Woodman, Barbara B., Borjeson, Tiffany M., Alt, Frederick W., Bassing, Craig H.
• Format: Journal Article
• Language: English
• Published: National Academy of Sciences 06.03.2007; National Acad Sciences
• Subjects: Biological Sciences; Cell lines; Exons; Genetic loci; Hybridomas; Lymphocytes; Polymerase chain reaction; Reed Sternberg cells; T cell antigen receptors; T lymphocytes; Thymocytes
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0700081104

T cell antigen receptor (TCR)β V(D)J variable region exon assembly is ordered, with Dβ to Jβ rearrangements occurring before joining of Vβs to a DJβ complex. Germ-line V(D)J segments are flanked by recombination signal (RS) sequences, which consist of heptamers and nonamers separated by a spacer of 12 (12-RS) or 23 (23-RS) bp. V(D)J recombination is restricted by the 12/23 rule; joining occurs only between gene segments flanked by 12-RSs and 23-RSs. Vβ segments have 23-RSs and Jβ segments 12-RSs, which based on the 12/23 rule should allow direct joining. However, Vβ segments rearrange only to DJβ complexes and not Jβ segments, because of restrictions beyond 12/23 (B12/23) that make the Vβ23-RS incompatible with the Jβ12-RS. To determine whether direct Vβ to Jβ joining occurs if flanking RSs are B12/23 compatible, we generated mice whose lymphocytes contained replacement of the Vβ1412-RS with the 3′Dβ112-RS on a TCRβ allele lacking Dβ segments (the ${\rm J}\beta 1^{{\rm M}6}$ allele). Mice heterozygous for the ${\rm J}\beta 1^{{\rm M}6}$ allele had dramatically increased Vβ14⁺ thymocyte and T cell numbers and decreased numbers of cells expressing other Vβs. This altered Vβ repertoire resulted from direct Vβ14 to Jβ1 rearrangements on the ${\rm J}\beta 1^{{\rm M}6}$ allele. Mice harboring lymphocytes homozygous for ${\rm J}\beta 1^{{\rm M}6}$ allele developed normal thymocyte and T cell numbers with all expressing Vβ14. Our findings show that selective RS modifications enforce rearrangement of a specific Vβ gene segment and demonstrate the importance of B12/23 mechanisms for ensuring generation of diverse TCRβ repertoires.