Complete cis Exclusion upon Duplication of the Eμ Enhancer at the Immunoglobulin Heavy Chain Locus

Abstract

Developing lymphocytes somatically diversify their antigen-receptor loci through V(D)J recombination. The process is associated with allelic exclusion, which results in monoallelic expression of an antigen receptor locus. Various cis-regulatory elements control V(D)J recombination in a developmentally regulated manner, but their role in allelic exclusion is still unclear. At the immunoglobulin heavy chain locus (IgH), the Eμ enhancer plays a critical role in V(D)J recombination. We generated a mouse line with a replacement mutation in the constant region of the locus that duplicates the Eμ enhancer and allows premature expression of the γ3 heavy chain. Strikingly, IgM expression was completely and specifically excluded in cis from the mutant allele. This cis exclusion recapitulated the main features of allelic exclusion, including differential exclusion of variable genes. Notably, sense and antisense transcription within the distal variable domain and distal V_H-DJ_H recombination were inhibited. cis exclusion was established and stably maintained despite an active endogenous Eμ enhancer. The data reveal the importance of the dynamic, developmental stage-dependent interplay between IgH locus enhancers and signaling in the induction and maintenance of allelic exclusion.

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Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00294-15.

ACKNOWLEDGMENTS

We thank K. Rajewsky for kindly providing B1-8 mice. We thank the IPBS animal facility staff and F. L'Faqihi and V. Duplan-Eche at the Purpan CPTP platform for their excellent work.

C.L. and Z.O. were supported by fellowships from the MREN and the MREN, FRM, and EMBO-STF, respectively. This work was supported by the Fondation ARC (grant PJA 20141201647), the Agence Nationale de la Recherche, the Institut National du Cancer, the Ligue contre le Cancer-Comité de Haute-Garonne, and the Cancéropôle Grand-Sud-Ouest.

N.P. and C.L. performed research; Z.O. and M.L.B. generated the A150 mouse line; M.M. managed the mouse lines; N.P., C.L., and A.A.K. analyzed data; and A.A.K. designed research and wrote the paper.

We declare that we have no conflicts of interest.