VH gene accessibility in pro-B cells

The generation of a diverse immunoglobulin repertoire is essential for humoral immunity and requires the participation of all V genes in V(D)J recombination. Efficient repertoire formation depends on the access of approximately 100 functional VH genes spread over 2.4 Mb of the Igh locus to the DH and JH segment clusters located in the recombination center (RC) with the intronic Em enhancer. A process termed locus contraction is thought to generate proximity of the distal VH genes to the RC. Here, we explore the function of newly discovered novel enhancers and a highly transcribed VH promoter and their impact on VH gene accessibility in chromatin. We demonstrate that these transcriptional elements determines regional Igh gene transcription but have little impact on chromatin accessibility. ATAC-seq was performed on BM derived Rag2-/-, Rag2-/-SiteI.3Pr-/- and Rag1-/-NE1-/- murine pro-B cells following 5 days of ex vivo IL7 expansion.