IL-7R Signalling Activates Widespread V H and D H Gene Usage to Drive Antibody Diversity in Bone Marrow B Cells

Generation of the primary antibody repertoire requires V(D)J recombination of hundreds of gene segments in the immunoglobulin heavy chain (Igh) locus. It has been proposed that interleukin-7 receptor (IL-7R) signalling is necessary for Igh recombination, but this has been challenging to partition from the receptor’s role in B cell survival and proliferation. By generating the first detailed description of the Igh repertoire of murine IL-7Rα-/- bone marrow B cells, we demonstrate that IL-7R signalling profoundly influences VH gene selection during VH-to-DJH recombination. We find skewing towards usage of 3’ VH genes during de novo VH-to-DJH recombination that is more severe than the fetal liver (FL) B cell repertoire, and we now show a role for IL-7R signalling in DH-to-JH recombination. Transcriptome and accessibility analyses suggests reduced expression of B lineage-specific transcription factors (TFs) and their targets, and loss of DH and VH antisense transcription in IL-7Rα-/- B cells.  These results refute models suggesting that IL-7R signalling is only required for survival and proliferation, and demonstrate a pivotal role in shaping the Igh repertoire by activating underpinning epigenetic mechanisms.