Ki67-mediated chromatin accessibility impedes B-cell antigen-receptor gene rearrangement

B and T cells can recognise and respond to a vast array of foreign pathogens by virtue of the diverse antigen-receptor repertoire generated by gene rearrangement during development. Here, we show that deficiency in Ki67, a nuclear protein ubiquitously expressed throughout the cell cycle, impairs B-cell development at specific, early stages. We identified that Ki67 maintains global chromatin accessibility in lymphocyte progenitors at stages where antigen-receptor gene rearrangements occur and that gene rearrangement is less efficient in the absence of Ki67. That the defects in B cell development are caused by disrupted antigen-receptor gene rearrangement is shown by pre-rearranged antigen-receptor genes fully compensating for loss of Ki67. Collectively, these results identify a unique contribution from Ki67 to somatic antigen-receptor gene rearrangement.