Lamin B1 regulates somatic mutations and progression of B cell malignancies

Somatic hypermutation (SHM) is a pivotal process in adaptive immunity that occurs in the germinal centre and allows B-cells to change their primary DNA sequence and diversify their antigen receptors. Here, we report that genome binding of Lamin B1, a component of the nuclear envelope involved in epigenetic chromatin regulation, is reduced during B cell activation and formation of lymphoid germinal centres. ChIP-Seq analysis showed that kappa and heavy variable immunoglobulin domains were released from the Lamin B1 suppressive environment when SHM was induced in B cells. RNAi-mediated reduction of Lamin B1 resulted in spontaneous SHM as well as kappa-light chain aberrant surface expression. Finally, Lamin B1 expression level was directly proportional to 5-year survival rate in chronic lymphocytic leukaemia, and was strongly involved in transformation of follicular lymphoma. In summary, here we report that Lamin B1 is a negative epigenetic regulator of SHM in normal B-cells and a "mutational gatekeeper", suppressing the aberrant mutations that drive lymphoid malignancy. Overall design: Lamin B1 ChIP sequencing data from two independent biological replicates in control vs somatic hypermutation-induced BL2 cells