DLBCL cell lines with endogenous MEF2B mutations (DB and SUDHL4) had lower BCL6 protein levels than those with WT MEF2B (WSU-DLCL2 and Karpas 422; Fig. 6b), consistent with our findings that MEF2B mutations decrease transcriptional activation. The gene discussed is MEF2B; the disease is diffuse large B-cell lymphoma.