While del(13q) in murine B cells (minimal deleted region of 13q14 includes DLEU1, DLEU2, and miR15a-16-1; Mdr mice), but not expression of Sf3b1-K700E, drives the initiation of CLL, we hypothesize that SF3B1 mutation accelerates CLL progression. The gene discussed is DLEU1; the disease is B-cell chronic lymphocytic leukemia.