These data along with downregulation of DNMT3A in human CLL and mutations detected in human PTCLs suggest that EμSRα-tTA;Teto-Cre;Dnmt3afl/fl;Rosa26LOXPEGFP/EGFP can serve as a new mouse model to study CLL and PTCL in mice. The gene discussed is DNMT3A; the disease is B-cell chronic lymphocytic leukemia.