DNMT3A and B-cell chronic lymphocytic leukemia: Although it had not been functionally proven at the time of this initial finding, independent studies have since demonstrated that either bi-allelic or mono-allelic loss of Dnmt3a in Dnmt3aΔ/Δ and Dnmt3a+/− mice is sufficient to induce CLL, indicating that Dnmt3a is a haploinsufficient tumor suppressor (8, 26).