BCL11B and acute lymphoblastic leukemia: On the other hand, the same group showed that mice born with homozygous BCL111B knockout show block of α/β T-cell differentiation and die but do not develop T-cell malignancies.12 In a large study on T-ALL, monoallelic BCL11B deletions or missense mutations were found in 9% (10 of 117) of cases.28 Some of them disrupted the structure of zinc finger domains required for DNA binding.