van der Weyden et al. [102] generated a B-ALL mouse model in which the expression of the ETV6-RUNX1 fusion gene (derived from the t(12;21)(p13;q22) translocation, the most common chromosomal rearrangement in B-ALLs) was combined to Pax5 haploinsufficiency. The gene discussed is PAX5; the disease is precursor B-cell acute lymphoblastic leukemia.