PAX5 and precursor B-cell acute lymphoblastic leukemia: In support of the role of biallelic alteration of PAX5 in the pathogenesis of this subtype, knock-in mouse models of germline Pax5 mutations have shown that heterozygous Pax5P80R/+ knock-in mice develop transplantable B-ALL, with genetic inactivation of the wildtype Pax5 allele [7].