Expression and production of aberrant PAX5 with deletion of exon 8 in B-lineage acute lymphoblastic leukaemia of children.

Summary We investigated PAX5 expression in childhood B-lineage acute lymphoblastic leukaemia (ALL). Seven of 21 children with B-lineage ALL had multiple PAX5 variants, while 14 children and healthy controls showed full-length (FL) and one variant PAX5. By Western blotting, healthy controls displayed Pax5-FL, while one short Pax5, derived from the deletion of exon 8 (Pax5-DeltaE8) was produced in 90% of ALL samples, as well as in ALL cell lines. PAX5-DeltaE8 lacked more than 50% of the transactivation domain, indicating that aberrant Pax5 production might lead to the arrest of B-cell differentiation, contributing to the pathogenesis of B-lineage ALL.