The C-terminal multimerization domain is essential for leukemia development by CBFß-SMMHC

The recurrent chromosome 16 inversion in acute myeloid leukemia generates a fusion gene between CBFB and MYH11, which in turn encodes a chimeric protein CBFß-SMMHC (core binding factor ß-smooth muscle myosin heavy chain). We previously demonstrated that CBFß-SMMHC needs its C terminal domains for leukemogenesis. In this study, we generated a new Cbfb-MYH11 knock-in mouse model to dissect the role of the multimerization domain at the C terminus of CBFß-SMMHC. Specifically, we mutated six amino acids in the helices D and E (mDE) of the assembly competent domain, which is important for SMMHC multimerization. We found that the embryos with the mDE mutation (Cbfb+/mDE) did not develop hematopoietic defects seen in embryos with full-length CBFß-SMMHC (Cbfb+/MYH11). More importantly leukemia development was abolished in the adult Cbfb+/mDE mice even after mutagenesis treatment. In addition, gene expression profile of the hematopoietic cells from the Cbfb+/mDE mice was more similar to that of Cbfb+/+ mice than the Cbfb+/MYH11 mice. Our data suggest that the C terminal multimerization domain is required for the defects in primitive and definitive hematopoiesis caused by CBFß-SMMHC, and it is also essential for leukemogenesis caused by CBFß-SMMHC. Overall design: RNA-seq of Bone marrow c-KIT+ cells from WT, Cbfb +/mDE, Cbfb +/MYH11 mice