Bi-Allelic CEBPA Mutation Combined with a Novel GATA2 Mutation Develops an Acute Erythroid Leukemia Through a Bi-Potent Leukemic Initiating Population

Acute erythroid leukemia (AEL) is a subtype of acute myeloid leukemia (AML) representing <5% of AML cases. There are two subtypes of AEL: pure erythroid leukemia and erythroleukemia (erythroid/myeloid leukemia). Sequencing studies has comprehensively characterized the mutational landscape of AML identifying mutations that are significantly associated such as the bi-allelic CEBPA and GATA2 mutations (Papaemmanuil et al.; 2016). Recently, sequencing AEL patients also found a high frequency of bi-allelic CEBPA and GATA2 co-mutated (Ping et al.; 2016). As there are currently no models of AEL we combined three knock-in mouse strains, a novel Gata2 point mutation in the N-terminal zinc finger crossed with a knock-in of the N-terminal Cebpa mutation, and a C-terminal Cebpa mutation to generate CebpaN/C;Gata2+/+ (NC genotype) and CebpaN/C;Gata2G320D/ + (NCG genotype). To bypass Cebpa mutation perinatal lethality we performed competitive transplantations using mutant fetal liver cells and wild type bone marrow (BM) competitor cells. By analyzing myeloid reconstitution over time in the peripheral blood we found the myeloid differentiation block caused by the N-terminal mutation in NC mice was prevented when co-expressed with Gata2G320D. This correlated with a more aggressive disease in NCG compared to NC transplanted mice. 100% of NC mice developed an AML while 50% of NCG mice developed an AML, and the remaining 50% developed an AEL of the erythroleukemia subtype, identified by the presence of both myeloblasts and erythroblasts in the BM, spleen and peripheral blood. NCG AEL mice had a significantly shorter overall survival than NCG AML mice. Secondary transplant of different sorted BM populations from NCG AML or NCG AEL mice showed that Lin-cKit+FcR+ GMP-like cells could propagate and fully replicate the two diseases, identifying the putative leukemic initiating cell (LIC) population. Together our study provides a novel model of the erythroleukemia subtype of AEL where both the myeloblasts and erythroblasts develop through a bi-potent LIC population.