3127 – MODELING PREDISPOSED AND SPORADIC CLONAL HEMATOPOIESIS USING INDUCED PLURIPOTENT STEM CELLS

Abstract

With age, HSCs accumulate somatic mutations that can increase their relative fitness and cause clonal expansion, triggering sporadic age-related clonal hematopoiesis (CH). In most people, CH is of little or no clinical significance as mature blood cell output is not typically affected. However, some individuals will accumulate further mutations that drive evolution to HSC failure, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Moreover, in patients with bone marrow failure syndromes caused by germline mutations that impair HSC function, this process of CH is markedly accelerated, with an amplified risk of MDS and AML in young adulthood. Here, we aimed to use gene editing and directed differentiation of human induced pluripotent stem cells (IPSCs) to model sporadic and predisposed CH. We found that hematopoietic stem and progenitor cells (HSPCs) derived from IPSCs and deficient for the Fanconi anemia gene FANCA showed poor hematopoietic potential compared to isogenic FANCA-expressing cells. Multiplexed editing of 10 CH-associated genes in FANCA-deficient HSPCs resulted in reversal of this hematopoietic failure and implementation of an aberrant program of sustained self-renewal. To model sporadic CH, we introduced a heterozygous P95H mutation in the SRSF2 gene - a mutation commonly observed in human CH and MDS. We found that in HSPCs, this mutation globally disrupted splicing, mildly impaired differentiation, and enhanced clonogenesis. Together, our data demonstrate that we can capture hallmarks of predisposed and sporadic CH in IPSC-based models as a basis for ongoing studies on mechanisms of clonal evolution in HSCs.