Ddx41 inhibition of DNA damage signaling permits erythroid progenitor expansion in zebrafish.

DEAD-box Helicase 41 (DDX41) is a recently identified factor mutated in hematologic malignancies whose function in hematopoiesis is unknown. Using an in vivo model of Ddx41 deficiency, we unveiled a critical role for this helicase in regulating erythropoiesis. We demonstrated that loss of ddx41 leads to anemia caused by diminished proliferation and defective differentiation of erythroid progenitors. Mis-expression and alternative splicing of cell cycle genes is rampant in ddx41 mutant erythroid progenitors. We delineated that the DNA damage response is activated in mutant cells resulting in an Ataxiatelangiectasia mutated (ATM) and Ataxia-telangiectasia and Rad3-related (ATR)-triggered cell cycle arrest. Inhibition of these kinases partially suppressed ddx41 mutant anemia. These findings establish a critical function for Ddx41 in promoting healthy erythropoiesis via protection from genomic stress and delineate a mechanistic framework to explore a role for ATM and ATR signaling in DDX41-mutant hematopoietic pathologies.