EC confers erythroid progenitor survival and function in vivo.Vav1-Cre–mediated Exosc3 ablation in the hematopoietic system is embryonically lethal after E14.5. Exosc3 expression is required for erythroid and myeloid progenitor activity. In Exosc3-ablated embryos, immunophenotypic BFU-Es are reduced, and progenitor activity is abrogated. MEPs can still be detected but have reduced activity. RNA-seq analysis of sorted GFP+ BFU-E revealed accumulation of proapoptotic genes, and Exosc3-ablated progenitors became apoptotic. During erythroid maturation, GATA1 represses genes encoding EC subunits.6,16,17 Before repression, the EC establishes and/or maintains functional erythroid progenitors, which involves conferring KIT expression/signaling, protection against DNA damage,6 and suppressing, directly or indirectly, a proapoptotic program.
