Targeting Autophagy as a Therapeutic Pathway in Diamond-Blackfan Anemia

Diamond-Blackfan anemia (DBA) is a congenital disorder characterized by the failure of erythroid progenitor differentiation, severely curtailing red blood cell production. Because many DBA patients fail to respond to corticosteroid therapy, there is considerable need for therapeutics for this disorder. We previously used unbiased drug screens in induced pluripotent stem cells (iPSCs) which identified SMER28 as a potential therpauetic for DBA. SMER28 acts by selectively modulating autophagy, but has distinct effects from the mTOR inhibitor rapamycin, highlighting the need for further study. Autophagy and mitophagy are critical metabolic pathways that mediate turnover of damaged organelles and mitochondria. Autophagy has been linked to regulation of hematopoietic stem cell function and terminal erythroid differentiation. However, the mechanisms by which autophagy regulates hematopoiesis are still poorly understood. We utilize primary cord blood and adult human progenitors and iPSCs to circumvent the paucity of primary patient blood stem and progenitor cells. To understand the role of autophagy, we have developed a lentiviral LC3-based reporter which allows real-time quantitation of autophagic flux. Using this reporter, we show that autophagy is dynamically regulated during erythroid differentiation and closely parallels mitochondrial mass and levels of reactive oxygen species. In our model, oxidative stress in erythroid precursors drives a stress response which involves activation of autophagy and mitophagy pathways. The interplay between oxidative stress and autophagy regulates erythropoiesis in normal and multiple disease contexts, including DBA and myelodysplastic syndromes (MDS). SMER28 and mitochondrial uncouplers promote homeostasis by facilitating mitochondrial clearance. In summary, therpauetic modulation of autophagy may be a broadly applicable therpauetic strategy in both inherited and acquired anemias.