Bcl11a preserves hematopoietic stem cell function in culture by restraining Ncf1-dependent ROS

Ex vivo expansion of hematopoietic stem cells (HSCs) is limited by culture-induced oxidative stress, yet the upstream transcriptional drivers remain poorly defined. Here, we show that the transcription factor Bcl11a is rapidly and persistently downregulated during HSC culture and that this decline drives functional deterioration. Bcl11a was both required and sufficient to maintain quiescence, clonogenic activity, and serially transplantable HSC function. Mechanistically, Bcl11a directly represses a Nox2 NADPH oxidase gene module, including Ncf1, encoding the p47^phox organizer subunit; Ncf1 deletion reduced ROS and partially rescued the defects of Bcl11a-deficient HSCs. Rapamycin—but not the ROS scavenger N-acetylcysteine—restored Bcl11a expression, suppressed Ncf1 and ROS, and improved HSC function, identifying Bcl11a as a candidate effector linking mechanistic target of rapamycin complex 1 inhibition to redox control. This axis was conserved in human hematopoietic stem and progenitor cells, revealing a druggable transcriptional vulnerability of cultured HSCs and a framework for improving ex vivo–expanded grafts.