Nupr1 Negatively Regulates Endothelial to Hematopoietic Transition in the Aorta‐Gonad‐Mesonephros Region

In the aorta of mid‐gestational mouse embryos, a specialized endothelial subpopulation termed hemogenic endothelial cells (HECs) develops into hematopoietic stem and progenitor cells (HSPCs), through a conserved process of endothelial‐to‐hematopoietic transition (EHT). EHT is tightly controlled by multiple intrinsic and extrinsic mechanisms. Nevertheless, the molecular regulators restraining this process remain poorly understood. Here, it is uncovered that, one of the previously identified HEC signature genes, Nupr1, negatively regulates the EHT process. Nupr1 deletion in endothelial cells results in increased HSPC generation in the aorta‐gonad‐mesonephros region. Furthermore, single‐cell transcriptomics combined with serial functional assays reveals that loss of Nupr1 promotes the EHT process by promoting the specification of hematopoiesis‐primed functional HECs and strengthening their subsequent hematopoietic differentiation potential toward HSPCs. This study further finds that the proinflammatory cytokine, tumor necrosis factor α (TNF‐α), is significantly upregulated in Nupr1‐deficient HECs, and the use of a specific TNF‐α neutralizing antibody partially reduces excessive HSPC generation in the explant cultures from Nupr1‐deficient embryos. This study identifies a novel negative regulator of EHT and the findings indicate that Nupr1 is a new potential target for future hematopoietic stem cell regeneration research.