Background Haematopoietic stem cells (HSCs) first arise during development in the aorta-gonad-mesonephros (AGM) region of the embryo from a population of haemogenic endothelial cells which undergo endothelial-to-haematopoietic transition (EHT). Despite the progress achieved in recent years, the molecular mechanisms driving EHT are still poorly understood, especially in human where the AGM region is not easily accessible. Results In this study, we take advantage of a human pluripotent stem cell (hPSC) differentiation system and single-cell transcriptomics to recapitulate EHT in vitro and uncover mechanisms by which the haemogenic endothelium generates early haematopoietic cells. We show that most of the endothelial cells reside in a quiescent state and progress to the haematopoietic fate within a defined time window, within which they need to re-enter into the cell cycle. If cell cycle is blocked, haemogenic endothelial cells lose their EHT potential and adopt a non-haemogenic identity. Furthermore, we demonstrate that CDK4/6 and CDK1 play a key role not only in the transition but also in allowing haematopoietic progenitors to establish their full differentiation potential. Conclusion We propose a direct link between the molecular machineries that control cell cycle progression and EHT.

中文翻译：

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在单细胞水平上对内皮细胞向造血细胞转变的分析确定细胞周期调节是分化的驱动因素

背景造血干细胞 (HSC) 最初是在胚胎的主动脉-性腺-中肾 (AGM) 区域的发育过程中从一群经历内皮到造血转化 (EHT) 的造血内皮细胞中产生的。尽管近年来取得了进展，但对驱动 EHT 的分子机制仍然知之甚少，尤其是在不易接近 AGM 区域的人类中。结果 在这项研究中，我们利用人类多能干细胞 (hPSC) 分化系统和单细胞转录组学在体外概括 EHT，并揭示造血内皮产生早期造血细胞的机制。我们表明，大多数内皮细胞处于静止状态，并在规定的时间窗口内进展到造血命运，他们需要在其中重新进入细胞周期。如果细胞周期被阻断，造血内皮细胞就会失去其 EHT 潜力并采用非造血特性。此外，我们证明 CDK4/6 和 CDK1 不仅在过渡中发挥关键作用，而且在造血祖细胞建立其完全分化潜能方面也发挥着关键作用。结论 我们提出了控制细胞周期进程的分子机制与 EHT 之间的直接联系。