1. A subset of megakaryocytes regulates development of hematopoietic stem cell precursors.
- Author
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Lan, Wenlang, Li, Jinping, Ye, Zehua, Liu, Yumin, Luo, Sifan, Lu, Xun, Cao, Zhan, Chen, Yifan, Chen, Hongtian, and Li, Zhuan
- Subjects
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HEMATOPOIETIC stem cells , *MEGAKARYOCYTES , *EMBRYOLOGY , *YOLK sac , *CELL differentiation , *ANIMAL rescue , *SOMATIC embryogenesis - Abstract
Understanding the regulatory mechanisms facilitating hematopoietic stem cell (HSC) specification during embryogenesis is important for the generation of HSCs in vitro. Megakaryocyte emerged from the yolk sac and produce platelets, which are involved in multiple biological processes, such as preventing hemorrhage. However, whether megakaryocytes regulate HSC development in the embryonic aorta-gonad-mesonephros (AGM) region is unclear. Here, we use platelet factor 4 (PF4)-Cre;Rosa-tdTomato+ cells to report presence of megakaryocytes in the HSC developmental niche. Further, we use the PF4-Cre;Rosa-DTA (DTA) depletion model to reveal that megakaryocytes control HSC specification in the mouse embryos. Megakaryocyte deficiency blocks the generation and maturation of pre-HSCs and alters HSC activity at the AGM. Furthermore, megakaryocytes promote endothelial-to-hematopoietic transition in a OP9-DL1 coculture system. Single-cell RNA-sequencing identifies megakaryocytes positive for the cell surface marker CD226 as the subpopulation with highest potential in promoting the hemogenic fate of endothelial cells by secreting TNFSF14. In line, TNFSF14 treatment rescues hematopoietic cell function in megakaryocyte-depleted cocultures. Taken together, megakaryocytes promote production and maturation of pre-HSCs, acting as a critical microenvironmental control factor during embryonic hematopoiesis. Synopsis: The contribution of immune cells to the emergence of hematopoietic stem cells (HSCs) during embryonic development remains unclear. Here, combined genetic and single-cell sequencing analyses reveal megakaryocytes as a critical niche component in the mouse embryonic aorta-gonad-mesonephros (AGM) region regulating HSC precursor generation. Megakaryocyte depletion reduces HSC activity in the AGM region. Megakaryocyte depletion decreases pre-HSC formation and maturation. CD226+ megakaryocytes most potently enhance HSC specification and promote endothelial-to-hematopoietic transition by secreting TNFSF14. TNFSF14 treatment rescues formation of hematopoietic cells in the megakaryocyte-deficient cocultures. CD226-positive megakaryocytes control hematopoietic stem cell specification in the developing mouse embryo. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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