JMCB:中科院上海生科院杨黄恬研究组揭示内质网钙离子通道三磷
2017年4月13日，国际学术期刊《Journal of molecular Cell Biology》在线发表了中国科学院上海生命科学研究院杨黄恬研究组联合北京大学深圳研究生院欧阳昆富研究组、同济大学教授高绍荣团队和美国加州大学圣地亚哥分校教授陈炬共同发表题为IP3R-mediated Ca2+ signals govern hematopoietic and cardiac divergence of Flk1+ cells via the calcineurin-NFATc3-Etv2 pathway 的最新研究发现。研究揭示了IP3Rs家族在调控胚胎干细胞(ESCs)向造血和心肌谱系分化命运决定中的重要作用和其作用机制。王毅洁和黄吉均等为论文第一作者，杨黄恬研究员为论文通讯作者。
细胞分化命运的决定依赖于多种信号分子和转录因子精确而严格的调控。钙离子(Ca2+)是细胞内重要的第二信使，参与调控细胞的增殖、凋亡和分化等多种重要生理过程，但对其在哺乳类细胞的确切调控作用和调控通路了解甚少。ESCs具有自我更新和多能分化的特性，其向特定细胞分化过程重现了体内胚胎早期发育的时空特点和调控模式，因此是解析基因敲除导致胚胎致死基因在发育早期功能的独特体系，对ESCs分化机制的研究有助于认识胚胎发育的调控机制。三磷酸肌醇受体(IP3Rs)是内质网重要的Ca2+释放通道。小鼠(m)ESCs中存在三种IP3Rs亚型，亚型间功能既有特异性又存在代偿。此前杨黄恬研究团队发现IP3R3介导的Ca2+释放通过调控ESCs心肌前体细胞的凋亡影响ESC向心肌谱系的分化，但IP3Rs家族在ESCs特定谱系决定中的精细调控作用和机制尚未阐明。造血和心肌谱系均来自中胚层来源心脏/造血祖细胞(Flk1+)的分化，然而尚不清楚Flk1+细胞是受何种信号调控从而选择造血或心肌谱系分化的。
本研究发现ESCs自我更新和三胚层形成并不依赖于IP3Rs，然而造血中胚层(Flk1+/PDGFRa-)的出现依赖于IP3Rs介导的钙信号，这一钙信号的缺失抑制中胚层向造血谱系分化但促进其向心肌谱系的分化。在机制方面，IP3Rs释放的Ca2+而非细胞外的Ca2+内流通过激活钙调磷酸酶(calcineurin)，进而使得下游的NFATc3结合到调控造血发生的转录因子Etv2启动子促进其表达，进而诱导造血细胞分化而防止心肌细胞分化。研究发现并揭示了IP3Rs在ESCs向造血和心肌这两种具有同一胚层祖先的谱系命运决定中的重要作用，进一步证实Ca2+信号对于细胞命运调控的重要性和精确性。
图：IP3Rs释放的Ca2+通过calcineurin-NFATc3-Etv2信号通路，调控造血谱系和心肌谱系分化命运决定
原文链接：
IP3R-mediated Ca2+ signals govern hematopoietic and cardiac divergence of Flk1+ Cells via the calcineurin-NFATc3-Etv2 pathway
原文摘要：
Ca2+ signals participate in various cellular processes with spatial and temporal dynamics, among which, inositol 1,4,5-trisphosphate receptors (IP3Rs)-mediated Ca2+ signals are essential for early development. However, the underlying mechanisms of IP3R-regulated cell fate decision remain largely unknown. Here we report that IP3Rs are required for the hematopoietic and cardiac fate divergence of mouse embryonic stem cells (mESCs). Deletion of IP3Rs (IP3R-tKO) reduced Flk1+/PDGFRα− hematopoietic mesoderm, c-Kit+/CD41+ hematopoietic progenitor cell population, and the colony-forming unit activity, but increased cardiac progenitor markers as well as cardiomyocytes. Concomitantly, the expression of a key regulator of hematopoiesis, Etv2, was reduced in IP3R-tKO cells, which could be rescued by the activation of Ca2+ signals and calcineurin or overexpression of constitutively active form of NFATc3. Furthermore, IP3R-tKO impaired specific targeting of Etv2 by NFATc3 via its evolutionarily conserved cis-element in differentiating ESCs. Importantly, the activation of Ca2+–calcineurin–NFAT pathway reversed the phenotype of IP3R-tKO cells. These findings reveal an unrecognized governing role of IP3Rs in hematopoietic and cardiac fate commitment via IP3Rs–Ca2+–calcineurin–NFATc3–Etv2 pathway.
作者：杨黄恬
