利用Bmp9/Bmp10基因替换小鼠模型研究Bmp10对心室壁发育的分子调控机制

Bmp10 and Bmp9 are two evolutionarily close related growth factors belonging to TGF-β super family, and specifically expressed in developing heart and liver, respectively. Bmp10 is a critical cardiac cytokine involved in regulating cardiac development and angiogenesis. Despite several studies pointing out the essential function of Bmp10 in ventricular wall growth, the underlying molecular mechanism remains unclear, largely due to its biological activity in vascular development which may impact on cardiac morphogenesis during early embryonic development, and also due to the early embryonic lethality caused by the combined complication of both cardiac and vascular failure in Bmp10-deficient mice. We recently generated a unique model in which Bmp10 was genetically substituted by Bmp9 (Bmp10^9/9), in which Bmp10 coding region was replaced by Bmp9 as such that Bmp9 expressed ectopically in early developing heart. Our initial analysis demonstrated that Bmp10^9/9 was able to correct abnormal vascular development. However, the poor ventricular wall development was remained in Bmp10^9/9 mutants, that clearly suggesting that despite close similarity and functionally redundant of Bmp10 and Bmp9 in vascular development, Bmp10 has a specific function in regulating cardiac development. In this proposal, by taking the advantage of having this unique Bmp10^9/9 mouse model, we will carry out a series of detailed analyses to determine the role of Bmp10 in cardiac development, which includes 1) further analysis of ventricular wall growth defect in Bmp10^9/9 hearts; 2) identifying the downstream signaling pathway through which Bmp10 functionally regulates ventricular wall development; 3) determine whether Bmp10, but not Bmp9, is able to regulate Tbx20 expression in embryonic cardiac development. Collectively, our proposal will reveal the unique Bmp10-mediated signaling pathway contributing to ventricular wall development.

Bmp10和Bmp9同属于TGF-β超家族，进化上非常同源，在胚胎发育中分别特异表达在心脏和肝脏中。Bmp10决定胎心的正常发育和血管的发生及形成，而Bmp9则主要调控出生后血管的形成。尽管有不少Bmp10在心脏发育中的相关研究，但由于胚胎的血管发生和心脏发育相互决定和影响，致使Bmp10调控心脏发育的具体机制尚不明确。我们构建的Bmp9原位替代Bmp10（Bmp10^9/9）的小鼠模型中，Bmp9在心脏的异位表达能够替代Bmp10对胚胎血管发生进行正常调控，但胚胎心脏，尤其是心室壁仍存在严重的发育缺陷，提示Bmp10利用了Bmp9不能替代的其他途径调控心室壁的发育。本项目拟利用已有的Bmp10^9/9小鼠模型，深入研究Bmp10在调节心室壁发育过程中的分子调控机制和下游信号途径，并进一步解析Bmp10在心室壁发育中对Tbx20表达的调节，为先心病的发病机理与临床干预的研究提供新切入点。

Bmp10和Bmp9同属于TGF-β超家族，进化上非常同源， Bmp10决定胎心的正常发育和血管的发生及形成，而Bmp9则主要调控出生后血管的发生。尽管已有不少Bmp10在心脏发育中的相关研究，但由于胚胎时期的血管发生和心脏发育相互决定和影响，致使Bmp10调控心脏发育的具体机制尚不明确。本项目利用特有的Bmp9 基因原位替换Bmp10 小鼠模型（Bmp10^9/9 小鼠模型）研究Bmp10 在心脏发育早期心室壁形成过程中的作用。发现Bmp10^9/9小鼠胎心在E12.5天出现发育缺陷表型，心肌细胞增殖减慢，表达谱芯片比较Bmp10^9/9 ，Bmp10^+/9 和正常对照胎心样品，聚类分析得到23个基因表达明显发生变化，其中中胚层发育关键转录因子Sox17的表达量在Bmp10^9/9 小鼠胎心（E14.5）中明显下调，已有研究已发现Sox17与Bmp信号通路相关。另外还发现多个与心血管发育及疾病相关基因的表达出现变化，其在发育中的作用需进一步探明，我们发现的这组表达变化基因将为先心病的发病机理与临床干预的研究提供新切入点. 为研究Bmp10在成体心脏中的功能，利用药物诱导心肌过量表达Bmp10模型进行心脏损伤修复能力评价，获得了令人欣喜的结果，我们明显发现成年鼠诱导表达Bmp10后，能够有效保护心脏，降低药物损伤程度，增强损伤后心肌细胞的修复能力，进而提示了Bmp10作为老年心血管高风险病人心脏保护防治干预手段的预防靶点的潜在可能。