An important role of Osr1 in outflow tract development

项目摘要 先天性心脏病(CHD)发生在近1,000名活产儿中，约三分之一涉及 心脏流出道畸形(OFT)。右室双出口(DORV)和主动脉(AO) 是由OFT未对准引起的异常。目前与OFT错位相关的先天性心脏病的病因 在很大程度上是未知的，OFT发展的细胞、遗传和分子基础仍然难以捉摸。OSR1编码 一种锌指蛋白，在心脏发育早期强烈表达于心脏背侧中膜。我们发现 表达Osr1的前体细胞参与了肺干，Osr1的缺失导致DORV或OA。 Osr1基因缺失的小鼠胚胎存在OFT旋转问题，并存在SHF前体细胞在 心背系膜，可能是SHF的增殖缺陷所致。有趣的是，我们和其他人报道 Pten是一种公认的负向扩散调节因子，它的减少可以挽救SHF的扩散缺陷， 提示Pten在调节Osr1调控的SHF增殖中具有抑制作用。我们进一步确定了潜在的 Osr1直接靶点：CDK6和CycD2参与细胞周期调节，以及HH信号调节剂Smo。后者 提出了Osr1和HH信号之间的相互作用，这一发现进一步支持了这一发现 Osr1和Smo复合杂合突变导致DORV的高穿透性。总体而言，这些结果强劲 提示OFT的发生与SHF中的Osr1、HH信号和细胞周期基因的遗传调控有关。我们 假设：与Pten抑制平衡，Osr1通过以下方式调节SHF的增殖 增殖相关基因转录调控与HH信号转导。为了检验这一假设，我们提出了 以下三个目标：(1)确定Osr1如何调节SHF细胞的增殖以正确地排列OFT；(2) 研究Osr1是否以及如何在HH信号的上游调控OFT的发育；(3)试图确定 Osr1对SHF和DORV增殖的调节被Pten抑制所平衡。这项工作将发现新的候选基因 常见形式的先天性心脏病的基因和机制。

Project Summary Congenital heart defect (CHD) occurs in nearly 1 of 1000 live births, and approximately one third involves malformations of the cardiac outflow tract (OFT). Double outlet right ventricle (DORV) and overriding aorta (AO) are anomalies resulting from OFT misalignment. Currently the etiology of CHDs associated with OFT misalignment is largely unknown and the cellular, genetic, molecular basis of OFT development has remained elusive. Osr1 encodes a zinc finger protein and is strongly expressed in the dorsal mesocardium during early heart development. We found that precursor cells expressing Osr1 contributed to the pulmonary trunk and deletion of Osr1 caused DORV or OA. The Osr1 null mouse embryos had OFT rotation problem and had abnormal patterning of the SHF precursor cells in the dorsal mesocardium, which might result from proliferation defects in SHF. Interestingly, we and others reported that reduction of Pten, a well-established negative proliferation regulator, could rescue SHF proliferation defects, implying an inhibition role of Pten in modulating Osr1 regulated-SHF proliferation. We further identified potential Osr1 direct targets: Cdk6 and CycD2 involving cell cycle regulators, and Hh-signaling modulator Smo. The latter suggested an interaction between Osr1 and Hh-signaling, which is further supported by the finding that double compound heterozygous mutation of Osr1 and Smo caused a high penetration of DORV. Overall, these results strongly suggested a genetic regulatory of Osr1, Hh-signaling and cell cycle genes in SHF for OFT development. We hypothesize: Balanced by Pten inhibition, Osr1 modulates proliferation in SHF during OFT development by transcriptional regulation of proliferation related genes and Hh-signaling. To test this hypothesis, we propose the following three aims: (1) to determine how Osr1 modulates SHF cell proliferation for proper OFT alignment; (2) to investigate if and how Osr1 functions upstream of Hh-signaling in regulating OFT development; (3) to determine that Osr1 regulation on SHF proliferation and DORV is balanced by Pten inhibition. This work will uncover new candidate genes and mechanisms underlying common forms of CHDs.