Mechanism of LV Hypoplasia in Hypoplastic Left Heart Syndrome Supplement

左心发育不良综合征（HLHS）是一种先天性心脏缺陷（CHD）， 心室（LV）和发育不全的主动脉和主动脉/二尖瓣。强烈提示HLHS的遗传病因学 但对HLHS的遗传基础了解甚少。临床研究表明 HLHS是多基因和遗传异质性的。对HLHS遗传学的见解来自我们的 最近从大规模小鼠诱变筛选中恢复了第一个HLHS小鼠模型。从8 回收了独立的HLHS小鼠品系，鉴定了330个突变，没有共同的基因 在8条线之间。这些发现表明HLHS具有深刻的遗传异质性，与 人类研究对一个突变小鼠品系Ohia的详细分析表明，HLSH是由两个突变引起的， 基因：Sap 130，染色质修饰组蛋白脱乙酰酶复合物（HDAC）中的Sin 3a相关蛋白， 和Pcdha 9，一种介导细胞-细胞粘附的原钙粘蛋白。LV发育不全被证明是由 Sap 130突变，这一发现证实了CRISPR产生的小心室表型的复制。 sap 130 a斑马鱼突变体。左室发育不全与心肌细胞增殖缺陷有关 和心肌细胞周期停滞。在本研究中，我们将探讨细胞和分子机制 和遗传相互作用驱动HLHS中的LV发育不全，利用斑马鱼的独特优势 和小鼠模型。在目标1中，我们将采用斑马鱼谱系追踪研究和Cre实验 在小鼠中缺失Sap 130，以检验Sap 130以细胞自主方式发挥功能的假设， 调节心室/LV生长。这些研究将描述Sap 130调节LV的细胞环境 增长在目的2中，我们将研究亚型Sap 130 Ohia突变导致LV的假设。 通过调节心肌细胞细胞周期和细胞增殖的靶基因的发育不全。这些研究将 Meis 1是一个Sap 130靶基因，也是已知调节心肌细胞细胞周期和出生后细胞增殖的基因。 循环停滞与此同时，通过Sap 130 ChIP-seq和RNA-seq分析鉴定的其他候选基因将在2015年10月25日至26日期间进行。 通过产生和分析CRISPR靶向胚胎来评估它们在LV发育不全中的作用， 小鼠在目标3中，我们将探索在细胞凋亡中染色质修饰剂与Ras/MAPK信号通路的相互作用。 用致敏基因敲低斑马鱼反义morpholino基因研究HLHS的发病机制 背景将使用突变体或CRISPR靶向的斑马鱼或小鼠验证阳性遗传相互作用。 这项研究的动机是意外恢复的突变染色质修饰和Ras/MAPK 在所有8个HLHS小鼠系中，表明染色质修饰剂与 Ras/MAPK信号通路的异常调节可能与左室发育不全和HLHS的复杂遗传学有关。 这些研究将有助于阐明驱动心室肌细胞的细胞和分子机制。 HLHS中的发育不全，这些发现可能为胎儿干预恢复LV生长产生新的治疗靶点。 !

Hypoplastic Left Heart Syndrome (HLHS) is a congenital heart defect (CHD) characterized by a small left ventricle (LV) and hypoplastic aorta and aortic/mitral valves. A genetic etiology for HLHS is strongly indicated by high recurrence risk, but the genetic underpinning for HLHS is poorly understood. Clinical studies suggest HLHS is multigenic and genetically heterogeneous. Insights into the genetics of HLHS has come from our recent recovery of the first mouse models of HLHS from a large-scale mouse mutagenesis screen. From 8 independent HLHS mouse lines recovered, 330 mutations were identified, with no genes shared in common between the 8 lines. These findings indicate HLHS is profoundly genetically heterogeneous, consistent with the human studies. Detailed analysis of one mutant mouse line, Ohia, showed HLSH is elicited by mutations in two genes: Sap130, a Sin3a associated protein in the chromatin modifying histone deacetylase complex (HDAC), and Pcdha9, a protocadherin mediating cell-cell adhesion. The LV hypoplasia was shown to be elicited by the Sap130 mutation, a finding confirmed with replication of a small ventricle phenotype in a CRISPR generated sap130a zebrafish mutant. The LV hypoplasia was associated with a cardiomyocyte cell proliferation defect and cardiomyocyte cell cycle arrest. In this study, we will investigate the cellular and molecular mechanisms and genetic interactions driving the LV hypoplasia in HLHS, leveraging the unique strengths of the zebrafish and mouse models. In Aim 1, we will employ lineage tracing studies in zebrafish and experiments with Cre deletion of Sap130 in mice to test the hypothesis that Sap130 functions in a cell autonomous manner to regulate ventricular/LV growth. These studies will delineate the cellular context in which Sap130 regulates LV growth. In Aim 2, we will investigate the hypothesis that the hypomorphic Sap130Ohia mutation causes LV hypoplasia via target genes that regulate cardiomyocyte cell cycle and cell proliferation. These studies will focus on Meis1, a Sap130 target gene, also known to regulate cardiomyocyte cell cycle and postnatal cell cycle arrest. In parallel, additional candidate genes identified via Sap130 ChIP-seq and RNA-seq analysis will be assessed for their role in LV hypoplasia with production and analysis of CRISPR targeted embryos and mice. In Aim 3, we will probe the interaction of chromatin modifiers with the Ras/MAPK signaling pathway in the pathogenesis of HLHS using antisense morpholino gene knockdown in zebrafish with a sensitized genetic background. Positive genetic interactions will be validated using mutant or CRISPR targeted zebrafish or mice. This study is motivated by the unexpected recovery of mutations in chromatin modifiers and Ras/MAPK pathway components in all 8 HLHS mouse lines, suggesting chromatin modifiers in combination with dysregulated Ras/MAPK signaling may contribute to the LV hypoplasia and complex genetics of HLHS. Together these studies will help to elucidate the cellular and molecular mechanisms driving the ventricular hypoplasia in HLHS, findings that may yield new therapeutic targets for fetal intervention to recover LV growth. !