Left-right patterning abnormalities and cardiac morphogenesis

摘要 先天性心脏病是发病率和死亡率的一个重要原因，影响着150多万人 美国的儿童和成年人。异质性综合征是一种多系统障碍，其特征是 先天性心脏病的频谱，至少部分可归因于异常的左右不对称。虽然链接 左右构型和随后的心脏形态发生之间的关系还不是很清楚，很明显 在异位畸形中可见的室腔形态缺陷比正常情况下更多样。 从左-右轴的简单破坏中预料到。这项研究将对细胞和分子进行研究 用两种小鼠模型观察心脏形态发生异常的机制 左右图案化缺陷：Foxj1和Zic3缺陷小鼠。Foxj1是纤毛发生和小鼠缺陷所必需的 因为这种基因不能在结节上形成纤毛，而纤毛是正常左右排列所必需的组织。Zic3，基因 负责X连锁的异质性，表现出包括结节在内的原始条纹的异常。 以前，我们证明Zic3的表达是原始人的中内胚层细胞所必需的 用于心脏正常发育的条纹，但不是心脏所必需的。后面的原始条纹产生了 至心脏祖细胞/心前中胚层(CPPM)，前原始条纹形成纤毛 因此，Zic3缺乏可能通过时间上不同的组合事件导致CHDS。这些结果可能 解释异育系中发现的广泛的表型变异，表明 “发展中的成功”模式。我们的发现提出了一种新的假设，即冠心病的不同谱系 在异质性中观察到的结果是心脏前体细胞的异常规格、增殖和/或细胞命运 这与后来的左向右模式对心脏循环的影响截然不同。我们将在这两种情况下测试这一假设 老鼠模型。本研究的目的是：1)确定CPPM和结节细胞是否独立地引起 CHDS，以及细胞极性异常是否是早期和/或晚期事件的基础；以及2)测试 假设不同的心脏谱系在冠心病中受到影响，来自具有不同遗传原因的左心衰小鼠。 右花纹异常。最重要的假设是PCCM异常和左右 异常对异位性CHD有不同的贡献，细胞中的异常 增殖或细胞极性是这些异常的基础。通过对早期中胚层Zic3功能的描述，我们发现 将获得关于正常基元条纹和节点形成、左右轴规范、 以及它们与心脏环路和心室形态发生的关系。细胞谱系的鉴定 异质性对CHD的贡献将提供关于病因和表型的新信息 异质性。总而言之，这些研究将确定原肠阶段和节期的要求 分子相互作用及其对正常心脏所必需的细胞命运的影响 形态发生。

ABSTRACT Congenital heart defects (CHDs) are a significant cause of morbidity and mortality, affecting over 1.5 million children and adults in the United States. Heterotaxy syndrome is a multisystem disorder characterized by a spectrum of CHDs that are attributable, at least in part, to abnormal left-right asymmetry. Although the link between left-right patterning and subsequent cardiac morphogenesis is not well understood, it is apparent that the ventricular chamber morphogenic defects seen in heterotaxy are more diverse than what would be expected from simple disruption of the left-right axis. This research will investigate the cellular and molecular mechanisms underlying abnormal cardiac morphogenesis observed in heterotaxy using two mouse models of left-right patterning defects: Foxj1 and Zic3 deficient mice. Foxj1 is required for ciliogenesis and mice deficient for this gene fail to develop cilia at the node, a tissue required for normal left-right patterning. Zic3, the gene responsible for X-linked heterotaxy, exhibits abnormalities of the primitive streak including the node. Previously, we demonstrated that expression of Zic3 is required by the mesendodermal cells of the primitive streak for normal cardiac development, but is not required in the heart. The posterior primitive streak gives rise to cardiac progenitor/precardiac mesoderm (CPPM), and the anterior primitive streak gives rise to the ciliated node, thus Zic3 deficiency may cause CHDs via temporally distinct, combinatorial events. These results could provide explanations for the wide phenotypic variability identified in heterotaxy, suggesting a “multiple developmental hits” model. Our findings suggest the novel hypothesis that the diverse spectrum of CHDs observed in heterotaxy results from abnormal specification, proliferation, and/or cell fate of cardiac progenitors that is distinct from the later left-right patterning effects on heart looping. We will test this hypothesis in both mouse models. The aims of this study are to: 1) determine whether CPPM and node cells independently cause CHDs, and whether cell polarity abnormalities underlie early and/or late stage events; and 2) test the hypothesis that distinct cardiac-lineages are impacted in CHDs from mice with different genetic causes of left- right patterning abnormalities. The overarching hypothesis is that PCCM abnormalities and left-right abnormalities have distinct contributions to the CHDs identified in heterotaxy and that abnormalities in cell proliferation or cell polarity underlie these abnormalities. By delineation of Zic3 function in early mesoderm, we will acquire essential information about normal primitive streak and node formation, left-right axis specification, and their relationship to cardiac looping and ventricular morphogenesis. Identification of the cell lineage contribution to CHDs seen in heterotaxy will provide novel information about causation and phenotypic heterogeneity. Collectively, these studies will define the requirement of gastrulation-stage and node-stage molecular interactions along with their impact on cell fate specification necessary for normal cardiac morphogenesis.