Left-right patterning abnormalities and cardiac morphogenesis

摘要 先天性心脏病（CHD）是发病率和死亡率的重要原因，影响超过150万人 美国的儿童和成人。异位综合征是一种多系统疾病， CHD的频谱，至少部分归因于异常的左右不对称。虽然链接 左-右模式和随后的心脏形态发生之间的关系还没有很好的理解，很明显， 在异位症中所见的心室腔形态发生缺陷比在异位症中所见的心室腔形态发生缺陷更多样化， 这是由于左右轴的简单破坏造成的这项研究将研究细胞和分子 使用两种小鼠模型在异位症中观察到的异常心脏形态发生的潜在机制 左右图案缺陷：Foxj 1和Zic 3缺陷小鼠。Foxj 1是纤毛发生所必需的， 因为这种基因不能在淋巴结处形成纤毛，而纤毛是正常的左右图案所需的组织。Zic 3基因 负责X连锁异位，表现出异常的原始条纹，包括节点。 以前，我们证明了Zic 3的表达是原始的中内胚层细胞所必需的。 正常心脏发育的条纹，但在心脏中不需要。后面的原始条纹 心脏祖细胞/心前中胚层（CPPM），前原条产生纤毛 节点，因此Zic 3缺陷可能会通过时间上不同的组合事件导致CHD。这些结果可能 提供了解释广泛的表型变异性确定在异位，提出了“多重 发展命中”模式。我们的研究结果提出了一个新的假设，即冠心病的多样性 在由心脏祖细胞的异常特化、增殖和/或细胞命运引起的异位症中观察到 这与后来的左右图案化对心脏循环的影响不同。我们将在两个方面检验这一假设。 小鼠模型。本研究的目的是：1）确定CPPM和结细胞是否独立地引起 CHD，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受到来自具有不同遗传原因的小鼠的CHD的影响， 右模式异常。总体假设是PCCM异常和左右 异常对异位症中确定的CHD有明显的作用， 增殖或细胞极性是这些异常的基础。通过描述Zic 3在早期中胚层中的功能，我们 将获得关于正常原始条纹和节点形成、左右轴规格、 以及它们与心脏循环和心室形态发生的关系。细胞谱系的鉴定 在异位症中观察到的对CHD的贡献将提供关于病因和表型的新信息。 异质性总的来说，这些研究将确定原肠胚期和结期的要求 分子相互作用沿着其对正常心脏所必需的细胞命运规范的影响 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.