Genetics of endocardial-myocardial interactions during zebrafish heart development

内皮细胞是衬在心管内部的特化内皮细胞，在心脏发育和生理学中具有重要作用。尽管其对心脏的正确功能的重要性，内皮祖细胞的发育起源和内皮祖细胞命运特化的分子机制在很大程度上仍然没有得到解决。该建议旨在表征内分泌细胞命运特化的分子机制，并开发转基因方法来诱导斑马鱼胚胎内分泌。这将使我们能够解决与内皮生物学、发育、生理学及其与心肌相互作用相关的基本机制和分子问题。首先，我们将产生稳定的斑马鱼转基因品系，用于在内皮细胞命运规范中起作用的候选因子的强制过表达。在细胞移植试验中，我们将这些转基因系的细胞导入野生型胚胎中，并评估它们对新生内膜的贡献。这种方法将揭示诱导内皮细胞命运所需的分子特征。在自己的初步工作中，我们最近发现，辅助Hedgehog受体Lrp2b的缺失完全删除了内膜组织，而心肌仍然存在。在这里，我们将进一步分析其作用和刺猬信号在内皮祖细胞生物学。特别感兴趣的将是Lrp2b和刺猬信号转导的遗传层次与其他监管机构的内皮细胞命运的规范。总之，这些研究将提供重要的新的见解，这种独特的血管床的发展起源。用于诱导内皮细胞命运的转基因编码构建体的产生将打开功能性操纵内皮祖细胞的新途径。

The endocardium is a specialized endothelium lining the interior of the heart tube with important roles in cardiac development and physiology. Despite its importance for the correct functioning of the heart, the developmental origin of endocardial progenitor cells and the molecular mechanisms of endocardial cell fate specification have largely remained unresolved. This proposal aims at characterizing the molecular mechanisms of endocardial cell fate specification and at developing transgenic approaches to induce endocardium in the zebrafish embryo. This will allow us to address fundamental mechanistic and molecular questions related to endocardial biology, development, physiology, and to its interactions with myocardium. First, we will generate stable transgenic lines of zebrafish for the forced overexpression of candidate factors with a role in endocardial cell fate specification. In cell transplantation assays, we will then introduce cells from these transgenic lines into wild-type embryos and assess their contribution to the nascent endocardium. This approach will reveal molecular signatures required for inducing endocardial cell fate. In own preliminary work, we recently found that loss of the auxiliary Hedgehog receptor Lrp2b completely deletes endocardial tissue while the myocardium is still present. Here, we will further analyse its role and that of Hedgehog signaling in endocardial progenitor cell biology. Of particular interest will be the genetic hierarchy of Lrp2b and of Hedgehog signaling in relation to other regulators of endocardial cell fate specification. Taken together, these studies will provide important novel insights into the developmental origins of this unique vessel bed. The generation of transgenically-encoded constructs for the induction of endocardial cell fate will open novel avenues to functionally manipulate endocardial progenitor cells.