Genetics of endocardial-myocardial interactions during zebrafish heart development

心内膜是一种特殊的内皮细胞，位于心管内部，在心脏发育和生理中起着重要作用。尽管心内膜前体细胞对心脏的正常功能很重要，但心内膜前体细胞的发育起源和心内膜细胞命运决定的分子机制在很大程度上仍未解决。本研究旨在研究斑马鱼胚胎心内膜细胞命运决定的分子机制，并开发转基因方法诱导斑马鱼胚胎心内膜形成。这将使我们能够解决与心内膜生物学、发育、生理学及其与心肌相互作用有关的基本机制和分子问题。首先，我们将建立稳定的斑马鱼转基因系，用于强制过度表达与心内膜细胞命运相关的候选因子。在细胞移植试验中，我们将把这些转基因品系的细胞引入野生型胚胎，并评估它们对新生心内膜的贡献。这种方法将揭示诱导心内膜细胞命运所需的分子信号。在我们自己的前期工作中，我们最近发现辅助Hedgehog受体Lrp2b的丢失完全删除了心内膜组织，而心肌仍然存在。在这里，我们将进一步分析它的作用和Hedgehog信号在心内膜前体细胞生物学中的作用。特别令人感兴趣的是Lrp2b和Hedgehog信号与心内膜细胞命运规范的其他调节因子相关的遗传层次。综上所述，这些研究将为这一独特的血管床的发育起源提供重要的新见解。用于诱导心内膜细胞命运的转基因编码构建体的产生将为从功能上操纵心内膜前体细胞开辟新的途径。

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.