Genetics of endocardial-myocardial interactions during zebrafish heart development

心内膜是位于心管内部的一种特殊的内皮细胞，在心脏发育和生理中起着重要作用。尽管心内膜祖细胞对心脏的正常功能具有重要意义，但心内膜祖细胞的发育起源和心内膜细胞命运规范的分子机制在很大程度上仍未得到解决。本研究旨在探讨心内膜细胞命运调控的分子机制，并开发转基因方法来诱导斑马鱼胚胎的心内膜。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相关的基本机制和分子问题。首先，我们将产生稳定的转基因斑马鱼系，用于强制过表达与心内膜细胞命运规范有关的候选因子。在细胞移植试验中，我们将把这些转基因细胞系的细胞导入野生型胚胎，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特征。在我们自己的前期工作中，我们最近发现，在心肌仍然存在的情况下，Hedgehog辅助受体Lrp2b的缺失完全删除了心内膜组织。在这里，我们将进一步分析其作用和刺猬信号在心内膜祖细胞生物学中的作用。特别令人感兴趣的将是Lrp2b和Hedgehog信号与心内膜细胞命运规范的其他调节因子的遗传层次关系。综上所述，这些研究将为这种独特的血管床的发育起源提供重要的新见解。诱导心内膜细胞命运的转基因编码结构的产生将为功能上操纵心内膜祖细胞开辟新的途径。

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.