From the Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany (F.G., A.G., S.G., D.Y.R.S., A.B.-B.).
German Centre for Cardiovascular Research (DZHK), Partner Site Rhine-Main, Bad Nauheim (F.G., S.G., D.Y.R.S., A.B.-B.).
Circ Res. 2020 Apr 10;126(8):968-984. doi: 10.1161/CIRCRESAHA.119.315992. Epub 2020 Feb 18.
The transcription factor NFATC1 (nuclear factor of activated T-cell 1) has been implicated in cardiac valve formation in humans and mice, but we know little about the underlying mechanisms. To gain mechanistic understanding of cardiac valve formation at single-cell resolution and insights into the role of NFATC1 in this process, we used the zebrafish model as it offers unique attributes for live imaging and facile genetics.
To understand the role of Nfatc1 in cardiac valve formation.
Using the zebrafish atrioventricular valve, we focus on the valve interstitial cells (VICs), which confer biomechanical strength to the cardiac valve leaflets. We find that initially atrioventricular endocardial cells migrate collectively into the cardiac jelly to form a bilayered structure; subsequently, the cells that led this migration invade the ECM (extracellular matrix) between the 2 endocardial cell monolayers, undergo endothelial-to-mesenchymal transition as marked by loss of intercellular adhesion, and differentiate into VICs. These cells proliferate and are joined by a few neural crest-derived cells. VIC expansion and a switch from a promigratory to an elastic ECM drive valve leaflet elongation. Functional analysis of Nfatc1 reveals its requirement during VIC development. Zebrafish mutants form significantly fewer VICs due to reduced proliferation and impaired recruitment of endocardial and neural crest cells during the early stages of VIC development. With high-speed microscopy and echocardiography, we show that reduced VIC formation correlates with valvular dysfunction and severe retrograde blood flow that persist into adulthood. Analysis of downstream effectors reveals that Nfatc1 promotes the expression of -a well-known regulator of epithelial-to-mesenchymal transition.
Our study sheds light on the function of Nfatc1 in zebrafish cardiac valve development and reveals its role in VIC formation. It also further establishes the zebrafish as a powerful model to carry out longitudinal studies of valve formation and function.
转录因子 NFATC1（活化 T 细胞的核因子 1）已被牵涉到人类和小鼠的心脏瓣膜形成中，但我们对其潜在机制知之甚少。为了在单细胞分辨率上获得对心脏瓣膜形成的机制理解，并深入了解 NFATC1 在这一过程中的作用，我们利用斑马鱼模型，因为它具有用于活体成像和易于遗传操作的独特属性。
了解 Nfatc1 在心脏瓣膜形成中的作用。
我们利用斑马鱼房室瓣，重点研究赋予心脏瓣膜小叶生物力学强度的瓣膜间质细胞（VIC）。我们发现，最初房室心内膜细胞集体迁移到心脏胶质中形成双层结构；随后，引领这种迁移的细胞侵入 2 个心内膜细胞单层之间的细胞外基质（ECM），经历细胞间黏附丧失的内皮到间充质转化，并分化为 VIC。这些细胞增殖，并与少数神经嵴衍生细胞融合。VIC 扩张以及从促迁移到弹性 ECM 的转变驱动瓣膜小叶伸长。Nfatc1 的功能分析显示其在 VIC 发育过程中的必要性。由于在 VIC 发育的早期阶段增殖减少和心内膜及神经嵴细胞募集受损，斑马鱼突变体形成的 VIC 明显较少。通过高速显微镜和超声心动图，我们表明 VIC 形成减少与瓣膜功能障碍和严重逆行血流相关，这些问题持续到成年期。对下游效应物的分析表明，Nfatc1 促进了 -上皮到间充质转化的一个众所周知的调节因子的表达。
我们的研究揭示了 Nfatc1 在斑马鱼心脏瓣膜发育中的功能及其在 VIC 形成中的作用。它还进一步确立了斑马鱼作为进行瓣膜形成和功能的纵向研究的强大模型。
