Division of Genomics of Development and Disease, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
Department of Anatomy & Physiology, The University of Melbourne, Melbourne, Victoria 3010, Australia.
Development. 2022 May 1;149(9). doi: 10.1242/dev.190421. Epub 2022 May 9.
The endocardium plays important roles in the development and function of the vertebrate heart; however, few molecular markers of this tissue have been identified and little is known about what regulates its differentiation. Here, we describe the Gt(SAGFF27C); Tg(4xUAS:egfp) line as a marker of endocardial development in zebrafish. Transcriptomic comparison between endocardium and pan-endothelium confirms molecular distinction between these populations and time-course analysis suggests differentiation as early as eight somites. To investigate what regulates endocardial identity, we employed npas4l, etv2 and scl loss-of-function models. Endocardial expression is lost in npas4l mutants, significantly reduced in etv2 mutants and only modestly affected upon scl loss-of-function. Bmp signalling was also examined: overactivation of Bmp signalling increased endocardial expression, whereas Bmp inhibition decreased expression. Finally, epistasis experiments showed that overactivation of Bmp signalling was incapable of restoring endocardial expression in etv2 mutants. By contrast, overexpression of either npas4l or etv2 was sufficient to rescue endocardial expression upon Bmp inhibition. Together, these results describe the differentiation of the endocardium, distinct from vasculature, and place npas4l and etv2 downstream of Bmp signalling in regulating its differentiation.
心内膜在脊椎动物心脏的发育和功能中发挥着重要作用；然而，目前仅鉴定出少数该组织的分子标记物，对其分化的调控机制也知之甚少。本文描述了 Gt(SAGFF27C);Tg(4xUAS:egfp) 品系作为斑马鱼心内膜发育的标志物。心内膜和全内皮之间的转录组比较证实了这两种细胞群体之间存在分子差异，并且时程分析表明分化早在 8 个体节时就已经开始。为了研究什么调控心内膜的特性，我们利用了 npas4l、etv2 和 scl 功能丧失模型。npas4l 突变体中心内膜表达缺失，etv2 突变体中心内膜表达显著减少，而 scl 功能丧失仅导致轻微影响。Bmp 信号通路也进行了研究：Bmp 信号通路的过度激活增加了心内膜的表达，而 Bmp 抑制则降低了表达。最后，上位性实验表明，Bmp 信号通路的过度激活不能在 etv2 突变体中恢复心内膜的表达。相比之下，在 Bmp 抑制时，npas4l 或 etv2 的过表达足以挽救心内膜的表达。综上所述，这些结果描述了心内膜的分化，与脉管系统不同，并将 npas4l 和 etv2 置于 Bmp 信号通路下游，调控其分化。
