Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Department of Cell Biology and Anatomy, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada.
Cell Commun Signal. 2022 Aug 19;20(1):126. doi: 10.1186/s12964-022-00874-8.
During development a pool of precursors form a heart with atrial and ventricular chambers that exhibit distinct transcriptional and electrophysiological properties. Normal development of these chambers is essential for full term survival of the fetus, and deviations result in congenital heart defects. The large number of genes that may cause congenital heart defects when mutated, and the genetic variability and penetrance of the ensuing phenotypes, reveals a need to understand the molecular mechanisms that allow for the formation of chamber-specific cardiomyocyte differentiation.
We used in situ hybridization, immunohistochemistry and functional analyses to identify the consequences of the loss of the secreted semaphorin, Sema3fb, in the development of the zebrafish heart by using two sema3fb CRISPR mutant alleles.
We find that in the developing zebrafish heart sema3fb mRNA is expressed by all cardiomyocytes, whereas mRNA for a known receptor Plexina3 (Plxna3) is expressed preferentially by ventricular cardiomyocytes. In sema3fb CRISPR zebrafish mutants, heart chamber development is impaired; the atria and ventricles of mutants are smaller in size than their wild type siblings, apparently because of differences in cell size and not cell numbers. Analysis of chamber differentiation indicates defects in chamber specific gene expression at the border between the ventricular and atrial chambers, with spillage of ventricular chamber genes into the atrium, and vice versa, and a failure to restrict specialized cardiomyocyte markers to the atrioventricular canal (AVC). The hypoplastic heart chambers are associated with decreased cardiac output and heart edema.
Based on our data we propose a model whereby cardiomyocytes secrete a Sema cue that, because of spatially restricted expression of the receptor, signals in a ventricular chamber-specific manner to establish a distinct border between atrial and ventricular chambers that is important to produce a fully functional heart. Video abstract.
在发育过程中，一群前体细胞形成具有明显转录和电生理特性的心房和心室腔的心脏。这些腔室的正常发育对于胎儿的足月存活至关重要，而发育偏差则导致先天性心脏缺陷。大量可能导致先天性心脏缺陷的基因突变，以及随之而来的表型的遗传变异性和外显率，揭示了需要了解允许形成腔特异性心肌细胞分化的分子机制。
我们使用原位杂交、免疫组织化学和功能分析来鉴定两个 sema3fb CRISPR 突变等位基因在斑马鱼心脏发育过程中缺失分泌的信号素 Sema3fb 的后果。
我们发现，在发育中的斑马鱼心脏中，sema3fb mRNA 由所有心肌细胞表达，而已知受体 Plexina3（Plxna3）的 mRNA 则优先由心室心肌细胞表达。在 sema3fb CRISPR 斑马鱼突变体中，心脏腔室发育受损；突变体的心房和心室比其野生型兄弟姐妹小，显然是由于细胞大小的差异而不是细胞数量的差异。对腔室分化的分析表明，在心室和心房腔之间的边界处存在腔特异性基因表达缺陷，心室腔基因溢出到心房，反之亦然，并且不能将专门的心肌细胞标记物限制在房室管（AVC）内。发育不良的心脏腔室与心输出量减少和心脏水肿有关。
基于我们的数据，我们提出了一个模型，即心肌细胞分泌一种信号素 cue，由于受体的空间限制表达，以心室腔特异性的方式发出信号，在心房和心室腔之间建立一个重要的独特边界，这对于产生一个功能齐全的心脏至关重要。视频摘要。
