脊椎动物的心脏发育需要线性管的复杂形态发生才能形成成熟的器官,对正确的心脏形态和功能至关重要的过程,需要协调胚胎侧向性,心脏生长,和区域化的细胞变化。虽然先前的研究已经证明了心脏形态发生中对细胞外基质(ECM)成分的广泛要求,我们假设ECM区域化可以在心脏发育过程中微调心脏形状.
使用斑马鱼胚胎的活体光片成像,我们描述了在心脏循环和腔室膨胀开始之前,ECM在心肌和心内膜之间的左侧扩张。使用ECM传感器的分析显示心脏ECM沿房室轴进一步区域化。心脏管中基因表达的空间转录组学分析鉴定了可能驱动ECM扩增的候选基因。这种方法确定了hapln1a的区域化表达,编码ECM交联蛋白。通过原位杂交对转录组数据的验证证实了心脏中区域化的hapln1a表达,在未来的心房和管的左侧表达水平最高,与观察到的ECM扩展重叠。对CRISPR-Cas9产生的hapln1a突变体的分析揭示了心房大小的减少和腔室膨胀的减少。功能损失分析表明,ECM扩展依赖于Hapln1a,共同支持Hapln1a在区域化ECM调节和心脏形态发生中的作用。对随机或不存在胚胎左右不对称性的斑马鱼突变体中hapln1a表达的分析显示,侧向性提示在心脏管的左侧不对称地定位hapln1a表达细胞。
我们确定了心脏管中区域化的ECM扩张,可促进正确的心脏发育,并提出了一种新的模型,通过该模型,胚胎侧向性线索将心脏中ECM不对称性的轴定向,这两个途径相互作用,促进强大的心脏形态发生。
Vertebrate heart development requires the complex morphogenesis of a linear tube to form the mature organ, a process essential for correct cardiac form and function, requiring coordination of embryonic laterality, cardiac growth, and regionalized cellular changes. While previous studies have demonstrated broad requirements for extracellular matrix (ECM) components in cardiac morphogenesis, we hypothesized that ECM regionalization may fine tune cardiac shape during heart development.
Using live in vivo light sheet imaging of zebrafish embryos, we describe a left-sided expansion of the ECM between the myocardium and endocardium prior to the onset of heart looping and chamber ballooning. Analysis using an ECM sensor revealed the cardiac ECM is further regionalized along the atrioventricular axis. Spatial transcriptomic analysis of gene expression in the heart tube identified candidate genes that may drive ECM expansion. This approach identified regionalized expression of hapln1a, encoding an ECM cross-linking protein. Validation of transcriptomic data by in situ hybridization confirmed regionalized hapln1a expression in the heart, with highest levels of expression in the future atrium and on the left side of the tube, overlapping with the observed ECM expansion. Analysis of CRISPR-Cas9-generated hapln1a mutants revealed a reduction in atrial size and reduced chamber ballooning. Loss-of-function analysis demonstrated that ECM expansion is dependent upon Hapln1a, together supporting a role for Hapln1a in regionalized ECM modulation and cardiac morphogenesis. Analysis of hapln1a expression in zebrafish mutants with randomized or absent embryonic left-right asymmetry revealed that laterality cues position hapln1a-expressing cells asymmetrically in the left side of the heart tube.
We identify a regionalized ECM expansion in the heart tube which promotes correct heart development, and propose a novel model whereby embryonic laterality cues orient the axis of ECM asymmetry in the heart, suggesting these two pathways interact to promote robust cardiac morphogenesis.