The transmembrane protein Crb2a regulates cardiomyocyte apicobasal polarity and adhesion in zebrafish

Abstract

Tissue morphogenesis requires changes in cell-cell adhesion as well as in cell shape and polarity. Cardiac trabeculation is a morphogenetic process essential for forming a functional ventricular wall. Here, we show that zebrafish hearts lacking Crb2a, a component of the Crumbs polarity complex, display compact wall integrity defects and fail to form trabeculae. Crb2a localization is very dynamic at a time when other cardiomyocyte junctional proteins also relocalize. Before the initiation of cardiomyocyte delamination to form the trabecular layer, Crb2a is expressed in all ventricular cardiomyocytes and colocalizes with the junctional protein ZO-1. Subsequently, Crb2a becomes localized all along the apical membrane of compact layer cardiomyocytes and is downregulated in the delaminating cardiomyocytes. We show that blood flow and Nrg/ErbB2 signaling regulate Crb2a localization dynamics. crb2a −/− display a multilayered wall with polarized cardiomyocytes: a unique phenotype. Our data further indicate that Crb2a regulates cardiac trabeculation by controlling the localization of tight and adherens junction proteins in cardiomyocytes. Importantly, transplantation data show that Crb2a controls CM behavior in a cell-autonomous manner in the sense that crb2a −/− cardiomyocytes transplanted into wild-type animals were always found in the trabecular layer. In summary, our study reveals a crucial role for Crb2a during cardiac development.

Pancreatic progenitor epigenome maps prioritize type 2 diabetes risk genes with roles in development

“…CRB2 is a component of the Crumbs protein complex involved in the regulation of cell polarity and neuronal, heart, retinal, and kidney development (Alves et al, 2013;Bulgakova & Knust, 2009;Dudok et al, 2016;Jimenez-Amilburu & Stainier, 2019;Slavotinek et al, 2015). However, its role in pancreatic development is unknown.…”

Left Ventricular Noncompaction Is Associated with Valvular Regurgitation and a Variety of Arrhythmias

“…Recent studies demonstrated that the polarity-dependent oriented cell division (OCD) and directional migration of cardiomyocytes in the single-cell-thick myocardium contribute to trabecular initiation, resulting in myocardium with multiple-layer cells in mice [13,[36][37][38][39]. However, in zebrafish, trabeculae are formed by polarity-dependent directional migration only [33,34,40]. Further study found that the cardiomyocyte in the outer and inner layers of the compact zone display different orientations during trabecular initiation, and disruption of their cellular orientation will result in trabecular initiation defects and LVNC [13,41].…”

Neuregulin-1 regulates cardiomyocyte dynamics, cell cycle progression, and maturation during ventricular chamber morphogenesis

“…We infer from our transcriptomics data that NRG1 regulates a morphogenetic process involving changes in cell behavior and/or shape, and whose disruption leads to profound changes in cardiomyocyte architecture. Our early stage LOF experiments show that NRG1 regulates the transcription of genes required for cell shape and morphology, including key components of polarity complexes, with NRG1 LOF leading to the depletion of the apical junction and polarity proteins PARD3 and CRUMBS2, which have been linked to trabeculation 47,56 (Figure 8). These changes were further associated with evidence of ventricular wall defects and altered redistribution of intercellular connections established by the cell junctional protein N-CADHERIN, which is required for structural integrity of the myocardium 6,7,53 .…”

“…In contrast, PARD3 staining was severely reduced in E8.5 and E9.5 Nrg1 flox ; Tie2 Cre ventricles (Figure 2E; Figure S7B-D’), further supporting the idea that A-B polarity is lost in mutant cardiomyocytes. A second polarity complex, Crumbs (CRB2A), has been shown to be required for the establishment of cardiomyocyte apicobasal polarity in zebrafish 56 . We readily detected CRB2 at the apical pole of the compact layer in E8.5 control cardiomyocytes (Figure 2F), but this expression was strongly depleted in Nrg1 flox ; Tie2 Cre mutants (Figure 2G), consistent with loss of A-B polarity in Nrg1 flox ; Tie2 Cre cardiomyocytes.…”