Endoderm convergence controls subduction of the myocardial precursors during heart-tube formation

Abstract

Coordination between the endoderm and adjacent cardiac mesoderm is crucial for heart development. We previously showed that myocardial migration is promoted by convergent movement of the endoderm, which itself is controlled by the S1pr2/Gα 13 signaling pathway, but it remains unclear how the movements of the two tissues is coordinated. Here, we image live and fixed embryos to follow these movements, revealing previously unappreciated details of strikingly complex and dynamic associations between the endoderm and myocardial precursors. We found that during segmentation the endoderm underwent three distinct phases of movement relative to the midline: rapid convergence, little convergence and slight expansion. During these periods, the myocardial cells exhibited different stage-dependent migratory modes: co-migration with the endoderm, movement from the dorsal to the ventral side of the endoderm (subduction) and migration independent of endoderm convergence. We also found that defects in S1pr2/Gα 13 -mediated endodermal convergence affected all three modes of myocardial cell migration, probably due to the disruption of fibronectin assembly around the myocardial cells and consequent disorganization of the myocardial epithelium. Moreover, we found that additional cell types within the anterior lateral plate mesoderm (ALPM) also underwent subduction, and that this movement likewise depended on endoderm convergence. Our study delineates for the first time the details of the intricate interplay between the endoderm and ALPM during embryogenesis, highlighting why endoderm movement is essential for heart development, and thus potential underpinnings of congenital heart disease.

The force within: endocardial development, mechanotransduction and signalling during cardiac morphogenesis

“…This causes cardia bifida -the formation of two lateral heart tubes that contain a central patch of endocardial cells (Holtzman et al, 2007;Osborne et al, 2008). Within endodermal cells, S1P signalling via the G-protein coupled receptor S1P receptor 2 (S1pr2) activates G-protein alpha 13a (Gα13; also known as Gna13a)/Rho guanine nucleotide exchange factor (RhoGEF)-dependent endodermal convergence movements (Ye and Lin, 2013;Ye et al, 2015) and ensures Yes-associated protein 1 (Yap1)-dependent endodermal survival (Fukui et al, 2014); this provides a permissive environment for both myocardial and endocardial cell migrations (Fig. 2C).…”

Spatiotemporally Controlled Mechanical Cues Drive Progenitor Mesenchymal-to-Epithelial Transition Enabling Proper Heart Formation and Function

“…On their way to the ventral midline HPCs traverse a dynamically changing mechanical microenvironment marked by fibronectin remodeling [10, 16, 20], changing tissue stiffness [19, 36], and tension from ventral convergent extension [15, 19, 29]. While MET is not a prerequisite for HPC differentiation or arrival at the ventral midline, the proper timing of MET is both sensitive to the mechanical environment of the HFR and required for proper heart structure (Figure 2H–I, Figure 5G, Figure S2) and function (Figure 7C and Figure S6D–H).…”

“…Since HPCs move in concert with the endoderm, it has been proposed that ventral convergence and active contraction of the endoderm drive HPC ventral displacement [15, 16] whereas autonomous HPC motility contributes minimally to their overall ventral movements [16–18]. Thus, endodermal convergent extension is crucial for proper heart formation, as endoderm deficient embryos exhibit abnormal extracellular matrix and disorganized myocardial epithelia [16]. …”

Strategies for analyzing cardiac phenotypes in the zebrafish embryo

“…For instance, mutations disrupting endoderm specification or integrity cause cardia bifida, indicating that interactions between the myocardium and the adjacent endoderm are crucial for promoting cardiomyocyte movement (e.g. (Kikuchi et al, 2000; Kupperman et al, 2000; Kikuchi et al, 2001; Osborne et al, 2008; Kawahara et al, 2009; Ye & Lin, 2013; Ye, Xie, Hu, & Lin, 2015)). In addition to the endoderm, the composition of the extracellular matrix (ECM) is important for the execution of cardiac fusion, since mutations causing either diminished or excessive ECM deposition can hinder cardiomyocyte motility (Trinh & Stainier, 2004; Trinh, Yelon, & Stainier, 2005; Arrington & Yost, 2009; Garavito-Aguilar, Riley, & Yelon, 2010).…”

“…Therefore, when investigating new cardia bifida phenotypes, it is important to examine the specification and morphogenesis of the anterior endoderm, using appropriate markers (e.g. Tg (-0.7 her 5: egfp), axial , sox17 (Kupperman et al, 2000; Osborne et al, 2008; Kawahara et al, 2009; Ye & Lin, 2013; Ye et al, 2015)), as well as the deposition and composition of the ECM, using immunofluorescent detection of relevant components (e.g. Fibronectin and Laminin (Trinh & Stainier, 2004; Arrington & Yost, 2009; Garavito-Aguilar et al, 2010)).…”