Dependence of cardiac trabeculation on neuregulin signaling and blood flow in zebrafish

Abstract

Maturation of the developing heart requires the structural elaboration of the embryonic ventricle through the process of trabeculation. Trabeculae form as the ventricular myocardium protrudes into the lumen of the chamber, thereby increasing muscle mass and altering functional output. Little is understood about the cellular basis for trabeculation and its genetic regulation. Here, we establish the utility of the zebrafish embryo for the analysis of the mechanisms driving trabeculation. In zebrafish, we can follow trabeculation in four dimensions and define morphologically discrete stages for the initiation, propagation, and network elaboration that form the ventricular trabeculae. We find that Neuregulin/ErbB signaling is required for the initial protrusion of the myocardium into the ventricular lumen. Additionally, we demonstrate that optimal blood flow through the ventricle is important for the advancement of trabeculation. Thus, our results indicate that the zebrafish provides a valuable model for investigating possible causes of congenital defects in trabeculation. Developmental Dynamics 240:446-456,

Cardiac contraction activates endocardial Notch signaling to modulate chamber maturation in zebrafish

“…In zebrafish, cardiac trabeculae begin to form around 55 hours postfertilization (hpf ) and are easily detectable at 3 days postfertilization (dpf ) by examining cross-sections of ventricle outer curvature Peshkovsky et al, 2011;Staudt et al, 2014). Although the basic structure of the heart can form in the absence of myocardial function, some morphogenic events require cardiac contraction.…”

“…As a part of chamber maturation, cardiac trabeculation is a tightly regulated process by which ventricular cardiomyocytes protrude and expand into the lumen of the ventricular chambers to form ridge-like muscular structures called cardiac trabeculae Peshkovsky et al, 2011). Trabeculae increase cardiac output and allow for nutrition and oxygenation of the myocardium before coronary vascularization and are required for establishment of the mature conduction system of the developing ventricle (Lai et al, 2010;.…”

“…Zebrafish cloche mutants that do not form endocardial cells fail to develop trabeculae and ultimately die, presumably from heart failure (Peshkovsky et al, 2011;Stainier et al, 1995). Mice deficient in the epidermal growth factor (EGF) receptor ligand neuregulin 1 (Nrg1), which is expressed in the endocardium and signals through the myocardial ErbB4-ErbB2 receptor complex, fail to form trabeculae (Gassmann et al, 1995;Lee et al, 1995;Meyer and Birchmeier, 1995).…”

“…Mice deficient in the epidermal growth factor (EGF) receptor ligand neuregulin 1 (Nrg1), which is expressed in the endocardium and signals through the myocardial ErbB4-ErbB2 receptor complex, fail to form trabeculae (Gassmann et al, 1995;Lee et al, 1995;Meyer and Birchmeier, 1995). Likewise, inhibition of Nrg1-ErbB signaling in zebrafish embryos completely blocks trabeculation Peshkovsky et al, 2011;Samsa et al, 2013;Staudt et al, 2014). Notch ligands and receptors are expressed in endocardial cells during development, and Notch signaling regulates many aspects of endothelial biology, including artery-vein specification, angiogenesis and proliferation (Benedito and Hellstrom, 2013;Corada et al, 2014;de la Pompa and Epstein, 2012;Gridley, 2010).…”

“…Interestingly, in zebrafish and chick embryos, reducing blood flow through the ventricle significantly impairs cardiac trabeculation (Peshkovsky et al, 2011;Sedmera et al, 1999;Staudt et al, 2014). Nonetheless, how the mechanical stimulus is sensed and translated into spatial and temporal signals to regulate cardiac trabeculation through regulatory interaction with other myocardial signals remains largely unexplored.…”