Nppa and Nppb act redundantly during zebrafish cardiac development to confine AVC marker expression and reduce cardiac jelly volume

Abstract

Atrial natriuretic peptide () and brain natriuretic peptide () form a gene cluster with expression in the chambers of the developing heart. Despite restricted expression, a function in cardiac development has not been demonstrated by mutant analysis. This is attributed to functional redundancy; however, their genomic location has impeded formal analysis. Using genome editing, we have generated mutants for and , and found that single mutants were indistinguishable from wild type, whereas/ double mutants displayed heart morphogenesis defects and pericardial oedema. Analysis of atrioventricular canal (AVC) markers show expansion of ,, and expression into the atrium of double mutants. This expanded expression correlates with increased extracellular matrix in the atrium. Using a biosensor for hyaluronic acid to measure the cardiac jelly (cardiac extracellular matrix), we confirmed cardiac jelly expansion in / double mutants. Finally, knockdown rescued the expansion of expression and cardiac jelly in double mutants. This definitively shows that and function redundantly during cardiac development to restrict gene expression to the AVC, preventing excessive cardiac jelly synthesis in the atrial chamber.

The flow responsive transcription factor Klf2 is required for myocardial wall integrity by modulating Fgf signaling

“…Reduction of the cardiac jelly, a gelatinous matrix between the endocardial and myocardial layers, is an important process during cardiac morphogenesis (Brutsaert et al, 1996; Stankunas et al, 2008; Bowers and Baudino, 2010; Tian and Morrisey, 2012; Rasouli and Stainier, 2017; Grassini et al, 2018). In order to investigate whether reduction of the cardiac jelly was affected in klf2 mutants, we used the TgBAC(etv2:EGFP) (Proulx et al, 2010) and Tg(myl7:mCherry-CAAX) (Uribe et al, 2018) lines to mark the endocardium and myocardium in green and red, respectively.…”

“…Cardiac jelly remodeling has been reported to be involved in the maturation of vertebrate hearts (Nakamura and Manasek, 1981; Ramasubramanian et al, 2013; Rasouli and Stainier, 2017; Grassini et al, 2018; Del Monte-Nieto et al, 2018). Although cardiac jelly thickness appears unaffected in klf2 mutants, our study does not exclude the potential role of ECM components in the appearance of the extruding cardiomyocytes.…”

Endothelial Cell Dynamics in Vascular Development: Insights From Live-Imaging in Zebrafish

“…When HA localization was visualized using the HA-binding domain of mouse Neurocan tagged with GFP, tmem2 mutants displayed ectopic HA accumulation in the ECM around the DA and the PCV consistent with a failure of HA turnover ( De Angelis et al, 2017 ). The use of this HA biosensor for live imaging has also now been applied to live-image ECM in the heart ( Grassini et al, 2018 ). A product of HA depolymerization, the small oligosaccharide fragment o-HA, was shown to be essential for proper Vegfa/Kdr/Kdrl signaling during primary angiogenesis ( Figure 1 ).…”

Asymmetric Hapln1a drives regionalised cardiac ECM expansion and promotes heart morphogenesis during zebrafish development

“…Therefore, to determine whether ECM left-right asymmetry is restricted to the 122 atrium of the heart tube or is maintained along the atrioventricular axis of the heart, we 123 performed fixed tissue imaging. Previous studies have demonstrated that hyaluronic acid (HA) 124 is present in the cardiac jelly during zebrafish heart development (Grassini et al 2018;125 data demonstrate that the heart tube exhibits an asymmetrically expanded ECM prior to onset 138 of looping morphogenesis. 139 140 hapln1a exhibits regionalised cardiac expression prior to heart morphogenesis.…”