Notch1 activation rescues efnb2a and nrg1 expression in non-contractile hearts. (A) Experimental schematic diagram of morpholino injection and heat-shock overexpression of NICD. qRT-PCR and imaging were performed to examine gene expression and trabecular phenotype at 2-3 and 4dpf, respectively. (B) Representative whole-mount images of cardiomyocytes (red) and Notch reporter (green) in (a,b) control and (c,d) tnnt2a morphants at 48hpf (a,c) without or (b,d) with NICD overexpression. (C,D) Expression of efnb2a and nrg1 in hearts isolated from (C) control morphants and (D) tnnt2a morphants, comparing gene expression in embryos with or without NICD overexpression. (E-H) Confocal mid-chamber optical section of 4dpf hearts, with dotted lines marking the inset magnified in E2-H2. #P≤0.075-0.05, *P≤0.05-0.01, **P≤0.01-0.001, ***P<0.001 compared with control morphants (one-sample t-test compared with control morpholino fold change=1). Error bars are s.e.m. White arrows highlight trabeculae. a, atrium; HS, heat shock control without NICD overexpression; HS+, heat shock control with NICD overexpression; NICD, Notch intracellular domain; v, ventricle. Scale bars: 50µm in H; 10µm in H′.