Fig. 1

Inhibition of endothelial Brg1 impairs myocardial proliferation and regeneration.

a, b Immunofluorescence staining of Brg1 and EGFP on paraffin sections of Tg(fli1:nucEGFP) transgenic hearts from sham-operated (a) and injured zebrafish hearts (b) at 7 dpa (arrowheads, Brg1- and EGFP-positive endothelial cell nuclei). c, d RNAscope in situ hybridization of brg1 and kdrl probes in frozen sections from sham-operated (c) and injured hearts (d) at 3 dpa (arrows, brg1- and kdrl-positive endothelial cells). The upper right corner presented in (a–d) is a high-magnification image of the framed area. e–h Representative images of Acid fuchsin orange G (AFOG) staining (e, f) and immunofluorescence with anti-myosin heavy chain (MF20) (g, h) of heart sections from control siblings Tg(ubi:LoxP-DsRed-STOP-LoxP-dn-xbrg1) (Ctrl) and endothelium-specific dominant-negative mutants Tg(ubi:LoxP-DsRed-STOP-LoxP-dn-xbrg1; kdrl:CreER) (DN) at 30 dpa, noting that, compared with robust regenerated myocardium and rare cardiac fibrosis in Ctrl group (e, g), the DN group failed to regenerate the myocardium (h) and had evident fibrin (red) and collagen (blue) deposition (f). Dashed lines mark the resection traces. N numbers indicate biological replicates. i, j Immunostaining of representative heart sections at 7 dpa identified cardiomyocyte nuclei (Mef2C⁺) and nuclei undergoing DNA replication (PCNA⁺). Noting fewer proliferative cardiomyocytes (Mef2C⁺/PCNA⁺) in the DN group than in the Ctrl group. Arrowheads, Mef2C⁺/PCNA⁺ proliferating cardiomyocytes. k Statistical analysis of experiments as in (i) and (j) (CM, cardiomyocyte; n = 17 or 14 biological replications; data were the mean percentage ± s.e.m.; ***p < 0.001, unpaired t-test). Scale bars, 100 μm.