Sc 1237

Immunoblot analysis was performed from isolated cardiac myocytes or mouse hearts using anti‐GATA4 (Santa Cruz, sc‐1237, diluted 1:500), STAT6 (Abcam, ab44718, diluted 1:500), cyclin A2 (Abcam ab38, diluted 1:400), cenpa (Cell Signaling C51A7, diluted 1:1,000), and anti‐GAPDH (Fitzgerald, 10R‐G109a, diluted 1:6,000) or anti‐actin (Sigma, A2066, diluted 1:10,000) antibodies following standard procedures. Densitometry analysis was conducted with Quantity One software (Bio‐Rad).

In preparation for immunocytochemistry, cells were fixed in 4% PFA for 15 min at room temperature and then permeabilised for 1 hr with 0.1% Triton X-100 in PBS. After blocking with 3% BSA, samples were incubated with primary antibodies for 1 h at room temperature or overnight at 4 °C, followed by reaction with fluorescent secondary antibodies for another hour. Antibodies used were rabbit polyclonal anti-active caspase 3 (1:500, Abcam, ab2302), rabbit anti-FGF5 (1:50, Proteintech, 18171-1-AP), goat polyclonal anti-GATA4 (1:200, SantaCruz, sc-1237), chicken polyclonal anti-GFP (1:500, Abcam, ab13970), rabbit polyclonal anti-HSD3B (1:500, gift from Ian. Mason), rat polyclonal anti-Ki67 (1:500, BioLegend, 652401), rabbit polyclonal anti-laminin (1:1000, gift from Harold Erickson), rabbit polyclonal anti-MVH (1:300, Novus Biologicals, NBP2-24558), rabbit polyclonal anti-OSR1 (1:200, Abcam, ab230627), anti-Pax2 (1:200, Novus Biologicals NPB2-57700), goat polyclonal anti-SOX2 (1:200, Novus Biologicals, AF2018), goat anti-SOX9 (1:200, Novus Biologicals, AF3075), rabbit polyclonal anti-SF1/NR5A1 (1:200, Novus Biologicals NPB1-52823), rabbit polyclonal anti-STAR (1:200, Biorbyt, orb7014), rabbit polyclonal anti-STRA8 (1:200, Abcam, ab49602) and rabbit anti-SYCP3 (1:200, Novus Biologicals, NB300-230).