Specifically, upon binding with the TGF-β1 receptor on the surface of myocardial fibroblasts, TGF-β1 stimulates phosphorylation of downstream SMADs protein (mainly SMAD2/3) and translocation into the nucleus in combination with SMAD4, induces myocardial fibroblast proliferation, phenotypic transformation, and collagen synthesis and ultimately promotes extracellular matrix formation and myocardial fibrosis. The gene discussed is SMAD4; the disease is Myocardial fibrosis.