COL1A1 and Myocardial fibrosis: Histological analyses revealed increased myocardial fibrosis in Musclin KO mice in response to TAC compared to WT mice (Fig. 4m, n), which was accompanied by upregulation of pro-fibrotic genes like Postn, Col1a1, Col3a1 and Fn1 (Supplementary Fig. 6i–l).