Filamin C is Essential for mammalian myocardial integrity.

FLNC, encoding filamin C, is one of the most mutated genes in dilated and hypertrophic cardiomyopathy. However, the precise role of filamin C in mammalian heart remains unclear. In this study, we demonstrated Flnc global (FlncgKO) and cardiomyocyte-specific knockout (FlnccKO) mice died in utero from severely ruptured ventricular myocardium, indicating filamin C is required to maintain the structural integrity of myocardium in the mammalian heart. Contrary to the common belief that filamin C acts as an integrin inactivator, we observed attenuated activation of β1 integrin specifically in the myocardium of FlncgKO mice. Although deleting β1 integrin from cardiomyocytes did not recapitulate the heart rupture phenotype in Flnc knockout mice, deleting both β1 integrin and filamin C from cardiomyocytes resulted in much more severe heart ruptures than deleting filamin C alone. Our results demonstrated that filamin C works in concert with β1 integrin to maintain the structural integrity of myocardium during mammalian heart development.