To test our hypothesis that FYN plays a protective role in hypertrophic cardiomyopathy in Fgf18-CKO mice, we used AAV9 vectors carrying FYN under the control of the murine cTNT core promoter (AAV9-cTNT-FYN; Fig. 7a). Here, FGF18 is linked to hypertrophic cardiomyopathy.