GRIK2 and familial dilated cardiomyopathy: Cardiomyocyte clusters marked by MYH6, MYL7 and GRIK2 displayed stronger expression of signature genes in donor samples, whereas cardiomyocyte clusters marked by ACTA1, ADGRL and NPPA/NPPB displayed stronger expression of signature genes in DCM samples (Extended Data Fig. 6).