When a Tnnt2 cDNA transgene with a human DCM mutation, Lys210 deletion (K210Δ), was introduced into mice retaining two endogenous alleles of Tnnt2 (TGK210Δ), they exhibited mild DCM, trending towards left ventricular dilation and impaired contractility. Here, TNNT2 is linked to familial dilated cardiomyopathy.