TNNT2 and familial dilated cardiomyopathy: The evident gene dosage effect in which phenotype severity is correlated with relative expression of mutant transcript is consistent with our previous findings in Tnnt2 null mice and transgenic mice with the Tnnt2 K210Δ mutation suggesting that TNNT2 mutations lead to DCM by production of abnormally functioning protein rather than haploinsufficiency, and that greater expression of mutant protein leads to a more severe phenotype [4].