However, it remains to be determined whether the actions of RGS proteins, directly or indirectly, have any role in the regulation of titin and/or related complexes, or whether aberrations in the expression and/or function of RGS proteins, particularly RGS2 and 5, or other related RGS proteins in the same family, play a causal role in the pathogenesis of DCM via their regulatory effects in the organization or function of molecular complexes involving titin in LV cardiomyocytes. Here, TTN is linked to familial dilated cardiomyopathy.