PITX2 and familial dilated cardiomyopathy: 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.