Abstract:The nematode Caenorhabditis elegans has become established as a major experimental organism with applications to many biomedical research areas. The body wall muscle cells are a useful model for the study of human cardiomyocytes and their homologous structures and proteins. The ability to readily identify mutations affecting these proteins and structures in C elegans and to be able to rigorously characterize their genotypes and phenotypes at the cellular and molecular levels permits mechanistic studies of the responsible interactions relevant to the inherited human cardiomyopathies. Future work in C elegans muscle holds great promise in uncovering new mechanisms in the pathogenesis of these cardiac disorders. (Circ Res. 2011;109:1082-1095.) Key Words: cardiomyopathies Ⅲ Caenorhabditis elegans sarcomere structure Ⅲ sarcomere assembly Ⅲ model genetics C ardiomyopathies are a diverse set of heart muscle diseases associated with mechanical and electric dysfunction and high risk of sudden cardiac death and cardiac failure. The 2 major clinical types of inherited cardiomyopathy are hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) 1-3 (Figure 1). Clinical histories indicate a positive family history in about 60% of HCM, and in 20% to 35% of DCM cases. The remaining primary HCM or DCM cases are strongly suspected to be unrecognized familial disease or new mutations. The most common inheritance pattern is autosomal dominant, but at a much lower frequency, autosomal recessive and X-linked recessive inheritance patterns are also observed. Over the past 20 years, more than 450 mutations in 20 genes have been discovered as causing HCM. Nearly all of the affected proteins are components of the sarcomere. The genes most commonly affected encode -myosin heavy chain 4,5 and myosin-binding protein C 6,7 (accounting for at least 25% each), and troponin T, troponin I, tropomyosin, and regulatory myosin light chain (accounting for approximately 2-5% each). 2,8 To date, mutations in more than 30 genes result in DCM. Most of these genes also encode sarcomeric proteins. Interestingly, different mutations in the same gene can result in either HCM or DCM. Currently, we only know the causative mutation for 50% of the cases of HCM, and 20% of the cases of DCM. Despite knowing that mutations in so many different sarcomere and sarcomere-associated proteins result in HCM and DCM, the exact molecular mechanisms by which these mutations result in clinical heart hypertrophy or dilatation, are unknown.