Inherited disorders of contractile proteins in skeletal and cardiac muscle.

The functional unit of muscle contraction is the sarcomere, a structure of strict cytoarchitecture constructed from a relatively small number of mostly identified contractile proteins. The messenger RNAs for seven muscle proteins combined together account for 20% of all the messenger RNA in mature muscle fibres. It should be anticipated that mutations in these and other highly expressed messages or proteins will cause inherited muscle disorders. In recent years, but especially in the past 12 months, disorders associated with some of these proteins have been identified. Familial hypertrophic cardiomyopathy, central core disease, nemaline myopathy, and autosomal recessive limb-girdle muscular dystrophy have all been shown to involve mutations in proteins associated with the sarcomere.