MYH

MYH refers to a family of genes that encode the heavy chains of myosin, the motor proteins that convert ATP energy into mechanical work in muscle and other cells. Myosin heavy chains are part of larger myosin complexes that drive muscle contraction, cell shape changes, and various forms of intracellular transport. Each heavy chain contains a catalytic head that binds actin and hydrolyzes ATP, a neck region that binds light chains, and a long coiled-coil tail that enables filament assembly.

In humans, the MYH family comprises muscle-specific and non-muscle isoforms. Muscle-associated MYH genes encode heavy chains that form thick filaments in skeletal, cardiac, and smooth muscle. Notable members include MYH6 (alpha heavy chain, largely in atrial cardiac muscle) and MYH7 (beta or slow heavy chain, prominent in cardiac ventricles and slow-twitch muscle fibers), along with fast skeletal isoforms such as MYH1 and MYH2. Non-muscle MYH genes encode heavy chains that participate in cellular processes beyond contraction, including MYH9 (non-muscle myosin IIa), MYH10 (IIb), and MYH14 (IIc).

Functionally, myosin heavy chains assemble with light chains to form motor complexes that move along actin filaments, generating force and enabling movement. In muscle, they form thick filaments; in non-muscle cells, they contribute to cytokinesis, cell migration, and maintenance of cell shape.

Clinical relevance varies by gene. Mutations in MYH7 are associated with cardiomyopathies such as hypertrophic and dilated forms. MYH9 variants cause macrothrombocytopenia with nephropathy and other features. Other MYH genes can be linked to skeletal muscle disorders or developmental anomalies, reflecting tissue-specific roles of different heavy chains.