MYH7 gene
The MYH7 gene provides instructions for making the myosin heavy chain-7 protein, which is essential for cardiac and skeletal muscle contraction.
Normal Function
The MYH7 gene provides instructions for making a protein known as myosin heavy chain-7. This protein is found in heart (cardiac) muscle and in certain skeletal muscles, which are the muscles used for movement. Specifically, myosin heavy chain-7 is found in type I skeletal muscle fibers, also known as slow-twitch fibers. These fibers are the primary component of skeletal muscles that do not tire easily, such as the muscles involved in maintaining posture.
Myosin heavy chain-7 helps generate the mechanical force needed for muscles to contract. It combines with other proteins to form the thick filaments found within structures called sarcomeres. Sarcomeres are the basic units of muscle contraction, composed of overlapping thick and thin protein filaments. These filaments undergo cycles of attachment and release, allowing the thin filaments to slide past the thick filaments. These movements shorten the sarcomere, causing the muscle to contract. Regular contractions of cardiac muscle pump blood to the rest of the body, while the coordinated contraction and relaxation of skeletal muscles allow the body to move.
Health Conditions Related to Genetic Changes
Laing distal myopathy
Pathogenic variants in the MYH7 gene can cause Laing distal myopathy, a condition characterized by muscle weakness that worsens over time. The weakness typically affects the ankles and toes first but may eventually spread to the hands, fingers, face, hips, and shoulders. Some affected individuals develop dilated cardiomyopathy, a condition in which the cardiac muscle becomes thin and enlarged.
Myosin storage myopathy
Pathogenic variants in the MYH7 gene can cause myosin storage myopathy, which leads to muscle weakness that can worsen slowly over time. These variants cause cells to produce a version of myosin heavy chain-7 that does not function properly. The altered proteins accumulate within skeletal muscle fibers, forming protein clumps that can be seen during a muscle biopsy.
Nonsyndromic hypertrophic cardiomyopathy
Pathogenic variants in the MYH7 gene are a common cause of nonsyndromic hypertrophic cardiomyopathy, a condition characterized by the thickening (hypertrophy) of the cardiac muscle. Most of these variants lead to the substitution of one amino acid for another in the myosin heavy chain-7 protein, likely resulting in protein dysfunction.
Other Related Conditions
- Congenital fiber-type disproportion
- Familial restrictive cardiomyopathy
- Nonsyndromic dilated cardiomyopathy