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URL of this page: https://medlineplus.gov/genetics/gene/myh7/

MYH7 gene

myosin heavy chain 7

Normal Function

The MYH7 gene provides instructions for making a protein known as myosin-7. This protein is found in heart (cardiac) muscle and in certain skeletal muscles, which are the muscles used for movement. Specifically, myosin-7 is found in type I skeletal muscle fibers, which are 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-7 helps generate the mechanical force that is needed for muscles to contract. It combines with other proteins to form the thick filaments that are found within structures called sarcomeres. Sarcomeres are the basic units of muscle contraction; they are composed of overlapping thick filaments and thin filaments. These thick and thin filaments undergo cycles of attachment and release, which allow the thin filaments to slide past the thick filaments. These movements shorten the sarcomere, which causes 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

Familial hypertrophic cardiomyopathy

Genetic changes that cause disease are called pathogenic variants. Pathogenic variants in the MYH7 gene are a common cause of familial hypertrophic cardiomyopathy, a condition that is characterized by the thickening (hypertrophy) of the cardiac muscle. 

Most of the pathogenic variants in the MYH7 gene that cause familial hypertrophic cardiomyopathy lead to the substitution of one protein building block (amino acid) for another in the myosin-7 protein. The altered proteins likely do not function properly. However, it is not clear exactly how these changes lead to the hypertrophy that is seen in people with familial hypertrophic cardiomyopathy.

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Laing distal myopathy

Pathogenic variants in the MYH7 gene can also cause Laing distal myopathy. This condition affects the muscles (myopathy) and is 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 caridac muscle becomes thin and enlarged (dilated). 

Many of the pathogenic variants that cause Laing distal myopathy result in changes to a region of myosin-7 that interacts with other proteins. However, it is unclear exactly how these variants lead to the muscle weakness seen in people with Laing distal myopathy. 

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Left ventricular noncompaction

Pathogenic variants in the MYH7 gene can also cause left ventricular noncompaction, which is a condition in which the lower left chamber of the heart (left ventricle) does not develop correctly. The signs and symptoms of left ventricular noncompaction can include an irregular heart rhythm (arrhythmia), shortness of breath (dyspnea), and heart failure.

During early development, cardiac muscle is normally condensed (compacted), becoming smooth and firm. People with left ventricular noncompaction have cardiac muscle that is not compacted but is thick and spongy. This weakens the cardiac muscle and prevents the heart from pumping blood efficiently. Although pathogenic variants in the MYH7 gene likely contribute to changes in cardiac muscle development, it is not clear exactly how these variants cause the specific features seen in people with left ventricular noncompaction. 

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Myosin storage myopathy

Pathogenic variants in the MYH7 gene can also cause myosin storage myopathy. This condition causes muscle weakness that can worsen slowly over time. Pathogenic variants in the MYH7 gene can cause cells to produce a version of myosin-7 that does not function properly. The altered proteins accumulate within the skeletal muscle fibers, forming protein clumps that can be seen when muscle tissue is removed for examination (muscle biopsy). It is unclear exactly how these changes lead to the muscle weakness seen in people with myosin storage myopathy.

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Congenital fiber-type disproportion

MedlinePlus Genetics provides information about Congenital fiber-type disproportion

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Nonsyndromic dilated cardiomyopathy

MedlinePlus Genetics provides information about Nonsyndromic dilated cardiomyopathy

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Familial restrictive cardiomyopathy

MedlinePlus Genetics provides information about Familial restrictive cardiomyopathy

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Other Names for This Gene

  • CMD1S

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

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  • Ritter A, Leonard J, Gray C, Izumi K, Levinson K, Nair DR, O'Connor M, Rossano J, Shankar V, Chowns J, Marzolf A, Owens A, Ahrens-Nicklas RC. MYH7 variants cause complex congenital heart disease. Am J Med Genet A. 2022 Sep;188(9):2772-2776. doi: 10.1002/ajmg.a.62766. Epub 2022 May 2. Citation on PubMed
  • Rojanasopondist P, Nesheiwat L, Piombo S, Porter GA Jr, Ren M, Phoon CKL. Genetic Basis of Left Ventricular Noncompaction. Circ Genom Precis Med. 2022 Jun;15(3):e003517. doi: 10.1161/CIRCGEN.121.003517. Epub 2022 May 12. Citation on PubMed
  • Tajsharghi H, Thornell LE, Lindberg C, Lindvall B, Henriksson KG, Oldfors A. Myosin storage myopathy associated with a heterozygous missense mutation in MYH7. Ann Neurol. 2003 Oct;54(4):494-500. doi: 10.1002/ana.10693. Citation on PubMed
  • Van Driest SL, Jaeger MA, Ommen SR, Will ML, Gersh BJ, Tajik AJ, Ackerman MJ. Comprehensive analysis of the beta-myosin heavy chain gene in 389 unrelated patients with hypertrophic cardiomyopathy. J Am Coll Cardiol. 2004 Aug 4;44(3):602-10. doi: 10.1016/j.jacc.2004.04.039. Citation on PubMed
  • Viswanathan MC, Tham RC, Kronert WA, Sarsoza F, Trujillo AS, Cammarato A, Bernstein SI. Myosin storage myopathy mutations yield defective myosin filament assembly in vitro and disrupted myofibrillar structure and function in vivo. Hum Mol Genet. 2017 Dec 15;26(24):4799-4813. doi: 10.1093/hmg/ddx359. Citation on PubMed

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