The MYO5A gene provides instructions for making a protein called myosin Va, which is part of a group of proteins called unconventional myosins. These proteins, which have similar structures, each play a role in transporting molecules within cells. Myosins interact with actin, a protein that is important for cell movement and shape. Researchers believe that myosins use long filaments of actin as tracks along which to transport other molecules.
Myosin Va is found in pigment-producing cells called melanocytes, where it helps transport structures called melanosomes. These structures produce a pigment called melanin, which is the substance that gives skin, hair, and eyes their color (pigmentation). Myosin Va interacts with proteins produced from the MLPH and RAB27A genes to form a complex that transports melanosomes to the outer edges of melanocytes. From there, the melanosomes are transferred to other types of cells, where they provide the pigment needed for normal hair, skin, and eye coloring.
Myosin Va also plays an important role in nerve cells (neurons) in the brain. Studies suggest that myosin Va transports various proteins and other molecules within neurons. It is also involved in the release of certain substances from these cells (exocytosis). The movement of these materials appears to be critical for normal brain function.
Health Conditions Related to Genetic Changes
At least two mutations in the MYO5A gene have been found in people with Griscelli syndrome. These mutations cause a form of the condition designated type 1, which is characterized by unusually light (hypopigmented) skin, silvery-gray hair, and neurological abnormalities resulting in delayed development, intellectual disability, and seizures. The known MYO5A gene mutations prevent the production of functional myosin Va. Because the nonfunctional protein cannot form a complex with the proteins made from the MLPH and RAB27A genes, melanosomes cannot be transported to the edges of melanocytes. Instead, these structures clump near the center of melanocytes, trapping melanin within these cells and preventing normal pigmentation of skin and hair. A loss of myosin Va in neurons disrupts the transport of proteins and other molecules within and out of these cells, which likely causes the neurological problems found in Griscelli syndrome type 1.More About This Health Condition
Other Names for This Gene
- dilute myosin heavy chain, non-muscle
- myosin VA (heavy chain 12, myoxin)
- myosin, heavy polypeptide kinase
- unconventional myosin-Va
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
- Mehta AD, Rock RS, Rief M, Spudich JA, Mooseker MS, Cheney RE. Myosin-V is a processive actin-based motor. Nature. 1999 Aug 5;400(6744):590-3. doi: 10.1038/23072. Citation on PubMed
- Pastural E, Barrat FJ, Dufourcq-Lagelouse R, Certain S, Sanal O, Jabado N, Seger R, Griscelli C, Fischer A, de Saint Basile G. Griscelli disease maps to chromosome 15q21 and is associated with mutations in the myosin-Va gene. Nat Genet. 1997 Jul;16(3):289-92. doi: 10.1038/ng0797-289. Erratum In: Nat Genet 1999 Nov;23(3):373. Citation on PubMed
- Pastural E, Ersoy F, Yalman N, Wulffraat N, Grillo E, Ozkinay F, Tezcan I, Gedikoglu G, Philippe N, Fischer A, de Saint Basile G. Two genes are responsible for Griscelli syndrome at the same 15q21 locus. Genomics. 2000 Feb 1;63(3):299-306. doi: 10.1006/geno.1999.6081. Citation on PubMed
- Rudolf R, Bittins CM, Gerdes HH. The role of myosin V in exocytosis and synaptic plasticity. J Neurochem. 2011 Jan;116(2):177-91. doi: 10.1111/j.1471-4159.2010.07110.x. Citation on PubMed
- Van Gele M, Dynoodt P, Lambert J. Griscelli syndrome: a model system to study vesicular trafficking. Pigment Cell Melanoma Res. 2009 Jun;22(3):268-82. doi: 10.1111/j.1755-148X.2009.00558.x. Epub 2009 Feb 25. Citation on PubMed