Myosin VIIA is protein that in humans is encoded by the MYO7A gene. Myosin VIIA is a member of the unconventional myosin superfamily of proteins. Myosins are actin binding molecular motors that use the enzymatic conversion of ATP - ADP + inorganic phosphate (Pi) to provide the energy for movement.
Myosins are mechanochemical proteins characterized by the presence of a motor domain, an actin-binding domain, a neck domain that interacts with other proteins, and a tail domain that serves as an anchor. Myosin VIIA is an unconventional myosin with the longest tail (1360 aa). The tail is expected to dimerize, resulting in a two-headed molecule. Unconventional myosins have diverse functions in eukaryotic cells and are primarily thought to be involved in the movement or linkage of intra-cellular membranes and organelles to the actin cytoskeleton via interactions mediated by their highly divergent tail domains.
MYO7A is expressed in a number of mammalian tissues, including testis, kidney, lung, inner ear, retina and the ciliated epithelium of the nasal mucosa.
Clinical significance
Mutations in the MYO7A gene cause the Usher syndrome type 1B, a combined deafness/blindness disorder. Affected individuals are typically profoundly deaf at birth and then undergo progressive retinal degeneration.
Model organisms
| Characteristic | Phenotype |
|---|---|
| Homozygote viability | Normal |
| Fertility | Normal |
| Body weight | Abnormal |
| Anxiety | Normal |
| Neurological assessment | Abnormal |
| Grip strength | Abnormal |
| Hot plate | Abnormal |
| Dysmorphology | Normal |
| Indirect calorimetry | Abnormal |
| Glucose tolerance test | Abnormal |
| Auditory brainstem response | Abnormal |
| DEXA | Abnormal |
| Radiography | Abnormal |
| Body temperature | Normal |
| Eye morphology | Normal |
| Clinical chemistry | Abnormal |
| Plasma immunoglobulins | Normal |
| Haematology | Normal |
| Peripheral blood lymphocytes | Normal |
| Micronucleus test | Normal |
| Heart weight | Normal |
| Tail epidermis wholemount | Normal |
| Skin Histopathology | Normal |
| All tests and analysis from |
Model organisms have been used in the study of MYO7A function. A spontaneous mutant mouse line, called Myo7ash1-6J was generated. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty three tests were carried out on mutant mice and ten significant abnormalities were observed. Male homozygous mutant mice displayed a decreased body weight, a decrease in body fat, improved glucose tolerance and abnormal pelvic girdle bone morphology. Homozygous mutant mice of both sex displayed various abnormalities in a modified SHIRPA test, including abnormal gait, tail dragging and an absence of pinna reflex, a decrease in grip strength, an increased thermal pain threshold, severe hearing impairment and a number of abnormal indirect calorimetry and clinical chemistry parameters.
External links
- GeneReviews/NCBI/NIH/UW entry on Usher Syndrome Type I
- Overview of all the structural information available in the PDB for UniProt: Q13402 (Human Unconventional myosin-VIIa) at the PDBe-KB.
- Overview of all the structural information available in the PDB for UniProt: P97479 (Mouse Unconventional myosin-VIIa) at the PDBe-KB.
Further reading
- Wolfrum U (2004). "The cellular function of the usher gene product myosin VIIa is specified by its ligands". Retinal Degenerations. Advances in Experimental Medicine and Biology. Vol. 533. pp. 133–42. CiteSeerX 10.1.1.501.2021. doi:10.1007/978-1-4615-0067-4_17. ISBN 978-1-4613-4909-9. PMID 15180257.
- el-Amraoui A, Sahly I, Picaud S, Sahel J, Abitbol M, Petit C (August 1996). "Human Usher 1B/mouse shaker-1: the retinal phenotype discrepancy explained by the presence/absence of myosin VIIA in the photoreceptor cells". Human Molecular Genetics. 5 (8): 1171–8. doi:10.1093/hmg/5.8.1171. PMID 8842737.
- Adato A, Weil D, Kalinski H, Pel-Or Y, Ayadi H, Petit C, Korostishevsky M, Bonne-Tamir B (October 1997). "Mutation profile of all 49 exons of the human myosin VIIA gene, and haplotype analysis, in Usher 1B families from diverse origins". American Journal of Human Genetics. 61 (4): 813–21. doi:10.1086/514899. PMC 1716000. PMID 9382091.
- Liu XZ, Hope C, Walsh J, Newton V, Ke XM, Liang CY, Xu LR, Zhou JM, Trump D, Steel KP, Bundey S, Brown SD (September 1998). "Mutations in the myosin VIIA gene cause a wide phenotypic spectrum, including atypical Usher syndrome". American Journal of Human Genetics. 63 (3): 909–12. doi:10.1086/302026. PMC 1377414. PMID 9718356.
- Kimberling WJ, Möller CG, Davenport S, Priluck IA, Beighton PH, Greenberg J, Reardon W, Weston MD, Kenyon JB, Grunkemeyer JA (December 1992). "Linkage of Usher syndrome type I gene (USH1B) to the long arm of chromosome 11". Genomics. 14 (4): 988–94. doi:10.1016/S0888-7543(05)80121-1. PMID 1478677.
- Hasson T, Heintzelman MB, Santos-Sacchi J, Corey DP, Mooseker MS (October 1995). "Expression in cochlea and retina of myosin VIIa, the gene product defective in Usher syndrome type 1B". Proceedings of the National Academy of Sciences of the United States of America. 92 (21): 9815–9. Bibcode:1995PNAS...92.9815H. doi:10.1073/pnas.92.21.9815. PMC 40893. PMID 7568224.
- Guilford P, Ayadi H, Blanchard S, Chaib H, Le Paslier D, Weissenbach J, Drira M, Petit C (June 1994). "A human gene responsible for neurosensory, non-syndromic recessive deafness is a candidate homologue of the mouse sh-1 gene". Human Molecular Genetics. 3 (6): 989–93. doi:10.1093/hmg/3.6.989. PMID 7951250.
- Bement WM, Hasson T, Wirth JA, Cheney RE, Mooseker MS (July 1994). "Identification and overlapping expression of multiple unconventional myosin genes in vertebrate cell types". Proceedings of the National Academy of Sciences of the United States of America. 91 (14): 6549–53. Bibcode:1994PNAS...91.6549B. doi:10.1073/pnas.91.14.6549. PMC 44240. PMID 8022818.
- Wagenaar M, ter Rahe B, van Aarem A, Huygen P, Admiraal R, Bleeker-Wagemakers E, Pinckers A, Kimberling W, Cremers C (November 1995). "Clinical findings in obligate carriers of type I Usher syndrome". American Journal of Medical Genetics. 59 (3): 375–9. doi:10.1002/ajmg.1320590319. hdl:2066/21703. PMID 8599365. S2CID 22357870.
- Weil D, Levy G, Sahly I, Levi-Acobas F, Blanchard S, El-Amraoui A, Crozet F, Philippe H, Abitbol M, Petit C (April 1996). "Human myosin VIIA responsible for the Usher 1B syndrome: a predicted membrane-associated motor protein expressed in developing sensory epithelia". Proceedings of the National Academy of Sciences of the United States of America. 93 (8): 3232–7. Bibcode:1996PNAS...93.3232W. doi:10.1073/pnas.93.8.3232. PMC 39588. PMID 8622919.
- Tamagawa Y, Kitamura K, Ishida T, Ishikawa K, Tanaka H, Tsuji S, Nishizawa M (June 1996). "A gene for a dominant form of non-syndromic sensorineural deafness (DFNA11) maps within the region containing the DFNB2 recessive deafness gene". Human Molecular Genetics. 5 (6): 849–52. doi:10.1093/hmg/5.6.849. PMID 8776602.
- Chen ZY, Hasson T, Kelley PM, Schwender BJ, Schwartz MF, Ramakrishnan M, Kimberling WJ, Mooseker MS, Corey DP (September 1996). "Molecular cloning and domain structure of human myosin-VIIa, the gene product defective in Usher syndrome 1B". Genomics. 36 (3): 440–8. doi:10.1006/geno.1996.0489. PMID 8884267.
- Weston MD, Kelley PM, Overbeck LD, Wagenaar M, Orten DJ, Hasson T, Chen ZY, Corey D, Mooseker M, Sumegi J, Cremers C, Moller C, Jacobson SG, Gorin MB, Kimberling WJ (November 1996). "Myosin VIIA mutation screening in 189 Usher syndrome type 1 patients". American Journal of Human Genetics. 59 (5): 1074–83. PMC 1914835. PMID 8900236.
- Lévy G, Levi-Acobas F, Blanchard S, Gerber S, Larget-Piet D, Chenal V, Liu XZ, Newton V, Steel KP, Brown SD, Munnich A, Kaplan J, Petit C, Weil D (January 1997). "Myosin VIIA gene: heterogeneity of the mutations responsible for Usher syndrome type IB". Human Molecular Genetics. 6 (1): 111–6. doi:10.1093/hmg/6.1.111. PMID 9002678.
- Kelley PM, Weston MD, Chen ZY, Orten DJ, Hasson T, Overbeck LD, Pinnt J, Talmadge CB, Ing P, Mooseker MS, Corey D, Sumegi J, Kimberling WJ (February 1997). "The genomic structure of the gene defective in Usher syndrome type Ib (MYO7A)". Genomics. 40 (1): 73–9. doi:10.1006/geno.1996.4545. PMID 9070921. S2CID 19026117.
- Liu XZ, Walsh J, Mburu P, Kendrick-Jones J, Cope MJ, Steel KP, Brown SD (June 1997). "Mutations in the myosin VIIA gene cause non-syndromic recessive deafness". Nature Genetics. 16 (2): 188–90. doi:10.1038/ng0697-188. PMID 9171832. S2CID 13506848.
- Weil D, Küssel P, Blanchard S, Lévy G, Levi-Acobas F, Drira M, Ayadi H, Petit C (June 1997). "The autosomal recessive isolated deafness, DFNB2, and the Usher 1B syndrome are allelic defects of the myosin-VIIA gene". Nature Genetics. 16 (2): 191–3. doi:10.1038/ng0697-191. PMID 9171833. S2CID 23555323.
- Liu XZ, Walsh J, Tamagawa Y, Kitamura K, Nishizawa M, Steel KP, Brown SD (November 1997). "Autosomal dominant non-syndromic deafness caused by a mutation in the myosin VIIA gene". Nature Genetics. 17 (3): 268–9. doi:10.1038/ng1197-268. PMID 9354784. S2CID 20566524.