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Gene Review

MYO9A  -  myosin IXA

Homo sapiens

Synonyms: FLJ11061, FLJ13244, MGC71859, MYR7, Unconventional myosin-9a, ...
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Disease relevance of MYO9A

  • From flies' eyes to our ears: mutations in a human class III myosin cause progressive nonsyndromic hearing loss DFNB30 [1].
  • A statistically significant increase in cell size, [3H]leucine incorporation, and expression of well-characterized markers of cardiac hypertrophy, namely cardiac alpha-actin and myosin light chain, were observed in response to leptin [2].
  • Shifted cells undergo a process of cell hypertrophy, as demonstrated by increased time of flight and forward scatter, as well as increased expression of the contractile proteins alpha-smooth muscle actin, myosin light chain kinase, and SM22 [3].
  • As mutations in the gene encoding NINAC, a Drosophila melanogaster class III myosin, cause retinal degeneration, human homologs of this gene are potential candidates for human retinal disease [4].
  • Quantification and characterization of myosin peptide-specific CD4+ T cells in autoimmune myocarditis [5].

Psychiatry related information on MYO9A

  • The segment of smooth muscle regulatory light chain essential for the phosphorylation dependent activation of actomyosin motor activity and the binding of myosin heavy chain was identified [6].
  • Cardiac myosin binding protein C gene is specifically expressed in heart during murine and human development [7].
  • After exercise, the recovery of phosphocreatine-an index of oxidative metabolic capacity of the muscle-was slower in the beta myosin heavy chain group (mean half time 0.65 (0.08) minutes) than in the troponin T group (0.60 (0.17) minutes) or controls (0.48 (0.14) minutes) [8].
  • In hyperthyroidism, the cross-bridge movement significantly preceded tension development, suggesting that hyperthyroid myosin (V1) has a longer latency period between the shift to the vicinity of the thin filament and force development [9].
  • Newly-reported structural information about certain proximities between points on bound nucleotide and points on the heavy chain of myosin S-1 are incorporated into a previously-reported [Botts, J. Thomason, J.F. & Morales, M.F. Proc. Nat. Acad. Sci. USA, 86, 2204-2208 (1989)] structure of S-1 [10].

High impact information on MYO9A

  • Kinetics shows that the binding of myosin to actin is a two-step process which affects ATP and ADP affinity [11].
  • Molecular genetics of myosin [12].
  • Structural and biochemical studies suggest that the position of tropomyosin (Tm) and troponin (Tn) on the thin filament determines the interaction of myosin with the binding sites on actin [13].
  • 3) The initial rate of force development depends mostly on the extent of Ca(2+) activation of the thin filament and myosin kinetic properties but depends little on the initial force level [13].
  • Second, the technology to measure picoNewton forces and nanometer distances has provided direct determinations of the force and step length generated by a single myosin molecule interacting with a single actin filament [14].

Chemical compound and disease context of MYO9A


Biological context of MYO9A

  • The Ku protein complex interacts with YY1, is up-regulated in human heart failure, and represses alpha myosin heavy-chain gene expression [20].
  • Muscle contraction results from the force generated between the thin filament protein actin and the thick filament protein myosin, which causes the thick and thin muscle filaments to slide past each other [21].
  • Actin-based propulsion is driven by the free energy released by ATP hydrolysis linked to actin polymerization, and does not require myosin [22].
  • Twenty-four are clustered around four specific locations in the myosin head that are (i) associated with the actin binding interface, (ii) around the nucleotide binding site, (iii) adjacent to the region that connects the two reactive cysteine residues, and (iv) in close proximity to the interface of the heavy chain with the essential light chain [23].
  • To assess whether this phenotype was specific for the FHC mutants and not generalizable to any myosin mutation, COS cells were transfected with a construct encoding an MHC with a 168-amino acid deletion of the hinge/rod region [24].

Anatomical context of MYO9A

  • Human aortic SMCs grown on polymerized collagen showed high expression levels of contractile markers (smooth muscle alpha-actin, myosin heavy chain, and calponin) [25].
  • This is accompanied by a coordinated increase in synthesis of other contractile proteins and, in skeletal muscle only, by isoform shifts of myosin light chains and of the TM-TN regulatory system [26].
  • In hair cells of the inner ear, evidence suggests that an extracellular tip link pulls on a channel, which attached intracellularly to actin via a tension-regulating myosin 1beta [27].
  • Wild-type alpha MHC transfected into COS cells forms structures previously shown to be arrays of thick filaments, which also resemble myosin structures observed early in differentiation of muscle cells [24].
  • Accumulation of mRNAs encoding alpha-skeletal, alpha-cardiac, beta- and gamma-actin, total myosin heavy chain, and alpha- and beta-tubulin also displayed discordant regulation, which has important implications for sarcomere assembly [28].

Associations of MYO9A with chemical compounds

  • As the differentiation in a culture progressed, 1,10-phenanthroline became less effective in blocking the accumulation of creatine kinase and myosin heavy chain [29].
  • These proteins include the following: integrin alpha-4, myosin heavy chain (nonmuscle type A), myosin light-chain alkali (nonmuscle isoform), and beta-actin [30].
  • Myocyte-specific enhancer factor 2 and thyroid hormone receptor associate and synergistically activate the alpha-cardiac myosin heavy-chain gene [31].
  • The expression of the dominant negative Cdc42 mutant inhibited contractile force and the increase in actin polymerization in response to acetylcholine stimulation but did not inhibit the increase in myosin light chain phosphorylation [32].
  • Ca(2+)-dependent calmodulin/myosin light-chain kinase-mediated contraction was examined by direct Ca(2+) (pCa8-5) stimulation to beta-escin permeabilized aortic strips; the pCa-force curve in Pkd2(+/-) strips was not shifted, thereby indicating that PE induced dosage-response alteration that resulted from Ca(2+)-independent mechanisms [33].

Analytical, diagnostic and therapeutic context of MYO9A

  • Advances in our knowledge of the regulation of cardiac myosin isoforms made possible by molecular cloning of the alpha- and beta-MHCs genes are reviewed [34].
  • Redifferentiation of smooth muscle cells after coronary angioplasty determined via myosin heavy chain expression [35].
  • The presence of differentiated human muscle fibers was assessed by quantitative PCR measurement of the human alpha-actin mRNA together with immunohistochemical staining using specific antibodies for spectrin and the slow adult myosin heavy chain [36].
  • As shown by in situ hybridization with cloned probes and analysis of in vitro translation products, M. occulta embryos do not accumulate high levels of alpha actin or myosin heavy chain mRNA [37].
  • Concomitantly, addition of BMP-7 stimulates the expression of SMC-specific markers, namely alpha-actin and heavy chain myosin as examined by RT-PCR and Northern blot analyses [38].


  1. From flies' eyes to our ears: mutations in a human class III myosin cause progressive nonsyndromic hearing loss DFNB30. Walsh, T., Walsh, V., Vreugde, S., Hertzano, R., Shahin, H., Haika, S., Lee, M.K., Kanaan, M., King, M.C., Avraham, K.B. Proc. Natl. Acad. Sci. U.S.A. (2002) [Pubmed]
  2. Direct effects of leptin on size and extracellular matrix components of human pediatric ventricular myocytes. Madani, S., De Girolamo, S., Muñoz, D.M., Li, R.K., Sweeney, G. Cardiovasc. Res. (2006) [Pubmed]
  3. Human bronchial smooth muscle cell lines show a hypertrophic phenotype typical of severe asthma. Zhou, L., Li, J., Goldsmith, A.M., Newcomb, D.C., Giannola, D.M., Vosk, R.G., Eves, E.M., Rosner, M.R., Solway, J., Hershenson, M.B. Am. J. Respir. Crit. Care Med. (2004) [Pubmed]
  4. A class III myosin expressed in the retina is a potential candidate for Bardet-Biedl syndrome. Dosé, A.C., Burnside, B. Genomics (2002) [Pubmed]
  5. Quantification and characterization of myosin peptide-specific CD4+ T cells in autoimmune myocarditis. Maier, R., Miller, S., Kurrer, M., Krebs, P., de Giuli, R., Kremer, M., Scandella, E., Ludewig, B. J. Immunol. Methods (2005) [Pubmed]
  6. Involvement of the C-terminal residues of the 20,000-dalton light chain of myosin on the regulation of smooth muscle actomyosin. Ikebe, M., Reardon, S., Mitani, Y., Kamisoyama, H., Matsuura, M., Ikebe, R. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
  7. Cardiac myosin binding protein C gene is specifically expressed in heart during murine and human development. Fougerousse, F., Delezoide, A.L., Fiszman, M.Y., Schwartz, K., Beckmann, J.S., Carrier, L. Circ. Res. (1998) [Pubmed]
  8. Abnormal skeletal muscle bioenergetics in familial hypertrophic cardiomyopathy. Thompson, C.H., Kemp, G.J., Taylor, D.J., Conway, M., Rajagopalan, B., O'Donoghue, A., Styles, P., McKenna, W.J., Radda, G.K. Heart (1997) [Pubmed]
  9. Cross-bridge and calcium behavior in ferret papillary muscle in different thyroid states. Yagi, N., Saeki, Y., Ishikawa, T., Kurihara, S. Jpn. J. Physiol. (2001) [Pubmed]
  10. The region in myosin S-1 that may be involved in energy transduction. Morales, M.F., Ue, K., Bivin, D.B. Adv. Exp. Med. Biol. (1993) [Pubmed]
  11. Structural mechanism of muscle contraction. Geeves, M.A., Holmes, K.C. Annu. Rev. Biochem. (1999) [Pubmed]
  12. Molecular genetics of myosin. Emerson, C.P., Bernstein, S.I. Annu. Rev. Biochem. (1987) [Pubmed]
  13. Regulation of contraction in striated muscle. Gordon, A.M., Homsher, E., Regnier, M. Physiol. Rev. (2000) [Pubmed]
  14. Actomyosin interaction in striated muscle. Cooke, R. Physiol. Rev. (1997) [Pubmed]
  15. Impaired recycling of synaptic vesicles after acute perturbation of the presynaptic actin cytoskeleton. Shupliakov, O., Bloom, O., Gustafsson, J.S., Kjaerulff, O., Low, P., Tomilin, N., Pieribone, V.A., Greengard, P., Brodin, L. Proc. Natl. Acad. Sci. U.S.A. (2002) [Pubmed]
  16. Expression of ventricular myosin subunits in the atria of children with congenital heart malformations. Shi, Q.W., Danilczyk, U., Wang, J.X., See, Y.P., Williams, W.G., Trusler, G.A., Beaulieu, R., Rose, V., Jackowski, G. Circ. Res. (1991) [Pubmed]
  17. Localization of porcine cardiac myosin epitopes that induce experimental autoimmune myocarditis. Inomata, T., Hanawa, H., Miyanishi, T., Yajima, E., Nakayama, S., Maita, T., Kodama, M., Izumi, T., Shibata, A., Abo, T. Circ. Res. (1995) [Pubmed]
  18. Alendronate inhibits lysophosphatidic acid-induced migration of human ovarian cancer cells by attenuating the activation of rho. Sawada, K., Morishige, K., Tahara, M., Kawagishi, R., Ikebuchi, Y., Tasaka, K., Murata, Y. Cancer Res. (2002) [Pubmed]
  19. Induction of myocarditis and valvulitis in lewis rats by different epitopes of cardiac myosin and its implications in rheumatic carditis. Galvin, J.E., Hemric, M.E., Kosanke, S.D., Factor, S.M., Quinn, A., Cunningham, M.W. Am. J. Pathol. (2002) [Pubmed]
  20. The Ku protein complex interacts with YY1, is up-regulated in human heart failure, and represses alpha myosin heavy-chain gene expression. Sucharov, C.C., Helmke, S.M., Langer, S.J., Perryman, M.B., Bristow, M., Leinwand, L. Mol. Cell. Biol. (2004) [Pubmed]
  21. Mutations in the skeletal muscle alpha-actin gene in patients with actin myopathy and nemaline myopathy. Nowak, K.J., Wattanasirichaigoon, D., Goebel, H.H., Wilce, M., Pelin, K., Donner, K., Jacob, R.L., Hübner, C., Oexle, K., Anderson, J.R., Verity, C.M., North, K.N., Iannaccone, S.T., Müller, C.R., Nürnberg, P., Muntoni, F., Sewry, C., Hughes, I., Sutphen, R., Lacson, A.G., Swoboda, K.J., Vigneron, J., Wallgren-Pettersson, C., Beggs, A.H., Laing, N.G. Nat. Genet. (1999) [Pubmed]
  22. Reconstitution of actin-based motility of Listeria and Shigella using pure proteins. Loisel, T.P., Boujemaa, R., Pantaloni, D., Carlier, M.F. Nature (1999) [Pubmed]
  23. Structural interpretation of the mutations in the beta-cardiac myosin that have been implicated in familial hypertrophic cardiomyopathy. Rayment, I., Holden, H.M., Sellers, J.R., Fananapazir, L., Epstein, N.D. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  24. Functional analysis of myosin missense mutations in familial hypertrophic cardiomyopathy. Straceski, A.J., Geisterfer-Lowrance, A., Seidman, C.E., Seidman, J.G., Leinwand, L.A. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
  25. Synergistic roles of platelet-derived growth factor-BB and interleukin-1beta in phenotypic modulation of human aortic smooth muscle cells. Chen, C.N., Li, Y.S., Yeh, Y.T., Lee, P.L., Usami, S., Chien, S., Chiu, J.J. Proc. Natl. Acad. Sci. U.S.A. (2006) [Pubmed]
  26. Developmental and functional adaptation of contractile proteins in cardiac and skeletal muscles. Swynghedauw, B. Physiol. Rev. (1986) [Pubmed]
  27. The molecules of mechanosensation. Garcia-Anoveros, J., Corey, D.P. Annu. Rev. Neurosci. (1997) [Pubmed]
  28. Differential patterns of transcript accumulation during human myogenesis. Gunning, P., Hardeman, E., Wade, R., Ponte, P., Bains, W., Blau, H.M., Kedes, L. Mol. Cell. Biol. (1987) [Pubmed]
  29. Metalloendoprotease inhibitors that block fusion also prevent biochemical differentiation in L6 myoblasts. Baldwin, E., Kayalar, C. Proc. Natl. Acad. Sci. U.S.A. (1986) [Pubmed]
  30. Redox regulation of surface protein thiols: identification of integrin alpha-4 as a molecular target by using redox proteomics. Laragione, T., Bonetto, V., Casoni, F., Massignan, T., Bianchi, G., Gianazza, E., Ghezzi, P. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  31. Myocyte-specific enhancer factor 2 and thyroid hormone receptor associate and synergistically activate the alpha-cardiac myosin heavy-chain gene. Lee, Y., Nadal-Ginard, B., Mahdavi, V., Izumo, S. Mol. Cell. Biol. (1997) [Pubmed]
  32. The small GTPase Cdc42 regulates actin polymerization and tension development during contractile stimulation of smooth muscle. Tang, D.D., Gunst, S.J. J. Biol. Chem. (2004) [Pubmed]
  33. Pkd2+/- vascular smooth muscles develop exaggerated vasocontraction in response to phenylephrine stimulation. Qian, Q., Hunter, L.W., Du, H., Ren, Q., Han, Y., Sieck, G.C. J. Am. Soc. Nephrol. (2007) [Pubmed]
  34. Regulation of myosin heavy chain genes in the heart. Morkin, E. Circulation (1993) [Pubmed]
  35. Redifferentiation of smooth muscle cells after coronary angioplasty determined via myosin heavy chain expression. Aikawa, M., Sakomura, Y., Ueda, M., Kimura, K., Manabe, I., Ishiwata, S., Komiyama, N., Yamaguchi, H., Yazaki, Y., Nagai, R. Circulation (1997) [Pubmed]
  36. Uncoupling protein-3 (UCP3) mRNA expression in reconstituted human muscle after myoblast transplantation in RAG2-/-/gamma c/C5(-) immunodeficient mice. Guigal, N., Rodriguez, M., Cooper, R.N., Dromaint, S., Di Santo, J.P., Mouly, V., Boutin, J.A., Galizzi, J.P. J. Biol. Chem. (2002) [Pubmed]
  37. Interspecific hybridization between an anural and urodele ascidian: differential expression of urodele features suggests multiple mechanisms control anural development. Swalla, B.J., Jeffery, W.R. Dev. Biol. (1990) [Pubmed]
  38. Bone morphogenetic protein-7 (osteogenic protein-1) inhibits smooth muscle cell proliferation and stimulates the expression of markers that are characteristic of SMC phenotype in vitro. Dorai, H., Vukicevic, S., Sampath, T.K. J. Cell. Physiol. (2000) [Pubmed]
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