myosin-VIIa (MYO7A USH1B)

Function

• myosins are actin-based motor molecules with ATPase activity
• unconventional myosins serve in intracellular movements
• their highly divergent tails are presumed to bind to membrane compartments, which would be moved relative to actin filaments
• in retina, myosin 7a might play a role in trafficking of ribbon-synaptic vesicle complexes & renewal of the outer photoreceptors disks
• in inner ear, it might maintain the rigidity of stereocilia during the dynamic movements of the bundle
• involved in hair-cell vesicle trafficking of aminoglycosides, which are known to induce ototoxicity (putative)
• interacts with PLEKHB1 (via PH domain) (putative)
• might homodimerize in a two headed molecule through the formation of a coiled-coil rod
• binds MYRIP & WHRN

Structure

• contains 2 FERM domains
• contains 5 IQ domains
• contains 1 myosin head-like domain
• contains 2 MyTH4 domains
• contains 1 SH3 domain

Compartment

• cytoplasm (probable)
• in photoreceptor cells, mainly localized in the inner & base of outer segments as well as in the synaptic ending region

Alternative splicing

• named isoforms=7
• additional isoforms seem to exist

Expression

• expressed in the retineal pigment epithelium & in retinal photoreceptor cells
• also found in kidney, liver, testis, cochlea, lymphocytes
• not expressed in brain
• detected in optic cup in 5.5 weeks-old embryos
• expressed in retinal pigment epithelium, cochlear & vestibular neuroepithelia, & olfactory epithelium at 8 weeks
• at 19 weeks, present in both retinal pigment epithelium & retinal photoreceptor cells
• at 24-28 weeks, expression in retinal pigment epithelium & retinal photoreceptor cells increases
• present in retinal pigment epithelium & retinal photoreceptor cells in adult

Pathology

• defects in MYO7A are the cause of
  • Usher syndrome type 1B
  • deafness autosomal recessive type 2
  • deafness autosomal dominant type 11

More general terms

• unconventional myosin
• phosphoprotein

Additional terms

• Usher syndrome type 1B/myosin VIIA mutation associated

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=4647
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:4647
• OMIM: https://mirror.omim.org/entry/276900
• OMIM: https://mirror.omim.org/entry/276903
• OMIM: https://mirror.omim.org/entry/600060
• OMIM: https://mirror.omim.org/entry/601317
• UniProt: http://www.uniprot.org/uniprot/Q13402.html