MYO7A is an unconventional myosin motor protein, expressed both in retinal photoreceptors and the retinal pigmented epithelium (RPE), especially in the apical part of the cell body and in the apical processes. In the photoreceptors, MYO7A is required for the normal transport of opsin through the ciliary plasma membrane to the outer segment, and, in the RPE, it functions in the movement of melanosomes and phagosomes.
MYO7A has been implicated in the spatiotemporal regulation of the visual retinoid cycle probably by mediating light-dependent translocation of the visual cycle enzyme, RPE65. Retinas lacking MYO7A contain less of RPE65, due to increased degradation. Besides, the enzyme that is present fails to undergo light-dependent translocation and the total isomerase activity is impaired.
Ammar-Khodja et al. (2009) applied a systematic approach, involving haplotyping and genotyping, to depict the molecular etiology of non-syndromic deafness in 50 families and 9 sporadic cases from Algeria. One family with non-syndromic deafness carried a novel unclassified variant of unknown pathogenic effect in the MYO7A gene. Additionally, Ammar-Khodja et al. (2009) carried out a molecular diagnosis on two Usher type I families and found pathogenic mutations in the MYO7A and the PCDH15 genes.
Weil et al. (1997) identified a homozygous mutation in the MYO7A gene in affected members of a southern Tunisian family with autosomal recessive non-syndromic sensorineural deafness and retinal degeneration; consistent with Usher syndrome type IB.