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C.P. Hamel, N. Renard, M. Surget, A. Dose, C. Ayuso, B. Burnside, M. Eybalin, C. Maubaret; MYOSINE 3A: Genomic Structure, Tissue Expression and Mutation Search in Usher Syndrome . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3550.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: NinaC is a non conventional myosin from Drosophila melanogaster which harbours a kinase domain in its N terminus. Mutations in ninaC are responsible for a slow dark adaptation and in some cases for photoreceptors losses. The human homologous MYO3A has been cloned and preferential expression in retina was reported. As many unconventional myosins are expressed in inner ear and may be involved in transduction adaptation, we assessed MYO3A expression in cochlea and screened patients suffering Usher syndrome (Retinitis Pigmentosa + Deafness). Methods: MYO3A expression was analysed by RT-PCR in human and mouse tissues. Isoforms were searched for in human retina. Genomic structure was obtain by sequence comparison in Blast HTGS software. DNAs from 33 Usher patients without mutations in MYO7A (Usher type I) or USH2A (Usher type II) were screened by Single Strand Conformation Polymorphism (SSCP) assay. Samples showing abnormal patterns were sequenced using the BigDye chemistry and 310 ABI sequencer. Results: MYO3A expression is the high in cochlea and testis and moderate in retina and brain. At least three coding isoforms were identified in human retina among which two are found in the mouse cochlea. The gene spans more than 300 kb and is composed of 35 exons. We identified 17 sequence changes. One of them, a 3035 G>A (Ala 1032 Thr) change was found at the heterozygote state in 3 usher patients and not in 332 control chromosomes. Conclusions: In this study, strong MYO3A expression in cochlea and testis was established. The fact that Ala 1032 is non conserved (Thr in Limulus polyphemus) and that non mutations were found on the other allele makes improbable that this change is pathogenic.
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