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W.J. Kimberling, D.J. Orten, V.A. Vogltanz, A.M. Hemje, J. Gold, N. Landauer, M. Neuringer, L.A. Lyons, S. Waltz, J.W. Kemnitz; Evaluation of Candidate Macaque USH2A Mutations . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3592.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Usher syndrome, a recessive disorder characterized by retinitis pigmentosa (RP) and sensorineural hearing loss, is the leading cause of combined hearing and vision loss in the industrialized world, affecting 25,000–30,000 people in the United States. Mutations in the USH2A gene account for over half of Usher syndrome cases and 25–50% of autosomal recessive RP cases, which affects about 67,000 people in the United States. Disparities in retina function indicate that rodents may not be ideal models for this type of RP. Based on the carrier rate for the average recessive gene, we predict that screening >500 macaques has a >95% probability of detecting a pathologic mutation. We are screening for macaque carriers of USH2A mutations because these mutations are a common genetic cause of RP in humans. Methods: Samples from 595 unrelated macaques were obtained from three National Primate Research Centers. Segments (323–486 bp) of USH2A exons plus flanking intronic DNA were amplified and sequenced. Pathology of putative mutations was evaluated based on frequency and predicted alteration of protein structure. Results: We found >15 polymorphic variants in 50% of the Macaca mulatta USH2A coding sequence. More than 80 rare variants were found, 30 of which altered amino acids. An alu insertion in IVS7 was predicted to be nonpathologic based on allele frequency (1.4%). Pathologic missense mutation candidates include alterations in partially conserved residues in the signal peptide, amino terminal region, laminin type VI and laminin EGF domains. The best candidate for a pathologic allele creates a strong splice donor site in exon 8, predicted to lead to a frameshift and stop codon. We plan to test USH2A mRNA from salivary gland biopsies from the putative splice mutation carrier to determine if aberrantly spliced mRNA is produced. Conclusions: If aberrantly spliced mRNA is indicated, mating or in vitro fertilization will be arranged to produce homozygous offspring. A macaque model will provide insights into pathologic mechanisms for retinitis pigmentosa, and may be better suited than mice for testing new treatments that could reduce or prevent inherited blindness.
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