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T. Ben-Yosef, A. Rebibo-Sabbah, I. Nudelman, Z. M. Ahmed, T. Baasov; Evaluating Suppression of Nonsense Mutations by Aminoglycoside Antibiotics as an Intervention for Vision Loss in Type I Usher Syndrome. Invest. Ophthalmol. Vis. Sci. 2008;49(13):462.
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© ARVO (1962-2015); The Authors (2016-present)
Type 1 Usher syndrome (USH1) is a recessively-inherited condition, characterized by profound prelingual deafness, vestibular areflexia, and prepubertal onset of retinitis pigmentosa (RP), which to date has no effective treatment. USH1 can be caused by mutations in each of at least six genes. While truncating mutations of these genes cause USH1, missense mutations of some of the same genes cause nonsyndromic deafness, suggesting that partial or low level activity of the encoded proteins may be sufficient for normal retinal function, although not for normal hearing. Interventions to enable at least some translation of full-length protein, may delay the progression of RP in individuals with USH1 due to nonsense mutations. The purpose of the current research is to evaluate one such possible therapeutic approach, suppression of nonsense mutations by aminoglycoside antibiotics, as an intervention for vision loss in USH1.
Suppression of nonsense mutations is initially tested in vitro, using a transcription/translation assay of a reporter plasmid harboring various nonsense mutations of CDH23 and PCDH15, underlying USH1D and USH1F, respectively. Ex vivo suppression is tested using expression constructs transfected into cultured cells. In parallel, we are developing a series of new aminoglycoside derivatives, which will maintain their suppressive activity, while having reduced toxicity.
We demonstrated up to 91% in vitro suppression of PCDH15 nonsense mutations by commercial aminoglycosides. We also demonstrated ex vivo suppression, by the same aminoglycosides, of the p.R245X mutation of PCDH15. We are now testing suppression of several CDH23 nonsense mutations. In parallel, we have designed and synthesized two new promising aminoglycoside derivatives, NB30 and NB54. In vitro transcription/ translation assays, as well as in vitro and in vivo toxicity assays of these compounds have been performed with encouraging results.
The research described here will have important implications for development of targeted interventions that are effective for patients with USH1 and nonsyndromic RP caused by various nonsense mutations.
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