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K. Nagel-Wolfrum, T. Goldmann, N. Overlack, U. Wolfrum; PTC124-Mediated Read-Through of a Nonsense Mutation Causing Usher Type 1c. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3116.
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The human Usher syndrome (USH) is the most frequent cause of inherited combined deaf-blindness. It is clinically and genetically heterogeneous, assigned to three clinical USH types of which the most severe type is USH1. So far no effective treatment for the ophthalmic component of USH exists. PTC124 is a promising compound for translational read-through of nonsense mutations leading to a premature termination stop, currently gauged in clinical phase II for nonsense mutation in non-ocular diseases. Here we investigated the potential of PTC124 as a treatment option for patients carrying nonsense mutations in the USH1c gene (p.R31X) causing the USH1 disease.
Read-through of PTC124 was validated in cell culture and in retinal explants. Restoration of scaffold function of the USH1c protein harmonin was tested in GST-pull downs. Biocompatibility was determined in murine and human retinal explants by TUNEL-assays. In all assays the application of the aminoglycoside gentamicin were used as controls and compared with PTC124 treatments.
PTC124-induced read-through of the USH1c p.R31X mutation was observed in HEK293T cells. GST-pull downs demonstrated binding activity of the recovered harmonin to the cytoplasmic tail of USH2A protein. Treatment of PTC124 resulted in a read-through in p.R31X transfected retinal explants. In contrast to gentamicin, PTC124 treatment did not induce cell death in murine and human retinas indicating a high retinal compatibility of PTC124.
The PTC124-mediated read-through of the p.R31X nonsense mutation in USH1c effectively restored full-length protein expression and recovered the scaffolding function of the USH1c protein harmonin. PTC124's high retinal compatibility combined with its transcriptional read-through efficacy emphasize the high potential of PTC124 as a therapeutic agent for the p.R31X nonsense mutation in USH1 as well as in other retinal genetic conditions.
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