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Christopher Ryan Starr, Nahum Sonenberg, Marina S Gorbatyuk; Restoring protein synthesis delays retinal degeneration. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2342.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously shown reduced protein synthesis in mice with retinal degeneration (RD). One way cells control translation is through regulation of eIF4E-binding proteins (4E-BPs). In a process controlled by mTOR, 4E-BP can bind eIF4E and inhibit translation. We previously showed that mTOR/4E-BP signaling is reduced in mice with RD. Despite advances in knowledge regarding translation in neurodegenerative diseases, it is unclear whether restoring translation could be a therapeutic strategy for RD. Therefore, we knocked out 4ebp1/2 in rd16 to validate the hypothesis that the restoration of protein synthesis is a viable strategy for treating RD. Retinas of rd16 mice, expressing a truncated centrosomal protein 290 (Cep290), degenerate rapidly due to defective ciliogenesis.
rd16 4ebp1/2-/- mice were compared to C57BL/6 (C57) and rd16 mice. Translation was analyzed using azidohomoalanine and click chemistry. Outer nuclear layer (ONL) nuclei were counted at P18 by a masked investigator. Electroretinography (ERG) was performed at P17. rd16 and C57 mice were injected with either anisomycin (aniso) (30mg/kg), an inhibitor of protein synthesis, or vehicle subcutaneously three times a day from P12-P14. Apoptosis was analyzed in retinal sections by TUNEL staining. Data was analyzed using one-way ANOVA.
We first checked if treatment with aniso increases retinal cell death. After aniso-treatment, more TUNEL-positive nuclei were found in the ONL and INL of both rd16 and C57 mice. We next assessed whether ablation of 4ebp1/2 resulted in a change in the level of translation. Consistent with our past study, rd16 mice exhibited a ~30% reduction in protein synthesis compared with C57, while knocking out 4ebp1/2 resulted in the complete recovery of protein synthesis. This restoration was associated with a significant improvement in ONL number (67%) and scotopic ERG A- (96%) and B-wave (67%). In addition, 4ebp1/2 deletion resulted in significantly fewer TUNEL-positive nuclei (39%) in the ONL at P15.
We show that chronic translational inhibition could be sufficient to induce cell death in healthy retinas and translational restoration could significantly delay cell death in RD. Knocking out 4ebp1/2 in the retinas of rd16 mice delayed apoptosis and promoted photoreceptor survival. Taken together, our results indicate that targeting translation could have therapeutic potential for the treatment of RD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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