• Cecile Lebon, Francine Behar-Cohen, and Alicia Torriglia.
• Inserm U1138. Centre des Recherches des Cordeliers, 15, rue de l'Ecole de Médecine, 78006 Paris, France; Université Pierre et Marie Curie, France; Université Paris Descartes, France.
• Neuroscience. 2019 Feb 21; 400: 728472-84.

AbstractSpino-cerebellar ataxia type 7 (SCA7) is a polyglutamine (polyQ) disorder characterized by neurodegeneration of the brain, cerebellum, and retina caused by a polyglutamine expansion in ataxin7. The presence of an expanded polyQ tract in a mutant protein is known to induce protein aggregation, cellular stress, toxicity, and finally cell death. However, the consequences of the presence of mutant ataxin7 in the retina and the mechanisms underlying photoreceptor degeneration remain poorly understood. In this study, we show that in a retinal SCA7 mouse model, polyQ ataxin7 induces stress within the retina and activates Muller cells. Moreover, unfolded protein response and autophagy are activated in SCA7 photoreceptors. We have also shown that the photoreceptor death does not involve a caspase-dependent apoptosis but instead involves apoptosis inducing factor (AIF) and Leukocyte Elastase Inhibitor (LEI/L-DNase II). When these two cell death effectors are downregulated by their siRNA, a significant reduction in photoreceptor death is observed. These results highlight the consequences of polyQ protein expression in the retina and the role of caspase-independent pathways involved in photoreceptor cell death.Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.

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