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S. Kim, N. Piri, J. M. Kwong, M. Song, J. Ahn, Y. Munemasa, J. Caprioli; Autophagy in the Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):55.
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Autophagy, an intracellular protein degradation process, is essential for cellular homeostasis, defense and adaptation to adverse environments. It can be activated in response to injury and plays an important role in neuronal survival. We investigated the expression of autophagy related proteins in normal retina and the regulation of autophagy related genes in the rat optic nerve crush injury model.
Retinal total RNA and protein were extracted from rat retinas after optic nerve crush 1 week, 2 weeks and 1 month after injury and from control rat retinas. (n=16, 4 per group). RNA expression levels in treated and control retinas were analyzed by semi-quantitative RT-PCR. Western blot and immunohistochemistry were used to determine the levels of protein expression and protein localization in the retina, respectively.
Immunoblot analysis of anti-microtubule associated protein 1 light chain 3 protein (LC3), which is essential for autophagy, showed the presence of two isoforms, LC3-I and LC3-II, in normal rat and optic nerve injury retinas. Expression of LC3-II protein suggests the presence of active autophagy in untreated retinas. Expression of LC3 protein in normal rat retinas was localized by immunohistochemisty predominantly to cells in the retinal ganglion cell layer as well as to photoreceptor cells. Semi-quantitative RT-PCR was performed to analyze mRNA expression levels of ATG (AuTophaGy)5, 7 and 12 genes, which are necessary for autophagy process. These genes were found to be expressed in both control and treated retinas, however the mRNA expression of ATG 5, 7 and 12 was approximately two-fold upregulated in retinas of optic nerve crush model 2 weeks and 1 month after injury compared to control retinas.
The results of this study showed that autophagy related genes LC3, ATG5, 7 and 12 are expressed in the retina and that autophagy mechanism may be involved in the retinal response to optic nerve crush injury.
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