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G. Lenaers, M. Chen–Kuo–Chang, C. Depeyre, S. Kamei, K. Cornille, N. Renard, C. Delettre, O. Payet, C. Arndt, A. Muller, P. Brabet, C. Hamel; Expression of Opa1 in Rat and Mouse Retina, With Emphasis on Retinal Ganglion Cells. OPA1 Down Regulation in RGCs Perturbates the Mitochondrial Function and Dynamic . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3119.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Mutations in the mitochondrial dynamin–related GTPase OPA1 is the predominant cause of autosomal dominant optic atrophy (ADOA), but the pathophysiology of this disease remains unknown. As a first step to functional studies, we have evaluated in rat and mouse the expression of Opa1 in whole retina and in isolated retinal ganglion cells (RGCs) and further tested the effects of Opa1 down regulation in cultured RGCs. Methods: Opa1 mRNA isoforms from total retina and from RGCs freshly isolated using Thy1 antibodies were determined by RT–PCR. Protein expression was examined by immunohistochemistry on whole retina and on purified RGCs and by Western blot using antibodies against Opa1, while the mitochondrial network was visualized using cytochrome c antibodies or MitoTracker® Red. siRNA targeting OPA1 mRNAs were transfected to cultured RGCs and mitochondrial network phenotypes were followed for 15 days, in comparison with those of cerebellar granule cells (CGCs) in culture. Results: In both models, Opa1 expression is found all over the retina and does not predominate in RGCs. The pattern of mRNA isoforms was similar in whole retina and RGCs. After few days in culture, RGCs showed fine mitochondrial punctiform structures in the soma and the neurites, that co–localized with cytochrome c and Opa1. Opa1 knock down in RGCs induced a mitochondrial network aggregation at a higher rate than in CGCs, and the loss of the mitochondrial membrane potential. Conclusions: Results suggest that the level of expression and the mRNA isoforms do not underlie the vulnerability of RGCs to OPA1 mutations. However, aggregation of the mitochondrial network induced by the down regulation of Opa1 appears more frequent in RGCs than in control CGCs.
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