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Alfred K Yu, Lanying Song, Karl D Murray, Deborah van der List, Gino A Cortopassi; Microglial activation and inflammatory response in a mouse model of Leber’s Hereditary Optic Neuropathy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1352.
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© ARVO (1962-2015); The Authors (2016-present)
Leber’s Hereditary Optic Neuropathy (LHON) is a retinal neurodegenerative disorder resulting from inheritance of mutations in mitochondrial complex I (NADH dehydrogenase). The mechanism of LHON pathogenesis is unknown, but multiple hypotheses have been advanced, including bioenergetic, apoptotic, and excitotoxic pathways. The recent development of ndufs4 knockout mice as a model of complex I deficiency has allowed for more rigorous testing of these hypotheses. To explore the pathogenesis of LHON we analyzed global gene expression using RNA sequencing (RNA-seq) in eyes of ndufs4 knockout and wild type littermate mice during a critical period for disease onset.
It has been reported that ndufs4 mice lose visual function at postnatal days 30 (P30). Therefore, we examined the pattern of gene expression before, during, and after this period. Ndufs4 knockout mice were sacrificed at P20, P30, and ~P40. Retinas were surgically removed and placed in RNAlater (Life Technologies). Total RNA was extracted from whole retinas using affinity column purification (Qiagen) and processed by the UC Davis DNA Technologies & Expression Analysis Core for RNA-seq. Remaining RNA was used to generate cDNA template (Bio-Rad) for validation of candidate genes by RT-PCR.
RNA-seq data from P30 retinas revealed an increase in immune and inflammatory genes in ndufs4 knockout mice. Quantitative RT-PCR data confirmed a significant increase in Cd68, Cd86, Aif1, and Mmp12, which are associated with microglia activation. In addition, RT-qPCR data showed an increase in B2m, Tlr2, Ccl2, Ccl12, and Cxcl10 suggesting both an induced immune and inflammatory response. In contrast, RT-qPCR data at P20 showed a significant increase only in Cd68 and B2m.
LHON results from a defect in mitochondrial complex I, which leads to loss of vision. The mechanism connecting mitochondrial dysfunction to vision loss has been unknown. In ndufs4 knockout mice there is a clear induction of immune and inflammatory response genes that coincides with vision loss, and markers for microglial activation may be present as early as P20. These data support the hypothesis that loss of mitochondrial function induces retinal inflammatory genes in ndufs4 mice, and suggests a potential route of therapeutic treatment in LHON.
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