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Tae-im Kim, Eung Kweon Kim, Kyung Eun Han, Ji Min Ahn, Sangmin Nam; Altered Mitochondrial Function In Type 2 Granular Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1099.
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Type 2 granular corneal dystrophy (GCD2) is caused by point mutation R124H in the β-transforming growth factor-induced gene and characterized by age-dependent progression of corneal deposits. We compared the morphology and function of mitochondria in wildtype and GCD2 mutated corneal tissues and fibroblasts, and discovered that the GCD2 mutation alters mitochondrial function, potentially explaining the age-dependent progression of the disease.
Mitochondrial morphology in heterozygous GCD2 and normal corneal tissues was evaluated by electron microscopy. Primary corneal fibroblasts of homozygous and normal corneas were cultured to passage 4 or 8. Cells were evaluated by electron microscopy, mitotracker and cytochrome C staining, JC-1 assay, MTS and CCK-8 measurement, and western blots for expression of complex I-V and proteins involved in mitochondrial function (PGC-1α, ANT-1, VDAC, AKT, and mTOR).
Keratocytes of normal corneal tissue have a narrow shape and the details of their intracellular organelles are difficult to distinguish. Keratocytes of heterozygous GCD2 tissues displayed many degenerative mitochondria. Wildtype cultured fibroblasts had small, healthy mitochondria, whereas homozygous cells had elongated, swollen mitochondria. Mitotracker and cytochrome C staining indicated increased mitochondrial activity in mutated cells at early passages, but decreased activity at later passages. Decreases in depolarized mitochondria, cellular proliferation, and complex I-V expression were observed in late passage mutant fibroblasts. PGC-1α, ANT-1 p-AKT, and p-mTOR expression showed a passage-dependent decrease in all cells.
Mitochondrial morphology and function were altered in mutated GCD2 keratocytes, particularly in older cells. The alteration of mitochondrial function is critical for understanding the pathogenesis of GCD2.
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