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P. Heiduschka, M. Alavi, U. Schraermeyer, B. Wissinger; Visual Function Is Impaired in Aged Opa1-Mice. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3113.
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Autosomal dominant optic atrophy is a juvenile onset, progressive ocular disorder characterised by central visual field defects and finally bilateral loss of vision. The disease is most frequently associated with mutations in OPA1 encoding a GTPase that localises to mitochondria. We have recently reported on a first mouse model carrying a splice site mutation (c.1065 + 5G => A) in the Opa1 gene. Whereas homozygous mutant mice die in utero, heterozygous mutants are viable and of normal habitus but exhibit an age-dependent loss of RGCs that eventually progresses to a severe degeneration of the ganglion cell and nerve fibre layer. In this study, we examined consequences of RGC loss in Opa1-heterocygotes on visual function.
Visual function was characterised by standard visual electrophysiology (electroretinography, ERG, and visual evoked potentials, VEP). Age-matched mice of the same genetic background (C57BL/6) were used as controls.
No significant differences in visual responses could be detected in animals at an age of 10-12 months. In two-years old animals, both scotopic and photopic VEP amplitudes were significantly lower in Opa1 mice (n=9) than in the wild-type controls (n=11). Latencies were not changed, indicating that mainly RGC loss could be responsible for the observed differences, and not changed properties nerve signal propagation. In the ERGs, slight differences were also seen between Opa1 mice and controls, however, they where not significant.
In aged Opa1 mice, functional consequences of RGC degeneration can be observed by decreased VEP amplitudes. In contrast, there are no differences in the ERG suggesting that function of photoreceptors and post-receptoral circuitries remains unaffected.
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