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C.D. Turnbull, J. Poulton, G.D. Vairavan, S. Das, S. Adams, S. Hornby, S.M. Downes; Evaluation of the OriB mtDNA (T16189C) Polymorphism Variant in Patients With Age Related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4342.
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Age related macular degeneration (AMD) is the commonest cause of blindness in the Western world. Genetic predisposition to AMD is well documented and a number of nuclear DNA candidate genes have been screened, particularly those causing similar phenotypes e.g. macular dystrophies. Mitochondrial mutations have not previously been evaluated in AMD. A mitochondrial DNA (mtDNA) mutation causes maternally inherited diabetes and deafness (MIDDM), a condition with a pattern type macular dystrophy. The OriB variant is a different, but common mtDNA polymorphism, which predisposes to both diabetes and deafness. This study was designed to determine whether the OriB variant has a role as a genetic susceptibility factor for AMD.
Blood samples were collected from 192 consecutive patients with AMD attending the Radcliffe Infirmary Eye Hospital. The Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) cohort (Casteels et al. 1999) was used as a control group. Both groups were screened for the OriB variant, with workers masked to the sample origin. Colour fundus photographs were taken using the Zeiss digital fundus FF450 camera and were graded using a modified form of the International Classification of AMD. The age of AMD patients with and without the OriB variant was analysed, as were the different AMD classification groups.
15 of 192 the AMD patients had the OriB variant (7.81%), compared to 54 of 634 (8.54%) of the control group. This is not a significant difference (chi test; p=0.76). The mean ages of the AMD patients with the OriB variant was 79 and without was also 79, which was not statistically significant (t–test; p=0.36). AMD subgroups were analysed for the presence of the OriB variant. There was no significant difference found (chi squared test; p=0.59).
These results suggest that there is no significant association between the OriB variant and AMD. However other mtDNA mutations or polymorphisms may merit screening as genetic susceptibility factors in AMD. Acknowledgements: We are grateful to Novartis for costs of consumables.
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