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J. Graw, A. Weber, J. Löster; Mapping of the Age–Related Emory Cataract: Indication for a Complex Trait . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2519.
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© ARVO (1962-2015); The Authors (2016-present)
The EMORY cataract is one of the very few mouse models for hereditary senile cataracts. Aim of the actual study is the mapping of the mutation to further identify candidate genes within the critical linkage intervals.
EMORY mice were imported from the Jackson Laboratory into the GSF animal facilities in 2003. Homozygous EMORY mice were outcrossed to wild–type Japanese fancy mice (JF1). Since no carriers were observed among the F1 generation, these heterozygotes were backcrossed to homozygous EMORY mice. A panel of microsatellite markers was used for genome–wide linkage analysis in the F2 generation. Mice were analyzed for cataracts between 4 and 9 months of age (using a slit lamp); in a few cases, eyes of dead mice have been investigated histologically to confirm cataracts. To calculate the recombination frequency, only confirmed carriers have been used; statistically significant deviation from Mendelian ratios were calculated using the chi–square test.
Outcrossing of the EMORY mice to wild–type JF1 mice did not lead to carriers of a cataractous phenotype up to the age of 9 months. Therefore, the EMORY mutation has to be considered as a recessive trait. In the F2 generation, 486 mice have been collected; surprisingly, 100 of them died within the first few months of their life. The remaining 386 F2 offspring (between 4 and 9 months old) have been investigated for lens opacities, and actually 54 carriers have been confirmed. Compared to the parental generation, the age of onset was shifted to younger animals, mainly 4–5 months of age (∼50% of the carriers). There was a slight association to the coat color (33 carriers = 61% are albino; chromosome 7), but it turned out to be statistically not significant. However, significant linkage (p<0.01) was found for chromosomes 5, 12 and 19. Therefore, it is obvious that the EMORY cataract does not fulfill the classical criteria for a Mendelian disorder; moreover, it has to be considered as a complex trait. Some candidate genes have been sequenced already, but no causative mutation has been identified up to now.
The EMORY mouse is a complex disorder; linkage has been established at least for chromosomes 5, 12 and 19.
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