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B. Zangerl, S.J. Lindauer, G.M. Acland, G.D. Aguirre; Polymorphism and Association Study to Identify a Canine Model for Retinal Disorders Caused by ABCA4 . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3176.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Mutations in the retina specific member of the ATP–binding cassette transporter superfamily (ABCA4) have been associated with a diverse group of human retinal diseases. While over 200 unique sequence variants have been reported from human patients affected with cone–rod dystrophy, Stargardt macular dystrophy, age related macular degeneration, and autosomal recessive RP, the mechanisms leading from mutations to disease remains elusive in many cases. The development of the dog as a model for human blinding disorders, and the cloning of the canine homolog of ABCA4, have presented this gene as an ideal candidate to search for association between sequence changes in ABCA4 and dogs affected by various forms of retinal degeneration. The ongoing study is investigating the naturally observed sequence diversity of ABCA4in the dog. This will establish a base line to identify disease associated mutation. Methods: PCR primers suitable for exon scanning have been designed for each of the 50 canine exons by comparing the published cDNA sequence of ABCA4 (NM_001003360) to the recent release of the dog genome (http://www.genome.gov/12511476). Genomic DNA has been isolated from 38 individual dogs, representing 26 different breeds; for each breed, dogs with clinically diagnosed inherited retinal degeneration and non–affected controls were included. Each PCR reaction primarily amplifies exonic sequence, including some flanking region and small introns in selected cases for each individual animal. Sequence comparisons to identify nucleotide changes have been carried out using Sequencher® 4.2 software. Results: To date we have finished screening 29 exons revealing overall 47 polymorphisms. Only about one quarter (eleven substitutions) of all observed sequence changes are located within the coding region of ABCA4, while all other polymorphisms have been found in adjacent intronic sequence. Sequencing is still in progress and will need to be completed before association studies are initiated. Conclusions: The presence of polymorphisms in the coding region is limited to a few less conserved regions of the canine gene, and none has been associated with a blinding retinal disorder to date. Our data provides a first SNP map for canine ABCA4, and will be further utilized in association studies for pedigrees known to inherit retinal degeneration.
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