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B Zangerl, Q Zhang, J Johnson, G Acland, G Aguirre; Independent Origin of Three Microdeletions in RPGR Exon ORF15 of Canids . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3674.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Investigations to determine the possible ancestral origin of mutations previously identified in the RPGR exon ORF15. Two of them, a five and two base pair deletion, were causally associated with the retinal degenerations XLPRA1 and XLPRA2, respectively; the XLPRA1 deletion is shared between at least two different dog breeds. An SNP based approach was used to determine phylogenetic relationship between the different mutations. Methods: To identify SNPs we screened BAC clones (RPCI81 library) associated with markers in a 30 cM interval which includes the 500 kb XLPRA zero recombination region. In short, 1 µg of purified BAC DNA was digested and subcloned into pUC18 vector, selecting insert sizes between 700 to 1000bp for subsequent random sequencing. Sequences were filtered to exclude repetitive elements and vector contamination, and sequenced in two heterozygous individuals for each of the deletions to identify sequence variations. For each polymorphism we developed a screening method either by discriminating the two possible alleles by restriction digestion or using the SNaPshotTM Multiplex Kit. SNPs were screened in 86 dogs from breeds identified with XLPRA, and about 50 DNA samples collected from other Canidae species to serve as outgroups. Resulting haplotypes were analyzed to infer history of the observed RPGR ORF15 mutations. Results: Each of the three observed deletions in ORF15 is linked to a distinct haplotype background in the canine XLPRA interval. Conclusion: The three different mutations identified in canine RPGR ORF15 arose independently in evolution. Haplotype analysis argues strongly that the deletion causing XLPRA1 in Siberian husky and Samoyed dogs originated in a common ancestor. Furthermore, SNP analysis of the RP3 region in several Canidae species demonstrates phylogenetic evolution of this chromosomal segment.
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