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Saija J Ahonen, Hannes Lohi; Progressive Retinal Atrophy in the Karelian Beardog; A Large Animal Model for Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3270.
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Progressive retinal degenerations are the most common causes of complete blindness both in human and in dogs. Canine progressive retinal atrophy (PRA) resembles human retinitis pigmentosa (RP) and is characterized by a progressive loss of rod photoreceptor cells followed by a loss of cone function. The dogs are commonly diagnoses with retinal vessel attenuation and retinal hyperreflectivity and as the disease progresses the complete retina is degenerated. The primary clinical signs are detected as vision impairment in a dim light. As the disease progresses to cone cells the normal day vision in impaired as well before leading to complete loss of vision. Although several causative genes for canine PRAs are known, there are still PRAs of unknown genetic cause. Karelian Beardog (KBD) breed is known to be affected with rod-cone degeneration caused by a mutation in the prcd-gene. In addition, another type of PRA is diagnosed in the breed not caused by the known mutation.
We have embarked a genetic study to identify the mutation causing the other type of PRA in the KBD. We have genotyped three cases and 44 controls using Illumina CanineHD BeadChip with 173000 markers.
The initial analysis identified three tentative loci on canine chromosomes 17, 24 and 26 (praw= 8.68*10-07, pgenome=0.7). Further genotyping with six additional cases is likely to confirm the association to one of the loci. After genotyping, the best candidate genes in the associated region will be studied further using capillary sequencing or targeted sequence capture.
We have identified three tentative loci for retinal degeneration in the KBD. Our further studies are likely to identify a second PRA causing mutation in the KBD breed and establish the breed as a large model for further characterization of gene biology and possible retinal gene therapy trials. In addition a gene test can be developed for KBD for breeding purposes.
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