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Maria Karla Kaukonen, Saija J Ahonen, Hannes Lohi; Hereditary cataract in Bichon Frisé dogs: Genome-wide association study suggests a new preliminary locus finding. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6417.
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Cataract is the leading cause of blindness both in humans and dogs and it is considered as hereditary in more than 100 different dog breeds. The unique breeding history of purebred dogs offers great opportunities for genetics research. In addition, dog serves as a large animal model for human eye diseases because of the similar physiology and living environment. Many diseases are shared by the two species and the causative genes are the same. The purpose of this study was to investigate the genetic background of cataract in purebred Bichon Frisé (BF) dogs. Cataract in BF is suspected to be recessively inherited based on the pedigree analysis. First signs of cataract are typically seen when the dogs are 6 years old and the initial site for cataract formation is in the cortical or posterior polar part of the lens.
Our study cohort consisted of 54 cases and 35 controls. All dogs were eye examined by a certified veterinary ophthalmologist. A dog was included to control group if it had been healthy in the eye examination over the age of seven years. The cases were further subdivided into primarily cortical (n=28), posterior polar (n=17) and unspecified cataract (n=9). A genome-wide association study was performed using Illumina’s CanineHD BeadChip SNP array with 173 000 markers. A case-control association test was performed using PLINK 1.07, GenAbel and Pseudomarker softwares.
The case-control association test in the whole study cohort identified a tentative association on canine chromosome 20 (CFA20) with p=2.76×10(-6). The same association was identified when analyzing only dogs with primary cortical cataract (p=2.87×10(-6)). However, no association was identified when analyzing only the posterior polar cases.
Our data suggests that region on CFA20 is associated with cataract in BF. Linkage- and covariate-analysis including age at the time of diagnosis and cataract type is currently being performed to validate the identified association and to further study the association to additional loci. After identification of the associated loci, the best candidate genes will be studied further to identify the disease causing variants.
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