A novel locus on canine chromosome 13 is associated with cataract in the Australian Shepherd breed of domestic dog
Hereditary cataract is a common ocular disorder in the purebred dog population and is a leading cause of visual impairment and blindness in dogs. Despite this, little is known to date about the genetics underlying this condition. We have used a genome-wide association study and targeted resequencing approach to identify a novel locus for cataracts in the Australian Shepherd breed of dog, using dogs that are clear of an HSF4 mutation, previously identified as the major susceptibility locus in this breed. Cataract cases were defined as dogs with bilateral posterior cataracts, or bilateral nuclear cataracts. Controls were at least 8 years of age with no evidence of cataracts or other ocular abnormality. Using 15 bilateral posterior polar cataract cases and 68 controls, we identified a genome-wide statistical association for cataracts in the Australian Shepherd on canine chromosome 13 at 46.4 Mb (P value: 1.5 × 10−7). We sequenced the 14.16 Mb associated region in ten Australian Shepherds to search for possible causal variants underlying the association signal and conducted additional fine-mapping of the region by genotyping 28 intronic variants that segregated correctly in our ten sequenced dogs. From this analysis, the strongest associated variants were located in intron 5 of the SCFD2 gene. Further study will require analysis of additional cases and controls and ocular tissue from dogs affected with bilateral cataracts that are free of the HSF4 mutation.
KeywordsCataract Bilateral Cataract HSF4 Gene Progressive Retinal Atrophy Canine Chromosome
We would like to thank all owners for providing samples from their dogs for this study. We also thank Saija Ahonen and Hannes Lohi (University of Helsinki, Finland) for provision of samples for the study. We would like to thank the Australian Shepherd Health & Genetics Institute, Inc. for their assistance with sample collection, study publicity and financial contributions. This work was funded by Morris Animal Foundation First Award grant D10CA-303. In addition to the Australian Shepherd Health & Genetics Institute, we would also like to thank the Orthopedic Foundation for Animals and the American Spaniel Club Foundation for their sponsorship of the study. SLR, LP, BM, CAJ and CSM are supported by the Kennel Club Genetics Centre at the Animal Health Trust. We thank the High-Throughput Genomics Group at the Wellcome Trust Centre for Human Genetics (funded by Wellcome Trust grant reference 090532/Z/09/Z and MRC Hub grant G090074791070) for the generation of the sequencing data. We also thank Claudia Hartley (BVSc CertVOphthal DipECVO MRCVS) for assisting with case definitions and Oliver Forman and Mike Boursnell for technical and bioinformatics assistance.
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