972: Identification of Mutations Associated with Hereditary Cataracts in Northern Breeds

Grant Status: Closed

Grant Amount: $100,000
Dr. Cathryn S Mellersh, Ph.D., Animal Health Trust
July 1, 2008 - September 30, 2010
Sponsor(s): Basset Hound Club of America, Inc., Karen & Jeffrey Flocker, Mastiff Club of America
Breed(s): Siberian Husky, American Eskimo Dog, Norwegian Elkhound, Norwegian Buhund, Schipperke, Alaskan Malamute
Research Program Area: Prevention

Project Summary

This study aimed to investigate the genetic cause of hereditary cataract (HC) in Northern breeds. The Investigators have collected samples from 228 dogs affected with bilateral cataract (both eyes) and 300 dogs with a clear eye examination from 15 Northern breeds, initially screening known human cataract-causing genes in 66 dogs from two of these breeds. They used a panel of 39 markers near to 20 genes involved in human inherited cataract and found no evidence for association of any markers with HC in the two breeds. Using genome-wide association (GWA) study (whole genome scanning) approaches they conducted an initial analysis of HC in the Finnish Lapphund, Icelandic Sheepdog, Samoyed and Siberian Husky. For the Samoyed they found evidence for an association with HC on chromosome 7, but no associations were identified in the other three breeds. These initial results suggested that HC in Northern breeds is not caused by a single gene mutation and may have a more complex genetic background. This finding is not entirely surprising when it is considered that to date only a single gene, HSF4, has been implicated in the development of HC in the dog despite the fact that close to 100 breeds are known to be affected by the condition. To detect mutations in numerous genes requires analysis of a larger number of samples using a rigorous definition for affected dogs ('cases') and unaffected dogs ('controls'). Therefore for their final investigation they concentrated their efforts on four breeds that display a clinically similar form of HC and for which we have sufficient numbers of cases and controls for analysis. They have conducted a GWA scan of HC in these four breeds-the Alaskan Malamute, Siberian Husky, Karelian Bear Dog and Samoyed-using an updated high-density genome scanning array comprising around 174,000 markers spanning the DNA. Their initial analyses of these data are promising and they have found evidence of HC-associated regions for at least three of the breeds. The Investigators are currently investigating these association signals and aim to design and conduct further studies to attempt to pinpoint the causal mutations.

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