01076-A: Determine Genomic Region Associated with Sebaceous Adenitis in the Standard Poodle

Grant Status: Closed

Grant Amount: $12,960
Dr. Cathryn S Mellersh, Ph.D., Animal Health Trust
June 1, 2008 - September 30, 2008
Breed(s): Standard Poodle
Research Program Area: Prevention

Project Summary

Sebaceous adenitis (SA) is a dermatological condition that has been described in several breeds of dog, most commonly in the Standard Poodle. It is a condition in which the sebaceous glands in the skin become inflamed and are eventually destroyed, leading to hair loss and secondary skin infections, and is a significant health and welfare problem. The Animal Health Trust has collected DNA samples from over 300 Standard Poodles. Using the latest genotyping techniques, (a Canine SNP (single nucleotide polymorphism) array of 22,362 genome-wide SNPs) we have genotyped a subset of 48 samples from dogs with a rigorous SA diagnosis, which included 20 affected dogs and 28 unaffected dogs. AHT has been helped enormously by the Standard Poodle Club UK in this choice of samples. Using this data, AHT has carried out careful computer analysis to try to identify the region of the genome in which the SA mutation lies. The preparation of the DNA samples and their genotyping have been achieved successfully. All 48 samples were genotyped, although 4 fell below rigorous acceptability standards and were not included in the analysis. The vast majority of the 22,362 SNPs on the array (over 99.7%) worked well. This is a very impressive result. The data was analysed using pedigree-based linkage software and association-based software. The analyses were carried out successfully: the researchers know this because using identical methods on other diseases and breeds, they have been able to identify genome locations linked to the diseases. However for the Standard Poodle samples both types of analysis failed to identify any regions of the genome which were significantly associated with the disease. They are confident that the genotyping data we generated was of a very high quality, so the likely explanation for our failure to identify a region of the genome associated with SA is because the disease is complex, and is either caused by more than one gene, or the interaction between gene(s) and the environment. Alternatively, their controls included a number of sub-clinically affected dogs whose skin biopsy results lead us to mis-categorise them. In either case, the solution is to collect and genotype more samples, and any new data can be added to what we already have, thus increasing the chances of success. This is a disappointing result, but as a result of this investigation AHT now can say fairly confidently that sebaceous adenitis in the Standard Poodle is not inherited as a simple autosomal recessive with a high degree of penetrance, and that more samples need to be analysed to identify a genomic region associated with the disease. AHT is committed to continuing their study of SA in the Standard Poodle and will continue to collect and store samples from affected and unaffected Standard Poodles at the AHT until we have sufficient samples to successfully analyse SA as a complex trait. Data generated during the current study will be saved, and added to additional data generated in this subsequent phase of the study.

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