Summary of Harlequin project

The goal of this research is to identify the gene that is responsible for the harlequin coat pattern. We have assembled four small, unrelated pedigrees comprised of 40 Great Danes. These pedigrees include 23 harlequins and 11 merles, the only coat color that unequivocally indicates that the dog does not carry the harlequin gene. For all dogs, blood samples were collected and used to isolate DNA. These samples are being used in a linkage approach to find the gene.

Presently, we are collecting genotypes for naturally occurring molecular signposts that are found throughout the canine genome. This process requires 70 reactions for each dog; 2800 reactions are required to complete the linkage analysis. The products of the reactions will be analyzed using computer software which will allow us to determine genotypes. We are looking for differences between the genotypes of harlequin dogs and merle dogs. A statistic will be calculated to determine how significant any observed differences are. When a significant difference is found, that region will be analyzed for genes that are important in pigmentation. Sequence from candidate genes will be collected for a harlequin dog and a merle dog and compared. Any sequence differences will be evaluated to determine if it is responsible for the harlequin coat pattern.

Keith E. Murphy, Ph.D.
Professor
Department of Veterinary Pathobiology
College of Veterinary Medicine and Biomedical Sciences
Texas A&M University
College Station, TX 77843-4467