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March 14, 2011

The Harlequin Gene Project ...

interview with Leigh Anne Clark

by Lucio Rocco

Dr. Leigh Anne Clark has worked since 2006 at the Clemson University (South Carolina) where she carries out the research of canine genetics. She studied and worked until 2004 at Texas A & M University, where she graduated in 2000 in Biomedical Sciences. Afterwards, she started the doctorate school and she joined the Canine Genetics Laboratory at the Faculty of Veterinary Medicine, where she earned a doctorate in 2004. She is currently researcher at the Department of Genetics and Biochemistry of the Clemson University. Dr. Clark started , as early as when she was in Texas, the studies on the merle mutation in dogs, and she continued her studies in South Carolina, expanding the research to the mutation harlequin, through a project funded by the name "The Harlequin Gene Project."

When did you start researching canine pigmentation patterns?

In 2005, I was collecting genetic data for a disorder in Shetland sheepdogs called dermatomyositis. I noticed that the dogs in the study had different coat colors: there were sables, tri-colors, and blue merles. I decided that I would to try to use the genetic data to map the gene for merle, and I was successful! I have worked on merle and related patterns ever since.

What is the ultimate intent of this research?

The goal of the harlequin research is to identify the gene that causes the coat pattern.

When did you identify the harlequin gene? And how did you realize the gene was present also in the Collie breed?

After I identified the gene causing merle, I read a journal article from the 1980’s describing the harlequin pattern found in Great Danes. I knew immediately that I wanted to try to map that gene, too. I did not become aware of harlequin dogs in other breeds until 2009, when I received an email about a unique collie in Finland. Even though the coat pattern looked just harlequin in Great Danes, I was not convinced that it was a form of harlequin until I was able to show that the collie was not a double merle.

All right, but what is the harlequin gene?

In Great Danes, harlequin is caused by a mutation in a gene that functions in the breakdown of proteins that are no longer needed by the body.

Can you explain how the harlequin gene works?

The harlequin gene modifies the merle coat. While a blue merle dog has black spots on a grey background, a dog with merle AND harlequin will have black spots on a white background. The harlequin gene erases the dilute background. The harlequin gene does nothing to the coat of a dog that is not merle.

And how is it transmitted?

The harlequin gene is dominant. In dogs with a merle coat, one copy of the harlequin gene will make the background white. That means that it only takes one parent with harlequin to have a litter with harlequin puppies. In Great Danes, puppies that inherit two copies of the harlequin mutation die soon after conception.

Have you any idea how the harlequin gene came in the breed?

The harlequin gene was not brought into collies by another breed. Collies do not have a mutation in the same gene as Great Danes. New gene mutations that are naturally acquired are most likely the cause of harlequin dogs in other breeds. This new mutation may have been in the breed for awhile, but only became apparent when it occurred in a merle dog. There is no way to detect the mutation in a non-merle collie.

What is the spread of this gene? How many countries has been found so far?

We have identified harlequin collies in America, Finland, Denmark, and The Netherlands. These collies probably do not all have the same mutation. Most likely, a new mutation occurred independently in each of these lines.

Can you explain why harlequin, as well as merle, is not a color?

Harlequin and merle do not determine the color of the coat. They cause a pattern of varying intensities (from full pigmentation to no pigmentation) of the base color, which is determined by other genes.

Do you think this research is useful for men, too?

The gene that causes harlequin in Great Danes is critical for normal protein breakdown. Our findings shed new light on important sequences within the gene, and the discovery of additional harlequin genes could identify other genes important in this pathway.

Well, Dr. Clark, we thank you very much, and we hope to get the best from your work!