One of the less heralded aspects of purebred dogs is their tremendous contribution to the study of human disease. Research into canine coat pigmentation patterns, specifically merle and harlequin, may have a human link because the responsible gene is part of a biological process involved in Parkinson’s and Alzheimer’s diseases. This exciting link has been found by Dr. Leigh Anne Clark and her colleagues at Clemson University who not only discovered the gene that causes the Harlequin phenotype ((PSMB7), but also that the harlequin gene isn’t a pigment producing gene at all. Put another way, all Harlequins are genetic merles.

Dr. Clark: “All harlequins are merles, but they are more than merle. There’s a separate gene for harlequin. It is a dominant modifier of merle that removes the dilute pigment, leaving the background white.”  The harlequin gene acts like bleach. It eliminates the merle’s light bleach spots on the base coat, resulting in white base-coat spots.  Dogs that aren’t merle, or only have red pigment, can’t express the Harlequin gene. Since two copies of Harlequin haven’t been observed, they’re presumed to be embryonic lethal, therefore, all Harlequin patterned dogs have only 1 copy of the mutation.

We also want to point out that Dr. Clark is the only researcher doing this work, and that something that may ultimately benefit all people has been funded by a purebred dog club, the Great Dane Charitable Trust. Remember this the next time someone gives you grief for owning and/or breeding a purebred dog.

“Maggie Mae” by Catherine Garneau is available as a print, greeting card and phone case here.