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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. |
