Health/Genetics Report Fall Canadian Icelandic Sheepdog Club 2007

Health/Genetics Report
by Sharon Schaefer

During the past few weeks an interesting email arrived which changed the focus of my article this issue from Persistent Pupillary Membrane (eye issues have already been covered in a general way) to the "possible S" gene series for white. Dr. Sheila Schmutz researcher and author/co-author of many of the recently published discoveries in gene codes for dog colours (Department of Animal & Poultry Science, University of Saskatchewan) contacted me for more DNA swabs from certain of my dogs. The kit just arrived and will be mailed back this week in mid-November.

Her page on Spotting was updated November 12, 2007 with two very recent breakthroughs by two separate research groups so we are right in the middle of exciting times. Quoting directly from her website: "The first gene that causes at least some spotting patterns in dogs has now been identified and published in 2007. Furthermore potential mutations causing some forms of spotting have been identified in this gene. This gene is MITF, microphthalmia associated transcription factor. MITF is a critical gene in the pigmentation pathway."

Note that she says ‘causes at least SOME spotting patterns’. Almost a year ago, I attended a seminar on Genetics & Dog Breeding presented by Sheila and her husband, Dr. Joe Schmutz. At that time she cautioned breeders to not make assumptions based on other species or even other breeds as the exploding area of gene mapping is proving that many conditions which appear phenotypically the same can be unique to only one breed or a few related breeds.

The discoveries so far involving white patterns support this cautious approach. While the MITF gene is involved in more than one breed and in producing various white patterns, there are so far two separate mutations discovered in this gene and in some white patterned dogs they do not both occur. More breeds are being examined, including Iceland Sheepdogs so we should have some solid breed related feedback sometime in 2008.

For example, English Springer Spaniels might look like they have the same colour patterns as Collies but until several are checked at the DNA level we are jumping to conclusions which could be wrong. At this point in time, checking DNA in one breed when a colour pattern has not been proven to occur at that particular mutation site could be both a waste of money and a mistake. Once a selection of breeds have all been checked and confirmed as having the same mutations associated with particular colour patterns then assuming that the remaining breeds’ DNA will also follow the rules becomes much more likely! At the speed of research and communications today we might be at that point by the end of this year or the new information might raise new questions instead of supporting the current hypotheses.

Boxers were one of the studied breeds which identified the MITF gene and both mutations so far identified. However Boxer colours behave phenotypically as though ‘Solid’ and ‘White’ are co-dominant which is very different from some other breeds. Remembering our high school biology, roan cattle resulted from a co-dominant solid white cow and solid red bull or pink flowers from a white and a red parent flower so too ‘flashy or Irish pattern Boxers’ are heterozygous.

Researchers are still searching for other causative gene locations for the occurrence of white spotting in dogs. Many locations common in other species have been eliminated as not involved. It will be very interesting and rewarding if our dogs can contribute to this effort.
http://homepage.usask.ca/~schmutz/dogcolors.html
http://homepage.usask.ca/~schmutz/dogspots.html