By Carolyn Arnold, BBCI Department of Education and Research
BBCI Participation
The Biewer Breed Club International (BBCI) participated in a genetic study on the Piebald (spotting) coat color recently completed by researchers at the University Of Saskatchewan Department Of Animal Science under the direction of Dr. Sheila Schmutz.
“We are trying to identify the genes which cause specific colors in dogs. Sometimes these are associated with diseases, but often simply normal colors for that breed or cross” say the researchers.
Dr. Schmutz requested DNA samples from three Biewers who are the most unrelated to be among the several breeds suspected of expressing the piebald gene in their study. BBCI Department of Education and Research, under direction of Carolyn Arnold, pulled together pedigrees from the most populated and popular Biewer lines for study. Criteria also sought dogs that had at the most generations of pure Biewer to Biewer breeding. The pedigrees were researched and all missing ancestors and their coat colors were recorded and inserted into a pedigree database. Reports for common ancestors and progeny generated from the database revealed which dogs were most suited to be submitted for the study. Three dogs were chosen whose lines fit the desired criteria. Their DNA samples were submitted in April 2008 just in time to be included in the study.
Results are in
Results communicated from Dr. Schmutz say “All 3 were homozygous for the SINE mutation in the MITF gene promoter. This is the same genotype (SINE/SINE) that has been found in all the other piebald dogs we have tested. Therefore this result "fits" our expectation.”
In other words, yes, the Biewer coat color is indeed the result of the piebald gene and homozygous (having two alleles that are the same and therefore breeding true).
Dr. Schmutz will present this study at the 4th International Conference on the advances in canine and feline genomics and inherited diseases in Saint Malo, France on May 21 – 25th 2008.
For further interpretation and background, pleases read on. Do you find genetics boring? Then skip the genetics and go to the end of this article to read what it all means for the Biewer breed.
Why study canine genetics?
The domestic dog is a species coaxed into hundreds of distinct types through selective breeding by humans over the past two centuries. In the course of breeding for desirable traits, disease-associated genes have also been inherited.
While dogs and humans often share the same living spaces, they are also susceptible to many of the same illnesses, including cancer, epilepsy, and diabetes. And since the two species share much of their DNA, efforts to pinpoint the genetic underpinnings of dog diseases have the potential to deepen the knowledge of diseases in humans. This explains why there are so many new canine studies and is good news for humans and good news for dogs and their breeders and fanciers.
In recent sequencing of the dog genome (full complement of genes carried by the cell), researchers have revealed another consequence of selective breeding – chunks of DNA that are roughly 100 times larger than those found in the human genome, providing researches with a critical shortcut. New mapping methods take advantage of the power of this reduced genetic diversity in dog breeds and the sharing of mutations across breeds to identify disease genes.
The Piebald (Spotting) Gene Study
Researchers have now pinpointed a variation in the genetic code at a specific point on the DNA called SNP’s that are associated with white coat color. The highest-ranking SNP from their analysis resides in a section of the dog genome that contains one gene, called MITF, an important developmental gene. Here is where the SINE mutation (an inherited change in the genetic material of an individual) takes place. (SINE is a type of small dispersed repetitive DNA sequence) SINE/SINE shows homozygous inheritance (having like alleles in the same location). This mutation is what is now identified to express the piebald coat.
Okay, so now what?
What does this mean to the Biewer world? The answer is two fold.
The Biewer breed’s white coat pattern is indeed a result of the piebald gene, not from another dog being bred into the Yorkshire Terrier.
Is the Biewer in any health danger due to being piebald? There is no data on this presently. White coat color has been identified in other studies as the cause of deafness in Dalmatians and anomalies in other breeds with white coat patterns. However, because Biewers have pigment of Blue/Black/Tan/Gold other than white around the ears and eyes on the head, it is suspected, not proven, that the Biewer escapes the anomalies due to the presence of darker pigment. This is a strong case supporting a practice to breed selectively in order to keep the strong head colors present.
Resources:
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Dog Coat Color Genetics)
4th International Conference: Advances in canine and feline genomics and inherited diseceses
ONE MITF MUTATION YIELDS MULTIPLE SPOTTING PHENOTYPES IN VARIOUS DOG BREEDS
Sheila M. Schmutz and Tom G. Berryere
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada