Was the first Blue Weimaraner, Cäsar von Gaiberg the product of a cross breeding or of a spontaneous genetic mutation? In order to answer this question, German scientist at Ruhr-University studied the DNA of 24 Blue Weimaraners and one Gray Weimaraner from two Blue parents. They also looked at 20 unrelated Grays. Most of these dogs were from German pedigrees. Their findings were published in the Journal of Animal Breeding and Genetics in September of 2010 – PDF.
The authors first verified what breeding records have shown all along: the B allele is what determines whether a Weimaraner is blue or gray. After examining other candidate genes, they looked at the TYRP1 gene (the B gene) and showed that Grays had two mutant (non-functioning) TYRP1 (B) alleles, and all Blues showed at least one functioning TYRP1 allele. Thus, Grays are bb and Blues are Bb or BB, and the blue coat color is dominant to the gray color in Weimaraners. See Weimaraner Coat Color Genetics to learn more about how the coat color is inherited.
To delve further, the authors were also able to mark and identify a unique intron (non-coding section of the gene) linked to this functional B allele in the Blues only; they were not present in the Grays. Based on this haplotype (a combination of alleles transmitted together) at least two mutations would have been necessary for a spontaneous reversion from Gray back to Blue.
The scientists also looked a the Y chromosome haplotypes of the Blues and Grays. In Grays there are four different Y chromosome haplotypes. The Blues share three of these, but the scientists indentifed a new Y chormosome haplotypes in the Blues which were not present in the German Grays.
The group then looked at a Gray eighth generation male descendant of Cäsar von Gaiberg, the acknowledged progenitor of Blues in the United States. Because this male was followed through the pedigree via his male ancestors back to Cäsar, the original Y haplotype should have been transmitted through these eight generations. Of note, this eighth generation male Gray descendant of Casar had this unique haplotype.
HOW this unique haplotype was introduced, whether from a cross breeding or not, was not studied here. The authors do say, “a different Y chromosomal haplotype could also be taken as an argument for cross-breeding, where a dog with diverging TYRP1 and Y chromosomal haplotypes was introduced into the Weimaraner population before or after the presence of the anecdotal Blue Weimaraner.”
So what does this mean? What has this paper proven? Technically, all this paper did was confirm what we knew from breeding records; that the B gene is responsible for the coat color difference between Blue and Gray Weimaraners. This has now been confirmed with genotyping. They were also able to conclude that the Blue Weimaraner’s origins come partially from an introduction of a “typical 377 -bp TYRP1 haplotype potentially along with a unique Y-chromosomal haplotype” which very strongly suggests cross breeding.
While it is satisfying to have some hard answers proven in the lab in order to quiet some of the debate on the origins of the Blue Weimaraner, what does it really change? The overwhelming significance of this paper in my mind is that it DOES put to rest misinformation, ”historical” anecdotes. But the practical question isn’t how the Blue Weimaraner came to be. The Blues are still here, and for all intents and purposes are considered a variety of the traditional Gray Weimaraner. The colors have been interbred for over 60 years, and Blues are registerable with the AKC, and as such are considered purebred Weimaraners. While this article provides compelling argument that Cäsar was the result of a cross breeding, today’s Grays and Blues are so intermingled, even outside the U.S., Blue Weims still remain the red headed step child… so nothing has really changed. The question is what do we do about it?