SCIENTIFIC PROOF THAT THE BIEWER TERRIER IS A SEPARATE BREED AND THE
PARTI YORKIE CAME ABOUT VIA INTENTIONAL OR “OOPS” CROSS BREEDING
By PHIL STINARD, GENETICIST
As you know, my opinion will be based on science, but I'll try to keep it simple. And I won't base my opinion on any particular agenda or fixed point of view, because I don't own a Biewer or have any close friends who own Biewers
Okay, I've formed my opinion on whether Biewers are a separate breed from Yorkshire Terriers based on the information I currently have. It could change based on new research, so it isn't set in stone, but here it is:
Based on the results of breed purity analysis conducted by MARS Labs, I can only conclude that the 100 Biewers that were tested do indeed contain DNA from other breeds of dogs. And the PCA analyses conducted by MARS Labs indicate that these Biewers are fairly uniform, and cluster in their own group separate from Yorkshire Terriers. To me, that meets the definition of a separate breed, but ultimately it's the AKC and other registries who will have to make that decision.
How these other breeds got mixed in Yorkshire Terriers to create the Biewer Terrier is somewhat a mystery to me (perhaps falsified pedigree records in the distant past or "oops" matings, but I am not going to point fingers because those people are long gone and we have no real way of knowing), but the DNA evidence is there, and it is very strong. For me, the smoking gun is the piebald spotting gene (MITF gene) on chromosome 20. This isn't a simple random mutation that can spontaneously occur over and over, but appears to have originated once during the domestication of dogs, and been transferred to the breeds with piebald spotting by crossbreeding and selection. In the breeds analyzed so far, all piebald spotting genes carry a unique DNA insertion called a SINE in the upstream regulatory region of the MITF gene (the part of the DNA that controls the expression of the MITF gene--where and when the gene will be expressed during the dog's growth and development) as well as a separate length polymorphism (segment of DNA that can vary in length) in the upstream regulatory region. The chances against both changes occurring at once spontaneously in a single Yorkshire Terrier are astronomical. My conclusion is that the piebald spotting gene had to have been bred in from another breed of dog during the development of the Biewer Terrier. The way to resolve this question once and for all would be to completely sequence the upstream regulatory regions of the MITF gene in Biewers and see whether it indeed carries the SINE and the length polymorphism. If it does, then it's a done deal as far as I am concerned that the Biewer arose from breeding a Yorkshire Terrier with another breed and re-extracting the piebald color gene.
Since I am a believer in the conservation of genetic resources, my recommendation is that Biewers be bred only with other Biewers in order to preserve their unique characteristics, which go beyond color, but also include behavioral differences. If you keep crossing Biewers back to Yorkshire Terriers, you are going to lose these unique characteristics, and end up with something more like a Yorkshire Terrier, but yet will never quite be a Yorkshire Terrier.
Okay, I'm stepping down off my soapbox now. If you disagree, it's all good, but please be kind and don't shoot the messenger. Thanks!
I understand everything except the piebald gene explanation. How do you explain how the parti yorkie got the piebald gene also and why are they considered yorkies if biewers arent
Oh dear, I don't want to create more controversy, but I think that Parti-Yorkies got their piebald gene in the same way that Biewers did--by crossing in from another breed. BUT, I have read absolutely nothing about DNA breed testing of Parti Yorkies, so I don't have as much data to go on as I do for Biewers--the evidence is much more clear in Biewers. It would be great to sequence the MITF (piebald) gene in Parti Yorkies too, just to try to get an idea of what is going on. I am willing to keep an open mind. We simply need more data.
I answered the Parti question in another post. But if Partis are testing as purebred Yorkshire Terriers, one explanation could be that they have been crossed for so many generations back to Yorkshire Terriers that traces of other breeds are being diluted out by Yorkie DNA. That's one possibility. Since I haven't seen any Parti test results with my own eyes, and since Partis have not been subjected to as much analysis by MARS as Biewers, I don't have enough information to draw any firm conclusions. Sequencing the MITF gene in Partis would help a lot in answering this question. With respect to AKC DNA testing, they only do parentage testing, not breed purity testing, and I'm certain that their parentage testing does not predate the appearance of the first Parti Yorkies. If you have any information to the contrary, let me know!
You have a good point about German Yorkies, but my understanding is that pedigree records for them are not as good as in the United States. And again, there was no DNA testing back in the days of Mr. Biewer.
About Biewer to Yorkie breeding, once that is stopped, and you start breeding Biewer to Biewer, the gene pool becomes fixed and the breed stops becoming more and more Yorkie-like. That would explain the MARS results showing that the Biewers they tested were in a unique and uniform group.
About the Biewers that were tested by MARS, yes those mostly came from one club. I don't know whether the person who submitted the DNA samples claimed to be a vet or not, but it doesn't matter, because DNA doesn't lie. If someone has serious issues about the validity of the samples, they should ask for them to be retaken and retested, but I'm sure the results would be the same. I agree that it would be great to test all Biewers from all clubs, but since that might include Biewers coming from Biewer by Yorkie crosses, that would basically be like throwing mixed breed dogs into a purebred test--the results would be interesting, but they wouldn't be informative or normative. I understand that there is some kind of turf war going on with respect to which clubs have the "true and authentic Biewers." I would recommend that all of the clubs doing Biewer by Biewer matings get together, submit their dogs' DNA for analysis, go over the results together, and try to reach some kind of consensus.
Oh, I forgot to mention that if you are getting a lot of different colored "Yorkies" (and I use the term loosely) from ONE litter, that is clearly a sign that breed standards for the Yorkshire Terrier are being ignored and flaunted, and people have been crossing Dog knows who to Dog knows what. Each color is not a separate breed--it's a sign of breeders gone wild.
I'm glad the AKC is satisfied that the Parti color can be produced in otherwise normal litters of Yorkshire Terriers, because I sure am not. Old records can be falsified, and the Parti color predates the era of DNA testing. And as I said in another post, if the trait did come from another breed and was crossed in to breed standard Yorkshire Terriers for generation after generation, eventually the sign of the evil deed is doing to disappear. In order for my curiosity to be satisfied, I would need to see a DNA breed analysis test done on as many Partis as possible, and I would like to see the MITF (piebald) gene and its upstream regulatory DNA sequenced. I'm a show-me kind of guy.
To relate to what I was talking about above, the "S" gene described in the article is the normal, functional MITF gene (found in breed standard Yorkshire Terriers), and the piebald gene is a mutant form of the MITF gene that is now known to have two unique mutations (a SINE DNA insertion, and a length polymorphism) in its regulatory region.
I've heard different stories as to which other breeds Mr. Biewer had at the time--I'm still waiting for the definitive answer to that question, because that could be the answer to where the piebald gene came from. But yes, DNA analysis could determine which breed supplied the piebald gene.
Here is another smoking gun. I was going to propose that someone cross a Biewer to a piebald Maltese to see whether the offspring would be piebald. If the offspring were piebald, that would prove that Biewers definitely carry the piebald gene. (This kind of cross is what geneticists call an allele test.) But I didn't say anything because I thought it would be unethical to ask someone to do that kind of cross. But guess what? While I was googling Biewer and Maltese, I found this ad: MORKIE German Biewer Yorkie / Maltese cross | North Port | eBay Classifieds (Kijiji) | 27676387. Someone has already done the cross, and the result is a piebald dog! Boo-yaaaa!!!!! I will attach a photo of the dog in case the ad disappears.
Just because a dog looks piebald doesn't mean that it is caused by a mutation in the piebald gene--there could be other as-yet undiscovered mutations in other genes that could cause the same appearance. I hadn't seen any proof that the Biewer coat color gene is due to a mutation in the MITF (piebald) gene. This Biewer/Maltese cross proves it to me. Maybe others have done this test, but I hadn't come across it yet. To me, the question remains, is the DNA sequence of the mutation in the piebald gene in Biewers the same as the DNA sequence of the mutation in the Maltese (and other breeds with proven piebald genes)? If so, that would prove to me that the origin of the piebald gene in Biewers is a cross of a Yorkshire Terrier with some other breed carrying a piebald gene. Genetically speaking, new mutations don't occur in the exact same place with exactly the same DNA sequence, and the piebald mutations in other breeds have a very distinctive DNA sequence. I don't care what Mr. Biewer said back in the 1980's, if the piebald gene came from some other breed that was crossed into his Yorkshire Terrier lines, then the Biewer is the result of a mixed breed dog. It wasn't necessarily Mr. Biewer who did this--it could have already been in the lines he got from England. I'm just trying to get at the truth.
Evidently, the Healthgene company knows the answer to this question, because they have a test for the piebald gene in Yorkshire Terriers and Biewers: Parti Color Yorkshire Terrier l Coat Color Test - HealthGene
I have sent them a technical email asking them for details about what they are testing for, and how they determine the difference between the piebald mutation and the normal Yorkshire Terrier MITF gene. If the answer is by the presence of the SINE DNA insertion and/or the length polymorphism in the regulatory region of the piebald version of the MITF gene, then it's case closed for me.
I have heard about the question of whether Biewers have Irish spotting (si) or piebald spotting (sp). They are both different mutations in the same gene. I can't answer that question based on appearance, because I've seen a broad range of degree of spotting in Biewers--some look Irish, and some look more piebald. Supposedly, the piebald gives more variation in the different patterns you see, so that's why I was guessing that Biewers are piebald, but hopefully the testing company will be able to answer the question for certain.
Jumping back in to the conversation, I wasn't able to get a direct reply from HealthGene on how they test for the presence of the piebald gene in Biewers and Parti Yorkshire Terriers, but HealthGene did refer me to Dr. Schmutz's 2009 paper on MITF and white spotting in dogs, and I found the answer buried in Table 2 of that paper. Here is the link to the paper:
MITF and White Spotting in Dogs: A Population Study
Table 2 lists the genotypes of 151 dogs from breeds in which individuals with random spotting were homozygous for the SINE insertion in the MITF gene. Two Biewers tested homozygous for the SINE insertion.
According to Dr. Schmutz's paper:
The SINE insertion 5′ of MITF-M first described by Karlsson et al. (2007) was associated with white markings in many and diverse breeds in this study, suggesting that it is an “old” mutation. There is considerable debate about the age of particular breeds. However, the Chinese Shar-Pei, Akita, and other Asian dogs are typically considered to be among the oldest breeds (Parker et al. 2004). The SINE insertion has been found in individuals with white markings in these breeds.
Since breed standard Yorkshire Terriers are solid colored and do not carry the piebald allele (the MITF gene with the SINE insertion), it had to have been bred in from some other dog breed to create the Biewer. Case closed.
I don't know how I missed this article...
Here is another fascinating research paper on DNA coat color testing in dogs that specifically references the Yorkshire Terrier:
Coat color DNA testing in dogs: Theory meets practice
It is behind a pay firewall, so I will quote the relevant parts:
These data illustrate that owners may be using coat color testing to help them understand the appearance of pups of unexpected coat colors in their litters. Using DNA testing will therefore help them to eliminate carriers of undesired alleles from future breeding. However, in some cases dog breeders are actually trying to create a line of dogs with a new coat color. An example of this is the Biewer Yorkshire Terrier, where random white spotting caused by a SINE insertion in MITF , is now selected for. The presence of the e allele in 9 of the commercially tested Yorkshire Terriers (Table 1), suggests that the random white spotting, called particolor in this breed, has likely been introduced from a breed where the e allele occurs commonly.
So according to this study, Biewers carry the piebald allele at the MITF gene, and Parti Yorkshire Terriers carry the "e" allele at the E (technically called the MC1R) gene. And BOTH were introduced from other breeds, because the likelihood of the exact same mutation arising independently in the Yorkshire Terrier is astronomically small. That article is a GOLDMINE of information, and I am going to curl up and read through it more carefully tonight. It also references people testing their Yorkies for the presence of the "b" (brown, or chocolate) allele at the B (technically called TYRP1) gene, and I need to see if this was introduced from other breeds as well--since they were testing for specific variations of the "b" allele found in naturally brown breeds, it's very likely that chocolate color in Yorkies came from some other breed. What a mess! DNA doesn't lie, folks!
Before I read that article, I had assumed that Biewers and Partis were both carriers of the piebald allele at the MITF gene because they supposedly both traced back to Streamglen (is that true, or just a theory that both trace back to Streamglen?). Now that some Partis have tested as "e" at the E gene, I'm not so sure. Biewers are definitely piebald, but maybe some lines of what people are calling Parti are piebald and others are "e"? I don't know--more testing of Partis is needed! Have any Parti breeders here had their dog's coat color genes tested?
What makes a dog lineage a separate breed is a unique appearance and genetic uniformity that is distinct and separates them from other breeds. The 100 Biewers that were tested in the MARS study fit that description because they could be separated from the Yorkshire Terrier group in the Primary Component Analysis. But those Biewers are from Biewer by Biewer matings, so that kind of breeding has kept them separated from the Yorkshire Terrier gene pool. The breeders who cross Biewers with Yorkshire Terriers to create "splitters" are breeding more Yorkshire Terrier into their DNA and they will test to be more like Yorkshire Terriers and may not be separable from Yorkshire Terriers by the MARS test.
Beiwer X Biewer = separate breed
Biewer X Yorkshire Terrier = becoming more like Yorkshire Terrier, and are not a separate breed.
Parti X Parti = No data on that, sorry!
Parti X Yorkshire Terrier = becoming more like Yorkshire Terrier and not a separate breed.
Chocolates -- No data on them either, but if they are being crossed back to Yorkshire Terriers, they are becoming more like Yorkshire Terrier and not a separate breed.
The upshot is that these colors were all bred into Yorkshire Terriers from some other breed in the (hopefully distant) past, and just because a dog is a different color, doesn't automatically make it a different breed. What makes a dog a different breed is more than just a single coat color gene--it involves multiple genes on multiple chromosomes that have become fixed by breeding within the emerging breed or population to keep it separate from other breeds, and you have to be able to distinguish the separate breed from other breeds by appearance, behavior, etc.