Yorkshire Terrier coat color thread.
 

Hi, I posted this earlier in the Parti vs. Biewer thread, but this article seems to be of enough general interest that it merits its own thread. It describes the nature of Biewer, Parti, and Chocolate coat colors in Yorkshire Terriers:

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 [11], 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 ("sp") 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!

Who knew we would be getting such and advanced course in genetics on a dog forum! I think it is very interesting and I am learning a lot and remembering stuff from college 20+ years ago...teehee...I think I'm paying better attention this time...:rolleyes:

Wow that is a hot mess. We used to have alot of parti breeders on here i wonder what they would say about that

How is it that the Akc missed this when they said partis, goldens and chocolates are yorkies purebred

They may have made that determination before the DNA evidence came out. I can understand the AKC waiting until the MARS test has become more accurate before using it in their determinations of breed purity, but analysis of individual genes is much more precise. People interested in the purity of the Yorkshire Terrier breed (and who have clout) might want to bring these more recent findings before the AKC to see if they will change their mind. As more and more of these kinds of studies are done, it will be harder for them to ignore.

Interesting! While your researching, throw in the dd gene! Save me some work! ;)

That is the dilute (Blue Born) gene! We had another thread with the genetic discussion--I'll try to find the links again and add them here. The other discussion started out about the health of Blue Borns. The conclusion was that not all Blue Borns will have health problems, but it greatly increases the likelihood of debilitating skin problems and hair loss. There is a genetic test to determine which dogs are carriers, so they can be spayed or neutered and kept out of breeding programs. Now let me find the links...

dilute (Blue Born) coat color information
 

Here is a summary of what I found on dilute (Blue Born) color:

DNA testing labs that test for the "D" locus and can determine which dogs are carriers of the "d" (recessive Blue Born) allele:

VetNostic Laboratories - Veterinary Genetic Testing - Yorkshire Terrier testing

D Locus

Recent research article on the association of the dilute (Blue Born) trait with Color Dilution Alopecia (hair loss and skin problems):

I was able to find an excellent review article from 2007 that discusses known coat color genes in dogs. Here is the citation:

"Genes affecting coat colour and pattern in domestic dogs: a review," by S. M. Schmutz and T. G. Berryere. 2007. Animal Genetics 38:539-549.

At that time, they had determined that Color Dilution Alopecia was due to a mutation associated with the MPLH (melanophilin) gene. Interestingly, not all dogs that had a mutation in that gene had alopecia (baldness) and other skin problems, so it might be a particular kind of mutation in that gene, or a mutation in a nearby gene on the same chromosome that is responsible for the skin and hair problems. In other words, the good news is that not all Blue Yorkies will necessarily become bald. On the other hand, at the time time this article had been written, they didn't have everything figured out. Here are some brief quotes from that article, then I have to get back to work. I'll try to find some more recent articles later.:

The melanophilin gene

"Many dog breeds have individuals that are grey or dilute in coat colour (Fig. 1i,j). However, blue is used to denote other phenotypes in various breeds. In some breeds, these blue individuals are born grey, whereas in other breeds individuals take several months to turn from black to grey. The latter characteristic was referred to as ‘progressive greying’ by Little (1957) and attributed to the G locus. In some dog breeds this is called ‘silver’. A few dog breeds have both types of grey occurring. Some Great Danes and all Weimaraners are born blue or dilute whereas Kerry Blue Terriers (Fig. 1k) and Old English Sheepdogs are born black and lighten as they grow into adulthood. Both of these inherited traits cause modification of both eumelanin and phaeomelanin pigmented areas to a paler shade, although the phaeomelanin change is not as dramatic as the eumelanin dilution. Fawn dogs with a melanistic mask (Schmutz et al. 2003a) are easier to observe because their mask is grey instead of black. Dilute fawn dogs have charcoal instead of black nose leather and pads (Fig. 1j). Dogs with an e/e genotype at MC1R (Newton et al. 2000) or clear red phenotype, such as the two Beagles in our previous study (Philipp et al. 2005) were very difficult to detect as dilute. Dogs that are brindle and dilute, such as some Whippets and Greyhounds, have grey stripes on a pale fawn background. Dogs, such as Weimaraners, that have two copies of the mutations in TYRP1 causing brown (Schmutz et al. 2002) and two dilute alleles are a pale brown. The nose leather and pads of such dogs are a similar pale brown. In some breeds such as Chinese Shar-Pei, the dogs are called lilac and in Doberman Pinschers, they are called Isabella."

"Recently, we reported that Doberman Pinschers, German Pinschers, Large Munsterlanders, and Beagles with a dilute phenotype, co-segregated with specific haplotypes of melanophilin (MLPH) (Philipp et al. 2005). A mutation in exon 2 of MLPH causes a splice junction problem in homozygous mice of the leaden phenotype (Matesic et al. 2001). The last seven amino acids of exon 2 are spliced out in leaden mice because a C-to-T transition introduces a premature stop codon. A human infant was reported to have Griscelli Syndrome Type III due to a R35W mutation near the end of exon 2 (Ménaschéet al. 2003). The hair colour of this child was not reported but this syndrome is considered a form of albinism."

"We have now extended our study of MLPH to include approximately 20 dog breeds. Although a mutation that co-segregates with blue in some breeds has been found (unpubl. data), no single mutation has been found that explains the blue in all these breeds. A couple of common mutations occur only in blue dogs (unpubl. data). Our study to identify all the alleles causing blue is ongoing."
-------------------
Diseases associated with pigmentation

"Some (n = 30) of the 119 grey/blue dogs we studied (unpubl. data) showed evidence of hair loss and much more rarely skin problems, symptoms typical of colour dilution alopecia (CDA) and black hair follicular dysplasia (Schmutz et al. 1998; von Bomhard et al. 2006). This was not true of all adult blue dogs however. The symptoms also appeared to vary by breed with the Large Munsterlanders displaying complete hair loss in all grey areas by 12 weeks whereas most dogs of other breeds were a few years old before this degree of hair loss occurred. Several dogs 5 years of age or older were reported to have no hair loss or skin problems. Several of the dogs were pups or <2 years of age or had large areas of white fur and therefore we could not determine whether these dogs had or would develop CDA. Dogs that were blue or blue fawn, male or female, long or short-haired and with or without white spots were affected. There may be a slight tendency for earlier symptoms in dogs with longer hair. CDA was reported in 26 of the 100 dilute dogs with a T/T genotype and four of the 19 dogs that showed a dilute phenotype but did not have a T/T genotype at the synonymous c.106C>T polymorphism in exon 2 of the MLPH gene (unpubl. data)."

"Not all ‘blue’ or genotypically d/d dogs (Fig. 1i,j), have problems associated with CDA and not all dogs that have symptoms develop them at a similar age of onset or with similar severity. For example although all Weimaraners are dilute and all of the eight dogs of this breed we studied had a T/T genotype, not all had CDA. Laffort-Dassot et al. (2002) likewise described variable symptoms in five Weimaraners. Miller (1990) suggested that there were possibly multiple recessive alleles of the dilution gene. Although this may be true, it does not appear that dogs with and without CDA necessarily have different mutations in MLPH. Since MLPH binds to RAB27A in the region (Strom et al. 2002) where we have identified some mutations in MLPH, we wanted to determine if a mutation in RAB27A might interact and cause some dogs to experience symptoms of CDA whereas others did not. We sequenced the entire coding region of RAB27A (GenBank DQ494380) in a Large Munsterlander that had severe symptoms of black hair follicular dysplasia, an Italian Greyhound with CDA symptoms, and a black-and-white Large Munsterlander and a chocolate Labrador Retriever which were not dilute and had no symptoms. No polymorphisms in the RAB27A sequence were detected."

Thanks! I've read a ton and never stumbled upon that article! Definitely true, not all blues develope CDA. (Well at least so far with my boy, Mack) I do believe however blues have a much lower immune system... I wish there was research on that! I'm always curious to read all research.... If you come across anymore, let me know!

Coat color of the day, black and tan, or saddle tan.
 

The color pattern seen in breed standard Yorkshire Terriers of the steel blue body with tan head and extremities is due to a certain mutation at the ASIP (agouti signalling protein) locus, classically called the "A" gene. Yorkshire Terriers carry the variation of the "A" gene called "at." Interestingly, there are four major variations of the "A" gene:

ay = "fawn" or solid golden-brown
aw = "wolf sable" or hairs that are banded black and brown
at = black and tan, with black body and tan extremities
a = recessive black

Interestingly, the order of dominance is ay > aw > at > a, which means that fawn is dominant to all the other color patterns, wolf sable is dominant to black and tan and recessive black, and black and tan is dominant only to recessive black.

There is a variation of black and tan called "saddle tan", which is due to an interaction of the "at" mutation with mutations at other modifier genes. In saddle tan dogs, the tan coloration comes up farther onto the body than in the black and tan pattern. I'm providing three links to research papers describing these interactions that are publicly available in their entirety below. Although neither of these studies specifically examined the DNA of the Yorkshire Terrier as far as I have read (a quick once-through), they postulate that Yorkshire Terriers are actually a form of saddle tan in coloration, with the tan not coming up quite as far on the body as in other saddle tan breeds. Here are the research articles:

A SINE Insertion Causes the Black-and-Tan and Saddle Tan Phenotypes in Domestic Dogs

eCommons - Gene interactions with Agouti Signaling Protein produce complex pigmentation phenotypes in the domestic dog

http://www.eebweb.arizona.edu/Facult..._etal_2013.pdf

After doing a little more reading up on the "e" mutation, I have found that it is more likely to be responsible for a golden yellow color rather than Parti colored white spotting. Perhaps Partis are piebald at the MITF gene as well. Either way, it still likely was bred into the Yorkshire Terrier from some other breed. Clearly, more coat color DNA testing of all nonstandard Yorkshire Terrier colors needs to be done.

Thanks for the update. I find all of this interesting! Glad your here to find the information and explain it to all of us! Looking forward to reading more about this! :)

One last coat color gene in Yorkshire Terrier: progressive greying
 

While I'm at it, there is another characteristic of Yorkshire Terrier coat color, and that is progressive greying (as opposed to dark black). Progressive greying is due to a dominant allele at the "G" locus. This gene explains why Yorkshire Terrier puppy coats start out black and progressively turn grey (steel blue or silver blue) over time. This gene has not been cloned yet (as far as I know!), so the underlying biochemical basis for it is not known, nor is there a DNA test for it. Here is a review article that describes a wide variety of dog coat color genes:

http://www.fleetfiretimbers.com/fft/...Review2007.pdf

More essential reading--a chapter from a recent book on the Genetics of the Dog: Molecular Genetics of Coat Colour, Texture and Length in the Dog:

http://research.hudsonalpha.org/Bars...hapter2012.pdf

well whatever causes it, I think its beautiful :p

:thumbup::thumbup::thumbup:

Hi everyone.
I was wondering whether you have information concerning the "silver gene" located at V locus.
Can this gene also be found in Yorkies?

If not, whats the genetic cause of the difference between dark steel blue and light steel blue for example.
Can this be caused by the incomplete dominance of the Graying gene?
Meaning that :
GG dog is a light steel blue
Gg dog is a dark steel blue and
gg dog is black

Thanks :)
Mike

Hi Mike,

I wrote to a canine coat color genetics researcher last summer, and she was interested in taking a closer look at the G (dominant greying) locus. She thought it could be a genetic variation of the same gene that causes Merle patterning. It's obviously not the same mutation as Merle, because the color patterning is different and Merle is homozygous lethal, but it could still be a variation in the same gene. I sent her a cheek swab DNA sample from my dear Bella, and she was going to have a student sequence Bella's Merle gene to see if they could find anything, but she never got back to me--I'll follow up with her tomorrow.

So the dominant greying gene in Yorkies is still somewhat of a mystery, but your hypothesis makes sense. My understanding is that GG is silvery blue, Gg is darker blue, and gg is black.

From reading up on the "V" locus you mentioned, it sounds exactly the same as the G locus. I'm pretty sure it's another name for the same gene. Here is a link to an article about the "V" locus:

http://www.havanesecolors.com/ggv.html

Thank you Phil for your reply!

This site for havanese and some other sites for poodles, were the reason I asked about the V gene (silvering gene).

Havanese and poodles also carry the Graying gene but its effects is somehow different than in yorkies, considering that both breeds have double coats instead of the singe coat found in our breed. Also they carry different alleles in other locii, so the final result is completely different.

In this quiz answer Quiz # 2 answer it says :

In a poodle site Color Genes in the Poodle I came across this :

It seems that havanese and poodles carry both genes (G and V) and their combination alters the final phenotypic result.

To add a little more confusion, Joan Gordon claims :

Color & Texture by Joan Gordon

Many stunning yorkies have maintained their TRUE (not enhanced) deep dark blue color to the age of 5 and sometimes later. On the contrary there are specimens that cant hold color up to 2 years of age. The blue dillutes and dilutes to a silver color and finally we come up with an almost white dog. Most of these dogs have routs of a darker color, but as the hair grows the dilution factor is so strong that can't hold correct color. Additionally these dogs have super silk quality, and amazing texture.
Somehow dilution factor of the Graying gene or the V gene or maybe both of them are connected to texture.
Moreover it seems to be a connection between gold and blue - in other words phaeomelanin and eumelanin.

To quote again Joan Gordon from http://dandugmore.netfirms.com/color.html:

My -short- experience with the breed, confirms Joan Gordon.
Light gold = light blue and rich gold = dark blue.

BUT on the other hand there is another cause of silver color, and that is lack of pigmentation in general. This can easily be seen if we check the skin under the blue, which should be pink instead of blue, or a very very light blue, meaning that there is not enough eumelanin.

It is also very interesting that both colors are connected through the patterns of each other - controlled by A locus. The allele responsible for their tan pattern is [As] (saddle tan) according to Malcolm Willis. Tan on the forelegs extends up to the elbow and on the hindlegs it extends from the foot to just below the stifle. As you have mentioned in a previous post, the tan is not coming up quite as far on the body as in other saddle tan breeds.

Under the blue coat, the skin has a bluish tint and under the tan coat the skin is pinkish in color. If the pink skin invades the blue skin or vise versa, we will get an unclear gold and an incorrect blue.

So how can we explain all these genetically? :confused:

As for the hypothesis concerning the incomplete dominance of Graying Gene, it can be probably explained through Red Legged yorkies.
I hypothesize that a Red Legged is a [gg] dog. When bred together they of course reproduce themselves (recessive homozygous) , but when bred with a [GG] dog they can produce a [Gg] dog.

Thanks again
Mike :)

It sounds like the jury is still out on whether the V (Silver) and G (Greying) loci are the same. From the definition on the poodle website (Color Genes in the Poodle), it seems that Yorkies, or at least my Bella, has what the poodle people would consider a Siver gene rather than a Grey gene. I base this conclusion on the fact that as Bella turned silver, the tips of the hairs were black, and silver grew in from the base. (The poodle site implies that Silver is gradual, whereas Grey is all or nothing: "The graying gene leads to a gradual accumulation of white hairs in both the inner and outer coat.... In silver dogs, as in blues, the transition from black to white for each hair is gradual, but occurs at an earlier age.") It looks like Joan Gordon agrees with this analysis, and also relates color to hair texture. Now whether or not this is a real distinction, I have to take their word for it. There is very little information about progressive greying and silvering in the canine coat color scholarly literature. Everything seems anecdotal at this point.

I agree with you about redleg Yorkies being gg--that's something I was thinking about before you brought it up. :)

I'll keep you posted if I hear anything back about Bella's DNA analysis, or if I spot a new research article.

Thanks :) I appreciate your time!

Achieving dark steel blue through graying gene only, is a bit confusing based on the information we have until now.
Its like racing against time before hair completely dilutes. There must be some kind of maintenance at a specific hue - preferable dark hue. The key word is "maintenance", otherwise color will keep diluting until silver or worse white is achieved. And unfortunately that's the case in too many yorkies - excellent species in soundness and conformation.

But that is not what's happening to yorkies that hold their color much longer. Interestingly the signs that a dog will keep color are apparent on phaeomelanin - like thumbprints for example.

So maybe we are dealing with 2 different genes, or a mutation of some kind - like you 've mentioned.

Looking forward for news concerning Bella's DNA and new researches. Its always a pleasure to read new findings!

Mike :)

This is a fascinating thread! Man, I have missed this forum!

I found a suprisingly informative article in Wikipedia about the genetic basis of coat color & pattern with a fairly simple explanation of each locus. They didn't have the V-locus, though, which is how I came across the article to begin with; searching for information on V-locus.
http://en.wikipedia.org/wiki/Coat_(dog)

Joan Gordon
 

What great questions and information!

Joan Gordon is a good source of information. Her last known address was
1651 West Ridgewood, Glennview, IL 60025. I know that she loves to share her knowledge and experience with Yorkies lovers. I don't have a phone number or email for her. At her age she may not email. Feel free to write her.

I just looked and there is a letter from Joan Gordon posted on a website:
Joan Gordon - Quality Traditional and Parti Yorkshire Terriers
It was difficult to read the address but it appears to be the same as listed above.

Recently I read Ann Seranne's book "The Joy of breeding your own show dog" where she writes about the "recessive “blue” silky coat".

Are we dealing with recessive here?
Because if we did, it would be easier for breeders to lock this trait in their lines.

Instead, breeding together 2 dark blue silky coats, the resulting pups are not always dark blue!
And this is easily explainable if we consider only the Graying Gene effect.
According to our knowledge for Graying Gene "anecdotal" principles, a dark steel blue dog must be Gg in G locus.
This simply means that the elusive DARK STEEL BLUE is a result of heterozygosity. :eek:

So breeding together with another Gg dog, the resulting pups will have 50% chances to be Gg, 25% to be GG (silvery color) and 25% to be gg (black).

To add (again :D) more confusion

Quoted from Yorky Club Magazine - United by passion for Yorkies.

**
Let assume that a black bitch is gg, and a silver dog is GG.
Bred together, ALL the resultant puppies will be Gg...

Hmmm :confused:

Part of the problem could be with terms. What one person might consider "blue" might not be what someone else considers "blue." And there is a recessive "blue" allele at the D locus that results in the "blue born." I agree with the conclusion of the person you quoted, "There [are] not enough puppies to draw the correct conclusion." What is really needed to figure this all out is a database of standardized photos (taken under the same lighting conditions, dogs of the same age, etc.) of dogs and their parents, taken at various stages in their development. An experienced canine coat color geneticist needs to look over all of these data and perform a meta-study. Unless the same pair is bred over and over again, litters are too small to draw any more than anecdotal information, and that seems to be all we've got. The G locus is barely in the scientific literature at all, and the V (Silver) locus, which may or may not be the same as the G locus, has even less information in the literature.

I have no idea what all that means. LOL Charlie is silver. I have a friend who calls him silver instead of Charlie. The other day someone told me he looked purple. LOL Is he a yorkie? haha

If it's any consolation, Bella is silver too. "Blue" is just a name for a desirable shade of greyish/black. Here's a link to a picture:

http://www.22dog.com/images2/Yorkshire-Terrier.jpg

Is this silver?

This looks more like the highly desirable classic "blue" to me. The lighter highlights in that photo are more of what I consider silver. I suspect that the dog in your photo is heterozygous Gg. My Bella is lighter than that, and I suspect that she is GG.