Tag Archives | albinism

Cornaz albinos

Patty
Patty, an albino Pekingese from an early 20th century experimental breeding program

So the mutation responsible for white Dobermans has been identified, and is similar to the Cream and Pearl dilutions in horses. So what about Angel, the albino Shih Tzu that started this discussion? Is she also the canine equivalent of a cremello?

Probably not. An albino Lhasa Apso tested negative for the mutation found in Dobermans. What’s more, she did not have a mutation to that gene (SLC45a2). Whatever caused her pink skin and cream coat, it appears to be unrelated to the color in Dobermans. Because the Shih Tzu and Lhasa Apso shared a stud book up until 1934, it seems more likely that Angel would have the same mutation as the Lhasa. Both breeds also share a history with the Pekingese, which has one of the most throughly documented families of albino dogs. The influence of that family may explain why albinism in dogs is often seen in the smaller Asian breeds.

The albino Pekingese were the focus of an experimental breeding program conducted around the turn of the last century. Extensive information on the foundation animals appears in A Monograph on Albinism in Man, published in 1913. Although the program was disrupted by World War I, it did continue for a time and a follow-up article was published in 1929. Because the information was so detailed, it is possible to know the founder for the color in the Pekingese.

AhCum

That is Ah Cum, the “grandfather” of the Pekingese breed. He was an ordinary red sable, but because he was the common ancestor in all the known albinos in that breed, the authors of the study believed that the albino gene came from him. There can be little doubt that his son, Ch. Goodwood Lo, carried the recessive gene for the color.

Lo

What is interesting about this particular family, and this experiment, is that many of the dogs were photographed. The written notes on the dogs can be less than helpful, because those studying the dogs did not yet understand something that those of us who study animal coloration take for granted now, which is the concept of base colors and modifiers. So instead of seeing these dogs as a basic color, like sable or black-and-tan, that had been diluted down to a nearly white color by a modifying gene, the researchers assumed they were dealing with separate colors. They called the near-white dogs “Dondo Albinos” and the somewhat darker dogs “Cornaz Albinos”. That latter term is still used for this color in many breeds where albinos are known to occur.

It should be noted that the authors knew these dogs did not have pink eyes, or even necessarily blue ones. They considered an eye to be albinotic if the pigment was reduced. In fact, their discussion of equine eyes touched on a question that has often been on my mind. We often hear that horses do not have “true albinism” because there has not yet been a documented case of pink eyes. What I have often wondered was whether a pink eye is actually possible in all animals given the varying structure of the eye. Is an eye without pigment always pink or red?

In regard to the colour of the iris as seen during life in the imperfectly albinotic eyes, the present observations confirm in an interesting manner our previous knowledge that when the mesoblastic pigment is absent the iris is either white (the so-called “wall” eye) or blue or slaty blue according to its thickness and texture, a thick and fibrous iris being white and opaque throughout or translucent only at its thinnest part. In the horse even the thinnest or pupillary zone is probably too thick to be translucent.

Here the authors – two of whom are ophthalmologists – seem to suggest that in some animals an eye without pigment might not necessarily appear pink or red. Yet they also mention the difficulty in finding a horse with perfectly unpigmented eyes.

We have hitherto not succeeded in meeting with a perfect albino horse; the epiblastic pigment of the iris seems peculiarly persistent.

The Pekingese family was considered an example of ‘imperfect’ albinism, which meant that there was some trace of pigment either in the eyes, skin or hair. That is still what this kind of coloring is called in the dog world: albino. If something like this turned up in the horse world, there is little doubt that it would be considered a dilution, just as champagne and pearl were when they were identified. But as I mentioned, when this breeding program was undertaken the concept of a diluting modifier was not understood. (To give some perspective on the understanding of inheritance at the time, James Cossar Ewart’s famed Penycuik Experiments disproving telegony – the idea that previous matings left a taint that could influence later offspring – had been published only a dozen years earlier. Crick and Watson’s discovery of the double-helix structure of DNA was still forty years away.)

To a modern student familiar with how diluting modifiers work, the underlying colors on some of these Pekingese is obvious. Hints of the dark ‘spectacle’ markings common in sable Pekingese can be seen in the photo of the dog at the top of this post. The dog below looks to be a dilution of the black-and-tan pattern, judging from the coloring on the face and forelegs.

Fo

It also appears that some of the darker dogs may have been carrying some combination of the Cornaz albino dilution and the more common dog dilution, Brown. The color of the darker Cornaz albinos was described as “scraped chocolate”. One of the ancestors of the foundation stock was described as “liver and white”, and there was at least one puppy from the experiment that was noted as having a brown, not pink, nose. When later generations were crossed on black Pomeranians – which the researchers, anticipating the “designer dog” trend by a hundred years, called Pompeks – one of the first generation litters resulted in two chocolate puppies. In this way, it seems possible that the Cornaz dilution combines with Brown to produce an intermediate shade, much like Cream combines with Pearl or Champagne in horses.

Some of the puppies were surprisingly dark at birth, but still had pink – not chocolate – noses. The authors noted that the color at birth tended to be darker than the mature color, which is also true for Champagne foals. This Japanese Chin shows the kind of deeper coloring that some of the adult dogs in the study were said to have. Although it is not (yet) possible to test for the Cornaz coloring, it would be interesting to test some of the darker Cornaz albinos for Brown.

Fe

One thing that I have found surprising, since the initial post about Angel, is the number of albino-like dogs, and the range of breeds where they have occurred. It is possible that some do share the same mutation as the Dobermans, either due to outcrossing or because the mutation predates the formation of those breeds. Others likely share whatever mutation is responsible for the albino Lhasa Apso. It is also possible that there are still more mutations unrelated to the one in Dobermans and the one in the Asian breeds. With the exception of Pearl, dilutions in horses have so far proven to be dominant, or at least incompletely dominant. Because the diluted colors in dogs are more often recessive, it is far easier for them to hide for generations, especially when they are rare in the population. If these are older dilutions, then it is possible that albinos may appear unexpectedly in different breeds, just as chocolates and blues do.

So what does this all have to do with horses? That’s the topic for the next post.

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More albino dogs

WhiteDobe
Casper, a “white” Doberman owned and photographed by Kira Vance.

In the previous post, I mentioned that one form of albinism in dogs had been formally identified in just the last few months. In October of last year, a group from Michigan State University discovered the mutation responsible for white (also called albino) Dobermans. Researchers looked at the four genes known to be involved in Oculocutaneous Albinism in human beings – OCA2, TYR, TRYP1 and SLC45A2. (“Oculocutaneous” means that both the skin and the eyes are involved.) The mutation was found on SLC45A2. Those familiar with the molecular end of horse color genetics might recognize that gene, which used to be called MATP. That is the gene where Cream was found. To someone familiar with horse color, these dogs would be the equivalent to cremellos.

There are differences, of course. In horses, Cream is quite infamously an incomplete dominant. That fact is so well known that the color is often the most effective way to explain the concept of incomplete dominance to a horseman. White in Dobermans is recessive, and so is invisible in the carriers. It might be more accurate to say this is like Pearl in horses, which is another SLC45A2 mutation. Pearl is recessive, but horses of that color typically have dark eyes.

In appearance, however, homozygous Cream and “Doberman White” are a lot alike. Both have faint residual color that is more visible where the animal would have been black. If you look at Casper, the white Doberman pictured above, you can see the faint outline of the black-and-tan pattern that a fully-pigmented individual would have. Double-diluted Cream horses are likewise not truly white, as can be seen in contrast between the white mane and tail and the pale cream of the body on the stallion below. Although not clearly visible in these photos, the dogs have pale blue eyes. Homozygous cream horse are, of course, known as blue-eyed creams (BEC) in many countries. 

cremello_3_by_sooty_bunnieSm
Cremello Saddlebred stallion, Denmarks Platinum Playboy, photographed by Estelle Low.

So is the horse above an albino? Are the horses below a carrier (palomino, to the left) and an affected (cremello, to the right)?

CremandPalo

The position of many within the horse community has been that cremellos, perlinos and smoky creams are not albinos because they do not have pink or red eyes, and because they do have some pigment. It is the position of the Doberman Club of America that because the mutation was assumed to have occurred in the same gene as Oculocutaneous Albinism in human beings, the dogs were by definition albinos. In fact, while referring to a cremello horse as in albino will probably engender a certain amount of derision in the horse community, arguing that these Dobermans are anything but albinos would get the same reaction among their breeders. So which is it? As I said in the last post, I suppose it all depends on whether you define albinism strictly or loosely.

It should be understood, too, that there are reasons behind both positions. There have been horsemen campaigning for some time to change the belief that double-diluted creams were defective. Most do say that the horses are somewhat sensitive to the sun, much like fair-skinned people are, but otherwise they contend that the horses are healthy. They would certainly not agree with the Doberman Pinscher Club of America that these horses are carrying a “deleterious mutation which affects the whole body” that is considered “a genetic defect in all creatures”, which is how that organization describes albinism. The desire not to have these horses, or other pink-skinned white horses, called “albino” is about avoiding that kind of stigma. Meanwhile, the insistence that these dogs be called albinos, and not white, is very much about placing that stigma on the dogs. Most breeders of Dobermans would like to have these dogs removed from the stud books. That is the official position of the breed club, though the structure of stud books in the dog world means that only the American Kennel Club (AKC) has that power. The AKC has a long history of inaction when it comes to denying papers based on color. Because the breed club lacks the power to ban the dogs, what is left is convincing breeders not to perpetuate the color, and buyers not to purchase the puppies. Statements made about the color have to be understood in that light.

This also ties back to the discussion about founders and their colors. However one defines albinism, and whatever one believes about the health of the white Dobermans, this statement about the source for the color is misleading.

In November 1976, a mutation occurred with the whelping of a cream colored Doberman.

The white color in Dobermans is recessive. As I mentioned in the previous post on Splashed White founders, an individual with a recessive color that appears unexpectedly is the not the founder. The initial mutation could not have first occurred in Padula’s Queen Sheba, the cream-colored female referenced in this statement, because she carried two copies of the same mutation. To be the founder, both copies of her SLC45A2 gene would have to have mutated at exactly the same time, in exactly the same way.

A 4,081 base pair deletion was identified between chr4:77,062,968-77,067,051. The deletion start site lies within the last exon of SLC45A2 and results in a loss of the last 50 amino acids of the normal protein, as well as the stop codon, and causes the addition of 191 new amino acids before a new stop codon occurs.

That is the precise change that was identified as causing the color. That exact error would need to happen twice, to the same dog, for Sheba to be the founder. That exact error would need to happen twice, to two different dogs, for her parents to be the original founders. Sheba may well have been the first ever occurrence of the color in the breed, but it did not start with her, nor with her parents. If she was purebred, and an investigation conducted by the AKC when she came to light concluded that she was, then the color came from somewhere on both sides of her extended pedigree. 

WhitePedigree

That means the mutation could be found in other lines, or outside the Doberman breed completely if it predated the formation of the breed. Sheba’s breeder claimed there was another white puppy born to this same pair prior to Sheba, but it did not survive. That would be completely expected. In fact, if this breeding were repeated it would be surprising not to have any other white puppies. Sheba was homozygous for a recessive mutation, or else she would not have been white herself. If she was homozygous, both parents were carriers. Bred together, two carriers would be expected to produce an average of 25% white puppies. After Sheba came to light, it was found that seven other unrelated dogs were registered as “white”. (Sheba’s registration attracted attention because her owner attempted to register her as “albino”, which was not an option.) Dr. Jim Edwards, then an official with the AKC, wrote to the following statement:

This investigation has uncovered an additional seven (7) Dobermans registered as “white” and not included in Shebah’s pedigree. These occur sporadically, with ages varying from two years to fifteen years. Only two of these have produced litters, and only three litters have been registered. We are continuing our investigation into these cases and will provide appropriate updates to the DPCA when our analysis is complete. I am encouraged that this number is small, remembering that color assignment is sometimes difficult for the novice breeder.

For someone interested in founders, those dogs would be of particular interest. The breed club believes that each case was one of a misidentified fawn; that is, a dog that has both the blue and the brown dilution. Fawns are an accepted, if not an especially popular, color in the Doberman breed. I am not sure of the basis for this determination, so I cannot comment on the ultimate color of those dogs. I can say that entries like that are where I look when I am searching for clues about color founders, and about the spread of color mutations in general. I would also add that when trying to track something down, confusion about color assignment works both ways; if registered whites may be in fact fawns, then registered fawns may in fact be white. I have often regretted that fact, because it would be a lot less work tracking down colors if this was not the case! But my interest in color research is purely academic, and motivated out of curiosity. Even if they were fawn – and it is quite possible they were – it would not change the fact that there were likely carriers outside of the one known line, at least at some point. Whether they still exist is an open question. Because this issue, in this breed, has been emotionally charged for some time, chances are that strict culling has been practiced in any cases of white puppies. This far down that path, it is unlikely that if the mutation was in other lines, it is anything but rare now. But the truth is that strong stigmas, while they do promote culling, also promote secrecy. When the stakes become so high, and the reaction to an unexpected white puppy less rational, even the most ethical breeder is forced to weigh the costs of total honesty. When doing my own research, I have learned to include this kind of situation in how I weigh the reliability of information.

With the discovery of the actual mutation, it should be possible to develop a test to identify the white mutation in Dobermans. Hopefully the breed club will support its development and encourage its use by all breeders. If the color is not wanted, then testing and avoiding crosses between carriers is the real answer to the problem. Widespread testing could also provide answers about where the color began, along with the facts about where it can still be found.

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Albino Shih Tzu

AngelFace1

This is Angel, the Shih Tzu with the mystery color mentioned in my previous post. When my friend Gretchen contacted me, she wondered if Angel might be a pale lilac dilute. That is a dog that has both the blue dilution (dd) and brown (bb). The palest shades of lilac are usually the lightest color, aside from white, that most dog owners are likely to see. Angel’s skin is not a muted brown, though, but a clear pink – quite a bit lighter than would be expected in a lilac dog.

Although lilac dogs have the palest overall tone, when it comes to skin coloring the lightest colors can often be found in recessive red dogs that are also homozygous for brown (ee and bb). In Labradors, this combination is sometimes called Dudley. As this comparison image shows, Angel’s nose color (left) is considerably lighter than the one on the Dudley Labrador (right).

Angel2

The pink skin was consistent on the pads of her paws as well. This extreme absence of skin pigmentation is particularly striking to anyone accustomed to looking at dogs. As I mentioned in the previous post, dogs do not have pink skin under their white markings in the same what that a horse will. Unlike horses, white markings that cover the nose do not give a dog a pink nose. Dogs seem very inclined to retain at least some pigment in their skin, which is what makes a truly pink-skinned dog stand out.

AngelPaw
Pink Angel toes!

Historically, dogs like Angel have been called albinos. That is true even though most have blue, green or even hazel eyes. They also have traces of color in their fur, making it possible to discern hints of things like black-and-tan patterns, black masks or white markings. To someone immersed in the world of horse color, that would sound like a mistake. It is an article of faith in the horse color community that albinos must be white with pink or red eyes. Yet albino is the term used not only by owners and breeders, but in scientific literature. Researchers have told me that albino is a term that can be used strictly or more loosely. That is one reason why it is so very difficult to get a definitive answer to the question, “Can a true albino have blue eyes instead of pink?” It really does depend on who you ask!

Angel3
Angel has hazel-colored eyes, but would still be called an albino dog

I had first become aware of dogs like Angel when I stumbled across a paper on albino Pekingese when doing research on the Hanoverian Creams. I was also aware of a handful of of other more modern cases, mostly among the smaller Asian breeds. What I did not realize until I began looking was that while still quite rare, this type of coloring is more widely distributed among the different breeds (and even among what are probably pariah dogs) than I had originally assumed.

The timing of this could not have been better, too, because at least one type of albinism (or extreme dilution, if you prefer) in dogs was identified in just the last few months. The particulars of that mutation will be especially interesting to horse color researchers, but it merits a separate post. In the meantime, I have set up a new Pinterest board with a wide range of images of albino dogs. I tried to pick ones that showed the range of color in the eyes and the fur. As with the other Pinterest boards, I have tried to be sure to link the pins back to their original site to preserve the photographic credits. In the case of some of these pins, following those links will take you to further information and more photos.

And just a final note. Angel is in the care of the Crossroads Shih Tzu Rescue in Tallahassee, Florida, and is looking for her forever home. You can find more information on her Petfinder page.

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