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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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All kinds of updates

CreamHorse

I apologize for neglecting this blog this past month. My time has been almost completely absorbed in the final production work for the book. The good news is that the book is just a few weeks away from publication, though I am almost afraid to jinx it by saying so! What time hasn’t been spent on the book has gone towards a handful of print articles. This has all meant that the blog has languished simply because I couldn’t face writing anything more.

Which is a shame because I sure haven’t lacked for things to share. While I have been quiet, all manner of interesting things have been piling up on my desk and in my inbox. One of them is the picture at the top of this blog. I truly wanted to include it in the book, but I never heard back from the Tyne & Wear Archives and Museums regarding commercial usage of the image. They do allow non-commercial use, though, so I thought I would share it here on the blog. The reason I wanted it for the book is that I have a chapter on the now-extinct Hanoverian Creams. Those were the ceremonial carriage horses that were once used by British royalty, but are now extinct. They have long held a certain fascination for horse color researchers because their exact color is not known. The other mystery is what ever became of them. It is known that some of their Continental relatives ended up in the Wulff Circus, and that a handful of the British horses ended up with Garrard Tyrwhitt-Drake. This image caught my eye because the horse has the same diluted coat with the very dark mane and tail that is seen in some of the later images of the Creams. But even more interesting, the photo is part of a group associated with Lord John Sanger’s circus. There is a connection between Sanger and Tyrwhitt-Drake, so it is quite plausible that this horse was one of the Creams, or was related to them. The photos are not dated, but the range from the other photos in the set are correct for the horses that were dispersed to have still be alive. If anyone recognizes the image and can place it or date it, I’d love to hear from them!

There have also been a couple of interesting horses that have come to light in just the last few weeks. The first is another white-born Standardbred recently foaled in New Jersey. Pictures of him can be seen here. Since both is sire Art Major and dam Coochie Mama are unmarked horses, he is quite likely a new dominant white mutation. Another suspected dominant white Standardbred, Macahan Loss, was born in 2008.

The other cool new horse is a confirmed silver dilute Pura Raza Espanola (PRE). That is the mare Trajana YR. She is actually chestnut, so the color is not visible on her, but she carries the gene. If she is bred to a bay or black horse she could produce a black or red silver (bay silver). Some readers might remember a few years ago there was a PRE stallion that was rumored to have been tested as a silver, but many questions were raised about his purity and his testing status. His owner stopped replying to questions (not that I can say I blame them, given the truly unpleasant tone that many took), and it became a dead end. Hopefully this mare puts an end to the debate over whether the gene is there or not.

Speaking of the silver dilution, I was able to get some really wonderful contrast shots a few weeks ago. The opportunity to have two visually similar, but genetically different, colors side-by-side only come up on rare occasions, so I was tickled to have gotten these shots. I haven’t had time to crop and size the photos, but eventually I will have those up on the blog. And I still have to post the “English translation” for the splash research, and some much-needed updates to the Splash Project page. And there are other cool things that just need to be sorted and composed. So like I said, there is a lot to share – just not enough hours in my days at the moment!

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