The FOXI3 Gene Mutation Causing Pattern Baldness in Dogs 1.

Part One: The Origin of the FOXI3 Mutation for Pattern Baldness. 

The locus of the baldness gene was discovered by Tosso Leeb of Basel Switzerland and was first published about in 2008.(Here is contact info)The FOXI3 gene does hair in dogs and other animals. The vast majority of dogs have hair, but once about 3- 4,000 years ago in Mexico, a mutation occurred on the FOXI3 gene which in its wild, state has only the hh gene) .

The mutation itself was dominant and named H. HH is the double dominant and it is lethal. It is thought that the HH zygotes don’t develop at all and are reabsorbed. The next possible combination is Hh. It causes the progeny with the H mutation to be single coated. The single coated dogs can have a bit of hair on the extremities up to a full single coat. The appearance of the Hh gene in a progeny also means the pups with  single coats also have less teeth at adulthood and their canines usually are strange and tusky looking.

In the Chinese Crested dog, Hh X Hh, = 3 possibilities:  HH, which is lethal, Hh which has the single coat, and affected teeth, with or without pattern baldness, and hh which has a normal double coat of hair. Hh x hh will give single coated and powder puff coat. It is well known that hh are born into every litter of Hh, statistically speaking The hh combination is all recessive and the dogs breed true to each other. All hh have a double coat and normal teeth and have “lost” the mutation.  The “hairless” Cresteds create single coats and powder puffs and the powder puffs create nothing but powder puffs. the single coats are variable in expression.

Back when the mutation was new, the few dogs expressing the  Hh, mutation found a place in some locals’ hearts. Some lines were raised for food in Mexico, but they also had sacred duties, like accompanying the soul of its owner through the underworld to reach their Final Destination. Also because they were hairless, and liked to snuggle, they became hot water bottles to the old or injured. Legends that still live today were built up around them.

Most people do not ever think about what it was like in Mexico 4,000 years ago. It seems to have been a prosperous time with many cultivated foods but still enough room to hunt. It was quite civilized, although warfare was fairly ongoing. Men had dogs. Dogs follow men. They can work cooperatively with men. Men of those days, usually had what would be called Rez Dogs today. tough, hardworking little dogs with short double coats and prick ears, though no one was bothered by dropped ears or any other variation on coat length or color that popped up. Dogs back then were about function first.

There is a also a dog gene, not limited to Mexico, that affects dog size, depending on which alleles meet in the zygote, so some alleles produce larger dogs than the parents, some produce smaller. The hunters like the standard size to larger sizes, but the tiny ones were also bred to each other, eventuating in a small landrace dogs looking very much like the big guys. By the time the Hh mutation arrived on FOXI3, there was already a range of dogs in Mexico with varying types of bone structure, coat length, tail carriage. there were no “breeds” or purebred dogs, but there were definite “types” . This is the very definition of landrace dogs. (see )
which fulfilled functions of the culture.

There was no Xolo breed for the Hh mutation to be born into, there were just the local dogs. Most of whom were small 12″ at the shoulder and had short hair. The small dog size was abidingly popular in the home and yard, as ancient artifacts suggest.  This Hh mutation could have been in a small dog, because there don’t seem to be many records of big dogs in Mexico until the conquest. However, once it happened, the Hh mutation can be transplanted into any other kind of dog. In this case, it was a short haired dog, because the “Hairy” xolo types had short hair and still do.

All you need is one hairless dog to produce more. There was a LOT of trade going on from coast to coast and far North to far south in Mexico in those days. The foot trade from what is now the US to Mexico City was well worn. The one going to South America was also heavily used. It is apparent to me, that some people wanted that hairless gene and got it in a stud dog or perhaps several. When they got home, they mingled it into their own landrace dogs. That is why the PIO and the Xolo pure breeds look a bit different from each other. I also dare say, knowing human nature, that some inbreeding of holders of the Hh was used to increase the population and the chances of getting the Hh type. However an Hh dog bred to any other dog will, by the law of averages, produce some pups with the Hh gene and some with the hh which means they have hair. The Hh gene is always dominant, so it is easy to breed for the gene.


Pearl Maven

Photo is of Ruthie, my "Hairless Chihuahua" at one year of age.


El Xolototl

Thank you for inviting me to read your article. I find it to be factually correct, but it is missing the importance of the birth of one of these hairless dogs into a home and community. I hope you will complete this in a later article.


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