402 – Insight on the Genetics of Hairlessness in Dogs

Insight on the Genetics of Hairlessness in DogsAdam Boyko, Chief science officer and co-founder of Embark, joins host Laura Reeves to talk about the Fox I3 gene, that causes hairlessness in many dog breeds.“So it's a gene that's gonna be involved in what we would call ecto dermal differentiation,” Boyko said. “So it's going to affect a lot of tissues that are in the ectoderm. Not just hair follicle formation but also things like the inner ear or the sweat glands or dentition. All of these things that are related because they're coming from the same developmental tissue.”“The canine genome was first sequenced in 2005, so we have a reference genome now from Tasha the boxer and this was a big $25,000,000 project,” Boyko noted.“(Some of) my colleagues worked on it. This was before I got into dog genetics. I was graduating from Purdue with a degree in biology but I was studying butterflies at the time. So I didn't join the dog field until after we had a genome. I switched because there's so much more cool stuff you can do with an organism that has a genome and particularly with dogs.“In 2008 (researchers) were able to identify the gene that's different between dogs that are hairless and dogs that aren't. This Fox I3 gene. The mutation itself is just this insertion of seven base pairs. Remember, the genome is like 2 1/2 billion base pairs. So that little mutation then is the difference between whether the dog has hair or doesn't.“One of the projects I started out with … we call the village dog project. Most of the dogs in the world aren't purebred dogs and they're not even mixed breed dogs the way you and I think of mixed breed dogs. They're actually natural populations of dogs that have been around for thousands of years and probably have some really interesting biology. If you look at village dogs across the new world, you do occasionally come across dogs that carry this mutation and have the hairless phenotype. If you look at dogs that have a very, very similar sequence, so that the same genetic background but don't have the mutation, these are the closest relatives for where the mutation occurred for dogs that don't have the mutation. It's actually like Alaskan Huskies and other northern dogs that are very puffy, puffy dogs, but they have DNA still in them that pre-Columbian Native American dogs had.“Genetically you get the signature that this is a mutation that arose in the new world before European contact and this is the basis for Mexican hairlessness right so the Xolo, the Peruvian Inca Orchids, as well as the Chinese Crested.Two copies is deadly“This mutation is actually lethal. A dog with two copies of the mutation dies in utero. So, every hairless dog has one copy of the broken Fox I3 gene and one good copy of the Fox I3 gene.“The “powder puff” have better dentition. This Fox I3 mutation not only effects the development of hair follicles and interrupts them throughout most of the body, but the dentition is also affected. The teeth, both the deciduous teeth and the permanent teeth, generally you don't see as many developed, they're not as well formed, they tend to be more conical, they're a little more tusk like, they point out a bit more. These are all kind of developmental defects. The powder puff doesn't have these defects, not because it has a better Fox I3 gene that you want to breed in, it just doesn't have the broken one.”Evolutionary purpose of hairless dogs“I think ultimately the purpose is that people really like unique and distinctive dogs,” Boyko said....