Friday, March 18, 2011

Selecting Dogs for Defect... and Disease

Science, the lead publication for the American Association for the Advancement of Science (AAAS) reports that:
A mutation responsible for the characteristically wrinkly skin of Shar-Peis may also make them sick.... In a study in which they compared the DNA of 24 Shar-Peis having Familial Shar-Pei Fever (FSF),  with 17 ones that don’t (not all of the breed suffers the fevers), an international team of researchers recently identified a region on chromosome 13 associated with increased susceptibility to the disease. In parallel, the same team, led by Kerstin Lindblad-Toh of Uppsala University in Sweden and the Broad Institute in Cambridge, Massachusetts, screened the Shar-Pei genome for signs of what gives the breed its characteristic wrinkles. A comparison of 50 Shar-Peis with a control group of canines from 24 other breeds pointed toward a location, near a gene that codes for an HA-producing enzyme called HAS2, that overlapped with the FSF susceptibility region. Looking more closely at this area, the team then identified a mutation—duplications of a DNA segment—that was present in highly wrinkled Shar-Peis but not in control breeds.

The researchers next looked at whether this same mutation was associated with FSF susceptibility, comparing 28 affected and 16 healthy Shar-Peis. A large number of the duplications appears to predispose animals to FSF, the team reports today in PLoS Genetics. Lindblad-Toh says she suspected that the genetic causes for the thickened skin and for the fever syndrome would be near each other but not that they “would be the same mutation.” Further studies on Shar-Pei skin cells by Lindblad-Toh’s team showed that the more times the duplicated DNA segment is repeated, the more HAS2 is produced.

Bottom Line:  The Sharpei is a breed of dog that is defective and diseased by design.   

This breed is a walking case statement for why Mother Nature and Father Time reject excessively wrinkled skin in natural canids. And, of course, Mother Nature and Father Time also reject and select against flat faces (brachycephalism) and dwarfism (achondroplasia), to name two other common defects found in the world of dogs.

So how do dog dealers (they like to call themselves "breeders") maintain these defects? 

Why through inbreeding, of course.  If you cross a defective mutant with another dog with the same defective mutation, you are likely to get more defective mutants.  And, of course, over time you are also more likely to get more diseased dogs; a predictable outcome of doubling down on genes associated with cancer, joint problems, autoimmune disorders, thyroid issues, and eye problems, to name just a few.


Viatecio said...

I love how some of the wrinkly-dog breeders like to trot out the "Oh, then why don't we just ban elephants and rhinos since they have wrinkly skin too?" argument.

The straw man is showing through their moral we used to say in grade school, "XYZ"!

Except, of course, that no zipper can cover it up.

Seahorse said...

I was at the vet today, dropping of my boy for his neuter, and sitting there were two aging Golden Retrievers. Really sweet, beautiful dogs, but both there to have HUGE tumors taken off. One looked like he had a good sized turtle on his back, and the other had a heavy, dangling tumor coming off his hind leg. I thought of everything I've read here through the years, and wondered at the "coincidence" of these two dogs of the same breed in one small country hospital on the same day.


belethien said...

I want to point out that M. Olsson is the brilliant woman who did a huge amount of work on this project. I can't think of a better person to have made this discovery, she deserves all the praise she can get! I'm really lucky to know her and I hope one day I'll to be as awsome as her in the field of doggy genetics. :D
The best part is that this is really a revolutionary discovery for the dog world; finally a solid fact that conformation selection can destroy a breed.

All eyes are on the shar pei club of Sweden, who helped a lot with funding & donating blood to the research. We'll see if they start selecting for the less wrinkled type, very exciting no doubt!

/Dijana, Uppsala