Posted by Wesley R. Elsberry on May 25, 2004 07:44 AM
A new genetic analysis of man’s best friend could help scientists explain why a border collie has knack for herding or why poodles sport a curly coat. In the May 21 issue of Science, researchers at Fred Hutchinson Cancer Research Center report the first extensive genetic comparison of domestic dog breeds.
The study, led by Fred Hutchinson researchers Drs. Elaine Ostrander, Leonid Krugylak and graduate student Heidi Parker, revealed distinct DNA blueprints for each of the 85 varieties of purebreds that were analyzed as well as similarities between certain breeds. The researchers expect that understanding these genetic relationships will help them uncover the genes responsible for the physical features and behaviors unique to each breed as well as the diseases to which they are commonly susceptible, such as cancer, deafness, blindness, heart disease and hip dysplasia.
The findings also have generated excitement among those who study diseases of the human animal. Because at least half of the more than 300 inherited canine disorders-including a number of cancers-resemble specific diseases of man, many scientists believe that the dog genome holds a wealth of information that will benefit human health.
There are a number of things claimed for this study, most of which confirm things that we already knew or suspected.
The nearest relatives of dogs are wolves.
Dog breeds are genetically distinct.
Dog breeds cluster into four large groups. One is more closely related to wolves, and includes the Alaskan Malamute and Siberian Husky. Another includes mastiff-like breeds. The third includes herding dogs. The fourth comprises hunting dogs.
The analysis is being used to find genetic bases for various canine diseases.
The clustering noted above is shaking up some notions of the history of certain breeds:
Noticeably absent from this ancient cluster were several breeds long
regarded as the most ancient by breeders, including the Pharaoh Hound and the
Ibizan Hound — depicted on Egyptian tomb walls. The researchers said their
analysis indicated that the modern representatives of these breeds were
recreated in more recent times from combinations of other breeds. The
researchers also found genetic evidence for a recent origin of the Norwegian
Elkhound, believed to be of ancient Scandinavian origin.
I think that it is important to note that this study is based on microsatellite analysis, not whole-genome data. The claim of the headline and press release that this study “may benefit human health” appears to be a long way from turning possibility into performance. It seems certain that the canine study will be useful in helping track down genetic diseases in dogs, but to have that carry over to humans we would have to know that many of the same microsatellite markers exist in both species, and that has not yet been established as far as I can tell. (As an organismal biologist skimming bioinformatics, though, I could easily be wrong on this. I would be grateful to anyone who can point to work where this has been accomplished.) Some microsatellite studies show useful cross-species comparisons are possible, and other studies show that they don’t work so well, depending upon the particular species under consideration. By contrast, comparative genomics has already identified the genetic basis of a human disease, Bardet-Biedl Syndrome (BBS).