Whenever I see Elaine Ostrander talk about dogs, I feel sorry for human geneticists. Ostrander, a researcher at the U.S. National Human Genome Research Institute on Bethesda, Maryland, studies the hundreds of dog breeds that exist in the world. And because human breeders have simplified dog genetics enormously, it’s a lot easier to answer questions about the genetic basis of all kinds of traits in dogs than it is in humans.
For instance, a few years ago, Ostrander’s group found that a single gene explains most of the variation in size that exists across dog breeds, from the massive Great Dane to the diminutive Chihuahua pictured below. And today, it almost seemed like Ostrander was showing off, as she revealed new results that shed light on the very same question I heard discussed here last night: how important are genetic parasites, called transposons, in diversity and disease?
Ostrander and her colleagues asked whether one genetic mutation underlies the short-legged, squat dog body type seen in breeds such as the basset hound and the corgi. (The technical term for this short and waddly body type is “chondrodysplasic.”) Her group studied 45,000 genetic markers in 95 dogs from 8 different “short” breeds and compared the same markers to 702 dogs from 64 larger breeds. Sure enough, they found that a single genetic variant appears to account for the squat body type across the eight “short” breeds.
Oddly, this variant consists of an extra copy of a growth gene that has been inserted into dog DNA by – you guessed it – a retrotransposon – one of those pesky genetic parasites that Jef Boeke was talking about last night. Ostrander said this is the first ever example of a retrotransposon causing variation within a single species of mammal. She said that the example shows the power of dog genetics to reveal how new forms of genetic diversity could indeed be important in humans.
Photo of a Great Dane and a Chihuahua by Deanne Fitzmaurice courtesy of Science magazine