ohmidog!

The same gene that causes some breeds of dogs to have short, stubby legs might also cause dwarfism in people, a new study says.

Scientists think this gene — called a retrogene — controls certain growth receptors. By comparing breeds like basset hounds, corgis and dachsunds to longer-legged breeds,  scientists isolated the gene that stunted growth in dogs, according to a paper in the new issue of the journal Science.

This gene hasn’t “been associated with dwarfism in the past,” says Heidi Parker, first author of the study, so it “opens up a new avenue, a new place to look,” for the cause of some types in humans

Parker, of the National Human Genome Research Institute in Bethesda, Md., compared the genomes of 95 short-legged dogs from eight breeds with the genomes of 702 dogs from 64 breeds without the trait. Then, in a more detailed analysis, the researchers pinpointed an extra stretch of DNA on chromosome 18 in every dog from the eight short-legged breeds, but in none of 204 control dogs they examined, according to an article in Science News.

The article continues:

This extra stretch of DNA turned out to have a sequence almost identical to another gene important for limb development, called FGF4. Located at the opposite end of chromosome 18 in dogs, the original FGF4 gene was duplicated at some point in the dog lineage, creating a new copy elsewhere called the fgf4 retrogene, the researchers say in their report.

In rare cases, messenger RNA — molecules made from DNA that carry information to cellular machinery, which then makes proteins—can get turned back into DNA. If this DNA then gets plopped back into the genome in a new neighborhood, and conditions are right for this genetic new kid on the block to become active, the extra DNA becomes a retrogene.

Parker and her colleagues also examined DNA from wolves, to see whether they could narrow the window of time during which the fgf4 retrogene originated. None of the wolves tested had the retrogene. Their paper appeared in the new issue of the journal Science.

The gene duplication probably happened after dogs first became domesticated and before division of early dogs into modern breeds, putting the range, Parker says, anywhere between 300 and 15,000 years ago.

(Photo: Shorty, a basset hound mix; by John Woestendiek)