Spliced-in gene lays dogs low

CHICAGO (Reuters) - An extra gene may explain why dachshunds, corgis and basset hounds have short, stubby legs, U.S. researchers said on Thursday in a finding that may also lend new clues about human dwarfism.

They said while most dogs have only one copy of a growth-related gene, nearly 20 different breeds of short-legged dogs have a second, slightly altered copy of the gene called fibroblast growth factor 4 or FGF4.

This so-called retrogene appears to be copy of a wolf gene that got spliced back into the dog genome some time after modern dog breeds diverged from wolves.

"We were surprised to find that just one retrogene inserted at one point during the evolution of a species could yield such a dramatic physical trait," Heidi Parker of the National Human Genome Research Institute, whose study appears in the journal Science, said in a statement.

Parker and colleagues think this gene may turn on growth mechanisms at the wrong time during foetal development, stunting the growth of long bones in the leg and making them curvy.

The trait affects only the legs, unlike the small-all-over effect seen in miniature or toy breeds, such as poodles, they said.

Parker said retrogenes may play a more important role in evolution than previously thought.

And she thinks researchers should start looking in humans to see if the FGF4 gene plays a role in a form of dwarfism called hypochondroplasia, which represents about one-third of the unexplained cases of dwarfism in humans.

(Editing by Maggie Fox and Sandra Maler)