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Short legged dogs studied for DNA differences Sunday, July 19, 2009

via Australian

The evolutionary secret of how the dachshund got its short legs has been uncovered. Dachshunds, corgis, basset hounds and Pekingese are among the common breeds that owe their short legs to the mutation of a single gene that occurred several thousand years ago. The discovery offers insight into the way genetic mutations drive evolution and may have implications for understanding dwarfism in humans.

A team from the American National Human Genome Research Institute, in Maryland, examined DNA samples from 835 dogs from 76 breeds, including 95 animals with short legs. The scientists found that dogs from all the short-legged breeds had an extra copy of a gene that produces a growth protein called FGF4, which is known to be implicated in dwarfism in humans. The extra gene is a mutant of a type known as a retrogene, which lacks parts of the normal DNA code.

The extra retrogene leads to an overproduction of the FGF4 protein, which appears to alter the times at which bones grow in embryonic development. This, the scientists believe, causes the legs of small dogs to remain short and out of proportion to their bodies. The findings are published in the journal Science. As the same gene is shared between all the short-legged breeds of dog studied, the mutation is likely to have emerged early in the evolution of dogs.

Fossil evidence suggests dogs were first domesticated from wolves at least 14,000 years ago, and genetic evidence suggests the evolutionary split may have happened earlier than that. Eric Green, scientific director of the National Human Genome Research Institute, said the research shows how genetic information can help us to understand the course of evolution.