Science: Newly Identified Gene Responsible for "Hairless" Trait in Dogs

Chinese crested dogs: hairless and coated (Powderpuff) variants.

[Image © & courtesy of Tosso Leeb]

Whether you find them cute or repulsive, hairless breeds of dogs certainly stand out. Now, researchers say they've identified an important scientific use for them: They have identified the specific gene that is responsible for the dogs' skimpy coats, and the discovery should shed new light on how animals' bodies develop over time.

For a dog, being "hairless" means having a patchy (or absent) coat of fur and abnormal teeth. The scientific term for this condition is called canine ectodermal dysplasia, or CED. Humans have admired this affliction in dogs for hundreds of years. The Aztecs considered hairless breeds of dogs sacred, and statues of the dogs date back to 1700 B.C.E.

Cord Drögemüller from the Institute of Genetics at the University of Bern in Switzerland along with colleagues in Finland and the U.S. located the gene responsible for this "hairless" trait in dogs, and they present their finding in the latest issue of Science.

The team of researchers studied Chinese crested hairless dogs as well as Mexican and Peruvian hairless breeds to identify a mutation in a putative transcription factor gene that they appropriately named FOXI3.

The mutation on FOXI3 revealed by Drögemüller and colleagues was present in the 140 hairless dogs and absent from the 87 coated dogs in the study. The researchers further tested their theory that the mutation on FOXI3 is responsible for CED by analyzing the expression of the gene in mouse embryos. They observed that the FOXI3 gene was expressed in the tissues that give rise to hair, whiskers, and teeth in mice, consistent with the gene's role in the development of these features.

A sequence analysis of the gene in both hairless and coated Chinese crested dogs exposed more details about the mutation that results in CED. The researchers say that deactivation of one of the two copies of the FOXI3 gene causes a severe lack of FOXI3 protein, and that the protein insufficiency is likely what manifests as CED in dogs.

This study provides an example of how the extreme genetic diversity of dogs and other animals can be used to gain insights into exactly how their bodies develop.

The Drögemüller report is printed as a Brevia in the 12 September issue of Science, the journal of AAAS.

Brandon Bryn

11 September 2008