A short report on the recent article in Science magazine about the hairless gene in dogs.

The title of the article is “A Mutation in Hairless Dogs Implicates FOX13 in Ectodermal Development” The researchers are from Sweden, Finland, Swizerland and the Broad Institute of Harvard U. and  MIT The people from the University of Bern in Swizerland seem to be the prime researchers. They are Cord Drogemuller, Elinor Karlsson, Marjo K. Hytonen, Gaudenz Dolf, Kirsi Sainio, Hannes Lohi, Kersten Lindblad-Toh and Tosso Leeb.

The phenotype (physical appearance) of the hairless dog’s in the Xolo line is classified as Canine Ectodermal Dysplasia. This is the near complete absence of hair and the effect on the teeth.Teeth and hair are classified as ectodermal appendages, because they form very late in the development of the fetus.  There are also some alterations in some of the exocrine glands in the human form which are not severe in the living dogs. This might also explain why some hairless dogs sweat through their skin because in this condition in humans the sweat glands can also be affected.

Ectodermal dysplasia in humans is a disorder involving two or more of the ectodermal structures, which include the skin, hair, nails, teeth, mucous membranes and sweat glands. How an individual is affected varies. For example, in one individual the hair and nails may be affected, while in another the disorder may involve the sweat glands and teeth. Each combination is considered a distinct type of ectodermal dysplasia.

They traced the gene to the 17th chromosome on the dogs where a sequence that is part of what is known as a FOX gene is duplicated. The Fox family of genes (which have nothing to do with foxes) are an important group of about 50 genes that encode for developmental regulators. This duplication is only 7 base pairs long but acts as an early “stop” signal for the production of the regulators. With only 1 gene the amount of the regulator is decreased but appears to be completely missing in the dogs with the two dominant genes. The lack of this regulator is thought to be the reason why the homozygous pups die.

The study was done using 140 hairless dogs, Chinese Crested, Xoloitzcuintle and Peruvians. The duplication was found in all of the dogs. When they tested coated dogs of the three breeds (55) and 32 other dogs from 19 other coated breeds there was no duplication on the gene.

They commented that “This study illustrated how the extreme morphological (body type) diversity of dogs can be harnessed to gain new insights into developmental biology.”

Kacie Johnson 
Tucson Arizona