Genetics

Gray Wolf © U.S. Fish and Wildlife Service, Hollingsworth ~  Golden Jackal © Tbjornstat

Three Gene Mutations involved in Inheritance of Canine Coat Type 
Summary by Dr. Dominique de Caprona 
© de Caprona 2009

In an article entitled "Coat variation in the Domestic Dog is Governed by Variants in Three Genes" by Cadieu et al (2009), the authors analyse for the first time the genes and their mutations underlying the inheritance of different coat lengths and curls in dog breeds. 

622 dogs representing all coat phenotypes and 108 of some 160 AKC recognized breeds*were sampled.

The authors find mutations in three distinct genes: RSPO2 (encoding R-spondin-2), FGF5 (fibroblast growth factor-5) and KRT71(keratin-71). These mutations together  influence 95% of coat types found in pure-bred dogs in the United States of America.

Ancestral state of these three genes:

The short haired dog breeds all have the ancestral state of these three genes found in Golden Jackal, Gray Wolf and Wolf.
Sighthound examples: Greyhound, Italian Greyhound, Whippet. African example: Basenji.

Italian Greyhound © Schwab ~ Whippet © Gail Wieberdink

Greyhound © Karen Lorenzo ~ 
Ancestral state of the three genes

The breeds with wire-hair, moustache and eyebrows show a mutation in the RSPO2 gene. Sighthound examples: Irish Wolfhound, Scottish Deerhound
The breeds with curly-wire hair, longer than wire-hair and kinked instead of straight, show mutations in the RSPO2 and KRT71 genes. Example: Airedale Terrier 
Long-haired breeds carry the mutation in the FGF5 gene. Sighthound examples:Borzoi, Saluki
Breeds with long soft coat, moustache and eyebrows carry the mutation in the FGF5 and RSPO2 genes. Example: Bearded Collie 
Breeds with curly long coat carry the mutations in both FGF5 and KRT71. Example: Bichon Frisé.

This study shows that most of the highly variable canine coat types can be explained by the combined effects of as few as 3 gene mutations.
Interestingly three breeds with very long coats, the Silky Terrier, the Yorkshire Terrier and the Afghan hound are the exception. These breeds do not show any difference to short coated breeds in FGF5 or its mutation, suggesting that other genes are involved in hair length.

I thank Heidi G. Parker for fine tuning this text and all the photographers for their pictures.