To do this they performed “genome-wide association studies of more than 1000 dogs from 80 domestic breeds to identify genes associated with canine fur phenotypes. Taking advantage of both inter- and intrabreed variability, (they) identified distinct mutations in three genes, RSPO2, FGF5, and KRT71 (encoding R-spondin–2, fibroblast growth factor–5, and keratin-71, respectively), that together account for most coat phenotypes in purebred dogs in the United States. Thus, an array of varied and seemingly complex phenotypes can be reduced to the combinatorial effects of only a few genes.” Ref 1

For the authors this project filled the missing space between research that had been performed on the genes responsible for dog coat color and dog size.

The reason that the research is so interesting to scientist is that unlike offspring in many species, including human, dog breeds show a stunning variability on the basic theme. How many other breeds have such variety in colour, size and behavioral traits – especially in such a short time of less than 15,000 years since evolving from the wolf? Sure this is a combination of natural selection and manmade inbreeding to create specific breeds, however the research expects to have flow on effects for other research studies in other biological projects.

They firstly identified three areas of fur variation in dogs to localize the genetic basis of three characteristics of the canine coat:

(i)  the presence or absence of “furnishings,” the growth pattern marked by a moustache and eyebrows typically observed in wire-haired dogs;

(ii) hair length; and

(iii) the presence or absence of curl.

The raw data was gathered from three groups of dogs. The first data set used of 96 dachshunds with three coat varieties: wire-haired with furnishings, smooth, and long-haired without furnishings. The second data set had 76 Portuguese water dogs while the last data set comprised 903 dogs from 80 breeds that had a wide variety of phenotypes.

Combinations of alleles at three genes create seven different coat phenotypes.

The table below shows how the three genes are responsible for seven of the major dog coat variations. The Phenotype letter (A to G) is shown as dog breed examples in the image at the start of this article.

Legend =  Combinations of alleles at three genes create seven different coat phenotypes. Plus (+) and minus signs (-) indicate the presence or absence of variant (non-ancestral) genotype. A characteristic breed is represented for each of the seven combinations observed in our data set: (A) short hair; (B) wire hair; (C) “curly-wire” hair; (D) long hair; (E) long, soft hair with furnishings; (F) long, curly hair; and (G) long, curly hair with furnishings.

DOG COAT RESULTS

The authors found that None of the mutations they observed were found in the gray wolves that they analysed. This suggests a commonality with short-haired dogs (as seen in the previous tables three negative markets) which indicates that short-haired dogs carry the ancestral alleles. Or at least in regard to coat type, short haired domestic dogs share the closest trait to the ancestral wild wolf.

This research also suggests that a single mutation occurred for each trait and was transferred multiple times to different breeds through hybridization. “Because most breeds likely originated within the past 200 years their results demonstrate how a remarkable diversity of phenotypes can quickly be generated from simple genetic underpinnings.” Ref 1

CONCLUSIONS

While the original research paper is particularly dense in its scientific language, the results are fairly clear. In domestic dogs the “appearance of phenotypic complexity can be created through combinations of genes of major effect, providing a pathway for rapid evolution that is unparalleled in natural systems.” Ref 1

Understanding the high diversity between dog breeds and now the ability of scientist to identify the genes and combinations of genes that have caused the difference coat variations is important. even within one specific dog breed such as the dachshund, that can go on to assist other scientist understanding of the evolution of other species, such as mammals and humans.

Article by Bruce Dwyer. If you wish to use any of this information please refer to the article as a reference and provide a link to http://www.dogwalkersmelbourne.com.au

Reference

Coat Variation in the Domestic Dog Is Governed by Variants in Three Genes - Edouard Cadieu, Mark W. Neff, Pascale Quignon et al  August 2009