Coat type is one of the most distinctive features by which dog breeds are defined. Some breeds, like huskies and German shepherds, have a double coat consisting of coarse guard hairs over a dense undercoat, while others, such as poodles and Dalmatians, carry only a single coat. Understanding the genetic basis of this variation helps trace breed development and adaptation.
In their 2019 paper, D. T. Whitaker and Elaine Ostrander used whole genome sequencing (WGS) and genome-wide association studies (GWAS) to pinpoint a locus on chromosome 28 linked to coat composition. Within this region, they identified an 18.4 kb locus containing 62 significant variants located in the intron of a long noncoding RNA upstream of the ADRB1 gene. These variants are predicted to function as a cis-regulatory module.
Importantly, two variants were found at high frequency in single-coated breeds but were rare in wolves, suggesting that the ancestral state was double-coated. This aligns with the coat structure of wild canids, while the derived single-coat condition appears linked to selective breeding in certain lineages. The identified variants likely influence transcription factor binding, altering the genetic regulation of coat development.
This work demonstrates how molecular genetics can uncover the roots of breed-defining traits. Beyond aesthetics, coat type has functional significance, influencing a dog’s thermal regulation, working ability, and environmental adaptation. The study also shows the power of WGS for mapping both structural and regulatory genetic variants in domestic animals.
Source: Whitaker, D. T., & Ostrander, E. (2019). Hair of the Dog: Identification of a Cis-Regulatory Module Predicted to Influence Canine Coat Composition. Genes, 10.
