Evolution of the Dog Genome

Abstract

The dog genome illuminates several important features of mammalian genome evolution. The dog is a distant relative to the primate and rodent clades, so its genome sequence can be used to identify genetic changes that occurred on these lineages and as an aid in annotating the human genome. The dog also has a complex population history, shaped by ancient domestication events and, recently, strong artificial selection to form distinct breeds. The dog genome sequence enabled studies that shed light on canid phylogeny, revealing that this history created a genomic haplotype structure that is highly amenable to the association mapping. Dogs also exhibit enormous phenotypic variation and suffer from many of the same disorders as humans, making them a powerful model organism for identifying genetic variants responsible for many common traits and diseases including cancer, diabetes, autoimmune disorders and epilepsy.

Key concepts:

  • The dog is distantly related to the primate and rodent clades.

  • Dog genome evolution was characterized with a large number of chromosomal fissions and a low activity of transposons.

  • Genetic evidence supports an ancient origin of dogs in East Asia.

  • Dog domestication involved two population bottlenecks, one during dog domestication, over 15‚ÄČ000 years ago, and one during the formation of modern breeds in the past few hundred years.

  • Modern dog breeds exhibit remarkable phenotypic diversity and increased rates of common diseases shared with humans, including cancer, diabetes, autoimmune disorders and epilepsy.

  • Patterns of genetic variation in dogs are highly amenable to trait mapping by association studies.

Keywords: molecular evolution; population genetics; association studies; domestication; dog breeds; artificial selection

Figure 1.

mtDNA tree of dogs and wolves. Sequencing of the mtDNA control region revealed at least four dog clades (blue) interspersed within wolf sequences (black). More than 70% of modern dogs belong to clade I. Modern dog breeds contain mtDNA haplotypes from more than one clade, consistent with a common origin of all breeds from a large and genetically diverse ancestral population.

Figure 2.

Population history and haplotype structure of the domestic dog. Two population bottlenecks in dog population history, one old and one recent, shaped haplotype structure in modern dog breeds. First, the domestic dog diverged from wolves approximately 15 000 years ago. Within the past few hundred years, modern dog breeds were created. Both bottlenecks influenced the haplotype pattern in current breeds. (1) Before the creation of modern breeds, the dog population had short LD and short haplotypes, as expected given its large size and long time since the domestication bottleneck. (2) In the creation of modern breeds, a small subset of chromosomes was selected from the pool of domestic dogs, thereby creating long‐range LD. (3) In the short time since breed creation, these long‐range patterns have not yet been substantially broken down by recombination. The short ancestral haplotypes are evident, however, when comparing chromosomes across many breeds.

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Further Reading

Ostrander EA, Giger U and Lindblad‐Toh K (eds) (2006) The Dog and its Genome. Woodbury: Cold Spring Harbor Laboratory Press.

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Webster, Matthew T, and Karlsson, Elinor K(Dec 2009) Evolution of the Dog Genome. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021780]