Dog and Human Genetics: Similarity and Difference

Your pup may be your “fur baby,” but how similar are you genetically? You may be surprised!

Did you know that dogs and people share over 17,000 special genes called orthologs? Each pair of orthologs is derived from the same common ancestor via vertical descent (speciation) and they tend to have similar functions. They are one of the main reasons why your pup is such an invaluable comparative animal model for studying human health. In fact, humans and dogs have numerous similarities even in those parts of the genome that aren’t genes (the noncoding part of the genome). When it comes to better understanding human health, your pup is our best friend!

Sometimes, the effects of a gene are identical between dogs and people. For example, the same version of EPAS1, a gene triggered by low-oxygen conditions, is shared by people living in the Tibetan Plateau and the dog lineages that developed there. Genetic changes in this gene have taken place to help kickstart the body’s responses to hypoxia, or low oxygen levels, at high altitudes.

In other cases, the effects of a gene may be similar but not identical. For instance, the gene SCN3A is important to brain function and affects the development of speech. In children, mutations in SCN3A have been reported to cause disorders like epilepsy. But in dogs, genetic changes near the canine ortholog of SCN3A are associated with the frequency of howling in dogs.^[1] The functions of this gene seem distinct (speech versus howling) but related!

For other health conditions shared by dogs and people, the same genes may not be responsible, but that doesn’t mean that research on those conditions in dogs isn’t helpful for humans! By learning more about how a dog’s genes are connected with a shared health condition, we can investigate the biological mechanisms involved and potentially make links to human health.

For example, people long suggested that narcolepsy might be a disease of the immune system: an autoimmune attack that causes daytime drowsiness and sudden sleep. In human studies, it was difficult to confirm the immune system link. It wasn’t until 1999^[2] that this connection was discovered in a lineage of Doberman pinscher dogs. The researchers discovered a gene that is involved in the interface between the nervous system and immune system.

Finally, you and your pup share more than just genetics. Your environments are also very similar! You sleep in the same house—maybe even the same bed!—go on walks together, and breathe the same air. Interactions between these environmental variables and your genetics (called gene by environment interactions) can have an important impact on health. For example, smoking is well known to increase risk of bladder cancer in humans^[3], but it is still unknown how secondhand smoke affects risk of bladder cancer in dogs.^[4]

Data from the Dog Aging Project should help us answer important questions like these!

1. Kathleen Morrill et al. 2022. Ancestry-inclusive dog genomics challenges popular breed stereotypes. Science 376: https://www.science.org/doi/10.1126/science.abk0639

2. Ling Lin et al. 1999. The Sleep Disorder Canine Narcolepsy Is Caused by a Mutation in the Hypocretin (Orexin) Receptor 2 Gene. Cell 98 (3): 365-376. https://doi.org/10.1016/S0092-8674(00)81965-0

3. JD Figueroa et al. 2014. Genome-wide interaction study of smoking and bladder cancer risk. Carcinogenesis 35 (8):1737-44. https://pubmed.ncbi.nlm.nih.gov/24662972/

4. Deborah Knapp. Canine Bladder Cancer. https://www.vet.purdue.edu/pcop/files/docs/CanineUrinaryBladderCancer.pdf (PDF)

Kathleen Morrill

William Thistlethwaite