Nearly two decades ago, a group of scientists sequenced and assembled the complete genome of a dog—a female boxer called Tasha—for the first time.1 Part of this team was Elinor Karlsson, a young research trainee, who then went on to study the genes underlying coat colors in dogs for her graduate studies.
Elinor Karlsson, a geneticist at the University of Massachusetts Chan Medical School and Broad Institute of MIT and Harvard, studies the genomes of cats and dogs to better understand animal and human health.
Michael Butts
“I didn't know anything about dogs. I'm not a dog person at all,” admitted Karlsson, now a comparative genomics researcher at the University of Massachusetts Chan Medical School and Broad Institute of MIT and Harvard. “But I am a complete genetics geek.”
Eventually, she recognized that she could leverage the genomes of dogs, which develop diseases similar to humans, to better understand human health. “I sort of realized that the biggest advantage in terms of genomics in dogs was that every single one of the dogs that we were studying lived with a human who was completely obsessed with them,” said Karlsson. This meant that she could gather important phenotypic information about the animals, which would otherwise be hard to do.
In 2018, Karlsson co-founded a citizen science project, called Darwin’s Ark, in which people signed up their pets—46,000 dogs and 14,000 cats—for genetic testing. So far, the dog genomes have shed light on genes underlying complex traits and diseases in the animals, which could also provide clues about similar disorders in humans. Karlsson and her team hope to conduct similar research with cats soon.
Darwin’s Dogs Debunked Breed Stereotypes and Offered Clues About Behavior
Karlsson and her team first set up Darwin’s Dogs, inviting dog owners to fill out detailed questionnaires about their pets. Those who donate some money to the initiative receive sampling kits to swab their dog’s mouth for DNA. “We can't actually afford to sequence all the dogs…although as a geneticist, I would absolutely love to be able to do that,” said Karlsson.
DNA sequences of thousands of dogs of various breeds, coupled with surveys filled out by their owners, helped Karlsson and her team identify genes linked to behavioral and physical traits.2 They observed that while genes underlying a dog’s appearance correlated with its breed, those associated with its behavior did not.
“Everybody has a lot of beliefs about dogs, and we really wanted to push back on that idea,” said Karlsson. “If you go and adopt a dog [of a certain] breed, you may not get the dog that you're expecting to get.”
Studying dog behavior also led the scientists to investigate psychiatric diseases like obsessive compulsive disorder (OCD) in the animals. According to Karlsson, dogs show signs of OCD similar to humans: repeating a normal behavior such that it disrupts the quality of life. While humans may continuously wash their hands, dogs may fixate on certain objects.
Survey questions focusing on such characteristics helped the scientists gauge whether a dog may have OCD. Over time, by comparing the genomes of dogs that did or did not show signs of OCD, Karlsson and her team mapped the genomic locations and genetic variants associated with the disorder in dogs.3,4
Darwin’s Cats Attempts to Unravel Cat Behavior
While Karlsson is not a dog person, she said, “I cannot claim such scientific disengagement when it comes to cats.” As someone who grew up surrounded by cats and a cat-parent herself, she hoped to conduct similar research in felines.
Karlsson and her team recently set up Darwin’s Cats, wherein cat-parents signed up their pets for genetic testing. As the parent of cats Hopper (left) and Beagle (right), Karlsson was motivated to better understand the biology of cats.
Elinor Karlsson
This led to the birth of Darwin’s Cats in 2024, wherein people answer detailed surveys about their cats. Similar to Darwin’s Dogs, Karlsson and her team mail DNA sampling kits to those who donate money. Since cats do not like having things stuck in their mouths, the scientists mail a tiny eyebrow comb to the participants. Brushing cats’ eyebrows can help collect DNA from their hair shafts. While the team has already sequenced the DNA of about 5,000 dogs, “we're just getting started on the cats,” said Karlsson.
Eventually, she hopes that studying complex traits in the animals could also provide clues about human diseases. “What we’ve been trying to show with our work is that the reason why dogs and cats are such an amazing resource for science is…because they share our environment,” said Karlsson. “In terms of a model for human disease, they’re basically almost the same as us, except that their lifespans tend to be much shorter, which means that we can get answers much faster.”
While some aspects of the project are in the early stages, the work engages people in science, which has been fulfilling, said Karlsson. “Being able to…bring new people into science in a way that they might not have expected…has been one of the most exciting things.”
- Lindblad-Toh K, et al. Genome sequence, comparative analysis and haplotype structure of the domestic dog. Nature. 2005;438(7069):803-819.
- Morrill K, et al. Ancestry-inclusive dog genomics challenges popular breed stereotypes. Science. 2022;376(6592):eabk0639.
- Tang R, et al. Candidate genes and functional noncoding variants identified in a canine model of obsessive-compulsive disorder. Genome Biol. 2014;15(3):R25.
- Noh HJ, et al. Integrating evolutionary and regulatory information with a multispecies approach implicates genes and pathways in obsessive-compulsive disorder. Nat Commun. 2017;8(1):774.
