Genes tell tale of cat domestication

Five DNA variations distinguish tame felines from wild cousins

HERE, KITTY  DNA from Cinnamon, a female Abyssinian cat that lived at the University of Missouri, is now the standard against which other cat genomes are compared. Comparison of Cinnamon’s DNA with that of other domestic and wild cats has revealed how domestication shaped cats’ genes.

Kristina Narfstrom/University of Missouri, Columbia

A peek into cats’ genetic makeup may help reveal how hissing wild felines became purring tabbies.

Five genes involved with embryo development differ between wild and domesticated cats, researchers report November 10 in the Proceedings of the National Academy of Sciences. The new genetic data support a recent hypothesis about why domesticated animals often have a juvenile appearance.

In July, three scientists proposed that certain physical features shared by domestic animals, described as domestication syndrome, might all result from mild defects in the function of cells known as neural crest cells (SN: 8/23/14, p. 7). Neural crest cells migrate to different parts of an embryo and give rise to several tissues including the bone and cartilage that shape faces, muscles, pigment cells and the adrenal glands, which control the flight-or-fight response.

The new findings are consistent with the hypothesis that changes in neural crest cell functions can lead to tameness, the researchers say. Genes involved in memory, fear and reward systems in the brain also differed between domestic and wild cats.  

It’s still too early to say how these genetic changes might affect brain development and lead to the evolution of tameness, says Greger Larson, an evolutionary biologist at the University of Oxford. Researchers are learning that many genes contribute to domestication. The combination of the neural crest cell hypothesis and supporting genetic evidence such as that provided by this study give researchers clues about which genes or biological systems might be most important for domestication, he says.

Most scientists consider cats only semidomesticated, says geneticist and study coauthor Wesley Warren of Washington University School of Medicine in St. Louis. Tame cats are independent and breed freely with their wild cousins. So the researchers were surprised that they could find genetic signatures of domestication in the animals at all.

Warren and colleagues first compiled the genome of a female Abyssinian cat named Cinnamon as a reference to compare with DNA of multiple cats and other species. To look for genetic variants associated with domestication, the researchers examined DNA from 22 cats from six domestic breeds (Felis silvestris catus), two European wildcats (F. silvestris silvestris) and two African wildcats (F. silvestris lybica).

The team looked for regions of the genome where domestic cats are genetically similar to each other but differ substantially from wildcats. The researchers concluded that the 13 genes in five genome regions that they found were associated with domestication. Five of those genes are involved in controlling survival and migration of neural crest cells in the embryo.

The researchers may be overinterpreting their data, says Anna Kukekova, a geneticist at the University of Illinois at Urbana-Champaign who studies tame and aggressive silver foxes. “They cannot say that the changes they found are associated with tameness,” she says.

Comparing the cat genome with those of other species, the researchers also discovered some genetic variants that help explain some feline characteristics, such as their keen eyesight and hearing.

Genes may also reveal what it takes to be a real carnivore. Cats are obligate carnivores: They can’t produce some necessary nutrients found only in meat. They also have trouble digesting plant-based foods. “No tofu for felids,” says study coauthor Leslie Lyons, a comparative geneticist at the University of Missouri College of Veterinary Medicine in Columbia.

Researchers have wondered how cats avoid heart disease when they eat such protein- and fat-laden diets. The researchers’ genetic analysis revealed that several genes involved in processing lipids have evolved rapidly in cats. Those fat-processing genes help the animals stave off the artery-clogging effects of a high-fat diet. Polar bears also eat a lot of meat and have developed similar adaptations, suggesting that those genetic changes may be a signal of a carnivorous lifestyle.

Editor’s Note: This article was updated November 21, 2014 to replace Near Eastern wildcat with the more commonly used name for F. silvestris lybica, African wildcat.

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