The domestic cat genome is decoded; Reveals clues about the domestication process

Domestication (which is not yet complete) began when farmers from 9,000 years ago used feral cats to control rodents, and gave them food as a reward for keeping them around

Humans and cats have shared households for the past 9,000 years, but we still know very little about how our feline friends became domesticated. Analysis of the cat genome reveals surprising findings.

Humans and cats have shared households for the past 9,000 years, but we still know very little about how our feline friends were domesticated. Analysis of the cat genome led by researchers from the Washington University School of Medicine in St. Louis reveal some interesting findings. The study appeared in the November 10 issue of PNAS.

Cats have a shorter history of domestication than dogs, having split from wolves over 30 years ago. "Cats, unlike dogs, are only semi-domesticated," says lead researcher Wes Warren, professor of genetics at the University of Washington's Genome Institute. ” They split not long ago from the wild cats and are even able to reproduce with their relatives in the wild. So we were surprised to find DNA evidence of their domestication."

One way scientists can understand the genetics of domestication is to study which parts of the genome have changed in response to living with humans," added Warren.

The researchers discovered changes in the domestic cat's genes that other studies have shown to be involved in behaviors such as memory, fear and reward seeking. These types of behavior, in particular reward seeking, are considered important in the domestication process.
"Humans welcomed the cats because they allowed them to exterminate rodents that ate their wheat crops," says Warren. "We hypothesize that humans offered the cats food as a reward for staying around."

This meant that some cats that would normally have lived solitary lives in the wild were given an added incentive to stay with humans. Over time, humans preferred to keep cats that were more docile and comfortable.

The Cat Genome Project

The cat genome sequencing project funded by the Human Genome Research Institute, which is part of the US Institutes of Health (NIH) began in 2007. The first goal of the project was to understand the origin of the hereditary diseases in domestic cats, which in some cases are similar to those affecting humans including neurological disorders, infections and diseases Metabolism.

To obtain a high-quality genome for research, the researchers sequenced the genes of a female Abyssinian cat named Cinnamon. They chose this particular cat because they can trace her lineage back several generations. This cat family also suffers from a dangerous eye disease that the researchers wanted to investigate.

To better understand domestication characteristics, researchers sequenced the genomes of purebred domestic cats. They looked at traits such as hair color, texture and patterns, as well as facial structure and how obedient the cat was. Cats are bred for many types of these characteristics. In fact, most modern breeds are the result of breeding cats by humans in order to achieve the desired hair pattern.

The researchers also looked at a breed of cat known as the Birman, which is characterized by white paws. The researchers traced the white structure to two small changes in the gene responsible for hair color. They found that this genetic signature that appears in all Birmans shows that humans most likely selectively bred these cats for their paws and that the changes in their genomes occurred in an incredibly short period of time.

The team members also compared the cat genome with those of other mammals including the tiger, the cow, the dog and humans to understand more about the genetics of the cat's biology. "We examined the basic genetics to understand why different abilities responsible for survival in the wild appeared in the cat and other mammals" says Dr. Michael Montage, the first researcher in the study and a postdoctoral fellow at the Genome Institute.

The differences they found in the cat genome make it possible to explain how the senses of sight, smell and touch differ from those of other animals such as dogs.

Solitary carnivores
In order to digest the fatty and heavy meat meals, the cats need to quickly break down fats. Team members discovered unique genes for fat metabolism in carnivores such as dogs and tigers that changed at a greater rate than can be explained by chance. The faster the change, it means that the genes provide a certain digestive advantage to carnivores that are only able to consume animal proteins. The researchers did not discover such changes in the genes of cows and humans, who consume a more varied diet and do not require such enrichment.

Cats also rely less on their sense of smell to hunt than dogs, so it's no surprise that the researchers found fewer smell genes in the cat than in the dog. They found many more genes that belong to an alternative form of smell that picks up substances called pheromones, which allows cats to monitor their social environment, including finding a mate for reproduction. This ability is not so important for dogs that tend to wander in groups (packs), but it is essential for cats that are more solitary and therefore have difficulty finding mates.
Cats also have better hearing than other predators, including the ability to hear in the subsonic range to better track prey. Their vision is also exceptional in low light.

"Cats tend to be more active at dawn and dusk," says Montage. "So they need to be able to detect movement in low light." Accordingly, the team members identified specific genes that most likely evolved to improve the cats' hearing range and their low-light vision.

Although domestic cats' genomes have changed little since they split from wild cats, the new study shows that evidence of cats' late domestication can still be seen. "Thanks to the use of the most advanced gene sequencing technologies, we are able to shed light on the genetic signatures of cats' unique biology and survival skills," says Warren. "We were able to significantly advance our knowledge of the evolution of cat domestication."

Researchers from the following institutions participated in the study: Texas A&M University, the University of Missouri in Columbia, the University of California at Davis, the Sanger Institute of the Wellcome Foundation in the United Kingdom, Bilkent University in Turkey, the University of Indiana, the Cancer Research Center in Maryland, the University of St. Petersburg in Russia, and Nova Southeastern University in Florida.

For the announcement of the researchers on the website of Washington University in St. Louis

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