Many of you will know that the iconic woolly mammoth lived in the depths of the Arctic tundra. They regularly had to deal with dramatic seasonal variations and temperatures dipping as low as –50°C (–58°F). To survive in this harsh environment, the animals evolved lots of different adaptations, including their thick fur and small ears. Now, researchers from the University of Chicago have revealed the genetic changes underlying these adaptations, following the first detailed analysis of the woolly mammoth genome.
“This is by far the most comprehensive study to look at the genetic changes that make a woolly mammoth a woolly mammoth,” explained Vincent Lynch, one of the authors of the study published in Cell Reports. “They are an excellent model to understand how morphological evolution works, because mammoths are so closely related to living elephants, which have none of the traits they had.”
By sequencing the genomes of two mammoths that died approximately 20,000 and 60,000 years ago and comparing the results with the genomes of three Asian elephants – their closest living relative – the researchers were able to identify an amazing 1.4 million genetic variants unique to the ice age beasts. They found that these variations caused changes in the proteins produced by over 1,600 genes.
But revealing genome sequences and knowing where variation occurs doesn’t actually tell you what these changes might do in a living animal. So in order for the team to infer the genes' functions, they ran multiple computational analyses comparing the mammoth variations to a huge database of known gene functions.
What they found was that the variations seen in the mammoth genome were most often associated, as you might expect, with cold weather adaptations. These included genes linked to fat metabolism, skin and hair development, temperature sensation and insulin signaling. They were also able to identify genes that regulated the shape of the animal’s skull, ears, and tail.
The researches then went a step further, looking specifically at the genes thought to be responsible for temperature sensation, which is also linked to hair growth and fat storage. The large, distinctive hump seen on mammoths is thought to have been a fat store, similar to that seen on camels. They took one of these genes, TRPV3, and inserted it into human cells. They found that the resulting cells produced a protein that is less responsive to heat when compared to the same protein found in elephants.
This result is fascinating, because mice that have the TRPV3 gene knocked out have shown a preference for cold environments, and develop long, wavy hair and curly whiskers. This suggests that the specific gene might have played a role in mammoths' adaptation to colder climes, giving them temperature tolerance, a long shaggy coat, and large fat deposits. But the question that remains, as always, is will we ever clone one?
“Eventually we'll be technically able to do it. But the question is: if you're technically able to do something, should you do it?” Lynch continued. “I personally think no. Mammoths are extinct and the environment in which they lived has changed. There are many animals on the edge of extinction that we should be helping instead.”
