A team of researchers at the University of Chicago carried out the first in-depth analysis of the woolly mammoth genome recently. The study, published in Cell Reports, shows how the biologists were able to catalogue extensive genetic differences between the mammoth and its closest living relatives – the Asian and African elephants – using ‘functional genomics’ to pinpoint the genes that make a woolly mammoth woolly and ‘mammothy’. The team even successfully resurrected one of the ancient proteins to test it in the laboratory.
Woolly mammoths roamed the icy tundra steppes approximately 10,000 years ago, yet the furry giants apparently continue to generate much curiosity among both scientists and the general public. Mammoths have been very well studied because of the number of well-preserved skeletons beneath the earth and recently made headlines due to scientists working towards resurrecting the woolly giants.
“This is by far the most comprehensive study to look at the genetic changes that make a woolly mammoth a woolly mammoth,” said Vincent Lynch, assistant professor of human genetic at University of Chicago. “They are an excellent model to understand how morphological evolution works because mammoths are so closely related to living elephants, which have [few] of the traits they had.” Lynch believes the woolly mammoth to be an ideal species to study the genetic and molecular mechanisms of evolution.
Lynch and his colleagues carried out a deep sequencing of two woolly mammoth genomes and three Asian elephants to identify which genes were mammoth-specific. These genomes were then compared with their next-closest kin, the African elephant. The study seemed to find 1.4 million genetic variants unique to woolly mammoths, affecting around 1,600 genes. Further computational analysis helped clarify the functions of these differences.
Genes most akin to the mammoth were those involved in fat metabolism, skin and hair development, circadian clock biology and temperature sensation. It is likely these traits are what allowed the mammoth to adapt so effectively to extreme colds.
Of particular interest, Lynch’s team found that a specific class of proteins, called TRP channels, involved in temperature sensation, shows mammoth-specific amino acid changes. Scientists suggest that these changes are what helped mammoths survive in icy cold environments. “Imagine that mammoths evolve cold preference [rather than cold tolerance], then as the world warmed at the end of the last ice age they preferred to retreat north with the cold temperatures contributing to their extinction,” Lynch pondered in a recent Reddit AMA. Ideally, creating a real mammoth may test the hypothesis by observing it in the flesh at an organismal level, however cloning technologies are still catching up. Instead, the team reproduced, or “resurrected”, proteins in the lab to test their functions at a molecular level.
Increased molecular understanding of ancient species often drives hope of reintroducing it into the present. “Despite the hype about cloning mammoths (and other things for that matter) and the advent of genome editing technologies such as CRISPR/Cas, ‘we’ (meaning biologists) are still pretty far away from actually being able to clone a mammoth,” explained Lynch during the AMA. “The technical limitations generally fall into two classes: genome engineering and growing a baby mammoth.” Current genome editing technologies make relatively few changes to the genome, while there are millions of genetic differences between elephants and mammoths.
The lab’s efforts are solely aimed towards understanding evolution at the genetic and molecular level. Even so, Lynch proclaims that their comprehensive analysis of the mammoth genome might serve as a molecular blueprint for team’s working to “de-extinct” the woolly mammoth. Lynch poses the question, “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?”
How might the resurrection of the woolly mammoth benefit the ecosystem?