Washington: Scientists have moved a step closer to bringing the woolly mammoth back to life, after they identified extensive genetic changes that allowed the extinct giant animals to adapt to Arctic life.
As a test of function, a mammoth gene involved in temperature sensation was resurrected in the laboratory and its protein product characterised.
The study sheds light on the evolutionary biology of these extinct giants, researchers said.
"This is by far the most comprehensive study to look at the genetic changes that make a woolly mammoth a woolly mammoth," said study author Vincent Lynch, assistant professor of human genetics at the University of Chicago.
Woolly mammoths last roamed the frigid tundra steppes of northern Asia, Europe and North America roughly 10,000 years ago.
To thoroughly characterise mammoth-specific genes and their functions, Lynch and his colleagues deep sequenced the genomes of two woolly mammoths and three Asian elephants - the closest living relative of the mammoth.
They then compared these genomes against each other and against the genome of African elephants, a slightly more distant evolutionary cousin to both mammoths and Asian elephants.
The team identified roughly 1.4 million genetic variants unique to woolly mammoths. These caused changes to the proteins produced by around 1,600 genes, including 26 that lost function and one that was duplicated.
To infer the functional effects of these differences, they ran multiple computational analyses, including comparisons to massive databases of known gene functions and of mice in which genes are artificially deactivated.
Genes with mammoth-specific changes were most strongly linked to fat metabolism (including brown fat regulation), insulin signalling, skin and hair development (including genes associated with lighter hair colour), temperature sensation and circadian clock biology - all of which would have been important for adapting to the extreme cold and dramatic seasonal variations in day length in the Arctic.
Of particular interest was the group of genes responsible for temperature sensation, which also play roles in hair growth and fat storage.
While his efforts are targeted towards understanding the molecular basis of evolution, Lynch acknowledged that the high-quality sequencing and analysis of woolly mammoth genomes can serve as a functional blueprint for efforts to "de-extinct" the mammoth.
The study was published in the journal Cell Reports.