|The woolly mammoth is a species of mammoth that became extinct from the mainland approximately 11,700 years ago / Photo by William Roberts via 123RF|
Woolly mammoths were exquisitely adapted to the ice age in which they lived, with insulating fur and a skin that did not feel the cold. It was known that the skin protein TRPV3 was involved in the mammoth’s ability to withstand cold, however exactly how the mammoth channel achieved this was unknown. Now a team of scientists has revealed the 3D structure of the TRPV3 channel, which suggests a possible way the mammoth channel is different to channels from other elephants. Humans do not have the advantage of the mammoth protein; however, a team of scientists has still braved the temperatures of Siberia and polar bear attacks to discover what they believe to be a new species of extinct golden-haired pygmy mammoths.
Humans once shared the planet with woolly mammoths
The woolly mammoth is a species of mammoth (Mammuthus primigenius) that became extinct from the mainland approximately 11,700 years ago. This was probably due to a combination of a shrinking habitat brought on by warmer temperatures and being hunted by people.
Humans had already domesticated pigs, sheep, and goats at the time. This was also about the time people began cultivating crops, however in a different part of the world from the mammoth’s home, in the mammoth steppe of northern Eurasia and North America. Isolated populations of woolly mammoth remained on islands until up to 4000 years ago.
The closest living relative of the woolly mammoth is the Asian elephant. Although the remains of mammoths had been long known, it was not until 1796 that Georges Cuvier deduced that they were from an extinct species of elephant.
The woolly mammoth was roughly the same size as modern African elephants. It was adapted well to the ice age in which it lived, covered in fur, with an outer layer of long guard hairs and a shorter undercoat. Its ears and tail were short in order to minimize frost-bite and conserve heat.
Woolly mammoths had a special TRPV3 protein that was insensitive to cold
In 2015 the genome sequences of three Asian elephants and two woolly mammoths were compared. The sequences of more than 1,600 proteins were different including the gene known as Transient Receptor Potential V3 (TRPV3), which is expressed in the skin. It is thought that at least some of these mutations are involved in allowing the woolly mammoth to survive the freezing temperatures it lived in.
The TRP superfamily to which TRPV3 belongs is the cation channels that depolarise cells by allowing cations to flow into the cytoplasm down their electrochemical gradients, either from extracellular sources or from the organelle known as the endoplasmic reticulum. Elevated cytoplasmic cations activate various signaling pathways leading to neurotransmitter release, cell proliferation, gene transcription, and cell suicide, to name a few.
The TRPV family comprises six members all of which may play a role in thermosensation or temperature perception. When comparing the TRPV3 channel of Asian elephants and woolly mammoths, side by side in human cells, it was found that woolly mammoth TRPV3 was less sensitive to temperature. Mice that lack TRPV3 have wavier hair and are more likely to spend time in cooler cage locations than normal mice.
Now a research team led by Alexander Sobolevsky at Columbia University Irving Medical Center, USA, has created a 3D structure of the TRPV3 channel that may help explain how the mammoth TRPV3 is less sensitive. The published their results in the journal Nature Structural and Molecular Biology.
The team used cryo-electron microscopy to take 2D pictures of TRPV3 proteins and then assemble them using computational tools into a 3D model.
The 3D model revealed that the mammoth TRPV3 mutation is located in a region that interacts with the lipid membrane of the cell. Temperature alters the interaction of the TRPV3 channel with the membrane lipids so it is very likely that the mutation changes the nature of this interaction making the channel less sensitive to temperature, presumably dulling the mammoth’s perception of cold.
In freezing Siberia a new golden pygmy mammoth has been discovered
On a Siberian island, a team of scientists led by Dr. Albert Protopopov has discovered what they believe could be a new species of golden-haired pygmy or mini-mammoth. However, the scientists nearly lost their prize when they were woken at 4 am by the sound of a polar bear, which had discovered their excavation.
The bear promptly tore a mammoth leg from the permafrost where the team had stored their excavation. The research party banged pots and pans and fired a flare gun to scare the bear off, which eventually dropped the mammoth leg. This was fortunate as the leg is crucial for their plans to prove the existence of the new pygmy mammoth species through DNA sequencing.
The golden pygmy mammoth is thought to be between 22,000 to 50,000 years old. It is expected that the majority of the mammoth will be excavated from the seabed permafrost in May next year.
|The closest living relative of the woolly mammoth is the Asian elephant / Photo by Corey A Ford via 123RF|