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格陵蘭島因紐特人 神祕基因不怕冷

Cold Tolerance Among Inuit May Come From Extinct Human Relatives

Inuit who live in Greenland experience average temperatures below freezing for at least half of the year. For those who live in the north, subzero temperatures are normal during the coldest months.

Given these frigid conditions, anthropologists have wondered for decades whether the Inuit in Greenland and other parts of the Arctic have unique biological adaptations that help them tolerate the extreme cold.

住在格陵蘭島的因紐特人,一年當中至少有一半的時間會碰上冰點以下的平均溫度。對住在北部的人來說,最冷的幾個月份零下的氣溫更是常態。

考量到這些寒冷的環境,數十年來人類學家一直想知道,格陵蘭島和北極圈其他地區的因紐特人是否具有獨特的生物適應性,幫助他們忍受極度寒冷。

A new study, published in Molecular Biology and Evolution, identifies gene variants in Inuit who live in Greenland that may help them adapt to the cold by promoting heat-generating body fat. These variants possibly originated in the Denisovans, a group of archaic humans who, along with Neanderthals, diverged from modern humans about half a million years ago.

“As modern humans spread around the world, they interbred with Denisovans and Neanderthals, who had already been living in these different environments for hundreds of thousands of years,” said Rasmus Nielsen, a professor of integrative biology at the University of California, Berkeley, and an author of the paper. “This gene exchange may have helped some modern humans adapt to and conquer new environments.”

有一份新研究結果發表在《分子生物與演化》期刊上,研究者發現格陵蘭島因紐特人身上有些基因變異,這些變異可能透過促生更多能產生熱量的體脂肪的方式,來幫助他們適應寒冷。這些變異可能源自於一群古老人類─丹尼索瓦人,而他們與尼安德塔人大約50萬年前從現代人類分化出去。

研究報告作者之一、柏克萊加州大學綜合生物學系教授雷斯穆斯.尼爾森說:「當現代人類散布到世界各地時,他們與丹尼索瓦人和尼安德塔人交配繁殖,而這些人已生活在這些不同環境數十萬年。這種基因交換可能有助於一些現代人類適應和征服新的環境。」

The new study follows earlier research by Nielsen and colleagues, which found genetic mutations that might help the Inuit metabolize unsaturated fatty acids common in their diet of whales, seals and fish.

In this study, Nielsen’s team focused on another distinct region in the Inuit genome, which seems to affect body fat distribution and other aspects of development. The researchers compared the genomes of nearly 200 Inuit with genomes of Neanderthals, Denisovans and modern populations around the world.

這項新研究接續著尼爾森與同事們的早期研究,早期研究發現因紐特人身上有一些基因突變,可幫助他們把常吃的鯨魚、海豹和魚類中的不飽和脂肪酸代謝掉。

在新的研究中,尼爾森的團隊專注於因紐特人基因組中的另個不同區塊,而它似乎影響身體脂肪的分佈與其他方面的發育。研究人員把近200名因紐特人的基因組跟尼安德塔人、丹尼索瓦人及全球各地現代人種進行比較。

Strikingly, all of the Inuit studied contained the same genetic variants in this particular region of their genomes. Compared to the same region in Neanderthals and other modern populations, the Inuit region showed at most a partial match. But compared to the Denisovan genome, it “was almost a complete match,” Nielsen said.

The region in question contains genes that may play a role in dictating levels of brown fat, a type that is abundant in newborns and generates heat by burning calories. In Inuit, the gene variants might promote more brown fat as a special adaptation to the cold, Nielsen said, although more study of this mechanism is needed.

引人注目的是,所有被研究的因紐特人在他們基因組的這個特定區塊內,均有著相同的基因變異。尼爾森表示,因紐特人的這個區塊與尼安德塔人及其他現代人種的同一區塊對照,最多只有部分吻合,但跟丹尼索瓦人基因組對照,卻「幾乎完全吻合」。

前述區塊包含了可能在決定棕色脂肪含量上發揮作用的基因,新生兒體內有很多棕色脂肪,可透過燃燒卡路里來產生熱。尼爾森表示,因紐特人的基因變異可能促生更多棕色脂肪,作為對寒冷的一種特殊適應方式,不過此一機制仍有待進一步研究。

文/Steph Yin  譯/陳韋廷

報導來源:聯合新聞網170223
https://udn.com/news/story/6948/2293393