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時間造就不同,尼安德塔人與現代人的大腦發育不同

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Dresden and Leipzig researchers find that stem cells in the developing brain of modern humans take longer to divide and make fewer errors when distributing their chromosomes to their daughter cells, compared to those of Neanderthals.

德國萊比錫及德勒斯頓市的研究人員們發現,相較於尼安德塔人的那些幹細胞,現代人發育中的大腦幹細胞,在將染色體分配到其子細胞時,花更長的時間來分裂,及產生較少錯誤。

 

 1. 於現代人類中的染色體分離錯誤比尼安德塔人的神經幹細胞少。左側:現代人新皮質之神經幹細胞,在細胞分裂過程中的染色體(青色)顯微鏡圖像。右側:相同類型的圖像。不過,細胞中涉及染色體分離的兩種蛋白質,KIF18aKNL1中,三個氨基酸已經從現代人,被改變成尼安德塔人的變體。此些“尼安德塔人化的”細胞,顯示多達兩倍的染色體分離錯誤(紅色箭頭)  (圖援用自原文)

 

 

Neanderthals are the closest relatives to modern humans. Comparisons with them can therefore provide fascinating insights into what makes present-day humans unique, for example regarding the development of the brain.

尼安德塔人是與現代人親緣關係最接近的人類。因此,與他們的比較能提供,是什麼使得當今人類與眾不同,譬如有關大腦發育,令人著迷的洞察力。

 

The neocortex, the largest part of the outer layer of the brain, is unique to mammals and crucial for many cognitive capacities. It expanded dramatically during human evolution in species ancestral to both Neanderthals and modern humans, resulting that both Neanderthals and modern humans having brains of similar sizes.

大腦外層的最大部分,新皮質是哺乳動物獨有的,且對諸多認知能力至關重要。於人類演化中,其在尼安德塔人及現代人,兩者祖先的物種中,顯著擴大。導致尼安德塔人與現代人兩者具有,相似大小的大腦。

 

However, almost nothing is known about how modern human and Neanderthal brains may have differed in terms of their development and function.

然而,有關現代人及尼安德塔人的大腦,從發育及功能方面來說,為何會是相異,幾乎一無所知。

 

Researchers from the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) in Dresden and the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig have now discovered that neural stem cells – the cells from which neurons in the developing neocortex derive – spend more time preparing their chromosomes for division in modern humans than in Neanderthals.

目前,來自德國馬克斯普朗克分子細胞生物學暨遺傳學研究所(MPI-CBG,位於德勒斯頓市),及馬克斯普朗克演化人類學研究所(MPI-EVA,位於萊比錫市)的研究人員們業已發現,在現代人中,神經幹細胞(發育中之新皮層神經元的來源)比在尼安德塔人中,花費更多準備其染色體的時間,以便進行分裂。

 

This results in fewer errors when chromosomes are distributed to the daughter cells in modern humans than in Neanderthals or chimpanzees, and could have consequences for how the brain develops and functions. This study shows cellular differences in the development of the brain between modern humans and Neanderthals.

這導致,當染色體被分配到子細胞時,於現代人中比在尼安德塔人或黑猩猩中,發生較少的錯誤。因此,可能對大腦如何發育及起作用,有諸多影響。這項研究顯示了,在大腦發育上,現代人與尼安德塔人之間的諸多細胞差異。

 

After the ancestors of modern humans split from those of Neanderthals and Denisovans, their Asian relatives, about one hundred amino acids, the building blocks of proteins in cells and tissues, changed in modern humans and spread to almost all modern humans.

在現代人的祖先與尼安德塔人及丹尼索瓦人(他們的亞洲親緣人類)分道揚鏢後,在現代人身中,大約一百種氨基酸(於細胞與組織中的蛋白質構材)發生了變化,且散播到幾乎所有現代人。

 

The biological significance of these changes is largely unknown. However, six of those amino acid changes occurred in three proteins that play key roles in the distribution of chromosomes, the carriers of genetic information, to the two daughter cells during cell division.

此些變化的生物學意義,絕大部分不詳。然而,其中六個氨基酸的變化發生於,細胞分裂中,將染色體(遺傳信息的載體)分配到兩子細胞上,扮演關鍵角色的三種蛋白質中。

 

To investigate the significance of these six changes for neocortex development, the scientists first introduced the modern human variants in mice. Mice are identical to Neanderthals at those six amino acid positions, so these changes made them a model for the developing modern human brain.

為了調查研究這六種變化,對新皮質發育的意義。此些科學家首度將現代人的變異體,引入小鼠中。在那六個氨基酸位置上,小鼠與尼安德塔人完全相同。因此,此些變化使它們成為,現代人大腦發育的一種模型。

 

Felipe Mora-Bermúdez, the lead author of the study, describes the discovery: “We found that three modern human amino acids in two of the proteins cause a longer metaphase, a phase where chromosomes are prepared for cell division, and this results in fewer errors when the chromosomes are distributed to the daughter cells of the neural stem cells, just like in modern humans.”

該項研究首要撰文人,Felipe Mora-Bermúdez描述此發現:「我們發現,三種現代人的氨基酸,於上述蛋白質的兩種中,導致較長的中期(染色體為細胞分裂作準備的階段)。因此,就像於現代人中,當染色體被分配到神經幹細胞的子細胞時,導致較少的錯誤。」

 

To check if the Neanderthal set of amino acids have the opposite effect, the researchers then introduced the ancestral amino acids in human brain organoids – miniature organ-like structures that can be grown from human stem cells in cell culture dishes in the lab and that mimic aspects of early human brain development.

為了查驗尼安德塔人的氨基酸組,是否具有相反的效果。因此,這些研究人員將此些祖先的氨基酸,引入人類大腦的類器官(在實驗室之細胞培養皿中,能從人類幹細胞培養出,並模仿早期人類大腦發育各個方面的微型器官樣結構物)中。

 

 “In this case, metaphase became shorter and we found more chromosome distribution errors.” According to Mora-Bermúdez, this shows that those three modern human amino acid changes in the proteins known as KIF18a and KNL1 are responsible for the fewer chromosome distribution mistakes seen in modern humans as compared to Neanderthal models and chimpanzees.

根據 Mora-Bermúdez 的說法:「在此情況下,中期變得較短。因此,我們發現較多染色體分配錯誤。」 這顯示,當與尼安德塔人模型及黑猩猩相較時,在被通稱為KIF18aKNL1的蛋白質中,那三種現代人之氨基酸的改變,是導致於現代人中,被發現之較少染色體分配錯誤的原因。

 

He adds that “having mistakes in the number of chromosomes is usually not a good idea for cells, as can be seen in disorders like trisomies and cancer.”

他附言:「在染色體數量上有錯誤,對細胞而言,通常不是一個好預感。因為,在諸如三染色體細胞及癌症等疾病中,能被發現。」

 

“Our study implies that some aspects of modern human brain evolution and function may be independent of brain size since Neanderthals and modern humans have similar-sized brains. The findings also suggest that brain function in Neanderthals may have been more affected by chromosome errors than that of modern humans,” summarizes Wieland Huttner, who co-supervised the study.

共同監督該項研究的Wieland Huttner總結:「我們的研究意味著,現代人類大腦演化及功能的某些方面,可能與大腦大小無關。因為,尼安德塔人與現代人類具有相似大小的大腦。此些研究發現也暗示,於尼安德塔人中的大腦功能,可能曾經比現代人的,更遭到染色體錯誤的影響。」

 

Svante Pääbo, who also co-supervised the study, adds that “future studies are needed to investigate whether the decreased error rate affects modern human traits related to brain function.”

共同監督該項研究的Svante Pääbo附言:「未來需要諸多研究,來調查研究降低的錯誤率,是否影響與大腦功能相關的現代人類特徵。」

 

 

網址:https://www.mpi-cbg.de/news-outreach/news-media/article/taking-your-time-makes-a-difference-brain-development-differs-between-neanderthals-and-modern-humans

翻譯:許東榮

台長: peregrine
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