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哺乳动物如何在发育中保持对称性

来源:环球科学

Developing mouse fetus. Credit: Steve Gschmeissner Science Source

发育中的小鼠胎儿。图源:Steve Gschmeissner Science Source

How Mammals Maintain Symmetry during Development

哺乳动物如何在发育中保持对称性

Communication with the placenta is key to ensuring body parts grow at the same rate

与胎盘的交流是保证身体各部分以相同速率生长的关键

By Maya Miller | Scientific American October 2018 Issue

作者:Maya Miller|科学美国人2018年10月出版

 

Species with symmetrical body plans have been roaming the earth for about 400 million years. Human beings have long shown an intense interest in this property in our own species—take the importance of symmetry in perceptions of beauty or the famous depiction of the outstretched human body in Leonardo da Vinci’s Vitruvian Man.

拥有对称的身体构造的物种已经在地球上遨游了将近4亿年。人类也早已对自己身上的这一特征表现出强烈的兴趣——如以“对称”作为定义“美”的重要指标,亦或是列奥纳多·达·芬奇的《维特鲁威人》中对人体伸展的著名描绘。

Now scientists have gone a step further. Alberto Roselló-Díez, a developmental biologist currently at the Australian Regenerative Medicine Institute at Monash University, led a study of how a mouse fetus maintains symmetry as it develops. By making one of the fetus’s limbs grow more slowly than the other, the team observed how cells communicate to ultimately correct the asymmetry. No study had successfully examined this phenomenon until now.

现在科学家们已经迈出了更远的一步。Alberto Roselló-Díez是一名发育生物学家,目前就职于莫纳什大学的澳大利亚再生医学研究所,他领导过一项关于小鼠胎儿如何在发育时维持对称的研究。通过使鼠胎的一侧肢体比另一侧生长得更慢,这个团队观察了细胞间如何交流,从而使不对称最终被矫正。之前还没有研究能成功地检验这一现象。

After a year of failed attempts, Roselló-Díez and his team created a model in mice. Borrowing a technique previously developed for modifying cells in a laboratory dish, the researchers injected into the mouse fetus’s left hind leg a type of cell that restricted the leg’s growth. They found that the cells surrounding the suppressed tissue communicated with the placenta, which then signaled the rest of the organism’s tissues—including the other hind leg—to slow their growth until the hindered limb caught up. Then, uniform growth resumed. The findings were published in June in PLOS Biology.

经历了一年的失败尝试后,Roselló-Díez和他的团队在小鼠上创造了一种模型。借助一种早先针对于改造培养皿里的细胞的技术,研究人员向鼠胎的左后腿注入了一种可以抑制腿部生长的细胞。他们发现这些细胞会围绕着受抑制的组织进行交流,然后向此生物体的其余组织发出信号——包括另一侧后腿——从而减缓它们的生长直到发育受阻的肢体追上进度。随后,均匀的生长会重新开始。这些发现发表在6月的PLOS Biology上。

Think of this process as a “three-legged race,” says Kim Cooper, a cell and developmental biologist at the University of California, San Diego, who was not involved in the study. “If one person is going faster, it’s harder to stay in sync. This placenta mechanism makes it possible for the slower one to catch up,” Cooper says.

把这个过程想象成一次“双人三腿赛跑”, Kim Cooper说。他是加州大学圣迭戈分校的一名细胞和发育生物学家,并未参与此次研究。“如果一个人前进得太快,要想保持平衡就很难。胎盘的这一机制则让更慢的那个人有机会迎头赶上。

The study offers insight into limb development and so-called catch-up growth. But the research also raises new questions: for example, once the limb has reached the same level of growth, how does the other limb know to start growing again? “We kind of expect symmetry in our limbs,” says Adrian Halme, a cell biologist at the University of Virginia, who was also not involved with the study. “But how they achieve that symmetry is really striking.”

这项研究洞悉了肢体的发育以及所谓的“追赶生长”。但也引申出新的问题:例如,一旦某一肢体达到了相同的生长水平,其余的肢体是如何得知信息从而重新开始生长的?“我们都指望自己的四肢是对称的,Adrian Halme说。他是弗吉尼亚大学的一名细胞生物学家,也未参与此次研究。“但它们究竟如何实现那种对称性才是真正引人关注的。”

This article was originally published with the title "Body Balance"

这篇文章起初以“身体的平衡”为标题发表

ABOUT THE AUTHOR(S)

Maya Miller

Maya Miller is an editorial intern for Scientific American.

关于作者

Maya Miler

Maya Miller是《科学美国人》的实习编辑

原文链接:https://www.scientificamerican.com/article/how-mammals-maintain-symmetry-during-development/

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