The Evolutionary Origins of Glia
The Evolutionary Origins of Glia
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DOI：
10.1002/glia.21149
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发表时间：
2011-09-01
期刊：
影响因子：
6.2
通讯作者：
Hartline, Daniel K.
中科院分区：
文献类型：
--
作者：
Hartline, Daniel K.
神经胶质的进化起源随着时间的推移而消失，因为软组织很少留下化石足迹，而且我们还没有破译它们可能留下的任何分子足迹。然而，由于越来越多的人认识到神经胶质在神经系统的发育和功能中的重要性，我们可以从不同分类群（包括脊椎动物）之间的共性中吸取教训，这些共性来自共同的起源，或者来自共同的适应压力，揭示了神经胶质在所有神经系统中的作用。Acoelomorpha是一种原始的间质性扁形虫，具有非常简单的细胞组织，目前处于两侧对称发育的基础，具有胶质样细胞。如果它们真的代表了所有其他双体动物的祖先，那么所有的胶质细胞都有可能来自一个共同的祖先。然而，缺乏令人信服的神经胶质细胞的基础类群中发现的最主要的系统线：尾索动物，半索动物，苔藓虫，轮虫，和基础扁形动物。由于目前深层神经胶质细胞的研究还在不断变化中，同样可能的是，不同细胞系中的神经胶质细胞有不同的起源。如果发育模式是任何迹象，神经胶质细胞从外胚层细胞进化而来，可能来自一个移动的谱系，甚至可能独立地在身体的不同区域。至于是什么功能导致了神经胶质的进化，副产品的清除、结构支持、吞噬需求、发育编程和电路调节可能更有可能。解释可能的神经胶质损失的情况更加困难，因为一旦进化，神经胶质似乎会不断发明新的功能，即使在原始的生成需求变得过时之后，也会继续发挥价值。在所有关于神经胶质起源的不确定性中，有一件事是肯定的：我们对这些起源的想法将随着深层神经元发生的每一次重排以及无脊椎动物分子和发育领域的不断进步而改变。(C)2011 Wiley-Liss，Inc.
The evolutionary origins of glia are lost in time, as soft tissues rarely leave behind fossil footprints, and any molecular footprints they might have been left we have yet to decipher. Nevertheless, because of the growing realization of the importance glia plays in the development and functioning of the nervous system, lessons we can draw about commonalities among different taxa (including vertebrates) brought about either from a common origin, or from common adaptational pressures, shed light on the roles glia play in all nervous systems. The Acoelomorpha, primitive interstitial flatworms with very simple cellular organization and currently at the base of the bilaterian phylogeny, possess glia-like cells. If they indeed represent the ancestors of all other Bilateria, then it is possible that all glias derive from a common ancestor. However, basal taxa lacking convincing glia are found in most major phyletic lines: urochordates, hemichordates, bryozoans, rotifers, and basal platyhelminths. With deep phylogenies currently in flux, it is equally possible that glia in several lines had different origins. If developmental patterns are any indication, glia evolved from ectodermal cells, possibly from a mobile lineage, and even possibly independently in different regions of the body. As to what functions might have brought about the evolution of glia, by-product removal, structural support, phagocytic needs, developmental programming, and circuit modulation may be the more likely. Explaining possible cases of glial loss is more difficult, as once evolved, glia appears to keep inventing new functions, giving it continued value even after the original generative need becomes obsolete. Among all the uncertainties regarding the origin of glia, one thing is certain: that our ideas about those origins will change with every rearrangement in deep phylogeny and with continued advances in invertebrate molecular and developmental areas. (C) 2011 Wiley-Liss, Inc.