Department of Neurobiology, Stanford University, School of Medicine, Stanford, CA 94305, USA.
Curr Opin Neurobiol. 2012 Jun;22(3):438-45. doi: 10.1016/j.conb.2011.10.003. Epub 2011 Oct 27.
Excessive synapses generated during early development are eliminated extensively to form functionally mature neural circuits. Synapses in juvenile and mature brains are highly dynamic, and undergo remodeling processes through constant formation and elimination of dendritic spines. Although neural activity has been implicated in initiating the synapse elimination process cell-autonomously, the cellular and molecular mechanisms that transduce changes in correlated neural activity into structural changes in synapses are largely unknown. Recently, however, new findings provide evidence that in different species, glial cells, non-neuronal cell types in the nervous system are crucial in eliminating neural debris and unwanted synapses through phagocytosis. Glial cells not only clear fragmented axons and synaptic debris produced during synapse elimination, but also engulf unwanted synapses thereby actively promoting synapse elimination non-cell autonomously. These new findings support the important role of glial cells in the formation and maintenance of functional neural circuits in development as well as in adult stages and neurodegenerative diseases.
在早期发育过程中产生的过多的突触会被大量消除，从而形成功能成熟的神经回路。幼年和成年大脑中的突触具有高度的动态性，通过树突棘的不断形成和消除来进行重塑过程。尽管神经活动已经被牵连到自主启动突触消除过程中，但将相关神经活动的变化转化为突触结构变化的细胞和分子机制在很大程度上仍是未知的。然而，最近的新发现提供了证据，表明在不同物种中，神经胶质细胞——神经系统中的非神经元细胞类型，通过吞噬作用来清除神经碎片和不需要的突触。神经胶质细胞不仅清除突触消除过程中产生的碎片化轴突和突触碎片，还吞噬不需要的突触，从而非自主地积极促进突触消除。这些新发现支持了神经胶质细胞在发育以及成年阶段和神经退行性疾病中形成和维持功能性神经回路中的重要作用。
