1 Centre for Neuroregeneration, University of Edinburgh, Edinburgh, UK.
Neuroscientist. 2018 Feb;24(1):7-21. doi: 10.1177/1073858417703030. Epub 2017 Apr 11.
Approximately half of the human brain consists of myelinated axons. Central nervous system (CNS) myelin is made by oligodendrocytes and is essential for nervous system formation, health, and function. Once thought simply as a static insulator that facilitated rapid impulse conduction, myelin is now known to be made and remodeled in to adult life. Oligodendrocytes have a remarkable capacity to differentiate by default, but many aspects of their development can be influenced by axons. However, how axons and oligodendrocytes interact and cooperate to regulate myelination in the CNS remains unclear. Here, we review recent advances in our understanding of how such interactions generate the complexity of myelination known to exist in vivo. We highlight intriguing results that indicate that the cross-sectional size of an axon alone may regulate myelination to a surprising degree. We also review new studies, which have highlighted diversity in the myelination of axons of different neuronal subtypes and circuits, and structure-function relationships, which suggest that myelinated axons can be exquisitely fine-tuned to mediate precise conduction needs. We also discuss recent advances in our understanding of how neuronal activity regulates CNS myelination, and aim to provide an integrated overview of how axon-oligodendrocyte interactions sculpt neuronal circuit structure and function.
人类大脑大约有一半由髓鞘化的轴突组成。中枢神经系统（CNS）的髓鞘由少突胶质细胞形成，对神经系统的形成、健康和功能至关重要。髓鞘曾一度被认为只是一种促进快速冲动传导的静态绝缘体，但现在已知它在成年期也会被制造和重塑。少突胶质细胞具有默认分化的显著能力，但它们的许多发育方面都可以受到轴突的影响。然而，轴突和少突胶质细胞如何相互作用和合作来调节中枢神经系统中的髓鞘化仍然不清楚。在这里，我们回顾了我们对这些相互作用如何产生体内存在的髓鞘化复杂性的理解的最新进展。我们强调了一些有趣的结果，这些结果表明，轴突的横截面积本身可能在很大程度上调节髓鞘化。我们还回顾了新的研究，这些研究强调了不同神经元亚型和回路的轴突的髓鞘化的多样性，以及结构-功能关系，这些关系表明，髓鞘化的轴突可以被精细地调整，以介导精确的传导需求。我们还讨论了我们对神经元活动如何调节中枢神经系统髓鞘化的理解的最新进展，并旨在提供一个综合的概述，说明轴突-少突胶质细胞相互作用如何塑造神经元回路的结构和功能。
