The emerging functions of oligodendrocytes in regulating neuronal network behaviour

Abstract

Myelin is required for efficient nerve conduction, but not all axons are myelinated to the same extent. Here we review recent studies that have revealed distinct myelination patterns of different axonal paths, suggesting that myelination is not an all or none phenomenon and that its presence is finely regulated in central nervous system networks. Whereas powerful reductionist biology has led to important knowledge of how oligodendrocytes function by themselves, little is known about their role in neuronal networks. We still do not understand how oligodendrocytes integrate information from neurons to adapt their function to the need of the system. An intricate cross talk between neurons and glia is likely to exist and to determine how neuronal circuits operate as a whole. Dissecting these mechanisms by using integrative systems biology approaches is one of the major challenges ahead.

Myelin plasticity in the central nervous system

“…Even small changes in conduction velocity could thus become important for action patterns to be selected to exert appropriate influence upon output control regions. A more in-depth discussion of this complex topic can be found in recent, excellent reviews (Pajevic et al 2014, de Hoz andSimons 2015).…”

Remodeling myelination: implications for mechanisms of neural plasticity

“…Such plastic regulation of myeli-nation has been appreciated recently (reviewed in refs. 69–72), but the mechanisms underlying this active regulation of myelination remain poorly understood.…”

“…In the adult CNS, oligodendrocyte precursor cells are broadly distributed and serve as a source of adult-born myelinating oligodendrocytes 69–72 . Early EM studies observed many unmyelinated axons 0.4–0.8 μm in diameter in the CNS 12 , and the recent study that reconstructed three-dimensional structure from large EM data sets even revealed long unmyelinated sections of otherwise myelinated axons in the adult cortex 26 .…”

Architecting the myelin landscape

“…This partial myelin coverage likely reflects the need to balance the advantages of myelination with overall energy [10] and space constraints, and likely contributes to the precise control of circuit timing [11], underscoring the importance of appropriate myelin localization. In the case of intermittent myelination along a single axon, unmyelinated gaps could provide space for new myelin formation to fine-tune myelination patterns as circuit activity changes in the adult.…”