Building glial microtubules

On page 661, Lee et al. show that oligodendrocytes (OLs) get their branchy shape from a microtubule-assembling protein called CNP. Loss of CNP in OLs leads to axonal degeneration in enveloped neurons.Axons depend on myelination by glial cells such as OLs for the transmission of action potentials. The myelin sheath contains a large amount of 2′3′-cyclic nucleotide 3′-phosphodiesterase (CNP), but what this protein was doing in OLs was not known. The new results reveal that CNP is a tubulin-binding protein that allows cells to extend long branched processes.

The authors find that CNP binds strongly to tubulin heterodimers. In vitro, CNP induces microtubule assembly and polymerizes along with the tubulin dimers. In cells, CNP rearranges both the microtubule and F-actin networks and induces the formation of processes, even in...