A protein that helps build the actin cytoskeleton enables Schwann cells to fashion the myelin insulation that speeds nerve conduction, Novak et al. reveal.

In the peripheral nervous system, a Schwann cell wraps its membrane around individual axons again and again, eventually producing a myelin coating. Researchers think that myelination requires renovation of the actin cytoskeleton, but they haven't worked out the mechanism. One possible link between actin and myelination is the neural Wiskott-Aldrich syndrome protein (N-WASP). N-WASP spurs actin polymerization by turning on the Arp2/3 complex.

To test whether N-WASP promotes myelination, Novak et al. engineered mice whose Schwann cells lacked the protein. The animals showed signs of peripheral nerve damage, including poor coordination and balance. Novak et al. also found that nerve impulses traveled much slower than normal in the rodents.

When the researchers scrutinized the sciatic nerves from the mice, they observed that most axons had no myelin at all, whereas a few axons showed thin, short myelin segments. Thus, Schwann cells in the engineered animals could enclose the axons, but they couldn't produce myelin sheaths. That finding indicates that N-WASP allows a Schwann cell to coil its membrane around an axon. The researchers now want to decipher the signals that control N-WASP activity during this process.

et al
J. Cell Biol.