Myelination: all about Rac 'n' roll

During the development of the peripheral nervous system, Schwann cells select individual axons from a nerve bundle and establish a one-to-one relationship through a process termed "radial sorting". Recent findings identify the Rho family GTPase Rac1 as the downstream effector molecule responsible for process extension and lamellipodia formation in Schwann cells, allowing for proper radial sorting and myelination. These findings begin to shed light on our understanding of the distinct and yet essential molecular mechanisms involved in developmental processes preceding myelination.