A tale of two nervous systems: Mechanisms regulating glial migration across nervous system boundaries

A functional nervous system consists of two halves: the central nervous system (CNS) and peripheral nervous system (PNS). Although these two halves are, for the most part, anatomically separate, their communication relies on specialized connections called transition zones (TZ) which form early in development. At these transition zones, axons cross in or out of the spinal cord, connecting CNS and PNS. Some glial cells migrate through TZs as part of normal nervous system development, while many others are restricted from migrating through, although they can send processes into the TZ and interact with glia on the other side. The mechanisms regulating TZ formation and migration of cells across TZ boundaries are not understood, although interactions between CNS and PNS cells are thought to play a major role. My research has discovered novel mechanisms regulating cell migration across TZs, focusing particularly on one type of glia, oligodendrocyte progenitor cells (OPCs). I have characterized a newly discovered cell type, motor exit point (MEP) glia, which are essential for preventing OPCs from migrating into the PNS. I have also discovered that neuronal modulation via adenosine signaling is an additional mechanism involved in regulating OPC migration. This work demonstrates the importance and specificity of cellular interactions in regulating cell migration and nervous system patterning.