Livin' On The Edge: glia shape nervous system transition zones

The vertebrate nervous system is divided into two functional halves; the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which consists of nerves and ganglia. Incoming peripheral stimuli transmitted from the periphery to the CNS and subsequent motor responses created because of this information, require efficient communication between the two halves that make up this organ system. Neurons and glial cells of each half of the nervous system, which are the main actors in this communication, segregate across nervous system transition zones and never mix, allowing for efficient neurotransmission. Studies aimed at understanding the cellular and molecular mechanisms governing the development and maintenance of these transition zones have predominantly focused on mammalian models. However, zebrafish has emerged as a powerful model organism to study these structures and has allowed researchers to identify novel glial cells and mechanisms essential for nervous system assembly. This review will highlight recent advances into the important role that glial cells play in building and maintaining the nervous system and its boundaries.