Neuronal migration in the developing cerebellar system

Abstract The cerebellum or “little brain” plays critical roles in motor control and more recently in several types of motor learning. With a near-crystalline array of neuronal laminae and stereotyped projections to and from functionally linked nuclear structures in the brainstem, the cerebellum has served as a powerful model for neuronal cell migrations in the developing central nervous system. This chapter will discuss the birthplaces and migration paths of the many neuronal cell types that compose the cerebellar system, including the cerebellar cortex and connected nuclei. Moreover, significant attention will be given to the molecular and cellular mechanisms governing cerebellar granule neuron migration, whose vast numbers and well-defined genetic tools make this cell type perhaps the best-characterized neuronal migration model in the entire brain. Finally, the chapter will present medulloblastoma as a model for perturbed cerebellar migration and germinal zone exit.