Within all cells a complex array of fiber-like protein assemblies form a scaffold for the support and organization of the cell and its components; this scaffold is referred to as the cytoskeleton. The cytoskeleton of cells of the brain is especially complex; each brain cell (neuron) is composed of two distinct regions, and each of these regions has unique components which are partitioned into that region alone. While significant progress has been made in recent years towards understanding the composition of the axonal cytoskeleton, factors governing its initial assembly, as well as the attainment of cytoskeletal stability, remain less well documented due to the inherent difficulties of studying these processes in the intact brain. To surmount these difficulties, a model system involving neurons in cell culture has been developed for manipulating the formative events in the brain that occur during development and maturation. These cells multiply continuously in culture and thus provide a virtually unlimited source for experimentation. Following defined chemical treatments, these cells cease multiplying and elaborate long axon-like processes that contain most if not all of the proteins comprising the axonal cytoskeleton of the brain. Exploitation of this model system by both established and newly- developed molecular biological, biochemical, immunological and electron microscopic analyses to examine the sequence of events accompanying the assembly of the axonal cytoskeleton will be investigated. The results obtained from these analyses will elucidate events critical for mediating axonal outgrowth, and stabilization, required for orderly development and maintenance of the nervous system.
