Ig superfamily adhesion molecules in the vertebrate nervous system: binding partners and signal transduction during axon growth

A large number of cell adhesion molecules (CAMs) of the immunoglobulin superfamily (IGSF) have been localized to the vertebrate nervous system, and the presence of unique combinations of domains in their molecular structures suggests distinct functions. The presence of many IGSF members on growing axons suggests a role for these molecules in axonal pathfinding and targeting. Nevertheless, the precise nature of that role is only now beginning to unfold. In this review, we will discuss the molecular structure, binding preference and potential signaling capabilities of IGSF CAMs expressed in the nervous system, with emphasis on studies of neurite outgrowth. In addition, the importance of naturally occurring mutations in one of these CAMs, L1, in human brain development will be described.