Nogo-A: Multiple Roles in CNS Development, Maintenance, and Disease.

Initially discovered as a potent neurite outgrowth inhibitor in the central nervous system (CNS), Nogo-A has emerged as a multifunctional protein. Involvement of this protein has been demonstrated in numerous developmental processes, ranging from cell migration, axon guidance and fasciculation, dendritic branching and CNS plasticity to oligodendrocyte differentiation and myelination. Although initially necessary and beneficial for shaping and later maintaining CNS structure and functionality, the growth restricting properties of Nogo-A can have negative effects on nervous system injury or disease. Hence, correlating with its various neurobiological roles, Nogo-A was implicated in a range of CNS disturbances, including trauma such as spinal cord injury or stroke, neurodegenerative diseases such as Alzheimer's disease, amyotrophic lateral sclerosis or multiple sclerosis, or in schizophrenia. In this review, we summarize the current state of knowledge for Nogo-A's involvement in these nervous system diseases and perturbations and discuss the possible underlying mechanisms. Furthermore, we provide a comprehensive overview on molecular signaling pathways as well as structural properties identified for Nogo-A and point to open questions in the field.