Glia in neurodegeneration: Drivers of disease or along for the ride?

While much of the research on neurodegenerative diseases has focused on neurons, non-neuronal cells are also affected. The extent to which glia and other non-neuronal cells are causally involved in disease pathogenesis versus more passively responding to disease is an area of active research. This is complicated by the fact that there is rarely one known cause of neurodegenerative diseases; rather, these disorders likely involve feedback loops that perpetuate dysfunction. Here, we will review genetic as well as experimental evidence that suggest that non-neuronal cells are at least partially driving disease pathogenesis in numerous neurodegenerative disorders, including Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis, Huntington's disease, multiple sclerosis, and Parkinson's disease.