GRN and early-onset autosomal dominant Alzheimer disease: With regard to the central nervous system, it is well established that PGRN is expressed in neurons and microglia [32] and plays important roles in lysosomal function, neuronal survival and function and neuroinflammation and as a therapeutic target in various neurological disorders including traumatic brain injury, Alzheimer’s disease, Parkinson’s disease and Huntington’s disease [33–35].