NRG1 and early-onset autosomal dominant Alzheimer disease: Indeed, NRG1 has shown the essential role in controlling rapid impulse conduction in the central nervous system through determining the myelination of an individual axon [27], and the disorders in NRG1-ErbB signaling have been etiologically implicated in schizophrenia [28], Parkinson's disease [29], Alzheimer's disease [30], and Hirschsprung disease [31].