NRG1 and Alzheimer disease: A NRG1 single nucleotide polymorphism, rs392499 (glycine to alanine), in the second exon of the NRG1 gene was found in 65 AD families.45 In addition, a recent paper reported that eight single nucleotide polymorphisms in the NRG3 gene were significantly associated with the risk of AD.46 These studies provide evidence that NRG may be responsible for the cellular alterations that produce the clinical phenotype of AD.