ADRA2C and Alzheimer disease: Thirdly, PD and AD have been found to share multiple differentially expressed genes, including Adrenoceptor Alpha (ADRA2A, ADRA2C), Glutamate Ionotropic Receptor (GRIN3A, GRIN2B, GRIN2C, GRIN2D), and Monoamine Oxidase A (MAOA) [51].