APP and Parkinson disease: We focus on five genes—Parkin (PRKN), Leucine Rich Repeat And Ig Domain Containing 2 (LINGO2), Microtubule Associated Protein Tau (MAPT), alpha-Synuclein (SNCA), and Amyloid Beta Precursor Protein (APP)—which may be relevant to neurological diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), or related disorders such as essential tremor (ET).