LRRK2 and Parkinson disease: Genetically, several genes or gene variants, including leucine-rich repeat kinase 2 (LRRK2), synuclein alpha (SNCA), glucosylceramidase beta-1 (GBA1), Parkin RBR E3 ubiquitin protein ligase (PARKIN), and PTEN-induced kinase 1 (PINK1), have been implicated in causing PD [33,34,35,36].