LRRK2 and Parkinson disease: Clarification of the mechanisms of pathogenic proteins in various neurodegenerative diseases, including synucleinopathies and tauopathies (18), (19), as well as elucidation of the basic mechanisms underlying neurodegeneration, for example, excessive lysosomal stress in relation to the function of LRRK2 linked to familial PD (20), will greatly facilitate the development of therapeutic strategies against PD.