Functionally, LRRK2 is known to play a key role in several cellular processes, including endo-lysosomal vesicle trafficking [31–33], mitochondrial homeostasis [34], autophagy [35], neurite outgrowth [36, 37], cytoskeletal maintenance [38, 39], and immune system function [40], some of which are relevant to PD and will be discussed in later sections. This evidence concerns the gene LRRK2 and Parkinson disease.