ITSN1 encodes a multidomain scaffold protein that orchestrates protein-protein interactions during clathrin-mediated endocytosis and synaptic vesicle recycling.36 Notably, several other PD risk genes function in synaptic vesicle trafficking, including SNCA, LRRK2, DNAJC6, SYNJ1, VPS35, and SH3GL2. Here, LRRK2 is linked to Parkinson disease.