VCP and Parkinson disease: For instance, mutations in the E3 ubiquitin ligase gene parkin are linked to familial forms of PD,16–18 while mutations in VCP (valosin-containing protein, also known as p97) are associated with inclusion-body myositis (IBM), characterized by protein aggregates in muscle and brain tissue.19,20 Many NDs are age-related and are thought to emerge from cumulative, stress-induced defects in cellular quality control systems.8,21