VPS35 and Parkinson disease: To further evaluate the impact of mutant VPS35 on PD‐related pathology (Spillantini et al., 1997), the expression of α‐syn was determined by immunohistochemistry and dramatically increased immunoreactivity of somatic α‐syn was found in SNpc of 15‐ to 16‐month‐old VPS35D620N/D620N mice compared with age‐matched WT controls (unpaired t test, p = 0.01) (Figure 3a,b).