As such, the notion is of interest that human α-synuclein overexpression in mouse serotoninergic neurons triggers progressive accumulation, phosphorylation, and aggregation of hα-synuclein protein in the serotoninergic system, resulting in a depressive-like phenotype, thus nicely modeling depression and anxiety in PD, which often precede the onset of motor symptoms (Miquel-Rio et al. 2022; Przuntek et al. 2004). Here, SNCA is linked to Parkinson disease.