GJB1 and multiple system atrophy: Although the reasons for the decrease in Cx32 levels within the primary regions affected by PD (substantia nigra) or MSA (putamen) remain relatively unknown, the discrepancy between the cellular and animal models compared to human PD may be explained by multiple factors, including the degree of α-syn pathology and/or the region associated with α-syn vulnerability, coupled to cell loss within affected brain regions [54, 64].