We chose mutations in the vasopressin 2 receptor (V2R-Y128S) [56,57], MLC1-P92S and -S280L [58], and the human Ether-à-go-go-Related Gene (hERG-G601S) [55], which cause diabetes insipidus (V2R), megalencephalic leukoencephalopathy (MLC1), and long QT type 2 syndrome (hERG), respectively, due to conformational defects, misprocessing and accelerated PM turnover of the respective membrane proteins [55–60]. The gene discussed is MLC1; the disease is leukoencephalopathy, megalencephalic.