RMDN3 and Parkinson disease: To determine whether α-synuclein also disrupts the VAPB–PTPIP51 interaction in Parkinson’s disease patient material, we utilized proximity ligation assays to probe ER–mitochondria associations and the VAPB-PTPIP51 interaction in iPS cell-derived dopaminergic neurons from a SNCA triplication patient (α-synuclein triplication; AST) and a non-disease first degree relative control (normal α-synuclein; NAS) [21].