Reduced cytoplasmic inclusion body formation and apoptotic cell death in the α-synuclein mutant S129A. Cells were transfected with empty vectors, vectors encoding the wild-type or the mutant α-synuclein S129A. They were treated with 20 μM retinoic acid for 7 days followed by incubation in 20 nM okadaic acid for 24 h (A, B, C). The mutant S129A demonstrated significantly decreased cytoplasmic inclusion body formation compared with the cells transfected with the wild-type α-synuclein.