Other studies have shown that α-synuclein oligomers, a neurotoxic form of α-synuclein found in PD, induce striatal TGF-β1 secretion by reactive astrocytes in order to protect them from neurotoxicity, further evidence of an interaction between TGF-β/Smad3 and α-synuclein dysfunction [118]. This evidence concerns the gene SMAD3 and Parkinson disease.