SNCA and multiple system atrophy: Absence of inocula carryover in our cell culture model system was confirmed by the lack of α-synuclein immunostaining in astrocytes isolated from the Snca0/0 line exposed to 0.5% TgM83-passaged MSA or TgM83+/+ control littermate brain homogenates, or exposed to 10 μg/mL recombinant α-synuclein fibrils (Additional file 1: Figure S8C).