B3GALT4 and Parkinson disease: We previously described significantly decreased expression of gene B3GALT4 and ST3GAL2 in residual dopaminergic neurons in the PD substantia nigra (Schneider, 2018), consistent with an earlier finding of decreased expression of the main brain gangliosides (GM1, GD1a, GD1b, and GT1b) in PD substantia nigra (Seyfried et al., 2018).