B3GALT4 and Parkinson disease: Since ganglioside expression is cell type-specific [21], interpretation of potential gene expression changes such as these in SN homogenates from PD brain could be complicated due to loss of SN neurons, glial responses, and signals from white matter, the current study was performed to examine B3GALT4 and ST3GAL2 gene expression in neuromelanin-containing neurons in the SN of PD patients and non-PD controls using in situ hybridization histochemistry.