For example, PD patients also feature high titer serum IgM anti-GM1 antibodies (Zappia et al., 2002) and in the substantia nigra of some PD patients GM1 staining is diminished near α-synuclein aggregates and neurons with reduced levels of tyrosine hydroxylase (TH; Wu et al., 2012). Here, SNCA is linked to Parkinson disease.