GAPDH and Parkinson disease: Normalization of lncRNA expression levels versus the geometric mean of NURR1-MAPT-GAPDH levels gave similar results, since all six lncRNAs -except GBAP1- were still dramatically and significantly under-expressed in the SN of PD patients (p < 0.05 for SNCA-AS1 and UCHL1-AS1; p < 0.01 for AK127687, PINK1-AS1, AX747125, and MAPT-AS1) (Supplementary Figure 3).