SIX3 and Parkinson disease: We next performed differential gene expression analysis between control and PD donor samples within the two largest subtypes, SIX3/FOXP2 and PAX5/POU6F2.We found that gene expression was largely preserved across these SNr subtypes between control and PD samples (Figure S5E) (Pearson correlation coefficient 0.98 for SIX3/FOXP2 and 0.99 for PAX5/POU6F2).