IGSF9B and Parkinson disease: The vulnerable, ventrally located DaN subtype—selectively depleted in PD samples—from the SNpc were most strongly enriched for the expression of PD risk genes identified by genome-wide association studies (GWAS), including SNCA, MAPT, GAK, WNT3, and IGSF9B [33, 35], suggesting that the presence of these genetic risk factors, and possibly their altered activity in these vulnerable neurons, comprises an inherent risk that influences their survival in PD.