CNTN1 and Parkinson disease: However, previous research has shown connections between these SNPs and three well-known PD-associated genes (INPP5F, GBA, SNCA) (Siddiqui et al., 2016; Berge-Seidl et al., 2017; Riboldi and Di Fonzo, 2019; Cao et al., 2020), and an additional gene (CNTN1).