GUCY1A1 and Parkinson disease: Beyond the potential common risk gene LRRK2, a genome-wide association study (GWAS) identified an overlap of seven genes presenting a risk for PD with CD (MROH3P, HLA, CCNY, LRRK2, APT, SYMPK and RSPH6A) and four with UC (GUCY1A3, HLA, BTNL2 and TRIM10, Witoelar et al., 2017).