POLG and Parkinson disease: Recently two genome-wide association studies (GWAS) performed in a North American, UK [24] and German material of Caucasian origin with sporadic PD and North American material of Caucasian origin with familial PD [25], screened for a missense polymorphism rs3087374 (Q1236H) in POLG1, but no significant association with PD was found.