PRKN and Parkinson disease: A study that performed sequence analysis for 12 PD genes (including SNCA, PARKIN, and TET) related to DNA methylation and hydroxymethylation in 1,657 patients and 1,394 controls identified TET1 as a major gene in PD, further suggesting that hydroxymethylation might play an important role in PD (Shu et al., 2019).