Epigenomic analysis of Parkinson’s disease neurons identifies TET2 loss as neuroprotective [PD_TET2_Bisulfite_Padlock_Seq]

Epigenetic control of enhancers is centrally involved in modifying neuronal functions and may contribute to Parkinson's disease (PD) pathogenesis. Here, we comprehensively profile DNA methylation at enhancers genome-wide in neurons of 57 PD patients and 48 healthy individuals. There is a widespread increase in cytosine modifications at enhancers in PD neurons, which is partly due to elevated hydroxymethylation levels. Epigenetic dysregulation of enhancers in PD converge on transcriptional abnormalities affecting neuronal signaling and immune activation pathways. In particular, PD patients exhibit an epigenetic and transcriptional upregulation of TET2, a master-regulator of cytosine modification status. TET2 inactivation in a neuronal cell line enriches for cytosine modification changes that are reciprocal to those observed in PD neurons. Furthermore, Tet2 inactivation in mice fully prevents dopaminergic neuronal loss in the substantia nigra induced by prior inflammation. Tet2 loss in mice also attenuates transcriptional immune responses to an inflammatory trigger. Thus, widespread epigenetic dysregulation of enhancers in PD neurons may, in part, be mediated by increased TET2 expression. Decreased Tet2 activity is neuroprotective, in vivo, and may be a novel therapeutic target for PD. To identify epigenetically perturbations at the TET2 gene in PD, we performed a targeted bisulfite deep sequencing approach at the entire TET2 gene and surrounding genomic area (±300 kb) in isolated prefrontal cortex neuronal nuclei from PD patients and healthy control individuals (30 individuals: 20 PD, 10 controls).