Transcript expression of both of these PD genes have been shown to be regulated by the epigenetic mark DNA methylation.220,232–234 PD risk factors, involving diet,235 inflammation236 and the microbiome237 are known to cause epigenetic changes,238,239 and may affect enteric neuron susceptibility to α-synuclein pathology. The gene discussed is SNCA; the disease is Parkinson disease.