ADORA2A and Huntington disease: In the putamen of HD patients and the striatum of R6/1 and R6/2 mice, 5-methylcytidine-5′-monophosphate and 5-hydroxymethylcytosine contents were detected in the 5′ untranslated region (5′UTR) region of the adenosine receptor gene-A2A (ADORA2A).