Increased 5-Methylcytosine and Decreased 5-Hydroxymethylcytosine Levels are Associated with Reduced Striatal A2AR Levels in Huntington’s Disease
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Adenosine A2A receptor (A2AR) is a G-protein-coupled receptor highly expressed in basal ganglia. Its expression levels are severely reduced in Huntington’s disease (HD), and several pharmacological therapies have shown its implication in this neurodegenerative disorder. The main goal of this study was to gain insight into the molecular mechanisms that regulate A2AR gene (ADORA2A) expression in HD. Based on previous data reported by our group, we measured the methylcytosine (5mC) and hydroxymethylcytosine (5hmC) content in the 5′UTR region of ADORA2A in the putamen of HD patients and in the striatum of R6/1 and R6/2 mice at late stages of the disease. In this genomic region, 5mC and 5hmC remained unchanged in both mice strains, although low striatal A2AR levels were associated with reduced 5mC levels in 30-week-old R6/1 mice and reduced 5hmC levels in 12-week-old R6/2 mice in exon m2. In order to analyze when this mechanism appears during the progression of the disease, a time course for A2AR protein levels was carried out in R6/1 mice striatum (8, 12, and 20 weeks of age). A2AR levels were reduced from 12 weeks of age onwards, and this downregulation was concomitant with reduced 5hmC levels in the 5′UTR region of ADORA2A. Interestingly, increased 5mC levels and reduced 5hmC were found in the 5′UTR region of ADORA2A in the putamen of HD patients with respect to age-matched controls. Therefore, an altered DNA methylation pattern in ADORA2A seems to play a role in the pathologically decreased A2AR expression levels found in HD.
KeywordsAdenosine A2A receptor ADORA2A 5-Methylcytosine 5-Hydroxymethylcytosine Huntington’s disease
We are grateful to Dr. Ellen Gelpí for providing HD cases (Neurological Tissue Bank, University of Barcelona—Hospital Clínic de Barcelona) and to Dr. Laura de Jorge (Molecular Genetic Diagnosis Center, IDIBELL) for technical advice in CAG repeat determination. We thank T. Yohannan for editorial assistance. This work was supported by the Ministerio de Ciencia e Innovación, Instituto de Salud Carlos III [CP08/00095 to M.B., PI10/01072 to E.P.N.]; and La Fundació La Marató de TV3 [090330 to M.B., 092331 to M.M.]. I.V.M. is the recipient of an IDIBELL predoctoral fellowship and S.T. is a fellow of the Generalitat de Catalunya (AGAUR ST06914).
Conflict of Interest
The authors declare no competing financial interests.
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