engleski

DNA methylation of serotonin receptor 2A gene promoter in control and autistic subjects

Serotonin (5-hydroxytryptamine, 5HT) is a monoamine neurotransmitter involved in a broad range of physiological functions. On the other hand, altered 5HT homeostasis, possibly due to the altered expression of 5HT-regulating genes, may serve as a neurobiological substrate of several neuropsychiatric disorders. Serotonin receptor 2A (5HT2Ar) has been indicated as one of the major candidates and potential markers of the 5HT disturbance seen in autism. Indeed, decreased platelet 5HT2A binding and reduced cortical 5HT2A density have been reported in autistic individuals. Regulation of the 5HT2A gene expression has been so far mainly attributed to the functional polymorphism -1438 A/G in the promoter region of the gene. However, it is possible that epigenetic changes, i.e. those involving modifications of DNA and histones including methylation of cytosine residues in the regulatory CpG islands, may also play an important role in the regulation of this gene. In this study, we analyzed DNA methylation pattern of the 5HT2A receptor gene promoter in white blood cell DNA samples of 92 autistic and 58 control subjects of Croatian origin. DNA methylation was analyzed by bisulfite conversion/sequencing method. We identified three putative DNA methylation sites located in the promoter region of the gene. The second methylation site is located just before the functional polymorphism -1438 A/G and the level of methylation at this locus directly corresponded to the subject’s genotype (6.1  6.3% for AA, 62.7  12.2% for AG, and 98.0  4.1% for GG genotype). Increased level of methylation in the presence of -1438 G allele may explain a molecular basis of the reported G allele-associated decrease in 5HT2A receptor expression. At all three identified methylation sites, the level of methylation (expressed as percentage of methylated DNA) was significantly higher in the autistic than in the control group (91% vs 86%, p<0.001 at locus 1 ; 71% vs. 62%, p<0.05 at locus 2 ; and 78% vs. 69%, p<0.001 at locus 3). Since higher degree of methylation is related to lower gene expression, this finding is in agreement with the reproted decrease in platelet and cortical 5HT2A levels in autistic individuals.

serotonin receptor 2A; autism; DNA methylation; polymorphism

rad je izrađen u sklopu bilateralnog hrvatsko-njemačkog projekta „Epigenetika serotoninske signalizacije: istraživanja metilacije gena za serotoninski prijenosnik, monoamin oksidazu B i serotoninski receptor 2A“, voditelja J. Štefulj i P. Zilla