title: Methylomic analysis of salivary DNA in childhood ADHD identifies altered DNA methylation in VIPR2.
abstract: BACKGROUND
  Peripheral epigenetic marks hold promise for understanding psychiatric illness and may represent fingerprints of gene-environment interactions. We conducted an initial examination of CpG methylation variation in children with or without attention-deficit/hyperactivity disorder (ADHD).
  
  
  METHODS
  Children age 7-12 were recruited, screened, evaluated and assigned to ADHD or non-ADHD groups by defined research criteria. Two independent age-matched samples were examined, a discovery set (n = 92, all boys, half control, half ADHD) and a confirmation set (n = 20, half ADHD, all boys). 5-methylcytosine levels were quantified in salivary DNA using the Illumina 450 K HumanMethylation array. Genes for which multiple probes were nominally significant and had a beta difference of at least 2% were evaluated for biological relevance and prioritized for confirmation and sequence validation. Gene pathways were explored and described.
  
  
  RESULTS
  Two genes met the criteria for confirmation testing, VIPR2 and MYT1L; both had multiple probes meeting cutoffs and strong biological relevance. Probes on VIPR2 passed FDR correction in the confirmation set and were confirmed through bisulfite sequencing. Enrichment analysis suggested involvement of gene sets or pathways related to inflammatory processes and modulation of monoamine and cholinergic neurotransmission.
  
  
  CONCLUSIONS
  Although it is unknown to what extent CpG methylation seen in peripheral tissue reflect transcriptomic changes in the brain, these initial results indicate that peripheral DNA methylation markers in ADHD may be promising and suggest targeted hypotheses for future study in larger samples.
authors: Division of Psychology, Oregon Health & Science University, Portland, OR, USA.
authors: Beth
authors: B
authors: Wilmot
authors: Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA.
authors: Rebecca
authors: R
authors: Fry
authors: Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA.
authors: Lisa
authors: L
authors: Smeester
authors: Department of Psychology, Florida International University, Miami, FL, USA.
authors: Erica D
authors: ED
authors: Musser
authors: University of Exeter Medical School, Exeter University, Exeter, UK.|Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.
authors: Jonathan
authors: J
authors: Mill
authors: Division of Psychology, Oregon Health & Science University, Portland, OR, USA.
authors: Joel T
authors: JT
authors: Nigg
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002648:Child; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D006801:Humans; D008297:Male; D009419:Nerve Tissue Proteins; D010865:Pilot Projects; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000235:genetics*; D012463:Saliva / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D015415:Biomarkers; C561020:MYT1L protein, human; D009419:Nerve Tissue Proteins; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D014157:Transcription Factors; C495509:VIPR2 protein, human
keywords: ADHD; epigenetic; methylation