title: Inter-individual methylation variability in differentially methylated regions between maternal whole blood and first trimester CVS.
abstract: BACKGROUND
  DNA methylation is the most studied form of epigenetic regulation, a process by which chromatin composition and transcription factor binding is altered to influence tissue specific gene expression and differentiation. Such tissue specific methylation patterns are investigated as biomarkers for cancer and cell-free fetal DNA using various methodologies.
  
  
  RESULTS
  We have utilized methylation DNA immunoprecipitation (MeDIP) and real-time quantitative PCR to investigate the inter-individual methylation variability of differentially methylated regions (DMRs) on chromosomes 18 and 21. We have characterized 15 newly selected and seven previously validated DMRs in 50, 1(st) trimester Chorionic villus samplings (CVS) and 50 female non-pregnant peripheral blood (WBF) samples. qPCR results from MeDIP and genomic DNA (Input) assays were used to calculate fold enrichment values for each DMR. For all regions tested, enrichment was higher in CVS than in WBF samples with mean enrichments ranging from 0.22 to 6.4 and 0.017 to 1 respectively. Despite inter-individual variability, mean enrichment values for CVS were significantly different than those for WBF in all DMRs tested (p < 0.01). This observation is reinforced by the absence of overlap in CVS and WBF enrichment value distributions for 15 of 22 DMRs.
  
  
  CONCLUSIONS
  Our work provides an expansion in the biomarker panel available for non-invasive prenatal diagnosis (NIPD) using the MeDIP-qPCR methology for Down syndrome and can eventually provide the starting point towards the development for assays towards the detection of Edwards syndrome. Furthermore, our data indicate that inter-experimental and inter-individual variation in methylation is apparent, yet the difference in methylation status across tissues is large enough to allow for robust tissue specific methylation identification.
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus ; Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus.
authors.forename: Marios
authors.initials: M
authors.lastname: Ioannides
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus ; NIPD Genetics Ltd, Nicosia, Cyprus.
authors.forename: Elisavet A
authors.initials: EA
authors.lastname: Papageorgiou
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
authors.forename: Anna
authors.initials: A
authors.lastname: Keravnou
authors.affiliation: NIPD Genetics Ltd, Nicosia, Cyprus.
authors.forename: Evdokia
authors.initials: E
authors.lastname: Tsaliki
authors.affiliation: NIPD Genetics Ltd, Nicosia, Cyprus.
authors.forename: Christiana
authors.initials: C
authors.lastname: Spyrou
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
authors.forename: Michael
authors.initials: M
authors.lastname: Hadjidaniel
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
authors.forename: Carolina
authors.initials: C
authors.lastname: Sismani
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus ; NIPD Genetics Ltd, Nicosia, Cyprus.
authors.forename: George
authors.initials: G
authors.lastname: Koumbaris
authors.affiliation: The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
authors.forename: Philippos C
authors.initials: PC
authors.lastname: Patsalis
keywords: Differentially methylated regions; Inter-individual variability; MeDIP; Non-invasive prenatal diagnosis