Ioannides Marios, Papageorgiou Elisavet A, Keravnou Anna, Tsaliki Evdokia, Spyrou Christiana, Hadjidaniel Michael, Sismani Carolina, Koumbaris George, Patsalis Philippos C
The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus ; Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus.
The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus ; NIPD Genetics Ltd, Nicosia, Cyprus.
Mol Cytogenet. 2014 Nov 1;7(1):73. doi: 10.1186/s13039-014-0073-8. eCollection 2014.
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.
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.
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.
DNA甲基化是研究最多的表观遗传调控形式，在这个过程中，染色质组成和转录因子结合发生改变，从而影响组织特异性基因表达和分化。人们使用各种方法研究这种组织特异性甲基化模式，将其作为癌症和游离胎儿DNA的生物标志物。
我们利用甲基化DNA免疫沉淀（MeDIP）和实时定量PCR研究了18号和21号染色体上差异甲基化区域（DMR）的个体间甲基化变异性。我们对50例孕早期绒毛取样（CVS）和50例非孕女性外周血（WBF）样本中的15个新选择的和7个先前验证的DMR进行了表征。来自MeDIP和基因组DNA（Input）检测的qPCR结果用于计算每个DMR的富集倍数。对于所有测试区域，CVS中的富集高于WBF样本，平均富集倍数分别为0.22至6.4和0.017至1。尽管存在个体间变异性，但在所有测试的DMR中，CVS的平均富集值与WBF的平均富集值显著不同（p < 0.01）。22个DMR中的15个在CVS和WBF富集值分布中没有重叠，这一观察结果得到了进一步证实。
我们的工作扩展了可用于使用MeDIP-qPCR方法进行唐氏综合征无创产前诊断（NIPD）的生物标志物面板，并最终可为开发检测爱德华兹综合征的检测方法提供起点。此外，我们的数据表明，甲基化的实验间和个体间变异是明显的，但不同组织间的甲基化状态差异足够大，足以实现可靠的组织特异性甲基化识别。
