title: Comparison of methods for quantification of global DNA methylation in human cells and tissues.
abstract: DNA methylation is a key epigenetic modification which, in mammals, occurs mainly at CpG dinucleotides. Most of the CpG methylation in the genome is found in repetitive regions, rich in dormant transposons and endogenous retroviruses. Global DNA hypomethylation, which is a common feature of several conditions such as ageing and cancer, can cause the undesirable activation of dormant repeat elements and lead to altered expression of associated genes. DNA hypomethylation can cause genomic instability and may contribute to mutations and chromosomal recombinations. Various approaches for quantification of global DNA methylation are widely used. Several of these approaches measure a surrogate for total genomic methyl cytosine and there is uncertainty about the comparability of these methods. Here we have applied 3 different approaches (luminometric methylation assay, pyrosequencing of the methylation status of the Alu repeat element and of the LINE1 repeat element) for estimating global DNA methylation in the same human cell and tissue samples and have compared these estimates with the "gold standard" of methyl cytosine quantification by HPLC. Next to HPLC, the LINE1 approach shows the smallest variation between samples, followed by Alu. Pearson correlations and Bland-Altman analyses confirmed that global DNA methylation estimates obtained via the LINE1 approach corresponded best with HPLC-based measurements. Although, we did not find compelling evidence that the gold standard measurement by HPLC could be substituted with confidence by any of the surrogate assays for detecting global DNA methylation investigated here, the LINE1 assay seems likely to be an acceptable surrogate in many cases.
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom ; Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom.
authors.forename: Sofia
authors.initials: S
authors.lastname: Lisanti
authors.forename: Wan A W
authors.initials: WA
authors.lastname: Omar
authors.forename: Bartłomiej
authors.initials: B
authors.lastname: Tomaszewski
authors.forename: Sofie
authors.initials: S
authors.lastname: De Prins
authors.forename: Griet
authors.initials: G
authors.lastname: Jacobs
authors.forename: Gudrun
authors.initials: G
authors.lastname: Koppen
authors.forename: John C
authors.initials: JC
authors.lastname: Mathers
authors.forename: Sabine A S
authors.initials: SA
authors.lastname: Langie
mesh_terms: D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D018899:CpG Islands; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015894:Genome, Human; D006367:HeLa Cells; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008297:Male; D017422:Sequence Analysis, DNA / Q000379:methods*
chemical_list: D004273:DNA, Neoplasm