title: Correlation of DNA methylation levels in blood and saliva DNA in young girls of the LEGACY Girls study.
abstract: Many epidemiologic studies of environmental exposures and disease susceptibility measure DNA methylation in white blood cells (WBC). Some studies are also starting to use saliva DNA as it is usually more readily available in large epidemiologic studies. However, little is known about the correlation of methylation between WBC and saliva DNA. We examined DNA methylation in three repetitive elements, Sat2, Alu, and LINE-1, and in four CpG sites, including AHRR (cg23576855, cg05575921), cg05951221 at 2q37.1, and cg11924019 at CYP1A1, in 57 girls aged 6-15 years with blood and saliva collected on the same day. We measured all DNA methylation markers by bisulfite-pyrosequencing, except for Sat2 and Alu, which were measured by the MethyLight assay. Methylation levels measured in saliva DNA were lower than those in WBC DNA, with differences ranging from 2.8% for Alu to 14.1% for cg05575921. Methylation levels for the three repetitive elements measured in saliva DNA were all positively correlated with those in WBC DNA. However, there was a wide range in the Spearman correlations, with the smallest correlation found for Alu (0.24) and the strongest correlation found for LINE-1 (0.73). Spearman correlations for cg05575921, cg05951221, and cg11924019 were 0.33, 0.42, and 0.79, respectively. If these findings are replicated in larger studies, they suggest that, for selected methylation markers (e.g., LINE-1), methylation levels may be highly correlated between blood and saliva, while for others methylation markers, the levels may be more tissue specific. Thus, in studies that differ by DNA source, each interrogated site should be separately examined in order to evaluate the correlation in DNA methylation levels across DNA sources.
authors.affiliation: Department of Epidemiology; Mailman School of Public Health of Columbia University; New York, NY USA; Department of Environmental Health Sciences; Mailman School of Public Health of Columbia University; New York, NY USA.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Wu
authors.affiliation: Department of Environmental Health Sciences; Mailman School of Public Health of Columbia University; New York, NY USA.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Departments of Pediatrics and Medicine; Columbia University Medical Center; New York, NY USA.
authors.forename: Wendy K
authors.initials: WK
authors.lastname: Chung
authors.affiliation: Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital; Toronto, ON Canada; Departments of Molecular Genetics and Laboratory Medicine and Pathobiology; University of Toronto; Toronto, ON Canada.
authors.forename: Irene L
authors.initials: IL
authors.lastname: Andrulis
authors.affiliation: Department of Clinical Genetics; Fox Chase Cancer Center; Fremont, CA USA.
authors.forename: Mary B
authors.initials: MB
authors.lastname: Daly
authors.affiliation: Cancer Prevention Institute of California; Fremont, CA USA; Division of Epidemiology; Department of Health Research & Policy; Stanford Cancer Institute, Stanford University School of Medicine; Stanford, CA USA.
authors.forename: Esther M
authors.initials: EM
authors.lastname: John
authors.affiliation: Cancer Prevention Institute of California; Fremont, CA USA; Division of Epidemiology; Department of Health Research & Policy; Stanford Cancer Institute, Stanford University School of Medicine; Stanford, CA USA.
authors.forename: Theresa H M
authors.initials: TH
authors.lastname: Keegan
authors.affiliation: Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital; Toronto, ON Canada; Dalla Lana School of Public Health; University of Toronto, TO Canada.
authors.forename: Julia
authors.initials: J
authors.lastname: Knight
authors.affiliation: Department of Medicine and Hematology/Oncology; Perelman School of Medicine; University of Pennsylvania; Philadelphia, PA USA; Department of Medical Ethics and Health Policy; Perelman School of Medicine; University of Pennsylvania; Philadelphia, PA USA.
authors.forename: Angela R
authors.initials: AR
authors.lastname: Bradbury
authors.affiliation: Department of Environmental Health Sciences; Mailman School of Public Health of Columbia University; New York, NY USA.
authors.forename: Maya A
authors.initials: MA
authors.lastname: Kappil
authors.affiliation: Department of Environmental Health Sciences; Mailman School of Public Health of Columbia University; New York, NY USA.
authors.forename: Irina
authors.initials: I
authors.lastname: Gurvich
authors.affiliation: Herbert Irving Comprehensive Cancer Center; Columbia University Medical Center; New York, NY USA; Department of Environmental Health Sciences; Mailman School of Public Health of Columbia University; New York, NY USA.
authors.forename: Regina M
authors.initials: RM
authors.lastname: Santella
authors.affiliation: Department of Epidemiology; Mailman School of Public Health of Columbia University; New York, NY USA; Herbert Irving Comprehensive Cancer Center; Columbia University Medical Center; New York, NY USA; Imprints Center; Columbia University Medical Center; New York, NY USA.
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Terry
mesh_terms: D000293:Adolescent; D002648:Child; D018899:CpG Islands; D004247:DNA / Q000097:blood / Q000378:metabolism*; D019175:DNA Methylation; D005260:Female; D005819:Genetic Markers; D006801:Humans; D011446:Prospective Studies; D012091:Repetitive Sequences, Nucleic Acid; D012463:Saliva / Q000378:metabolism*; D013223:Statistics as Topic
chemical_list: D005819:Genetic Markers; D004247:DNA
keywords: DNA genomic methylation; LINE-1; buccal cells; pyrosequencing; saliva; white blood cells
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