title: Seasonality modifies methylation profiles in healthy people.
abstract: DNA methylation is a well-characterized epigenetic modification that plays an important role in the regulation of gene expression. There is growing evidence on the involvement of epigenetic mechanisms in disease onset, including cancer. Environmental factors seem to induce changes in DNA methylation affecting human health. However, little is known about basal methylation levels in healthy people and about the correlation between environmental factors and different methylation profiles. We investigated the effect of seasonality on basal methylation by testing methylation levels in the long interspersed nucleotide element-1 (LINE-1) and in two cancer-related genes (RASSF1A and MGMT) of 88 healthy male heavy smokers involved in an Italian randomized study; at enrolment the subjects donated a blood sample collected in different months. Methylation analyses were performed by pyrosequencing. Mean methylation percentage was higher in spring and summer for the LINE1, RASSF1A and MGMT genes (68.26%, 2.35%, and 9.52% respectively) compared with autumn and winter (67.43%, 2.17%, and 8.60% respectively). In particular, LINE-1 was significantly hypomethylated (p = 0.04 or 0.05 depending on the CpG island involved) in autumn and winter compared with spring and summer. Seasonality seems to be a modifier of methylation levels and this observation should be taken into account in future analyses.
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy; Department of Mathematics, University of Turin, Turin, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Ricceri
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Morena
authors.initials: M
authors.lastname: Trevisan
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Fiano
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Grasso
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Fasanelli
authors.affiliation: IARC, Lyon, France.
authors.forename: Chiara
authors.initials: C
authors.lastname: Scoccianti
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: De Marco
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Anna Gillio
authors.initials: AG
authors.lastname: Tos
authors.affiliation: Human Genetics Foundation (HUGEF), Turin, Italy; Imperial College, London, United Kingdom.
authors.forename: Paolo
authors.initials: P
authors.lastname: Vineis
authors.affiliation: Unit of Cancer Epidemiology - CERMS, Department of Medical Sciences, University of Turin and Città della Salute e della Scienza Hospital, Turin, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Sacerdote
mesh_terms: D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D015254:DNA Modification Methylases / Q000235:genetics; D045643:DNA Repair Enzymes / Q000235:genetics; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D059647:Gene-Environment Interaction; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D008297:Male; D011401:Promoter Regions, Genetic; D012621:Seasons; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D045643:DNA Repair Enzymes