title: Methylation of the circadian Clock gene in the offspring of a free-living passerine bird increases with maternal and individual exposure to PM10.
abstract: The consequences of exposure to particulate matter (PM) have been thoroughly investigated in humans and other model species, but there is a dearth of studies of the effects of PM on physiology and life-history traits of non-human organisms living in natural or semi-natural environments. Besides toxicological relevance, PM has been recently suggested to exert epigenetic effects by altering DNA methylation patterns. Here, we investigated for the first time the association between the exposure to free-air PM10and DNA methylation at two loci ('poly-Q exon' and '5'-UTR') of the Clock gene in blood cells of the nestlings of a synanthropic passerine bird, the barn swallow (Hirundo rustica). The Clock gene is a phylogenetically highly conserved gene playing a major role in governing circadian rhythms and circannual life cycles of animals, implying that change in its level of methylation can impact on important fitness traits. We found that methylation at both loci significantly increased with PM10levels recorded few days before blood sampling, and also with PM10exposure experienced by the mother during or shortly before egg laying. This study is the first where methylation at a functionally important gene has been shown to vary according to the concentration of anthropogenic pollutants in any animal species in the wild. Since early-life environmental conditions produce epigenetic effects that can transgenerationally be transmitted, DNA methylation of genes controlling photoperiodic response can have far reaching consequences for the ecology and the evolution of wild animal populations.
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Romano
authors.affiliation: EPIGET - Epidemiology, Epigenetics and Toxicology Lab - Department of Clinical Sciences and Community Health, University of Milan, via San Barnaba 8, I-20122 Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: De Giorgio
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Parolini
authors.affiliation: EPIGET - Epidemiology, Epigenetics and Toxicology Lab - Department of Clinical Sciences and Community Health, University of Milan, via San Barnaba 8, I-20122 Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Favero
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Cristina Daniela
authors.initials: CD
authors.lastname: Possenti
authors.affiliation: EPIGET - Epidemiology, Epigenetics and Toxicology Lab - Department of Clinical Sciences and Community Health, University of Milan, via San Barnaba 8, I-20122 Milan, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Iodice
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Caprioli
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Rubolini
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano Bicocca, Piazza della Scienza, 1, I-20126 Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ambrosini
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy. Electronic address: luca.gianfranceschi@unimi.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Gianfranceschi
authors.affiliation: Department of Biosciences, University of Milan, via Celoria 26, I-20133 Milan, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Saino
authors.affiliation: EPIGET - Epidemiology, Epigenetics and Toxicology Lab - Department of Clinical Sciences and Community Health, University of Milan, via San Barnaba 8, I-20122 Milan, Italy. Electronic address: valentina.bollati@unimi.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Bollati
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D000818:Animals; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000187:drug effects; D019175:DNA Methylation; D005260:Female; D006801:Humans; D008297:Male; D018811:Maternal Exposure; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D046388:Swallows / Q000502:physiology*; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Air pollution; Barn swallow; Clock gene; DNA methylation; Epigenetics