title: Epigenetic modulation of the IGF2/H19 imprinted domain in human embryonic and extra-embryonic compartments and its possible role in fetal growth restriction.
abstract: Genomic imprinting, resulting in parent-of-origin-dependent gene expression, is mainly achieved by DNA methylation. IGF2 and H19, belonging to the same cluster of imprinted genes and regulated by ICR1, DMR2 and H19 promoter elements, play a major role in fetal/placental growth. Using quantitative approaches, we explored the epigenetic modulation of IGF2/H19 during human development in 60 normal and 66 idiopathic IUGR (Intrauterine Growth Restriction) pregnancies, studying embryonic (cord blood) and extraembryonic (placenta and umbilical cord) tissues. We found ICR1 normal methylation levels ( approximately 50%) and H19 promoter/DMR2 hypomethylation in extra-embryonic tissues. In contrast, in embryonic samples the three loci displayed normal methylation values comparable to those in postnatal blood. This feature is stably maintained throughout gestation and does not vary in IUGR cases. We reported asymmetric allelic expression of H19 and IGF2 as a common feature in pre- and post-natal tissues, independent of H19 promoter and DMR2 methylation levels. In addition, we excluded in IUGR post-transcriptional IGF2 interference possibly related to miRNA 483-3p (IGF2, intron 2) expression defects. Through LINE1 methylation analysis, we observed a methylation gradient with increasing methylation from pre- to post-natal life. The involvement of UPD (Uniparental Disomy) in IUGR aetiology was excluded. Our data indicate that: (1) ICR1 methylation status is a necessary and sufficient condition to drive the imprinting of IGF2 and H19 present in embryonic as well as in extra-embryonic tissues; (2) hypomethylation of H19 promoter and DMR2 does not influence the expression pattern of IGF2 and H19; (3) there is a gradient of global methylation, increasing from extra-embryonic to embryonic and adult tissues. Finally, because of placental hypomethylation, cautions should be exercised in diagnosis of imprinting diseases using chorionic villi.
authors.affiliation: Department of Medicine, Surgery and Dentistry, Unit of Medical Genetics, Università degli Studi di Milano, Milano, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Tabano
authors.forename: Patrizia
authors.initials: P
authors.lastname: Colapietro
authors.forename: Irene
authors.initials: I
authors.lastname: Cetin
authors.forename: Francesca R
authors.initials: FR
authors.lastname: Grati
authors.forename: Susanna
authors.initials: S
authors.lastname: Zanutto
authors.forename: Chiara
authors.initials: C
authors.lastname: Mandò
authors.forename: Patrizio
authors.initials: P
authors.lastname: Antonazzo
authors.forename: Paola
authors.initials: P
authors.lastname: Pileri
authors.forename: Franca
authors.initials: F
authors.lastname: Rossella
authors.forename: Lidia
authors.initials: L
authors.lastname: Larizza
authors.forename: Silvia M
authors.initials: SM
authors.lastname: Sirchia
authors.forename: Monica
authors.initials: M
authors.lastname: Miozzo
mesh_terms: D000328:Adult; D000483:Alleles; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D044127:Epigenesis, Genetic; D005321:Extraembryonic Membranes / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005317:Fetal Growth Retardation / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018392:Genomic Imprinting / Q000235:genetics*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D010920:Placenta / Q000378:metabolism / Q000473:pathology; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000235:genetics; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics* / Q000378:metabolism; D024182:Uniparental Disomy / Q000175:diagnosis / Q000235:genetics / Q000473:pathology
chemical_list: C094335:H19 long non-coding RNA; C035170:IGF2 protein, human; D035683:MicroRNAs; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II