rs10732516 polymorphism at the IGF2/H19 locus associates with a genotype-specific trend in placental DNA methylation and head circumference of prenatally alcohol-exposed newborns

Abstract

Study Question Does prenatal alcohol exposure (PAE) affect regulation of the insulin-like growth factor 2 (IGF2)/H19 locus in placenta and the growth-restricted phenotype of newborns? Summary Answer PAE results in genotype-specific trends in both placental DNA methylation at the IGF2/H19 locus and head circumference (HC) of newborns. What is Known Already PAE can disturb development of the nervous system and lead to restricted growth of the head, even microcephaly. To clarify the etiology of alcohol-induced growth restriction, we focused on the imprinted IGF2/H19 locus known to be important for normal placental and embryonic growth. The expression of IGF2 and a negative growth controller H19 are regulated by the H19 imprinting control region ( H19 ICR) with seven-binding sites for the methylation-sensitive zinc-finger regulatory protein CTCF. A single nucleotide polymorphism rs10732516 G/A in the sixth-binding site has shown to associate with genotype-specific DNA methylation profiles at the H19 ICR. Study Design, Size, Duration By grouping 39 alcohol-exposed and 100 control samples according to rs10732516 polymorphism we explored alcohol-induced, genotype-specific changes in DNA methylation at the H19 ICR and the promoter region of H19 ( H19 differentially methylated region). Also, IGF2 and H19 mRNA expression level in placenta as well as the phenotypes of newborns were examined. Participants/Materials, Setting, Methods We explored alcohol-induced, genotype-specific changes in placental DNA methylation by MassARRAY EpiTYPER and allele-specific changes by bisulphite sequencing. IGF2 and H19 expression in placenta were analyzed by quantitative PCR and the HC, birthweight and birth length of newborns were examined using national growth charts. Main Results and the Role of Chance We observed a consistent trend in genotype-specific changes in DNA methylation at H19 ICR in alcohol-exposed placentas. DNA methylation level in the normally highly methylated paternal allele of rs10732516 paternal A/maternal G genotype was decreased in alcohol-exposed placentas. In addition to decreased IGF2 mRNA expression in alcohol-exposed placentas of this specific genotype ( P = 0.03), we observed significantly increased expression of H19 in relation to IGF2 when comparing all alcohol-exposed placentas to unexposed controls ( ...

Alcohol‐Related Alterations in Placental Imprinted Gene Expression in Humans Mediate Effects of Prenatal Alcohol Exposure on Postnatal Growth

“…Of note, our finding that alcohol exposure was associated with increased IGF2 expression in this sample is consistent with previous reports of alcohol-related increases in expression in human placenta trophoblast cultures (Joya et al, 2015), rat placental tissue (G ardebjer et al, 2014), hippocampus (Tunc-Ozcan et al, 2016), and human whole blood through age 5 years (Aros et al, 2011). Two studies have shown decreased placental IGF2 expression (1 human [Marjonen et al, 2017], 1 mouse [Downing et al, 2011]). For 5 imprinted genes (ZIM2, PEG10, IFG2AS, NNAT, and IGF2), alcohol-related alterations in placental expression statistically mediated the effects of prenatal alcohol exposure on length, suggesting that alcohol-related expression changes in these genes (i) serve as a marker for physiologic processes that lead to postnatal growth restriction, (ii) set off a cascade of downstream events that contribute to postnatal growth restriction, and/or (iii) represent expression changes that persist postnatally and contribute to postnatal growth restriction.…”

“…(1 human [Marjonen et al, 2017] and 1 mouse [Downing et al, 2011]) LGA, large-for-gestational age; FASD, fetal alcohol spectrum disorders; IUGR, intrauterine growth restricting; DMR, differentially methylated region; ICR, imprinting control region.…”

Early prenatal alcohol exposure alters imprinted gene expression in placenta and embryo in a mouse model

“…In previous studies, it has been shown that hypermethylation at H19 ICR in Beckwith-Wiedemann syndrome with fetal over-growth leads to overexpression of IGF2 and downregulation of H19 , and conversely, hypomethylation of H19 ICR in Silver-Russell syndrome with growth restriction leads to downregulation of IGF2 and biallelic expression of H19 [ 34 , 35 ]. In addition, in our previous human study, we observed significantly increased expression of H19 in relation to IGF2 when comparing all alcohol-exposed placentas to unexposed controls [ 5 ]. Therefore, we decided to explore if prenatal alcohol exposure has affected the DNA methylation level of the locus and consequently the regulation of Igf2 and H19 .…”

“…The molecular mechanisms of PAE have been under extensive research, and the epigenetic variation induced in utero is a strong candidate mediator [ 3 – 5 ]. Previously, we have developed a mouse model of early PAE, based on maternal ad libitum ingestion of 10% (v/v) alcohol and took advantage of a mouse strain C57BL/6, which has a strong drinking preference for 10% alcohol [ 6 , 7 ].…”

“…Furthermore, in our previous study we observed genotype-specific decreased DNA methylation level at the H19 ICR in the IGF2/H19 locus in placentas of PAE newborns. A single nucleotide polymorphism rs10732516 in the sixth binding site for CTCF protein associated with the alcohol-induced alterations in DNA methylation profiles and head circumference in a parent-of-origin manner [ 5 ].…”