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

Study Question: Does prenatal alcohol exposure (PAE) affect regulation of the 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 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 locus known to be important for normal placental and embryonic growth. The expression of and a negative growth controller are regulated by the imprinting control region ( 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 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 ICR and the promoter region of ( differentially methylated region). Also, and 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. and 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 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 mRNA expression in alcohol-exposed placentas of this specific genotype ( = 0.03), we observed significantly increased expression of in relation to when comparing all alcohol-exposed placentas to unexposed controls ( = 0.006). Furthermore, phenotypic examination showed a significant genotype-specific association between the alcohol exposure and HC of newborns ( = 0.001).

Limitations Reasons For Caution: Owing to the exceptional character of the alcohol-exposed human samples collected in this study, the sample size is restricted. An increased sample size and functional studies are needed to confirm these data and clarify the biological significance or causality of the observed associations.

Wider Implications Of The Findings: Our results suggest that the rs10732516 polymorphism associates with the alcohol-induced alterations in DNA methylation profiles and head growth in a parent-of-origin manner. We also introduce a novel genotype-specific approach for exploring environmental effects on the locus and ultimately on embryonic growth.

Study Funding/competing Interests: This work was supported by the Academy of Finland (258304), The Finnish Foundation for Alcohol Studies, Finnish Cultural Foundation, Juho Vainio Foundation, Yrjö Jahnsson Foundation and Arvo and Lea Ylppö Foundation. No competing interests are declared.