Prenatal alcohol exposure is one of the most significant causes of developmental disability in the Western world. Maternal alcohol consumption during pregnancy leads to an increased risk of neurological deficits and developmental abnormalities in the fetus. Over the past decade, several human and animal studies have demonstrated that alcohol causes alterations in epigenetic marks, including DNA methylation, histone modifications, and non-coding RNAs. There is an increasing amount of evidence that early pregnancy is a sensitive period for environmental-induced epigenetic changes. It is a dynamic period of epigenetic reprogramming, cell divisions, and DNA replication and, therefore, a particularly interesting period to study the molecular changes caused by alcohol exposure as well as the etiology of alcohol-induced developmental disorders. This article will review the current knowledge about the in vivo and in vitro effects of alcohol exposure on the epigenome, gene regulation, and the phenotype during the first weeks of pregnancy.

Background Prenatal alcohol exposure (PAE) affects embryonic development, causing a variable fetal alcohol spectrum disorder (FASD) phenotype with neuronal disorders and birth defects. We hypothesize that early alcohol-induced epigenetic changes disrupt the accurate developmental programming of embryo and consequently cause the complex phenotype of developmental disorders. To explore the etiology of FASD, we collected unique biological samples of 80 severely alcohol-exposed and 100 control newborns at birth. Methods We performed genome-wide DNA methylation (DNAm) and gene expression analyses of placentas by using microarrays (EPIC, Illumina) and mRNA sequencing, respectively. To test the manifestation of observed PAE-associated DNAm changes in embryonic tissues as well as potential biomarkers for PAE, we examined if the changes can be detected also in white blood cells or buccal epithelial cells of the same newborns by EpiTYPER. To explore the early effects of alcohol on extraembryonic placental tissue, we selected 27 newborns whose mothers had consumed alcohol up to gestational week 7 at maximum to the separate analyses. Furthermore, to explore the effects of early alcohol exposure on embryonic cells, human embryonic stem cells (hESCs) as well as hESCs during differentiation into endodermal, mesodermal, and ectodermal cells were exposed to alcohol in vitro. Results DPPA4, FOXP2, and TACR3 with significantly decreased DNAm were discovered—particularly the regulatory region of DPPA4 in the early alcohol-exposed placentas. When hESCs were exposed to alcohol in vitro, significantly altered regulation of DPPA2, a closely linked heterodimer of DPPA4, was observed. While the regulatory region of DPPA4 was unmethylated in both control and alcohol-exposed hESCs, alcohol-induced decreased DNAm similar to placenta was seen in in vitro differentiated mesodermal and ectodermal cells. Furthermore, common genes with alcohol-associated DNAm changes in placenta and hESCs were linked exclusively to the neurodevelopmental pathways in the enrichment analysis, which emphasizes the value of placental tissue when analyzing the effects of prenatal environment on human development. Conclusions Our study shows the effects of early alcohol exposure on human embryonic and extraembryonic cells, introduces candidate genes for alcohol-induced developmental disorders, and reveals potential biomarkers for prenatal alcohol exposure.

Alcohol affects embryonic development, causing a variable fetal alcohol spectrum disorder (FASD) phenotype with neuronal disorders and birth defects. To explore the etiology of FASD, we performed the first genome-wide DNA methylation and gene expression analyses of 80 severely alcohol-exposed and 68 control human placentas. DPPA4, FOXP2, and TACR3 with significantly decreased DNA methylation were discovered - particularly the regulatory region of DPPA4 in the early alcohol-exposed placentas. When human embryonic stem cells (hESCs) were exposed to alcohol in vitro, significantly altered regulation of DPPA2, a closely linked heterodimer of DPPA4, was observed. While the regulatory region of DPPA4 was unmethylated in both control and alcohol-exposed hESCs, alcohol-induced decreased DNA methylation similar to placenta was seen in in vitro differentiated mesodermal and ectodermal cells. Furthermore, common genes with alcohol-associated DNA methylation changes in placenta and hESCs were linked exclusively to the neurodevelopmental pathways, which emphasizes the value of placental tissue when analyzing the effects of prenatal environment on human development. Our study shows the effects of early alcohol exposure on human embryonic and extraembryonic cells, introduces candidate genes for alcohol-induced developmental disorders, and reveals potential biomarkers for prenatal alcohol exposure.