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Assessing Teratogenic Changes in a Zebrafish Model of Fetal Alcohol Exposure
Published on: March 20, 2012
Early prenatal alcohol exposure alters imprinted gene expression in placenta and embryo in a mouse model
Heidi Marjonen1, Mia Toivonen1, Laura Lahti2
1Department of Medical and Clinical Genetics, Medicum, University of Helsinki, Helsinki, Finland.
Insights
Early prenatal alcohol exposure (PAE) in mice did not alter DNA methylation but affected imprinted gene expression. This suggests PAE impacts embryonic and placental development through mechanisms other than DNA methylation changes.
Area of Science:
- Developmental Biology
- Epigenetics
- Toxicology
Background:
- Prenatal alcohol exposure (PAE) causes developmental harm and lifelong health issues.
- Growth restriction is a common phenotype in PAE offspring, linked to imprinted genes.
- Imprinted genes like Igf2, H19, Snrpn, and Peg3 regulate embryonic and placental growth.
Purpose of the Study:
- To investigate the molecular mechanisms of PAE using a mouse model.
- To assess the impact of early PAE on DNA methylation and imprinted gene expression.
- To analyze alterations in Igf2, H19, Snrpn, and Peg3 in developing embryos and placentas.
Main Methods:
- A mouse model with maternal ethanol ingestion during early gestation (GD 0.5-8.5).
- DNA methylation analysis at specific imprinted gene regions and Line-1 elements using MassARRAY EpiTYPER.
- Gene expression analysis of imprinted genes in E9.5 embryos and E9.5/E16.5 placentas via quantitative PCR.
Main Results:
- No significant alcohol-induced changes in DNA methylation levels were observed.
- Decreased Igf2 expression in alcohol-exposed E9.5 and E16.5 placentas.
- Increased H19 expression in E9.5 embryos and decreased expression in placentas; increased Snrpn expression in E9.5 embryos.
Conclusions:
- Early PAE affects imprinted gene expression in developing embryos and placentas.
- Observed gene expression changes occur independently of detectable DNA methylation alterations at studied loci.
- PAE may disrupt embryonic and placental development through epigenetic or other regulatory pathways affecting imprinted genes.
Abstract:
Prenatal alcohol exposure (PAE) can harm the embryonic development and cause life-long consequences in offspring's health. To clarify the molecular mechanisms of PAE we have used a mouse model of early alcohol exposure, which is based on maternal ad libitum ingestion of 10% (v/v) ethanol for the first eight days of gestation (GD 0.5-8.5). Owing to the detected postnatal growth-restricted phenotype in the offspring of this mouse model and both prenatal and postnatal growth restriction in alcohol-exposed humans, we focused on imprinted genes Insulin-like growth factor 2 (Igf2), H19, Small Nuclear Ribonucleoprotein Polypeptide N (Snrpn) and Paternally expressed gene 3 (Peg3), which all are known to be involved in embryonic and placental growth and development. We studied the effects of alcohol on DNA methylation level at the Igf2/H19 imprinting control region (ICR), Igf2 differentially methylated region 1, Snrpn ICR and Peg3 ICR in 9.5 embryonic days old (E9.5) embryos and placentas by using MassARRAY EpiTYPER. To determine alcohol-induced alterations globally, we also examined methylation in long interspersed nuclear elements (Line-1) in E9.5 placentas. We did not observe any significant alcohol-induced changes in DNA methylation levels. We explored effects of PAE on gene expression of E9.5 embryos as well as E9.5 and E16.5 placentas by using quantitative PCR. The expression of growth promoter gene Igf2 was decreased in the alcohol-exposed E9.5 and E16.5 placentas. The expression of negative growth controller H19 was significantly increased in the alcohol-exposed E9.5 embryos compared to controls, and conversely, a trend of decreased expression in alcohol-exposed E9.5 and E16.5 placentas were observed. Furthermore, increased Snrpn expression in alcohol-exposed E9.5 embryos was also detected. Our study indicates that albeit no alterations in the DNA methylation levels of studied sequences were detected by EpiTYPER, early PAE can affect the expression of imprinted genes in both developing embryo and placenta.
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