Hippocampal transcriptome analysis following maternal separation implicates altered RNA processing in a mouse model of fetal alcohol spectrum disorder

Abstract

Fetal alcohol spectrum disorders (FASD) are common, seen in 1-5% of the population in the United States and Canada. Children diagnosed with FASD are not likely to remain with their biological parents, facing early maternal separation and foster placements throughout childhood. We have modeled FASD in mice via prenatal alcohol exposure and further induce early life stress through maternal separation. We report an association between adult hippocampal gene expression and prenatal ethanol exposure followed by postnatal separation stress that is related to behavioral changes. Clustering of expression profiles through weighted gene co-expression network analysis (WGCNA) identifies a set of transcripts, module 19, associated with anxiety-like behavior (r = 0.79, p = 0.002) as well as treatment group (r = 0.68, p = 0.015). Genes in this module are overrepresented by genes involved in transcriptional regulation and other pathways related to neurodevelopment. Interestingly, one member of this module, Polr2a, polymerase (RNA) II (DNA directed) polypeptide A, is downregulated by the combination of prenatal ethanol and postnatal stress in an RNA-Seq experiment and qPCR validation (q = 2e-12, p = 0.004, respectively). Together, transcriptional control in the hippocampus is implicated as a potential underlying mechanism leading to anxiety-like behavior via environmental insults. Further research is required to elucidate the mechanism involved and use this insight towards early diagnosis and amelioration strategies involving children born with FASD.SUMMARY STATEMENTMouse hippocampal gene expression alterations following prenatal alcohol exposure and maternal separation are associated with behavioral deficits. Transcriptomic analysis implicates systems defect involving RNA processing, specifically including downregulation of Polr2a.

Hippocampal DNA Methylation in a Mouse Model of Fetal Alcohol Spectrum Disorder That Includes Maternal Separation Stress Only Partially Explains Changes in Gene Expression

“…Our main objective was to understand how early life stresses may complicate molecular changes underlying behavioral deficits that arise following prenatal ethanol exposure. Previously, behavioral changes resulting from prenatal ethanol exposure and postnatal maternal separation stress have been characterized , with lasting changes to the hippocampal transcriptome also being reported (Alberry et al, 2019). Here we focus on alterations to promoter DNA methylation in the same mice.…”

“…We previously reported changes in gene expression in association with behavioral deficits following prenatal ethanol exposure and maternal separation in these mice (Alberry et al, 2019). Interestingly the module of genes most closely associated with treatment and anxiety-like behavior includes genes important for transcriptional regulation and neurodevelopment.…”

“…While many brain regions may be relevant, the hippocampus forms the focus of this study for its essential role in spatial learning (Jarrard, 1993). To this end, we have also reported changes in hippocampal gene expression that persist into adulthood following prenatal ethanol exposure combined with postnatal maternal separation in B6 mice (Alberry et al, 2019). Given that the initiation and maintenance of aberrant gene expression in response to prenatal ethanol exposure includes epigenetic mechanisms, primarily DNA methylation, noncoding RNA, and histone modifications (Chen et al, 2013;Laufer et al, 2013;Chater-Diehl et al, 2016), these processes are expected to be critical in other models of FASD.…”

“…Arpp21 was introduced previously as it was also implicated by stress alone. Of these, Dlg3 is one of the most significantly altered transcripts in response to Stress and Ethanol + Stress treatments that we previously reported (Alberry et al, 2019). It codes for synapse-associated protein 102, a protein important for synapse formation.…”

“…Genes represented by promoter DMRs for each treatment group were compared to previously reported transcript-level expression analysis from an RNA-Seq experiment using RNA isolated from the same samples (Alberry et al, 2019). Briefly, RNA-Seq was carried out by The Centre for Applied Genomics (The Hospital for Sick Children, Toronto, Ontario, Canada).…”