Hippocampal transcriptome reveals novel targets of FASD pathogenesis

Abstract

Introduction Prenatal alcohol exposure can contribute to fetal alcohol spectrum disorders (FASD), characterized by a myriad of developmental impairments affecting behavior and cognition. Studies show that many of these functional impairments are associated with the hippocampus, a structure exhibiting exquisite vulnerability to developmental alcohol exposure and critically implicated in learning and memory; however, mechanisms underlying alcohol‐induced hippocampal deficits remain poorly understood. By utilizing a high‐throughput RNA‐sequencing (RNA‐seq) approach to address the neurobiological and molecular basis of prenatal alcohol‐induced hippocampal functional deficits, we hypothesized that chronic binge prenatal alcohol exposure alters gene expression and global molecular pathways in the fetal hippocampus. Methods Timed‐pregnant Sprague–Dawley rats were randomly assigned to a pair‐fed control (PF) or binge alcohol (ALC) treatment group on gestational day (GD) 4. ALC dams acclimatized from GDs 5–10 with a daily treatment of 4.5 g/kg alcohol and subsequently received 6 g/kg on GDs 11–20. PF dams received a once daily maltose dextrin gavage on GDs 5–20, isocalorically matching ALC counterparts. On GD 21, bilateral hippocampi were dissected, flash frozen, and stored at −80°C. Total RNA was then isolated from homogenized tissues. Samples were normalized to ~4nM and pooled equally. Sequencing was performed by Illumina NextSeq 500 on a 75 cycle, single‐end sequencing run. Results RNA‐seq identified 13,388 genes, of these, 76 genes showed a significant difference (p < 0.05, log2 fold change ≥2) in expression between the PF and ALC groups. Forty‐nine genes showed sex‐dependent dysregulation; IPA analysis showed among female offspring, dysregulated pathways included proline and citrulline biosynthesis, whereas in males, xenobiotic metabolism signaling and alaninine biosynthesis etc. were altered. Conclusion We conclude that chronic binge alcohol exposure during pregnancy dysregulates fetal hippocampal gene expression in a sex‐specific manner. Identification of subtle, transcriptome‐level dysregulation in hippocampal molecular pathways offers potential mechanistic insights underlying FASD pathogenesis.

Effects of Genetics and Sex on Acute Gene Expression Changes in the Hippocampus Following Neonatal Ethanol Exposure in BXD Recombinant Inbred Mouse Strains

“…Development of the nervous system is a highly regulated and organized molecular process controlled by gene expression in response to environmental cues. This well controlled system is extremely vulnerable to alcohol during development which has been shown to alter expression of genes involved in a range of critical processes [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Developmental alcohol exposure has been shown to have both short-term [ 28 , 30 ]; and long-term consequences to the transcriptome [ 25 , 27 , 31 ].…”

Gene expression profiling in the hippocampus of adolescent rats after chronic alcohol administration

“…We found that chronic alcohol administration led to changes in genes associated with cell cycle arrest and negative regulation of cell proliferation in the hippocampus of adolescent rats. On the other hand, in the study by Lunde‐Young et al that investigated gene expression profiling in the hippocampus of foetus of timed‐pregnant rats exposed to chronic binge alcohol, genes related to xenobiotic metabolism signalling and alanine biosynthesis were changed in male offspring, while genes involved in proline and citrulline biosynthesis were changed in females . Their results demonstrated indirect chronic exposure to alcohol during pregnancy affects mainly amino acid synthesis in the developing hippocampus.…”

“…Recently, the effects of alcohol on the hippocampus at the cellular and molecular levels have been studied through large‐scale transcriptome profiling. The Lunde‐Young group found vulnerable genes to alcohol in the hippocampus of prenatal offspring of timed‐pregnant Sprague‐Dawley rats and their genetic networks after indirect exposure to alcohol on gestational day using RNA‐sequencing (RNA‐Seq) technology . Their results help understand neuropathogenesis of foetal alcohol spectrum diseases (FASD).…”

Corticostriatal deficits underlying cognitive impairments induced by fetal exposure to alcohol

“…On the contrary, in adult females LTP is intact (80) and even enhanced in early adults exposed to EtOH during late developmental stages (78). The sex-specific effects on synaptic plasticity are corroborated by sexually dimorphic transcriptional FAE-induced modifications in hippocampal gene expression (82).…”