Transcriptomic changes due to early, chronic intermittent alcohol exposure during forebrain development implicate WNT signaling, cell‐type specification, and cortical regionalization as primary determinants of fetal alcohol syndrome

Abstract

Background Fetal alcohol syndrome (FAS) due to gestational alcohol exposure represents one of the most common causes of nonheritable lifelong disability worldwide. In vitro and in vivo models have successfully recapitulated multiple facets of the disorder, including morphological and behavioral deficits, but far less is understood regarding the molecular and genetic mechanisms underlying FAS. Methods In this study, we utilized an in vitro human pluripotent stem cell‐based (hPSC) model of corticogenesis to probe the effects of early, chronic intermittent alcohol exposure on the transcriptome of first trimester‐equivalent cortical neurons. Results We used RNA sequencing of developing hPSC‐derived neurons treated for 50 days with 50 mM ethanol and identified a relatively small number of biological pathways significantly altered by alcohol exposure. These included cell‐type specification, axon guidance, synaptic function, and regional patterning, with a notable upregulation of WNT signaling‐associated transcripts observed in alcohol‐exposed cultures relative to alcohol‐naïve controls. Importantly, this effect paralleled a shift in gene expression of transcripts associated with regional patterning, such that caudal forebrain‐related transcripts were upregulated at the expense of more anterior ones. Results from H9 embryonic stem cells were largely replicated in an induced pluripotent stem cell line (IMR90‐4), indicating that these patterning alterations are not cell line‐specific. Conclusions We found that a major effect of chronic intermittent alcohol on the developing cerebral cortex is an overall imbalance in regionalization, with enrichment of gene expression related to the production of posterodorsal progenitors and a diminution of anteroventral progenitors. This finding parallels behavioral and morphological phenotypes observed in animal models of high‐dose prenatal alcohol exposure, as well as patients with FAS.

Cell type-specific changes in Wnt signaling and neuronal differentiation in the developing mouse cortex after prenatal alcohol exposure during neurogenesis

“…Neural progenitor cells in general have been shown to be less affected by ethanol-induced cell death (Santillano et al, 2005). Furthermore, previous studies have shown that compared to very high doses of EtOH, more moderate doses, such as that used in this study, do not result in significant cell death (Fischer et al, 2021). As already mentioned, apoptosis may not be accurately detected using scand snRNAseq.…”

Decreased tubulin-binding cofactor B was involved in the formation disorder of nascent astrocyte processes by regulating microtubule plus-end growth through binding with end-binding proteins 1 and 3 after chronic alcohol exposure

“…At 7 days, cells in each group were collected and used for IF ( n = 6), WB ( n = 6), and RT-PCR ( n = 6). The medium with the same alcohol concentration was changed regularly everyday to maintain the alcohol concentration (Ethanol evaporation after 24 h was 10–20%) (Fischer et al, 2021 ). To analyze the concentration-dependent effect of alcohol, cells were exposed to varying concentrations of alcohol (0, 30,100 mM) (Tomas et al, 2005 ).…”

“…Symptom severity of FAS varies greatly with timing, duration, and dose of alcohol exposure and genetic and metabolic factors (Burd et al, 2003 ). In vitro and in vivo models have successfully summarized multiple aspects of the disorder, including morphological and behavioral defects—still, the molecular and genetic mechanisms underlying FAS are poorly understood (Fischer et al, 2021 ). Astrocytes are the most abundant glial cells in the brain (Han et al, 2020 ), whose main functions include providing nutrients to the neuron, maintaining the extracellular ion balance, releasing transmitters, regulating synaptic plasticity, maintaining synaptic connection, and so on (Acosta et al, 2017 ; Palmer and Ousman, 2018 ; Munger et al, 2019 ).…”

ERK1/2 Signalling Pathway Regulates Tubulin-Binding Cofactor B Expression and Affects Astrocyte Process Formation after Acute Foetal Alcohol Exposure

“…Foetal alcohol syndrome (FAS) is one of the most severe types of FASD [ 2 ]. Many aspects of FASD disorder have been successfully summarised in vitro and in vivo, including morphological and behavioural defects, but the pathogenesis of the disease is still unclear [ 3 , 4 ]. The unawareness of pregnancy or addictive alcoholism in women during pregnancy has led to FASD in recent years.…”

“…Almost all current research on the pathogenesis of FASD has focused on neurons [ 4 ]. Alcohol can trigger a robust neurodegenerative response and neuronal apoptosis [ 14 , 15 ] and impact synaptic formation [ 1 , 16 ].…”