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We previously showed that ethanol did not kill fetal neural stem cells (NSCs), but that their numbers nevertheless are decreased due to aberrant maturation and loss of self-renewal. To identify mechanisms that mediate this loss of NSCs, we focused on a family of Gag-like proteins (GLPs), derived from retroviral gene remnants within mammalian genomes. GLPs are important for fetal development, though their role in brain development is virtually unexplored. Moreover, GLPs may be transferred between cells in extracellular vesicles (EVs) and thereby transfer environmental adaptations between cells. We hypothesized that GLPs may mediate some effects of ethanol in NSCs.Sex-segregated male and female fetal murine cortical NSCs, cultured ex vivo as nonadherent neurospheres, were exposed to a dose range of ethanol and to mitogen-withdrawal-induced differentiation. We used siRNAs to assess the effects of NSC-expressed GLP knockdown on growth, survival, and maturation and in silico GLP knockout, in an in vivo single-cell RNA-sequencing dataset, to identify GLP-mediated developmental pathways that were also ethanol-sensitive.PEG10 isoform-1, isoform-2, and PNMA2 were identified as dominant GLP species in both NSCs and their EVs. Ethanol-exposed NSCs exhibited significantly elevated PEG10 isoform-2 and PNMA2 protein during differentiation. Both PEG10 and PNMA2 were mediated apoptosis resistance and additionally, PEG10 promoted neuronal and astrocyte lineage maturation. Neither GLP influenced metabolism nor cell cycle in NSCs. Virtual PEG10 and PNMA2 knockout identified gene transcription regulation and ubiquitin-ligation processes as candidate mediators of GLP-linked prenatal alcohol effects.Collectively, GLPs present in NSCs and their EVs may confer apoptosis resistance within the NSC niche and contribute to the abnormal maturation induced by ethanol.

Most persons with fetal alcohol spectrum disorders (FASDs) remain undiagnosed or are diagnosed in later life. To address the need for earlier diagnosis, we previously assessed miRNAs in the blood plasma of pregnant women who were classified as unexposed to alcohol (UE), heavily exposed with affected infants (HEa), or heavily exposed with apparently unaffected infants (HEua). We reported that maternal miRNAs predicted FASD-related growth and psychomotor deficits in infants. Here, we assessed whether fetal sex influenced alterations in maternal circulating miRNAs following prenatal alcohol exposure (PAE). To overcome the loss of statistical power due to disaggregating maternal samples by fetal sex, we adapted a strategy of iterative bootstrap resampling with replacement to assess the stability of statistical parameter estimates. Bootstrap estimates of parametric and effect size tests identified male and female fetal sex-associated maternal miRNA responses to PAE that were not observed in the aggregated sample. Additionally, we observed, in HEa mothers of female, but not male fetuses, a network of co-secreted miRNAs whose expression was linked to miRNAs encoded on the X-chromosome. Interestingly, the number of significant miRNA correlations for the HEua group mothers with female fetuses was intermediate between HEa and UE mothers at mid-pregnancy, but more similar to UE mothers by the end of pregnancy. Collectively, these data show that fetal sex predicts maternal circulating miRNA adaptations, a critical consideration when adopting maternal miRNAs as diagnostic biomarkers. Moreover, a maternal co-secretion network, predominantly in pregnancies with female fetuses, emerged as an index of risk for adverse birth outcomes due to PAE.

Prenatal ethanol exposure can result in loss of neural stem cells (NSCs) and decreased brain growth. Here, we assessed whether a noncoding RNA (ncRNA) related to the NSC self-renewal factor Oct4/Pou5f1, and transcribed from a processed pseudogene locus on mouse chromosome 9 (mOct4pg9), contributed to the loss of NSCs due to ethanol. Mouse fetal cortical-derived NSCs, cultured ex vivo to mimic the early neurogenic environment of the fetal telencephalon, expressed mOct4pg9 ncRNA at significantly higher levels than the parent Oct4/Pou5f1 mRNA. Ethanol exposure increased expression of mOct4pg9 ncRNA, but decreased expression of OCT4/POU5F1. Gain- and loss-of-function analyses indicated that mOct4pg9 overexpression generally mimicked effects of ethanol exposure, resulting in increased proliferation and expression of transcripts associated with neural maturation. Moreover, mOct4pg9 associated with Ago2 and with miRNAs, including the anti-proliferative miR-328-3p, whose levels were reduced following mOct4pg9 overexpression. Finally, mOct4pg9 inhibited Oct4/Pou5f1-3’UTR-dependent protein translation. Consistent with these observations, data from single-cell transcriptome analysis showed that mOct4pg9-expressing progenitors lack Oct4/Pou5f1, but instead overexpress transcripts for increased mitosis, suggesting initiation of transit amplification. Collectively, these data suggest that the inhibitory effects of ethanol on brain development are explained, in part, by a novel ncRNA which promotes loss of NSC identity and maturation.

• Epigenetic modifications change global gene expression in response to environmental factors.