Effects of the Developmental Teratogens Ethanol and Nicotine on Long Noncoding RNA Expression in Mouse Fetal Neural Stem Cells of the Cortex

Abstract

Research on long noncoding RNAs (lncRNAs) has increased significantly over the past few decades. However, investigation of lncRNA continues to lag behind that of other noncoding RNAs species like microRNA (miRNA). One subject receiving limited consideration to date is how teratogens impact the expression patterns and functions of lncRNAs as well as their interactions with other noncoding RNAs. To that end, research was undertaken to determine how six lncRNAs present in the developing nervous system are affected by ethanol and nicotine exposure.

After identifying Malat1, Cyrano, Sox2ot, TUNA, Emx2os, and MIAT as neurodevelopmentally-regulated transcripts, initial experiments probed the expression patterns of each lncRNA in mouse fetal cortical neurosphere cultures treated with ethanol, nicotine, and ethanol and nicotine in combination. While expression of the transcripts of interest was not significantly impacted by ethanol exposure, nicotine treatment reduced expression of TUNA, MIAT, Cyrano, and Malat1. Treatment with both ethanol and nicotine also yielded reduced expression of Cyrano, TUNA, and MIAT. Experimentation progressed to investigations of the potential for interactions between miRNAs, TUNA, MIAT, and Emx2os. These studies focused on whether such associations were mediated by the Argonaute 2 (Ago2) protein, if they were disrupted by ethanol and nicotine treatment, and where these interactions localized within cells. Although bioinformatics tools predicted multiple binding sites between ethanol- and nicotine-sensitive miRNAs and the six lncRNAs of interest, there was no evidence of Ago2-mediated interactions in either treated or untreated mouse fetal neurosphere cultures. As such, there was also no evidence of disrupted localization of these complexes. However, RNA immunoprecipitation (RIP) experiments with Ago2 did provide insight into the miRNAs actively associated with the RNA-induced silencing complex (RISC) and the compartmentalization patterns of these miRNAs within cells of the developing cortex. Ultimately, this work expands knowledge on the expression patterns of several lncRNAs in the developing brain and serves as the first report detailing the impacts of ethanol and nicotine on lncRNAs in this developmental context.