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Published on: September 19, 2019
Ethanol-induced methylation of cell cycle genes in neural stem cells
Steven D Hicks1, Frank A Middleton, Michael W Miller
1Department of Neuroscience and Physiology, State University of New York - Upstate Medical University, Syracuse, NY 13210, USA.
Abstract:
Ethanol inhibits the proliferation of neural precursors by altering mitogenic and anti-mitogenic growth factor signaling and can affect global methylation activity in the fetus. We tested the hypothesis that epigenetic modification of specific cell cycle genes underlies the ethanol-induced inhibition of growth factor-regulated cell cycle progression. Monolayer cultures of neural stem cells (NSCs) were treated with fibroblast growth factor 2 or transforming growth factor (TGF) β1 in the absence or presence of ethanol. Ethanol increased the total length of the cell cycle by elongating the amount of time spent in the gap 1 (G1) and synthesis (S) phases of the cell cycle. Ethanol induced the hypermethylation of multiple cell cycle genes associated with the G1/S and gap 2/mitotic phase (G2/M) checkpoints and increased the expression and activity of DNA methyltransferases. These changes were most pronounced in the presence of TGFβ1. Epigenetic alterations paralleled the down-regulation of associated transcripts and other checkpoint-related mRNAs both in vitro (NS-5 cell culture) and in vivo (fetal mouse cortex). Ethanol-induced hypermethylation was accompanied by decreases in the proportion of NSCs expressing associated cell cycle proteins. Thus, ethanol disrupts growth factor-related cell cycle progression by inducing checkpoint restriction at the G1/S transition through a feed-forward system involving the methylation of G2/M regulators.
Insights
Ethanol exposure disrupts fetal neural stem cell (NSC) proliferation by altering cell cycle gene methylation. This epigenetic modification inhibits growth factor signaling, impacting neural development.
Area of Science:
- Neuroscience
- Epigenetics
- Developmental Biology
Background:
- Ethanol exposure during development affects fetal neurogenesis.
- Growth factors regulate neural stem cell (NSC) proliferation and cell cycle progression.
- Epigenetic mechanisms, like DNA methylation, play a crucial role in gene regulation during development.
Purpose of the Study:
- To investigate if epigenetic modifications of cell cycle genes mediate ethanol's inhibition of growth factor-regulated neural precursor proliferation.
- To understand the role of DNA methylation and DNA methyltransferases in ethanol's effects on the cell cycle.
Main Methods:
- Neural stem cells (NSCs) were cultured and treated with fibroblast growth factor 2 or transforming growth factor beta 1 (TGFβ1) with or without ethanol.
- Cell cycle progression, DNA methylation, DNA methyltransferase activity, and gene/protein expression were analyzed.
- In vitro and in vivo (fetal mouse cortex) models were used to assess epigenetic alterations.
Main Results:
- Ethanol prolonged the cell cycle by increasing time in the G1 and S phases.
- Ethanol induced hypermethylation of cell cycle genes at G1/S and G2/M checkpoints, increasing DNA methyltransferase activity.
- These epigenetic changes correlated with reduced gene and protein expression, observed both in vitro and in vivo, particularly with TGFβ1 exposure.
Conclusions:
- Ethanol disrupts growth factor-mediated cell cycle progression in neural precursors.
- Ethanol induces epigenetic alterations, specifically hypermethylation of cell cycle genes, leading to checkpoint restriction at the G1/S transition.
- This disruption involves a feed-forward mechanism including methylation of G2/M regulators, impacting fetal neurodevelopment.
