Environmentally relevant developmental methylmercury exposures alter neuronal differentiation in a human-induced pluripotent stem cell model

• Published in: Food and chemical toxicology 2021-06, Vol.152, p.112178-112178, Article 112178
• Main Authors: Prince, Lisa M., Neely, M. Diana, Warren, Emily B., Thomas, Morgan G., Henley, Madeline R., Smith, Kiara K., Aschner, Michael, Bowman, Aaron B.
• Format: Article
• Language: English
• Subjects: Cell Differentiation - drug effects; Cell Proliferation - drug effects; Cell Survival - drug effects; Developmental neurotoxicity; Doublecortin Domain Proteins; Doublecortin Protein; Forkhead Transcription Factors - metabolism; Glutamatergic neurons; Glutathione - metabolism; Human-induced pluripotent stem cells; Humans; Induced Pluripotent Stem Cells - drug effects; Methylmercury; Methylmercury Compounds - toxicity; Microtubule-Associated Proteins - metabolism; Nerve Tissue Proteins - metabolism; Neurons - drug effects; Neuropeptides - metabolism; No-Observed-Adverse-Effect Level
• ISSN: 0278-6915; 1873-6351
• DOI: 10.1016/j.fct.2021.112178

Developmental methylmercury (MeHg) exposure selectively targets the cerebral and cerebellar cortices, as seen by disruption of cytoarchitecture and glutamatergic (GLUergic) neuron hypoplasia. To begin to understand the mechanisms of this loss of GLUergic neurons, we aimed to develop a model of developmental MeHg neurotoxicity in human-induced pluripotent stem cells differentiating into cortical GLUergic neurons. Three dosing paradigms at 0.1 μM and 1.0 μM MeHg, which span different stages of neurodevelopment and reflect toxicologically relevant accumulation levels seen in human studies and mammalian models, were established. With these exposure paradigms, no changes were seen in commonly studied endpoints of MeHg toxicity, including viability, proliferation, and glutathione levels. However, MeHg exposure induced changes in mitochondrial respiration and glycolysis and in markers of neuronal differentiation. Our novel data suggests that GLUergic neuron hypoplasia seen with MeHg toxicity may be due to the partial inhibition of neuronal differentiation, given the increased expression of the early dorsal forebrain marker FOXG1 and corresponding decrease in expression on neuronal markers MAP2 and DCX and the deep layer cortical neuronal marker TBR1. Future studies should examine the persistent and latent functional effects of this MeHg-induced disruption of neuronal differentiation as well as transcriptomic and metabolomic alterations that may mediate MeHg toxicity. •Human-induced pluripotent stem model of early developmental MeHg neurotoxicity.•Developmental MeHg causes changes in neuronal differentiation and energetics.•No Observed Adverse Effect Concentration (NOAEC) for MeHg cytotoxicity and GSH levels.•Neuron hypoplasia by MeHg may be due to inhibition of neuronal differentiation.