Prenatal Low-dose Methylmercury (MeHg) Exposure Causes Premature Neuronal Differentiation and Autism Spectrum Disorder (ASD)-like Behaviours in a Rodent Model

Abstract

Methylmercury (MeHg) is a global pollutant that can elicit a range of adverse health effects in both humans and wildlife populations. Humans are often exposed to MeHg through the consumption of contaminated seafood. Developing fetuses are especially susceptible to the effects of MeHg as it can cross the blood-brain barrier and the placenta. At high doses in utero MeHg causes developmental disorders and congenital disabilities, but long-term low-dose effects are still not fully known. Using a culture model of cerebral cortex development, our lab has shown that low-dose MeHg promotes premature neuronal differentiation. Autism spectrum disorder (ASD) has been associated with prenatal MeHg exposure and is correlated with neuronal overproduction, but a cause-effect relationship has not been shown. In this thesis, I aim to test the hypothesis that prenatal exposure to low-dose MeHg can cause ASD-like symptoms in the offspring following premature neuronal differentiation. My results showed that adult mice prenatally exposed to MeHg exhibited key ASD characteristics including impaired communication, reduced sociability, and increased restrictive repetitive behaviours. Furthermore, I explored the underlying cellular and molecular mechanism that promotes premature neuronal differentiation caused by prenatal MeHg exposure. To reverse the MeHg-induced premature neuronal differentiation, I utilized metformin, an FDA-approved diabetes drug. Overall, these findings provide insights into the toxicology of MeHg and its relationship with ASD etiology, including the underlying mechanism, and a potential therapeutic strategy.