Michela Di Criscio: Epigenetic Insights into the Impact of Endocrine Disruptors on (Neuro)phenotype - From Developmental to Multigenerational Effects

Abstract

Anthropogenic chemicals are pervasive in the environment, posing significant challenges due to their potential effects on human and wildlife health. Among these, endocrine disrupting chemicals (EDCs) are particularly concerning, as developmental exposure to EDCs has been linked to adverse outcomes later in life and across generations. Epigenetic mechanisms, which are crucial for embryonic development and play a key role in cell specification and the determination of phenotypic traits, may provide insights into how EDCs exert long-term effects. This thesis explores the connection between real-life developmental exposure to EDCs and epigenetic alterations, with a particular focus on neuro-phenotypical effects. 

A previous epidemiological study demonstrated an association between prenatal co-exposure to eight EDCs (referred to as Mixture N1) and language delay in children, suggesting an impact of this mixture on neurodevelopment. Further research showed that in utero exposure to Mixture N1 altered gene expression and behavior in adult mice. In this study, the potential role of epigenetic mechanisms underlying these long-term effects was investigated by analyzing DNA methylation. Mixture N1 decreased DNA methylation in males at three genes associated with the hypothalamus-pituitary-adrenal (HPA) axis: glucocorticoid receptor (Nr3c1), mineralocorticoid receptor (Nr3c2), and corticotropin-releasing hormone receptor 1 (Crhr1). The decrease in Nr3c1 methylation was correlated with increased gene expression and with behavioral alterations. However, in vitro experiments did not provide evidence that Mixture N1 induced these epigenetic alterations during development.

This thesis also explored multi-generational effects of exposure to perfluorooctanesulfonic acid (PFOS) and perfluorobutanesulfonic acid (PFBS), two environmental pollutants with endocrine-disrupting properties. Zebrafish were exposed to chemicals during development at environmentally relevant concentrations. The exposure led to changes in behaviors, transcriptome, and DNA methylation, with significant DNA methylation changes observed in neuro-related genes. These alterations were also detected in their offspring (F1) and extended to the subsequent generation (F2). The investigation then focused on the potential mechanisms behind these transgenerational effects. Changes in RNA levels and RNA methylation, specifically m6A, were analyzed during early development in F2. PFOS was selected for this analysis due to its higher impact on neuro-phenotypical alterations. It was found that transcript levels and m6A patterns were altered in F2. These changes were associated with genes involved in epigenetic processes and translation, suggesting a possible role in the inheritance of neuro-phenotypical traits. 

Overall, this thesis offers new insights into the connections between real-life exposure to EDCs, their impact on neuro-phenotypes, and the potential underlying epigenetic mechanisms.