NRXN1 Deletion and Exposure to Methylmercury Increase Astrocyte Differentiation by Different Notch-Dependent Transcriptional Mechanisms.

Marilena Raciti,Mirko Conti,Giulia Gaudenzi,Sandra Ceccatelli,Britt-Marie Anderlid,Jahan Salma,Stefan Spulber,Zahra Khalajzeyqami,Anna Falk,Ola Hermanson

doi:10.3389/fgene.2019.00593

Marilena Raciti, Mirko Conti + Show 8 more

Open Access

https://doi.org/10.3389/fgene.2019.00593

Copy DOI

Abstract

Controversial evidence points to a possible involvement of methylmercury (MeHg) in the etiopathogenesis of autism spectrum disorders (ASD). In the present study, we used human neuroepithelial stem cells from healthy donors and from an autistic patient bearing a bi-allelic deletion in the gene encoding for NRXN1 to evaluate whether MeHg would induce cellular changes comparable to those seen in cells derived from the ASD patient. In healthy cells, a subcytotoxic concentration of MeHg enhanced astroglial differentiation similarly to what observed in the diseased cells (N1), as shown by the number of GFAP positive cells and immunofluorescence signal intensity. In both healthy MeHg-treated and N1 untreated cells, aberrations in Notch pathway activity seemed to play a critical role in promoting the differentiation toward glia. Accordingly, treatment with the established Notch inhibitor DAPT reversed the altered differentiation. Although our data are not conclusive since only one of the genes involved in ASD is considered, the results provide novel evidence suggesting that developmental exposure to MeHg, even at subcytotoxic concentrations, induces alterations in astroglial differentiation similar to those observed in ASD.

Highlights

IntroductionEpidemiological and experimental evidence points to a direct link between adverse events during early life and the pathogenesis of neurodevelopmental disorders (Grandjean et al, 1998; Rice and Barone, 2000; Seckl, 2004; Mueller and Bale, 2008; Onishchenko et al, 2008; Cottrell and Seckl, 2009; Perera and Herbstman, 2011; Tran and Miyake, 2017)
In the attempt to evaluate whether MeHg exposure could induce alterations in healthy cells similar to those observed in cells derived from autism spectrum disorders (ASD) patient (N1), we started by investigating cell proliferation and differentiation
Gene expression and protein analyses in 4 weeks differentiated cells (DD28) showed that in healthy cells MeHg induced a strong increase of GFAP and GFAP positive cells, to what was observed in N1 cells (Figures 2A–C)

Summary

Introduction

Epidemiological and experimental evidence points to a direct link between adverse events during early life and the pathogenesis of neurodevelopmental disorders (Grandjean et al, 1998; Rice and Barone, 2000; Seckl, 2004; Mueller and Bale, 2008; Onishchenko et al, 2008; Cottrell and Seckl, 2009; Perera and Herbstman, 2011; Tran and Miyake, 2017). NRXN1 Deletion and Methylmercury Alter Astrogliogenesis neurodevelopment and lead to long-term detrimental effects on the nervous system structure and function (Lauwerys et al, 1978; Koger et al, 2005; Perera and Herbstman, 2011; Ceccatelli et al, 2013; Tran and Miyake, 2017; Raciti and Ceccatelli, 2018) Both experimental and clinical studies indicate that the developing brain is susceptible to toxicants even at exposure levels exerting no effects in adults (Palmer et al, 2006; Perera and Herbstman, 2011; Ceccatelli et al, 2013; Lanphear, 2015; Edoff et al, 2017). Epidemiological studies report a clear association between prenatal/early postnatal exposure to MeHg in fishconsuming populations and adverse neurodevelopmental outcomes, including neurological, cognitive and behavioral deficits (Harada, 1978; Grandjean et al, 1997, 1999; Murata et al, 1999, 2004; Jedrychowski et al, 2007; Grandjean and Landrigan, 2014; Strain et al, 2015)

Results

Discussion

Conclusion