Effects of developmental toxicants on microRNA expression during neural differentiation of murine embryonic stem cells

Studying chemical disturbances during neural differentiation of murine embryonic stem cells (mESC) has been established at ZEBET as an alternative in vitro testing approach for the identification and classification of developmental toxicants. Many studies have shown an essential role of microRNAs in posttranscriptional regulation of gene expression during developmentand ESC differentiation. Thus, neural differentiation of ESC in vitro allows investigation of the role of miRNAs in chemicalmediated developmental toxicity. The main goal of this projectwas to analyze the expression of neural-specific miRNAs during neural differentiation of mESC while being exposed to the developmental neurotoxicants. The substances we mainly focused on comprise valproic acid (VPA), arsenic and curcumin. All these substances have been shown in vitro and/or in vivo to exert effects on miRNA expression and to affect neural development. The developmental neurotoxicity of these substances as well as their effects on miRNA expression during neural differentiation of mESC will be discussed. We could demonstrate that neural-specific or enriched miRNAs show different expression patterns during neural differentiation of mESC when cells are being exposed to VPA. So, the expression of mir-128a and mir-124a decreased with increasing VPA concentrations, whereas let-7c was 2-fold upregulated. The downregulation of mir-128aand mir-124a in cells treated with VPA was stronger compared to the concurrent downregulation of the neuron-specific markerƒ ÀIII-tubulin. The effects of VPA on neuron-specific mir-124a expression may point to possible compound-mediated mechanisms exerted through mir-124a-dependent regulation pathways.