FIG. 5.

Arsenic inhibits neuronal differentiation by repressing neurogenic transcription factors. Neurogenin 1, neurogenin 2, and NeuroD mRNA expression on day 5 and day 9 of cells derived from EBs after exposure to 0, 0.1, 0.5, and 1.0μM arsenite were quantified by qPCR. Each sample was run in triplicate (n = 3), results were normalized to GAPDH, and are expressed as the number of molecules per 100ng cDNA. ANOVA followed by Tukey’s post hoc test (p < 0.05) was performed to determine statistical differences between concentrations (*) and between days (#) (A). Differentiated control cells and cells exposed to 0.5μM arsenite were fixed on day 12, and Tuj1 expression was examined by immunofluorescence (B). Pictures are representative examples from 198 independent EBs/time point/group. Tuj1 protein expression was examined by immunoblotting, using EBs exposed with or without 0.5μM arsenic on day 12, with GAPDH used as a loading control (C).