PFOS perturbs neural development. Immunofluorescence staining of neural progenitor cells (SOX2), early-stage neurons (Tuj1), midbrain floor plate progenitor cells (FOXA2) in one-month-old hMOs and dopaminergic neurons (TH) in two-month-old hMOs (a) and the corresponding quantification (b) after a 7-day exposure in the control (vehicle) and PFOS (300 μM) groups (mean ± s.e.m., unpaired t-test, n = 5 organoids, from 3 independent experiments). (c) qPCR analysis of relative gene expression of SOX2, PAX6, Tuj1, FOXA2, TH and NURR1 after a 7-day exposure in control group (vehicle treated with 0.05 % DMSO) and PFOS group (300 μM) (mean ± s.e.m., unpaired t-test, n = 3 organoids, from 3 independent experiments). Scale bar: 20 μm.