Molecular characterization of a toxicological tipping point during human stem cell differentiation

Endoderm gives rise to the gut tube in the early embryo. We differentiated human induced pluripotent stem cells (hiPSCs) to embryonic endoderm to identify a "tipping point" at which the developing system did not recover from perturbations caused by exposure to all-trans retinoic acid (ATRA). Differentiating hiPSC-derived endoderm exposed to five concentrations of ATRA between 0.001 and 10 μM at 6 h, 96 h, or 192 h was assessed for forkhead box A2 (FOXA2) protein expression and global gene transcript expression. A tipping point of 17 ± 11 nM was identified where patterns of differentially expressed genes supported a developmental trajectory shift indicating a potential teratogenic outcome. This concentration is between women's endogenous ATRA blood plasma levels and teratogenic levels of circulating isotretinoin, an ATRA isomer used to treat acne. Taken together, these data suggest that this approach is a sensitive method to identify a point of departure for chemicals that impact early embryonic development.