Molecular characterization of a toxicological tipping point in human induced pluripotent stem cell (hiPSC)-derived endoderm exposed to all-trans retinoic acid (ATRA)

Embryonic development commences with the formation of three germ layers from the primitive streak during gastrulation. The endoderm layer gives rise to the gut tube, leading to development of several internal organs, including the thyroid, thymus, lungs, stomach, liver, pancreas, and intestines. We differentiated human induced pluripotent stem cells (hiPSCs) to embryonic endoderm and sought to identify a tipping point at which the developing system did not recover from perturbations caused by exposure to a known teratogen, all-trans retinoic acid (ATRA). Differentiating iPSC-derived endoderm was exposed to five concentrations of ATRA between 0.001 and 10 µM at 6h, 96h, or 192h and assessed for forkhead box A2 (FOXA2) protein expression and global gene transcript expression measured by RNA-sequencing. A tipping point of 17±11 nM was identified where patterns of differentially expressed genes supported a shift in the developmental trajectory away from embryonic endoderm in favor of mesoderm and extraembryonic endoderm. Overall design: Five concentrations of all-trans retinoic acid (ATRA) between 0.001 and 10 µM were compared to time-matched 0.1% DMSO controls at three timepoints (6h, 96h, and 192h) in differentiating endoderm. Two biological replicates were used. Undifferentiated controls (not in DMSO) were also included in duplicate as internal controls for 6h, 96h, and 144h.