FIG. 4.

Kinetic analysis of marker expression during ATRA-induced differentiation of pluripotent stem cells into neuronal progenitor cells. (A) Loss of Oct4 expression during ATRA-induced differentiation by FACS. GFP⁺ cells were quantified as described above, and a total of 10,000 cells were counted. For comparison, the fraction of GFP⁺ cells was normalized to the number of GFP⁺ cells at day 0 and plotted. Note the surprising reactivation of Oct4 promoter activity at day 4 of ATRA induced differentiation in both ESCs and FMR cells. (B) Graphical representation of the mean GFP fluorescence contents per cell for GFP⁺ mESCs, iPSCs, and FMRCs during ATRA-induced differentiation. Note that GFP levels are represented as the geometric mean GFP contents per cell. (C) Assessment of Oct4 promoter activity by phase and fluorescence microscopy, respectively, at day 4 of ATRA-induced differentiation for the cell lines used in this study. All panel pairs show residual Oct4-driven GRP levels after 4 days of ATRA treatment. Note the presence of numerous GFP⁺ colonies in mESC1, mFMR, and mFMR2 cells as compared to iPSCs.