Fig. 1

Fluorescent tagged episomal vectors allow for enrichment of OKSM-positive cells. a Schematic of engineered reprogramming episomal plasmids. Fluorescent protein expression cassettes were inserted downstream of the reprogramming factor expression cassettes, indicated by color. b Tiled laser-scanning confocal maximum projections capture the heterogeneity of episome-carrying cells. Confluent human foreskin fibroblasts at 2 days post transfection of plasmids are shown. Arrowheads indicate cells with discrepant levels of fluorescent proteins, significantly favoring expression of one episome over another. Scale bars = 150 μM. c FACS discrimination of the OKSM population. Left: whole population (black) gated for mCherry (Oct 3/4) (O) and E2-Crimson (Klf4) (K). The double-positive population (OK) is shown in Quadrant 2 (red). Right: whole population (black) and OK (red), subsequently gated for eGFP (Sox2) (S) and mTAGBFP2 (L-Myc-2A-Lin28) (M). Cyan contours designate the OKSM population (Color figure online). OKSM Oct3/4 + shp53, Klf, Sox2, and L-Myc + Lin28