The perinuclear actin cap progressively forms in hESCs following onset of differentiation.

<p>A–H. Status of apical perinuclear actin cap (A–D) and basal stress fibers (E–H) in undifferentiated hESCs at day 0 (A and E), as well as two (B and F), five (C and G), and ten days (D and G) after induction of differentiation (+VEGF and collagen IV). Red, purple, and orange arrows indicate examples of cells showing no actin cap, a disrupted/disorganized actin cap, and a well-organized actin cap, respectively. Cells were stained for differentiation marker TRA-1-81, nuclear DNA (DAPI), and actin. Scale bar, 20 µm. I. Evolution of the fraction of TRA-1-81-negative hESCs showing an actin cap. No actin cap was present in TRA-1-81-positive hESCs. J. Proportion of TRA-1-81-positive and TRA-1-81-negative hESCs showing an organized actin cap, a disorganized actin cap, or no actin cap, two and five days after onset of differentiation. K. Distribution of cells showing an actin cap in hESCs after 10 days of differentiation compared to HLFs. At least 100 cells in triplicate for a total of 300 cells were probed per condition.