Sox2-low iPSCs exhibit increased plasticity in vivo
(A) Phase and red fluorescence images of E7.5 chimaeras of Sox2−/− (−/−) Sox2-low iPSCs expressing constitutively MST-dsRed (red fluorescence). Arrow indicates presumptive contribution to extraembryonic lineage(s). A non-chimeric embryo is included above the chimeric embryo with the yellow arrow (toward the left) to act as a negative control. Scale bars = 200μm.
(B) Phase and GFP images of E6.5 chimeric embryos generated with either −/− Sox2-low or WT iPSCs constitutively expressing a GFP transgene. Please note that apparent difference in size is due to −/−Sox2 chimeric embryos having been imaged with some maternal tissue still attached. Scale bars = 200μm.
(C) Single confocal microscopy sections of indicated genotype chimeric E6.5 embryos stained with trophoblast (AP-2γ) and epiblast (Oct4) markers. Filled arrowheads indicate examples of chimeric cells co-expressing Oct4 and AP-2γ markers. Non-filled arrowheads indicate examples of chimeric cells expressing AP-2γ only. Epiblast (EPI) and Trophoblast/trophectoderm (TE) embryo domains are separated by dashed line. Scale bars = 100μm.
(D) Table showing compartmental contribution of WT or −/− Sox2-low iPSCs constitutively expressing a GFP transgene. Values in tables represent number of embryos. Fisher's exact test statistical analysis was used to calculate the significance of the difference in the proportion of embryos exhibiting trophectoderm contribution in the two groups. This was performed using GraphPad Prism software.