Figure 3.

Blastocyst Chimera Contribution by FS Cells and Formative Epiblast

(A) Bright-field and fluorescent images of E9.5 embryos generated after blastocyst injection of mKO2 reporter FS cells. Scale bar, 1 mm.

(B) Sagittal section from one chimera, stained for mKO2 and DAPI. (B’), mKO2-positive cells in foregut endoderm (yellow arrowheads) and cardiac mesoderm (green arrowheads). (B’’) (rotated 90°), Sox2 immunostaining (white arrowheads) in the hindgut region. Scale bars, 200 μm (B) and 100 μm (B’and B”).

(C) mKO2-positive cells expressing Oct4 and Mvh PGC markers in E12.5 chimeric gonad. Triple-positive cells are highlighted with dashed circles. Scale bars, 75 μm.

(D) Fluorescent images of organs from post-natal day 21 (P21) chimera overlaid with 20% opacity bright-field image. Scale bars, 2 mm.

(E) Coat color chimeras generated from NBRA3.2 FS cells at 7 weeks (above) and 4 weeks (below).

(F) Blastocysts injected with GFP reporter ESCs or FS cells and cultured for 24 h. ESCs are Klf4⁺Oct6⁻ (n = 11) (F’), whereas FS cells are Klf4⁻Oct6⁺ (F’’) (n = 15). Scale bars, 40 μm.

(G) E9.5 chimeras obtained from blastocyst injection of mTmG expressing E5.5 epiblast cells. Scale bars, 500 μm.

(H) Section from left embryo in (G) stained with anti-RFP to visualize membrane-tdTomato; DAPI in blue. Scale bar, 200 μm.