Cells expressing DN Rac1 are less likely to contribute to endodermal tissues. (A–D) Lateral view of an embryo 22 h after fertilization containing donor endodermal cells from Tg(sox17:GFP) embryos expressing DN Rac1 as well as donor control cells from Tg(sox17:dsRed) embryos. Host embryo is labeled with phalloidin. Images in C and D are taken from the boxed regions in A and B, respectively. Arrows point to DN Rac1–expressing cells that appear to aberrantly reside in the somites. Bars, 100 µm. (E and F) In situ hybridization analyses of myoD (E) or ntla (F) expression show that some DN Rac1–expressing donor cells (arrows) express markers for muscle (E) or notochord (F), respectively, despite also being labeled with the Tg(sox17:GFP) transgene (green). Bars, 25 µm. (G) Quantification of donor cell contribution to endodermal or nonendodermal tissues. Expression of DN Rac1 significantly increased the likelihood of cells contributing to nonendodermal tissues. n = 23 embryos. *, P < 0.05 by χ2 test. (H–K) Frames from a time-lapse video (Video 7) showing the relative movements of control (red) and DN Rac1–expressing cells (green) from mid-gastrulation to early somitogenesis. Numbers indicate hours elapsed. Bars, 100 µm. (inset) Enlarged region of the boxed area showing DN Rac1–expressing cells that have migrated into the notochord. Bar, 25 µm.
