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Fig. 3. Sagittal sections of pricked embryos and a control embryo, showing the origin of globinpositive
mesodermal cells. (A) Schematic image of the tracing experiment. Two prospective dorsal
blastomeres of either pricked or intact embryos at the 16-cell stage were injected with b-galactosidase
RNA (0.5 ng/embryo) and cultured for 2 days (stage 35/36). (B) Expression of a-globin in a pricked
embryo. An embryo cultured for 2 days (stage 35/36) was processed for whole-mount in situ
hybridization. The globin-positive cells exist in the involuted mesodermal cells, which face the animal
pole-derived ectoderm layer. (C and D) Cell lineage was traced by injection of b-galactosidase RNA,
followed by staining with X-gal. Note that labeled cells in the pricked embryos (C, arrowheads) have
migrated to the same area as that of globin-expressing cells in B, while those in the intact embryos (D)
have become the muscle and surrounding mesenchyme. Scale bar in D indicates 0.5 mm. |
