Fig. 7. Analysis of alginate-embedded embryos. Normal embryos without injection or embryos labeled with Cre recombinase were cultured in alginate gel to maintain their position. (A) The angle (a) between the first cleavage plane (P) and the embryonic-abembryonic axis (E-Ab) of the blastocyst was measured by comparing photographs. Only the embryos in which the first cleavage plane was orthogonal to the bottom of culture plate were used for the analysis. (B) The angle was found to be 80° in 28 out of 123 of the normal uninjected embryos. The angle was greater than 50° in 90 embryos (73%) (columns are colored in dark red). (C) In the case of DNA-injected embryos, similar distribution in angles were observed after analyzing 71 embryos. (D-I) Examples of uninjected embryos used for analysis. In the embryo in D-F, the angle was 70°, and the first blastomere to divide contributed mainly to the embryonic part of the embryo. In another normal embryo shown in G-I the angle was 80°, and the early-dividing blastomere contributed to the abembryonic part of the embryo. (J-Q) Two examples of labeled embryos. (J-M) The injected blastomere divided later than the other blastomere and contributed to the embryonic part in the embryo as can be seen from the X-gal staining in this region (M). In the embryo shown in N-Q, the injected blastomere also divided late. The labeled cells were seen in the trophectoderm of the abembryonic part and around the boundary zone. Scale bar: 30 µm.

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