FIG. 3.

Morphological and histological analysis of wild-type and mutant embryos. (A) Whole-mount gross morphology of wild-type and COX17(−/−) embryos at E6.5 and E8.5. The embryos are oriented such that the embryonic region is located at the bottom and the extraembryonic structures are on the top. All embryos were genotyped by PCR after photography. Morphologically, wild-type embryos were indistinguishable from heterozygotes. No significant differences were observed between wild-type and mutant embryos at E6.5 (left panel; magnification, ×50). Whereas wild-type embryos at E8.5 have proceeded into organogenesis, E8.5 mutant embryos retain large extraembryonic regions and the embryonic regions have atrophied (middle panel; magnification, ×25). The right panel reveals a dissected wild-type embryo (magnification, ×25), and organogenesis has already started. E, embryonic region; EE, extraembryonic region; S, somites. (B) Hematoxylin and eosin staining of sagittal sections of wild-type and COX17(−/−) E6.5 (magnification, ×100), E7.5 (magnification, ×50) and E8.5 (magnification, ×25) embryos. A, amniotic cavity; All, allantois; Dec, decidua; E, embryo; EC, exocoelomic cavity; N, neural tube. (C) Magnified images of hematoxylin-and-eosin-stained embryos at E8.5 (magnification, ×1,000). In the mutant embryonic region, many atrophied cells (thin arrows) and nuclear condensation (thick arrows) can be seen (right panel). Conversely, in the wild-type embryo, few apoptic cells can be observed (left panel).