Figure 3. Localization of
apx-1 mRNA in C. elegans embryos by whole-mount in situ hybridization. The left column shows embryos hybridized to
apx-1 antisense probe visualized using alkaline-phosphatase-mediated detection (purple color indicates presence of
apx-1 RNA). Micrographs of each embryo stained with the DNA-binding dye DAPI are shown at right. Maternal
apx-1 mRNA is uniformly distributed in early embryos (A-F). By the 12-cell stage (G,H), maternal RNA is being degraded rapidly in somatic blastomeres so that
apx-1 RNA is present in the germline precursor P3, but little is detectable in other cells, includingMS. (I,J) Beginning at approximately the 36-cell stage, double spots of nuclear staining (arrowhead), presumably the result of embryonic
apx-1 transcription (Seydoux and Fire, 1994), are evident in 1 (shown here) to 5 unidentified cells. No staining is detected in embryos containing more than 100 cells (bottom embryo). All embryos are oriented with anterior at left and dorsal at top. Embryos measure approximately 50 µm alongtheir anterior-posterior axis. Images in the left column were obtained using Nomarski differential interference optics; images on the right were obtained using epifluorescence with UV illumination. The highly condensed DAPI-staining foci at the anterior tip of the 1-cell embryo (B) and in the upper-left of the 4-cell embryo (F) are polar bodies.