Fig. 5

Detection of mitotic B6.4 cells during gastrulation. Localization of pum1 transcripts in embryos at gastrulation stage (panels a to d) and confocal images of an embryo stained for phosphorylated histone H3, a mitosis-specific marker (panels e to f). In panels a to d are shown representative images of different embryos at gastrulation stage hybridized with a DIG-labeled pum1 RNA probe. Vegetal (a to c) or posterior (d) views are shown. pum1 expression is detected in each of the B6.4 cells. Two nuclei (marked with black asterisks) are observed in one of the two B6.4 cells of the embryos shown in panels a to c (note: the nuclei of the other B6.4 cell are out of the focal plane in these three panels). In panel d, however, two nuclei are seen in both B6.4 cells (marked with white and black asterisks, respectively). In panel e is shown a vegetal view of an embryo labeled for phosphorylated histone H3 (phosphorylated serine 28, H3S28p; red). In overlay is also shown labeling for microfilaments (green) and DNA (blue). In all cells except the B6.4 cells, chromosomes appear pink due to the overlay of DNA and H3S28p staining. In panel f is shown a close-up view of the B6.4 cells with heavily condensed chromosomes (blue). In these B6.4 cells, the anti-H3S28p antibody stained a large non-chromosomal subcellular domain (red; marked by white arrow heads). Scale bar is 50 µm in panel E and 15 µm in panel f.