Fig. 4. 14-3-3-deficient embryos fail to execute syncytial divisions properly. Wild-type (A,D) and 14-3-3-deficient (B,C,E-G) embryos were fixed and stained for DNA (red) and an anti--tubulin antibody (C-F) to visualize microtubules (blue). (A) A wild-type embryo at the end of fourth embryonic mitosis. Nuclei are clearly separated. Embryonic cycle number is determined by counting nuclei (n = 2 at the end of M1, n = 4 at the end of M2, etc.). (B) A 14-3-3-deficient embryo at the end of M4 shows nuclei pairs connected by chromosome bridges. One such pair is indicated with a bracket and is shown rotated and magnified in E (arrowhead indicates bridge). (C) A 14-3-3-deficient embryo in a later syncytial cycle. Arrows point to MTOCs that have no obvious nuclei associated with them. Brackets indicate nuclei pairs connected by bridges. These are magnified and shown in F and G. Arrowhead indicates bridges. Notice the presence of robust microtubules around the chromosome bridge in F, the region in which the spindle mid-body normally resides at a similar stage of mitosis in wild-type embryos (D). The red stain in the middle of the embryo in C indicates a large yolk DNA mass. Bar, 15.7 µm in A and B, 8.3 µm in C and 5.5 µm in D-G.