Fig. 4. (A-H) Mitotic divisions in the neural plate stage. (A-D) The neural plate of an embryo carrying the transgenic insertions Tg(H2AF/Z)^kca37 and Tg(H2AF/Z)^kca66 was photographed from above. The first photograph (A) shows three metaphase plates (arrows). The other frames, taken 3 minutes (B), 5 minutes (C) and 7 minutes (D) later, show anaphase and telophase. Note that the plane of cleavage is perpendicular to the neuroepithelium in all three. (E-H) Time-lapse photographs from a sequence taken at 45 second intervals of a mitotic cell (arrows) in the neural plate of an embryo injected with tau:egfp mRNA. The neural plate was photographed from above. Notice the appearance of the centrosome, its division (F), the migration of the daughter centrosomes to opposite sides of the cell and formation of the spindle (G), which lies parallel to the plane of the neuroepithelium. Planar movements of the metaphase plate (the dark zone between spindle fibres, arrows in F,G) are relatively weak in this particular case. (I-P) Two sequences of four time-lapse confocal photographs each to illustrate mitotic divisions in the neural tube. The photographs in I-L (from 0' to 14') show the neural tube of an embryo carrying the transgenic insertions Tg(H2AF/Z)^kca37 and Tg(H2AF/Z)^kca66, flanked by somites on either side. Several mitoses are visible, two of which are indicated by the arrows. Notice that the plane of cleavage is perpendicular to the neurocoel (neur). (M-P) An embryo injected with tau:egfp mRNA. The earliest sign of an impending cell division is the duplication of the centrosome (arrows in 0'), and the daughters migrate to opposite poles of the cell. The spindle can be seen in N,O. Note that the mitotic spindle is parallel to the neurocoel (neur). Anterior is towards the top in all photographs.

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