Fig. 3. Two different embryos (A-D and E-H) that have received an injection of mRNA encoding tau:GFP. The photographs show orthogonal sections (z-scans) obtained from sequences of 250 frames (60 second intervals). The white line above the neural plate cells in each plate corresponds to the section of the coverslip (refer to Materials and Methods). The drawings beneath each photograph illustrate the profile of the epithelial cells. One cell (arrows in A-D) has lost the connections to the basement membrane at time point 0, and divides apically 9 minutes later (B). One of the daughter cells reintegrates into the epithelium (D) in the plane of focus. The embryo at E-H is slightly older. The photographs show one cell (arrows) leaving the epithelium (E-G) to divide apically 60 minutes later (H). not, notochord.