Fig. 2. Effects of P446L mutant importin-ß on cleavage chromatin following its injection into wild-type cleavage embryos expressing histone-GFP. Approximately 200 picolitres P446L protein solution (1.2 µM, approximately the endogenous importin-ß concentration) was injected into the posterior end of a wild-type cleavage embryo in which histone-GFP highlighted chromatin. Chromatin organization was followed in a laser-scanning microscope. Optical sections from the anterior (A-C) and the posterior (D-F) regions of the same embryo are shown. While the anterior section was devoid of P446L, the P446L mutant protein was present at the posterior region. A and D represent interphase chromatin following P446L protein injection. B and E show segregating chromosomes. C and F show chromatin during the upcoming interphase. Note that the nuclei doubled in number and the chromosomes segregate both at the anterior (control) and posterior (`experimental') regions of the embryo. Bar, 20 µm.