Fig. 4. SoxB1 protein is released into the cytoplasm during mitosis. Two blastomeres of embryos at the 16-cell stage are shown in interphase (left side) or in mitosis (right). Measurements of pixel densities show that the cytoplasmic signal increases 1.7-fold in blastomeres in mitosis (arrowheads). Chromosomes in these cells lack detectable SoxB1 staining, whereas most of the SoxB1 signal in interphase cells is in nuclei. Scale bar: 5 µm.