Figure 6.

Cortical ER clusters are not present in mitotic one-cell embryos. Fertilized (A) and parthenogenetic (B) one-cell embryos were injected with DiI at different times of the first mitotic division. These stages were the Pn stage 2–4 h before the expected time of NEBD, in mitosis after NEBD, and after cleavage to the two-cell stage. Bright field (top row), confocal equatorial (middle row), and cortical (bottom row) sections are illustrated. Note that in the cortical sections there is no evidence of ER clusters. Pn and two-cell stages show a typical interphase ER organization with a diffuse cytoplasmic network that is continuous with the nuclear envelope. In the NEBD stage embryos there is an accumulation of ER around the mitotic spindle. Data are from at least seven embryos at each stage.