Disappearance and reformation of the nuclear lamina structure during specific stages of meiosis in oocytes.

The nuclear lamina is a rigid, proteinaceous layer underlying the inner nuclear membrane of eucaryotic cells. It is present in somatic cell nuclei, disappears during mitosis, and is absent from male meiotic cells. We have investigated the disappearance and reformation of the nuclear lamina during meiosis in oocytes, using immunofluorescence and electron microscopy. We find that the status of the nuclear lamina during meiosis of oocytes differs from the reversible depolymerization seen in mitosis in two respects. First, the lamina disappears during meiotic prophase without affecting the structure of the nuclear membranes or the nuclear pores. Second, the proteins of the dissociated lamina are undetectable by immunological methods in pachytene oocytes, whereas they persist in the cytoplasm during mitosis.