Subcellular expression of CD9 and CD81 in the mouse oocyte demonstrates that these are predominantly localized in the PVS and zona pellucida respectively.
Work in mouse oocytes has demonstrated that homologous chromosome pairs (bivalents) lack end-on kinetochore-microtubule interactions during prometaphase (Brunet et al., 1999), and stable attachments are not achieved until they have already congressed to the metaphase plate (Kitajima et al., 2011).
When analysed by qRT-PCR, Amh is the most differentially expressed with an average 4-fold higher expression in CCs associated with NSN oocytes, demonstrating its robustness as a further non-invasive diagnostic marker for the selection of developmentally competent or incompetent mouse antral oocytes.
Of note, in vitro fertilization (IVF) using light-stimulated sperm was successful using zona pellucida-intact oocytes, demonstrating that a cAMP increase, at least in vitro, is sufficient to restore fertility in Slc9a10-null mice.
To establish whether human oocytes demonstrate the same molecular changes as the mouse, we assessed expression of these targets in GV oocytes obtained from patients undergoing IVF treatment.
Furthermore, ESC lines derived from cloned embryos using Oct4-knockout oocytes demonstrated full pluripotency by generating completely ESC-derived mice through the tetraploid complementation test, the most stringent test for pluripotency [ 37].
Following cryopreservation, group 1 oocytes demonstrated a 63% survival rate and 68% maturation rate in vitro.
By inactivating condensin I or II before the first meiotic division in mouse oocytes, Nasmyth and colleagues demonstrate that condensin is needed for chromatin thread formation and chromosome rigidity.
By live imaging of mouse oocytes, Verlhac and colleagues demonstrate that actin-coated vesicles together with myosin Vb participate in centring of the nucleus by creating a gradient of cytoplasmic forces.
The requirement of a functional nucleolus for proper embryonic development was demonstrated when enucleolated mouse oocytes were fertilized or parthenogenetically activated (Ogushi et al., 2008).
