A research group from the Oregon Health & Science University demonstrated SCNT procedures developed for primates successfully using skin cells. The key to their success was utilizing oocytes in metaphase II (MII) of the cell cycle. Egg cells in MII contain special factors in the cytoplasm that have a special ability in reprogramming implanted somatic cell nuclei into cells with pluripotent states. When the ovum's nucleus is removed, the cell loses its genetic information. This has been blamed for why enucleated eggs are hampered in their reprogramming ability. It is theorized the critical embryonic genes are physically linked to oocyte chromosomes, enucleation negatively affects these factors. Another possibility is removing the egg nucleus or inserting the somatic nucleus causes damage to the cytoplast, affecting reprogramming ability.