Aug. 29, 2011 Most cells rely on structural tethers to position
chromosomes in preparation for cell division. Not so oocytes.
Instead, a powerful intracellular stream pushes chromosomes far-
off the center in preparation for the highly asymmetric cell
division that completes oocyte maturation upon fertilization of
the egg, report researchers at the Stowers Institute for Medical
Research. Their findings illustrate how oocytes repurposed a
dynamic cellular mechanism capable of generating considerable
intracellular forces and widely used by migrating cells to
propel them forward, to set the stage for asymmetric cell
division -- the kind of cell divisions that generate two
different daughter cells. It might also lead to improvements in
the selection criteria used to choose the most promising oocytes
for in-vitro fertilization. As a mammalian egg develops, it
undergoes two highly asymmetric cell divisions, known as meiosis
I and II. During each of these divisions, the cytoplasm divides
unequally, giving rise to a l