© The Rockefeller University Press $30.00
The Journal of Cell Biology, Vol. 179, No. 3, November 5, 2007 397402
In Caenorhabditis elegans embryos, the oocyte has no develop-
mentally important polarity (Goldstein and Hird, 1996). After
fertilization, the oocyte and sperm pronuclei are usually at
opposite ends of the oblong embryo, and the oocyte pronucleus
undergoes two meiotic divisions, extruding two polar bodies
before polarity induction and mitosis (Oegema and Hyman, 2006).
Posterior polarity is induced via an unknown centrosome-
dependent signal brought in by the sperm (Goldstein and
Hird, 1996; O'Connell et al., 2000; Sadler and Shakes, 2000;
Wallenfang and Seydoux, 2000; Cowan and Hyman, 2004, 2006).
This is thought to locally down-regulate actin contractility,
leading to anterior movement of the anterior PAR (partitioning
defective) polarity proteins PAR-3, PAR-6, and PKC-3 through