Axis determination in C-elegans: initiating and transducing polarity

The anterior-posterior axis in Caenorhabditis elegans is determined by the sperm and leads to the asymmetric localisation of PAR (partitioning-defecti ve) proteins, which are critical for polarity. New findings demonstrate tha t sperm asters play a critical role and suggest models for how PAR asymmetr y is established. In addition, studies of blastomere fate determination and heterotrimeric G proteins have started to uncover how initial polarity may be translated into the asymmetric distribution of maternal proteins and th e control of spindle position.