P granules are normally redistributed to the posterior of the embryo before the first cell division. Hird et al. We have filmed fluorescent P granules and cytoplasmic flows in the same embryos, and created overlays of these films. We are currently testing whether P granules fail to move in these mutants by filming mutant embryos similarly. First, PAR-1 might be part of a complex that anchors P granules in place once they reach the posterior cortex, preventing further movement along the cortex, even as cortical flows continue.
Experiments testing the safe haven hypothesis are currently underway.