The Life of PIE

All plants and animals start out life as a single cell, the egg. In the course of development it is crucial to produce many different cells that differ in their function; for example, muscles, neurons or skin. The type of cell is decided by molecules known as fate determinants. During cell divisions, fate determinants can be passed unequally so that the two daughter cells will have different identities.

The eggs of the small soil worm Caenorhabditis elegans undergo unequal cell divisions to generate the many different types of cells in the worm. These pictures illustrate the first unequal division of a living egg: the fate determinant PIE-1 becomes enriched in one half of the cell and is passed on to only the smaller daughter cell, which will make the eggs and sperm in the adult worm. Time-lapse recording of living C. elegans one-cell embryo, GFP expressingworm, LSM 510 confocal, pseudo-coloured, 63x oil lens.