Stable segregation of PAR proteins in the early C elegans embryo

PAR proteins, collectively termed the anterior and posterior PAR proteins, establish distinct intracellular spatial domains in the one cell C elegans embryo, polarizing the cell. This polarization is persistent, lasting approximately 10-20 minutes until first cleavage. It has been established experimentally that the anterior and posterior PAR proteins interact through mutual phosphorylation, and recent genetic studies indicate that the anterior PAR proteins are capable of oligomerizing. Using mathematical modelling, I show that known interactions between the PAR proteins give rise to a bistable switch that may account for the stable segregation of the PAR proteins. The presence of a bistable switch in the C elegans embryo is verified experimentally by depleting the anterior PARs using RNA interference, providing a direct test of the mathematical model.