Despite a critical role for the actin cytoskeleton in inducing an initial asymmetry in PAR proteins, recent evidence from our and other labs points increasingly towards a role for self-assembly in PAR domain organisation. Specifically, our work indicates that there are no physical barriers or transport processes required for keeping PAR proteins on the two halves of the cell separate (Goehring, et al. JCB 2011). Rather, once an asymmetry is induced, interactions between PAR proteins appear to be sufficient to promote and maintain the polarised state.
These observations point towards a class of reaction-diffusion mechanisms in generating the observed localisation patterns, and indeed, we can recapitulate the observed patterns with a simplified theoretical model (Goehring, et al. Science 2011). Extensive literature on theoretical systems has identified a number of core ingredients required for pattern formation. By combining mathematical modeling with experimental manipulation of embryos, current work is focused on uncovering which core features of the PAR interaction network are critical for pattern formation in the embryo.