Cell polarity is important for many of the functions of animal cells, such as migration, axis formation, and asymmetric cell division. Many of the known molecules involved in cell polarity are conserved across animals, however, the mechanisms by which these function are not well understood and additional cell polarity genes remain to be discovered. The C. elegans one-celled embryo is one of the best understood and most experimentally amenable systems for study of polarity induction and transduction. Over the course of one hour, an unpolarised oocyte is transformed into a highly polarised two-cell embryo, with cells of different sizes, cell contents, cell cycle times and developmental potentials.
The PAR proteins are key regulators of cell polarity in C. elegans and in other animals. We are studying how the embryo is initially polarized, how this leads to PAR protein asymmetry and how PAR proteins control downstream asymmetries.
We showed that the initial polarity signal involves microtubules (Tsai et al, 2007). After polarization, PAR proteins direct posterior placement of the first mitotic spindle through asymmetric regulation of receptor independent heterotrimeric G protein signalling (Gotta et al, 2001; Gotta et al, 2003). This regulation involves casein kinase I regulation of a PIP2 synthesis enzyme (Panbianco et al, 2008). PAR proteins also induce asymmetric localization of the Polo-like kinase PLK-1 and CDC-25.1 for differences in cell cycle lengths of the first two daughter cells (Rivers et al, 2008).
We study functions of genes involved in cell polarity using a range of techniques, including real-time fluorescent cell imaging, genetics, and biochemistry. We are particularly interested in the roles of phosphoinositides in polarity events. We are also undertaking a large number of genetic interaction RNAi screens to identify new cell polarity genes and build models.
