Although centrioles are composed of several hundred proteins, mutant and genome-wide RNAi screens have identified only a small number of proteins that are essential for centriole duplication in flies (and this set of proteins is remarkably similar to the those identified as being essential for centriole duplication in worms). Thus, we believe that all the proteins essential for centriole assembly in flies have now been identified (Sak/Plk4, Sas6, Ana2/STIL, Sas4 and Asl/Cep152), as have several other proteins that strongly influence this process (such as Ana1, Cep135, CP110, Cep97 and Klp10A). Our goal is to understand how these proteins interact with one another and how their interactions are regulated to ensure that the right number of centrioles assemble at the right place and time.
To this end we are taking a structural approach to identify and then mutate the key interaction interfaces (so allowing us to disrupt individual protein-protein interactions one at a time) (see, for example, Cottee et al., eLife, 2013., Cottee et al., eLife, 2015) and live cell microscopy, super-resolution microscopy and electron microscopy approaches to quantify normal and mutant protein behaviour and dynamics (see, for example, Novak et al., Curr. Biol., 2014; Franz et al., JCB, 2013). We believe that a near complete molecular understanding of how centrioles assemble, and how this process is regulated in space and time, will emerge over the next few years. A crucial tool for out studies will be Sas6/Ana2 particles (SAPs), which form when Sas6 and Ana2 are overexpressed together in cells (Stevens et al., Dev. Cell, 2010). These particles bear a striking resemblance to the centriole cartwheel and, crucially, they can form and recruit other centriole and centrosome proteins even when other key duplication proteins are absent.