How do cells assemble actin networks of specific identities?
Key words: Actin cytoskeleton; Yeast genetics; Cell imaging and Single molecule imaging.
The actin cytoskeleton is a complex and dynamic system involved in several force-generating processes such as cell motility or cell division . Depending on their function in cells, actin filaments can be organized into different structures. For example, crawling cells form a lamellipodium made of branched actin filaments at the front and filopodia which are composed of parallel actin filaments (see Fig. 1). In these structures, new actin filaments are generated and elongated by various families of nucleation factors. These structures are also constantly remodeled by multiple families of actin binding proteins (ABPs).
Importantly, the different actin structures present in cells are differently regulated because they interact with distinct sets of ABPs. Many conserved families of ABPs are found only associated with specific actin structures, while excluded from others . How cells organize their interior is one of the central questions in biology. While it applies also to actin networks, the community largely ignores how ABPs are sorted efficiently to distinct sub-structures of actin filaments.Two non-exclusive hypotheses may explain how actin filaments within actin networks may acquire a specific identity to recruit ABPs selectively . First, actin filaments may be assembled from distinct actin isoforms. Second, actin filaments may be decorated by some specific additional factors while they are being assembled. The aim of this PhD will be to verify these hypotheses and to determine whether the mechanisms by which cells generate a diversity of actin substrates. The candidate will use yeast genetics to test his/her hypotheses in cells and top-end single molecule imaging to understand these mechanisms in vitro.The host team is interdisciplinary and composed of physicists, chemists and biologists. The candidate should be interacting actively with the team members and be driven by his/her curiosity. The team is also international, so speaking and presenting in English is expected.
Please send your CV, a letter of motivation and con- tacts for references.
Michelot lab Institut de Biologie du Développement de Marseille (IBDM), Aix-Marseille Université
 Blanchoin et al., Actin dynamics, architecture, and mechanics in cell motility, Physiol Rev, 2014
 Kovar et al., Three’s company: the fission yeast actin cytoskeleton, Trends Cell Biol, 2010
 Michelot and Drubin, Building distinct actin filament networks in a common cytoplasm, Curr Biol, 2011