Positioning of an artificial centrosome in a dynamic actin network

The centrosome is one of the main microtubule-organizing centers in cells, spawning filaments that define the cells shape and polarity. Peculiarly, it is almost always positioned either at the center of the cell or at its periphery, rarely in between.

Precise centrosome positioning is crucial: when positioned in the center, the centrosome has the fundamental task of integrating information from the whole cell via the microtubule network. Instead, its swift transition to the periphery is a key step of cell differentiation and polarization.

Yet, despite its importance, the mechanism regulating this transition is unknown: several factors are probably involved and regulated in the process, including forces due to molecular motors or to the dynamics of the actin and microtubule networks.

In particular, the role of the actin network inside which the microtubules are embedded is starting to be understood as a fundamental player, yet the precise physical mechanism is not understood.

This project consists in resorting to the in vitro reconstitution of both the actin and the microtubule networks at the same time, to study their interaction in a minimal biomimetic system.

Using an artificial centrosome spawning microtubules and embedding it inside an artificial actin cortex in a dynamic state, adding molecular motors to provide activity and confining it inside cell-sized microwells, we aim to understand how a sharp center to periphery transition can occur and what are the physical processes involved.

The possibility to add different purified components one at a time will allow exploring what role factors such as motor- and polymerization-based forces or the mechanical coupling to a contractile actin network play, individually and combined, in defining and controlling precise centrosome positioning.

The project paves the way for the understanding of centrosome positioning in cells but also represents an big step in the ongoing effort to build a synthetic cell ""from scratch"".