  In this work, we investigate the dynamics of a non-local model describing
spontaneous cell polarisation. It consists in a drift-diffusion equation set in
the half-space, with the coupling involving the trace value on the boundary. We
characterize the following behaviours in the one-dimensional case: solutions
are global if the mass is below the critical mass and they blow-up in finite
time above the critical mass. The higher-dimensional case is also discussed.
The results are reminiscent of the classical Keller-Segel system in double the
dimension. In addition, in the one-dimensional case we prove quantitative
convergence results using relative entropy techniques. This work is
complemented with a more realistic model that takes into account dynamical
exchange of molecular content at the boundary. In the one-dimensional case we
prove that blow-up is prevented. Furthermore, density converges towards a non
trivial stationary configuration.
