  Certain cellular processes take the form of activity pulses that can be
interpreted in terms of noise-driven excitable dynamics. Here we present an
overview of different gene circuit architectures that exhibit excitable pulses
of protein expression, when subject to molecular noise. Different types of
excitable dynamics can occur depending on the bifurcation structure leading to
the specific excitable phase-space topology. The bifurcation structure is not,
however, linked to a particular circuit architecture. Thus a given gene circuit
design can sustain different classes of excitable dynamics depending on the
system parameters.
