Polarizing without a c(l)ue.

Most cells polarize in response to an asymmetric signal but some can spontaneously establish a discrete axis of polarity in the absence of a directional cue. Many mathematical models predict that locally acting positive feedback loops and globally acting negative regulators are required for pattern formation. Here, we summarize recent progress towards identifying some of the molecular components involved in these positive and negative feedback mechanisms. In addition, we describe the increasing evidence suggesting that the actin cytoskeleton is fundamentally important for the spontaneous symmetry breaking observed in a range of different organisms.