Hedgehogs tryst with the cell cycle.

Hedgehog proteins play an essential role during pattern formation in animal development and, increasingly, much of our appreciation of their modes of action is emanating from studies of their signalling mechanisms at the cellular level. Recent work has provided insights into how Hedgehog controls the cell cycle in a variety of circumstances. The data suggest that this influence may be direct and operates through interaction of the signalling pathway with cell cycle regulators at multiple points within the cell cycle. These new findings have profound implications in the context of clinical conditions - especially cancers - that arise from de-regulated cell proliferation in response to aberrant Hedgehog signalling activity.