Coordinating developmental signaling: novel roles for the Hippo pathway.

Genetic and biochemical studies have defined the Hippo pathway as a central mediator of developmental and pathogenic signals. By directing intracellular signaling events, the Hippo pathway fine-tunes cell proliferation, cell death, and cell-fate decisions, and coordinates these cues to specify animal organ size. Recent studies have revealed that Hippo pathway-mediated processes are interconnected with those of other key signaling cascades, such as those mediated by TGF-β and Wnt growth factors. Moreover, several reports have described a role for cell contact-mediated polarity proteins in Hippo pathway regulation. Emerging details suggest that crosstalk between these signals drives fundamental developmental processes, and deregulated intercellular communication influences disease progression, such as cancer. We review recent data with a focus on how the Hippo pathway integrates its activity with other signaling pathways.