Fat flies expanded the hippo pathway: a matter of size control.

By simultaneously inhibiting cell proliferation while promoting apoptosis, the Hippo signaling pathway provides a robust mechanism to restrict organ size during Drosophila development. Despite impressive progress in revealing the key intracellular components of this growth-regulatory pathway, the nature of the signal that regulates Hippo signaling in vivo has remained elusive. Several studies now implicate the atypical cadherin protein Fat as a cell surface receptor for the Hippo signaling pathway, thus potentially linking the Hippo kinase cascade with the extracellular milieu.