ESCRTing cell proliferation off the beaten path -: Lessons from the Drosophila eye

A series of recently published studies have established that defects in endocytic sorting can elicit dramatic tissue overgrowth phenotypes in developing organs of the fruit fly Drosophila melanogaster. Such a link had been suggested by mammalian cell culture experiments almost ten years ago, but in vivo evidence of this link, and the mechanisms through which it might occur, had remained elusive. Drosophila has now proven to be an excellent developmental system in which to both document the effects of endocytic defects on tissue growth and patterning, and to probe the basis of these phenotypes. This work has begun to illuminate some surprising connections between the endocytic trafficking of protein cargoes and the control of cell proliferation and tissue architecture. These connections touch major cell biological processes, including cell division, growth, death, and polarity, and have begun to paint a complex, yet intriguing, picture of how defective endocytic sorting can affect developing tissues.