Patterning the fly eye: the role of apoptosis.

Early development in many tissues is characterized by a rapid expansion in cell number. Excess cells are removed through activation of their intrinsic apoptotic machinery. This over-expansion followed by selective removal is important for the sculpting of these tissues, and how specific cells are selected to die is one of the central questions in development. The Drosophila eye is a unique example of such patterning through cell death. Because of its remarkable reiterative design, the fly eye lends itself to studies of mutants with increased or decreased apoptosis. We know that the process of elimination of lattice cells is highly regulated. And we have learned that each ommatidial unit is involved in the life-death decision of lattice cells through cell-cell signaling. But, we have yet to understand how this signaling is regulated spatially to result in such precision. In this article, we describe and speculate on the role of selective cell death during maturation of the fly eye.