Patterning the eye: A role for the cell cycle?

Although highly regulated cell cycle behavior accompanies specification of cell types in the Drosophila retina, no evidence has previously existed that cell cycle phase influences cell fate choice. Meserve and Duronio have now used genetic techniques to trace the fate of a sub-population of cells that accumulate in G2-phase of the cell cycle, discovering that they contribute to a particular fate, the precursor of the sensory inter-ommatidial bristles. Meserve and Duronio further show that G2 cells have an advantage acquiring inter-ommatidial bristle fate. This is the first evidence for a functional contribution of cell cycle phase to cell fate determination in the Drosophila eye and indicates that the fate of one population of retinal cells is established much earlier than previously recognized, during the larval stages when cell-cell interactions influence cell cycle phase. Inter-ommatidial bristle fate had been thought to arise much later, in the pupal stage, and models for how these neuronal eye structures arise will now have to be revised.