Cell fate specification in the Drosophila eye.

With the passing of the furrow over a uniformly equivalent group of cells, a spectacular array of cell types, each different in structure and function arises in the developing eye disc of Drosophila. A small number of ubiquitously expressed transcription factors combine with an even smaller number of signals emanating from the furrow and the developing clusters and generate cell-specific expression of a panoply of transcription factors (reviewed in Kumar and Moses 1997).The challenge is to understand how the cell-specific transcription factors are placed in their respective cells and how they then function in assigning different identities to each cell type. Here, we have presented our current understanding of this process. The aim is to be eclectic rather than comprehensive, and we apologize in advance to those investigators whose work we have not fully cited.