Cellular communication in the developing Drosophila eye

Undetermined cells are directed to their fate in the Drosophila eye by positional cues which are probably presented by adjacent differentiating cells. The sevenless protein is thought to function as a signal-receiving protein on the plasma membrane of the cell destined to form the seventh photoreceptor, R7. Localization of the protein indicates the interactions between undetermined and differentiating cells and suggests the existence of other receptor proteins similar to sevenless.