Morphogenesis of the eggshell in Drosophila.

The Drosophila eggshell is a specialized extracellular matrix that forms between the oocyte and overlaying somatic follicle cells during the latter stages of oogenesis. Largely proteinaceous, the eggshell is a highly organized multilayered structure with regional specializations designed to perform a variety of functions. Production of a functional eggshell features: (1) the differentiation of subsets of follicle cells in response to ovarian signals, (2) directed migrations of the follicle cells within the developing egg chamber, (3) expression of eggshell structural genes by the follicle cells in a defined temporal and spatial order, (4) postdepositional modifications of the eggshell proteins including several temporally regulated proteolytic cleavage events, and (5) regulated trafficking of several eggshell proteins in the assembling structure. By exploiting the genetic advantages of Drosophila and using evolution as a guide, the eggshell provides an excellent experimental system to study, in vivo, molecular mechanisms used to regulate protein-protein interactions throughout the assembly of a complex extracellular architecture in a developing organism.