The role of gene cassettes in axis formation during Drosophila oogenesis.

Establishment of the anteroposterior and dorsoventral axes of the fly originates during oogenesis and relies on signaling between the oocyte and the surrounding somatic follicle cells. Some genes originally identified as playing a role in signaling during embryonic development also mediate cell-cell communication during oogenesis. These genes have previously been grouped on the basis of their functions during embryogenesis, and this classification is largely maintained in oogenesis. The EGF receptor, the transmembrane protein rhomboid and proteins in the ras signal transduction pathway are required to initiate dorsoventral polarity, whereas the products of the neurogenic genes Notch and Delta are necessary for formation of the anteroposterior axis in the oocyte.