Misexpression of argos, an inhibitor of EGFR signaling in oogenesis, leadsto the production of bicephalic, ventralized, and lateralized Drosophila melanogaster eggs

Epidermal growth factor receptor (EGFR) signaling pathways are frequently i nvolved in generating cell fate diversity in a number of organisms. During anterior-posterior and dorso-ventral polarity in the Drosophila egg chamber and eggshell, EGFR signaling leads to a number of determinative events in the follicle cell layer. A high level of Gurken signal leads to the-express ion of argos in dorsal midline cells. lateral follicle cells, receiving a l ower level of Gurken signal, can continue to express the Broad-Complex (BR- C) and differentiate into cells which produce chorionic appendages. Misexpr ession of argos in mid-oogenesis causes the midline cells to retain express ion of BR-C, resulting in a single fused large appendage. Evidence that arg os can directly repress Gurken-induced EGFR signaling is seen-when prematur e expression of argos is induced earlier in oogenesis. it represses the Gur ken signal ai stage 5-6 of oogenesis which determines posterior follicle: c ells and occasionally leads to eggs with anteriors at both ends. We propose that the Gurken signal ai stage 9 of oogenesis induces follicle cells to t ake on two fates, dorsal midline and lateral, each producing different part s of the eggshell and that argos is one of the key downstream genes require d to select between these two fates. Dev. Genet. 25:375-386, 1999. (C) 1999 Wiley-Liss, Inc.