The polar cells are a pair of specialized somatic cells at each end of the developing egg chamber. While their importance in follicle cell specification and border cell migration are understood, relatively little is known about their functions in late stages of oogenesis. The micropyle is a conical structure with a central lumen at the anterior of the egg and serves as the entry point for sperm during fertilization. Its formation is known to be dependent upon the timely migration of the border cells. If border cell migration is delayed, the micropyle exhibits defects, among which are blockage of the central lumen. Here we present evidence that the polar cells have a critical role in formation of a functional micropyle. It has been described that the polar cells form an extension into the developing micropyle, but the function or mechanisms driving its formation are unknown. We observed that upd3 mutants have an increased incidence of unfertilized eggs and failure to form the micropyle channel. The polar cell/border cell cluster still migrates to the anterior of the oocyte, but the polar cell extension misses the micropyle resulting in blockage. Using live imaging and fixed ovaries with GFP labeled polar cells, we characterized the dynamics of polar cell extension and micropyle development in wild type eggs. Results show that extension morphology during micropyle formation is highly dynamic and predictable. Furthermore, the polar cell extension forms prior to appearance of the micropyle and seems to mark the location where the micropyle will form. We are currently characterizing polar cell behavior in wild type and upd3 mutant egg chambers and these results will be reported. While autocrine Jak/Stat activity in the polar cells is not required for process formation but, its reduction does affect process morphology and polar cell adhesion. To determine when polar cell involvement is required for micropyle formation, we are impairing polar cell functions through genetic manipulation of cytoskeletal dynamics, signaling, and viability to examine the nature and timing of polar cell formation of the micropyle channel. Results from these experiments will be reported.