IDENTIFICATION AND BEHAVIOR OF EPITHELIAL STEM-CELLS IN THE DROSOPHILA OVARY

Throughout their lives, adult Drosophila females continuously produce oocytes, each surrounded by an epithelial monolayer of follicle cells. To characterize the somatic stem cells that give rise to ovarian foll icle cells, we marked dividing cells using FLP-catalyzed mitotic recom bination and analyzed the resulting clones. Each ovariole in young fem ales contains, on average, two somatic stem cells located near the bor der of germarium regions 2a and 2b. The somatic stem cells do not coor dinate their divisions either with each other or with the germline ste m cells. As females age, initially mosaic ovarioles become monoclonal, indicating that functional somatic stem cells have a finite life span . Analysis of agametic flies revealed that somatic cells continue to d ivide in the absence of a germline. Under these conditions, the somati c stem cells develop near the tip of the ovariole (the normal site of the germline stem cells), and a subpopulation of somatic cells that no rmally separates the germline and somatic stem cells is missing.