Abstract
Animal oocytes undergo a highly conserved developmental arrest in prophase of meiosis I. Often this marks a period of rapid growth for the oocyte and is necessary to coordinate meiotic progression with the developmental events of oogenesis. In Drosophila, the oocyte develops within a 16-cell germline cyst. Throughout much of oogenesis, the oocyte remains in prophase of meiosis I. By contrast, its 15 mitotic sisters enter the endocycle and become polyploid in preparation for their role as nurse cells. How germline cysts establish and maintain these two independent cell cycles is unknown. We demonstrate a role for the p21(CIP)/p27(Kip1)/p57(Kip2)-like cyclin-dependent kinase inhibitor (cki) dacapo in the maintenance of the meiotic cycle in Drosophila oocytes. Our data indicate that it is through the differential regulation of the cki Dacapo that two modes of cell-cycle regulation are independently maintained within the common cytoplasm of ovarian cysts.
Highlights
During metazoan development, cells alter their cell cycles in response to specific developmental cues
In order to determine the precise onset of the differential regulation of Dap in the nurse cells versus the oocyte, we stained wild-type ovaries with an antibody against Dap
There is a clear gradient with respect to meiosis, this is not reflected in the distribution of the Dap protein
Summary
Cells alter their cell cycles in response to specific developmental cues. Two common examples of this phenomenon occur during Drosophila oogenesis when cells within a germline cyst undergo either the reductional divisions of meiosis and produce a functional gamete or enter the endocycle and develop as a highly polyploid nurse cell. The single pro-oocyte arrests in prophase of meiosis I for most of the growth phase of oogenesis, while the 15 nurse cells go on to complete 10-12 endocycles to become highly polyploid. During these endocycles the nurse cells cycle asynchronously
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