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(186) MOUSE OVARIAN GERM CELL CYSTS: FORMATION AND FUNCTION. Pepling, Melissa1, Spradling, Allan1, 1 Howard Hughes Medical Institute, Baltimore, MD ABSTRACT- In males and many invertebrate females, an important phase of early germline development takes place within cysts of interconnected cells. We have recently identified a similar process within the developing mouse ovary. Synchronous germ cell divisions in 10.5-13.5 dpc ovaries produce germ cell clusters connected by intercellular bridges that can be visualized by electron microscopy. We have now studied the fate of these germ cell cysts during subsequent development. Mouse cysts undergo programmed breakdown between 20.5-22.5 dpc, during which approximately one third of the oocytes survive to form primordial follicles. Individual cysts examined with an apoptosis marker usually contained only one or two dying cells suggesting that only a subset of the cells of a cyst die rather than whole cysts. In addition, cytoplasmic markers become differentially localized within the cysts again suggesting that there are two types of cells, cells that die and cells that become oocytes. The breakdown of cysts is coupled to a massive rearrangement of cytoplasmic organelles. The function of cysts may be to ensure that oocytes inherit highly functional organelles. KEY WORDS: germline cysts, oocyte determination |
