Published on SDB CoRe: Mar 11 2013
The Germline: Oogenesis
Stage of Development: Oogenesis
Drosophila oogenesis occurs in an assembly line fashion within a structure called an ovariole. In the germarium, stem cells divide to produce another stem cell and cystoblast. The cystoblast divides 4 times to produce a cluster of 16 cells that remain connected to each other by cytoplasmic bridges called ring canals. One of these cells differentiates as an oocyte while the other 15 become polyploid nurse cells. The nurse cells produce maternal RNAs, proteins and organelles that are delivered to the developing oocyte via the ring canals. The nurse cell/oocyte cluster, surrounded by a somatic follicle cell epithelium, constitutes an egg chamber. Egg chambers progress through the ovariole in 14 morphologically distinct stages. At the end of stage 10, the nurse cells contract and ‘dump’ their contents into the oocyte; they are then eliminated by apoptosis. Vigorous streaming of the oocyte cytoplasm that accompanies nurse cell dumping mixes the incoming nurse cell cytoplasm with the ooplasm (see inset and movie). The follicle cells, which migrate to enclose the oocyte, secrete both the vitelline membrane and the chorion or egg shell to protect the mature egg.
A figure based on this one was published in: Becalska, A.N. and Gavis, E.R. Lighting up mRNA localization in Drosophila oogenesis. Development, 2009, 136: 2493-2503.