The shut-down gene of Drosophila melanogaster encodes a novel FK506-binding protein essential for the formation of germline cysts during oogenesis

In Drosophila melanogaster, the process of oogenesis is initiated with the asymmetric division of a germline stem cell. This division results in the self-renewal of the stem cell and the generation of a daughter cell that undergoes four successive mitotic divisions to produce a germline cyst of 16 cells. Here, we show that shut-down is essential for the normal function of the germline stem cells. Analysis of weak loss-of-function alleles confirms that shut-down is also required at later stages of oogenesis. Clonal analysis indicates that shut-down functions autonomously in the germline. Using a positional cloning approach, we have isolated the shut-down gene. Consistent with its function, the RNA and protein are strongly expressed in the germline stem cells and in 16-cell cysts. The RNA is also present in the germ cells throughout embryogenesis. shut-down encodes a novel Drosophila protein similar to the heat-shock protein-binding immunophilins. Like immunophilins, Shut-down contains an FK506-binding protein domain and a tetratricopeptide repeat. In plants, high-molecular-weight immunophilins have been shown to regulate cell divisions in the root meristem in response to extracellular signals. Our results suggest that shut-down may regulate germ cell divisions in the germarium.

The anterior-posterior and dorsal-ventral axes have a common origin in Drosophila melanogaster

The mechanisms governing anterior-posterior and dorsal-ventral polarity in Drosophila melanogaster had previously been considered as independent processes. However, two papers(1,2) now reveal that both axes are initiated during oogenesis by the same pathway, and also clearly demonstrate that one is dependent on the other.