ABSTRACT
The efficient removal of dead cells is an important process in animal development and homeostasis. Cell corpses are often engulfed by professional phagocytes such as macrophages. However, in some tissues with limited accessibility to circulating cells, engulfment is carried out by neighboring non-professional phagocytes such as epithelial cells. Here, we investigate the mechanism of corpse clearance in the Drosophila melanogaster ovary, a tissue that is closed to circulating cells. In degenerating egg chambers, dying germline cells are engulfed by the surrounding somatic follicular epithelium by unknown mechanisms. We show that the JNK pathway is activated and required in engulfing follicle cells. We find that the receptor Draper is also required in engulfing follicle cells, and activates the JNK pathway. Overexpression of Draper or the JNK pathway in follicle cells is sufficient to induce death of the underlying germline, suggesting that there is coordination between the germline and follicular epithelium to promote germline cell death. Furthermore, activation of JNK bypasses the need for Draper in engulfment. The induction of JNK and Draper in follicle cells occurs independently of caspase activity in the germline, indicating that at least two pathways are necessary to coordinate germline cell death with engulfment by the somatic epithelium.
Subject(s)
Drosophila Proteins/metabolism , Drosophila melanogaster/cytology , Drosophila melanogaster/metabolism , Epithelial Cells/cytology , Germ Cells/cytology , Membrane Proteins/metabolism , Ovarian Follicle/cytology , Animals , Drosophila Proteins/genetics , Epithelial Cells/metabolism , Female , Germ Cells/metabolism , MAP Kinase Signaling System/genetics , MAP Kinase Signaling System/physiology , Membrane Proteins/genetics , Signal TransductionABSTRACT
Drosophila is a powerful model system for the identification of cell death genes and understanding the role of cell death in development. In this chapter, we describe three methods typically used for the detection of cell death in Drosophila. The TUNEL and acridine orange methods are used to detect dead or dying cells in a variety of tissues. We focus on methods for the embryo and the ovary, but these techniques can be used on other tissues as well. The third method is the detection of genetic interactions by expressing cell death genes in the Drosophila eye.
Subject(s)
Apoptosis , Drosophila/cytology , Animals , Cell Death , Drosophila/embryology , Drosophila/genetics , Drosophila/metabolism , Eye/metabolism , Female , Gene Expression Regulation , Genes, Insect , Ovary/metabolismABSTRACT
The Drosophila melanogaster ovary is a powerful yet simple system with only a few cell types. Cell death in the ovary can be induced in response to multiple developmental and environmental signals. These cell deaths occur at distinct stages of oogenesis and involve unique mechanisms utilizing apoptotic, autophagic and perhaps necrotic processes. In this review, we summarize recent progress characterizing cell death mechanisms in the fly ovary.
