Germline cyst formation in Drosophila.

In a wide variety of organisms, gametes develop within clusters of interconnected germline cells called cysts. Four major principles guide the construction of most cysts: synchronous division, a maximally branched pattern of interconnection between cells, specific changes in cyst geometry, and cyst polarization. The fusome is a germline-specific organelle that is associated with cyst formation in many insects and is likely to play an essential role in these processes. This review examines the cellular and molecular processes that underlie fusome formation and cyst initiation, construction, and polarization in Drosophila melanogaster. The studies described here highlight the importance of cyst formation to the subsequent development of functional gametes.