Multiple Functions of the DEAD-Box Helicase Vasa in Drosophila Oogenesis.

The DEAD-box helicase Vasa (Vas) has been most extensively studied in the fruit fly, Drosophila melanogaster, and numerous roles for it in germline development have been discovered. Here, we summarize the present state of knowledge about processes during oogenesis that involve Vas, as well as functions of Vas as a maternal determinant of embryonic spatial patterning and germ cell specification. We review literature that implicates Vas in Piwi-interacting RNA (piRNA) biogenesis in germline cells and in regulating mitosis in germline stem cells (GSCs). We describe the functions of Vas in translational activation of two mRNAs, gurken (grk) and mei-P26, which encode proteins that are important regulators of developmental processes, as Grk specifies both the dorsal-ventral and the anterior-posterior axis of the embryo and Mei-P26 promotes GSC differentiation. The role of Vas in assembly of polar granules, ribonucleoprotein particles that accumulate in the posterior pole plasm of the oocyte and are essential for germ cell specification and posterior embryonic patterning, is also described.