Maelstrom , a Drosophila spindle -class gene, encodes a protein that colocalizes with Vasa and RDE1/AGO1 homolog, Aubergine, in nuage

Abstract

A hallmark of germline cells across the animal kingdom is the presence of perinuclear, electron-dense granules called nuage. In many species examined,Vasa, a DEAD-box RNA helicase, is found in these morphologically distinct particles. Despite its evolutionary conservation, the function of nuage remains obscure. We have characterized a null allele of maelstrom(mael) and shown that Maelstrom protein is localized to nuage in a Vasa-dependent manner. By phenotypic characterization, we have definedmaelstrom as a spindle-class gene that affects Vasa modification. In a nuclear transport assay, we have determined that Maelstrom shuttles between the nucleus and cytoplasm, which may indicate a nuclear origin for nuage components. Interestingly, Maelstrom, but not Vasa, depends on two genes involved in RNAi phenomena, aubergine andspindle-E (spn-E), for its nuage localization. Furthermore,maelstrom mutant ovaries show mislocalization of two proteins involved in the microRNA and/or RNAi pathways, Dicer and Argonaute2,suggesting a potential connection between nuage and the microRNA-pathway.