A role for vasa in regulating mitotic chromosome condensation in Drosophila.

Vasa (Vas) is a conserved DEAD-box RNA helicase expressed in germline cells that localizes to a characteristic perinuclear structure called nuage. Previous studies have shown that Vas has diverse functions, with roles in regulating mRNA translation, germline differentiation, pole plasm assembly, and piwi-interacting RNA (piRNA)-mediated transposon silencing. Although vas has also been implicated in the regulation of germline proliferation in Drosophila and mice, little is known about whether Vas plays a role during the mitotic cell cycle. Here, we report a translation-independent function of vas in regulating mitotic chromosome condensation in the Drosophila germline. During mitosis, Vas facilitates robust chromosomal localization of the condensin I components Barren (Barr) and CAP-D2. Vas specifically associates with Barr and CAP-D2, but not with CAP-D3 (a condensin II component). The mitotic function of Vas is mediated by the formation of perichromosomal Vas bodies during mitosis, which requires the piRNA pathway components aubergine and spindle-E. Our results suggest that Vas functions during mitosis and may link the piRNA pathway to mitotic chromosome condensation in Drosophila.