Vasa is a broadly conserved DEAD-box RNA helicase associated with germ line 
development and is expressed in multipotent cells in many animals. During 
embryonic development of the sea urchin Strongylocentrotus purpuratus, Vasa 
protein is enriched in the small micromeres despite a uniform distribution of 
vasa transcript. Here we show that the Vasa coding region is sufficient for its 
selective enrichment and find that gustavus, the B30.2/SPRY and SOCS box domain 
gene, contributes to this phenomenon. In vitro binding analyses show that 
Gustavus binds the N-terminal and DEAD-box portions of Vasa protein 
independently. A knockdown of Gustavus protein reduces both Vasa protein 
abundance and its propensity for accumulation in the small micromeres, whereas 
overexpression of the Vasa-interacting domain of Gustavus (GusΔSOCS) results in 
Vasa protein accumulation throughout the embryo. We propose that Gustavus has a 
conserved, positive regulatory role in Vasa protein accumulation during 
embryonic development.