It begins to be transported to the oocyte during stage ten, where it is first found in the perinuclear nuage, the same location as early Gurken protein. Vasa protein soon accumulates at the posterior pole of the oocyte. The Vasa transcript is not localized. After fertilization and the completion of mitotic cycle 9, Vasa protein accumultes in the pole cells. The posterior group of maternal genes is required for the development of the abdominal region in the Drosophila embryo.
Nanos protein can restore normal abdominal development in posterior group mutants.
Embryos from females mutant for these genes lack the specialized posterior pole plasm and consequently fail to form germ-cell precursors. Several vasa alleles exhibit a wide range of early oogenesis phenotypes. A detailed analysis of Vasa function during early oogenesis is reported using novel as well as previously identified hypomorphic vasa alleles. The polarity defects of vasa mutants appear to be caused by a reduction in the amount of Gurken protein at stages of oogenesis critical for the establishment of polarity. Vasa is required for translation of Gurken mRNA during early oogenesis and for achieving wild-type levels of Gurken mRNA expression later in oogenesis.