Disease relevance of vas

• Reduction in Vas-eIF5B interaction during oogenesis leads to female sterility, with phenotypes similar to a vas null mutation [1].

High impact information on vas

• This gene turns out to be vasa, which is required maternally for the formation of polar granules and germ cells [2].
• Of the eight genes necessary for germ cell formation at the posterior, only three, oskar, vasa and tudor, are essential at an ectopic site [3].
• The product of the Drosophila gene vasa is very similar to eukaryotic initiation factor-4A [4].
• Accumulation of vasa protein at the posterior pole of treated oocytes was also disrupted [5].
• Genetics has revealed three additional genes, staufen, vasa, and tudor, that are also essential for pole plasm formation [6].

Biological context of vas

• Eight of nine vas point mutations cause codon substitutions in a region conserved among DEAD-box genes [7].
• The Drosophila gene vasa encodes a DEAD-box protein, which is localized during early oogenesis to the perinuclear region of the nurse cells and later to the pole plasm at the posterior end of the oocyte [7].
• These observations show that germ-line-specific vas expression is promoted by autonomous function of maternal Nos and Pum in the germ-line progenitors during embryogenesis, and is regulated differentially in embryogenesis and oogenesis [8].
• However, several vasa alleles exhibit a wide range of early oogenesis phenotypes [9].
• A gus mutation blocks posterior localization of VAS, as does deletion of a segment of VAS containing the GUS binding site [10].

Anatomical context of vas

• Initial recruitment of vasa to the pole plasm must consequently depend upon protein-protein interactions but, once localized, vasa must bind to RNA to mediate germ cell formation [7].
• Very little is known about the specific role of this organelle, but in Drosophila three nuage components have been identified, the Vasa, Tudor and Aubergine proteins [11].
• No vas RNA expression is evident in either diplotene primary spermatocytes, secondary spermatocytes, spermatids or spermatozoa [12].
• In the testis, vas signals are strong in spermatogonia and decrease in early primary spermatocytes [12].
• Identification and characterization of genes differentially expressed in the testis/vas deferens of the fed male tick, Amblyomma hebraeum [13].

Associations of vas with chemical compounds

• Two new ethyl methane sulfonate-induced, female sterile alleles of vas have been isolated [14].

Regulatory relationships of vas

• However, GRK accumulation in the oocyte is severely reduced in the absence of vasa function, suggesting a function for VASA in activating gurken translation in wild-type ovaries [15].

Other interactions of vas

• These results suggest that the Oskar-Vasa interaction constitutes an initial step in polar granule assembly [6].
• These cells retain the morphological features of GSCs, i.e., expression of Vasa and Nanos and spectrosomes, even after several months of culture [16].
• We used GFP-tagged versions of Vasa and Aubergine to characterize and track nuage particles and polar granules in live preparations of ovaries and embryos [11].
• Ziwi, the zebrafish homologue of the Drosophila piwi: co-localization with vasa at the embryonic genital ridge and gonad-specific expression in the adults [17].
• Oocyte polarity depends on regulation of gurken by Vasa [9].

Analytical, diagnostic and therapeutic context of vas

• Third, pole cell transplantation experiments reveal that maternal Nos and Pum are required autonomously in pole cells for proper expression of vas [8].
• Three vas-related genes (N. girellae vasa-like gene, Ngvlg1, Ngvlg2 and Ngvlg3) were isolated by PCR and Ngvlg1 and Ngvlg2 were shown to be expressed only in germ cells [18].
• Results of Northern blot analysis of AhT/VD16 and AhT/VD146 demonstrate that both clones hybridized with mRNA transcripts that were up-regulated in the testis/vas deferens of fed compared to unfed males [13].
• Crystallization and preliminary X-ray analysis of the helicase domains of Vasa complexed with RNA and an ATP analogue [19].

References