An evolutionary conserved region in the vasa 3'UTR targets RNA translation to the germ cells in the zebrafish.
BACKGROUND
In many animals, germ cells are set aside from somatic cells early during development to give rise to sperm in males and eggs in females. One strategy to achieve this separation is to localize special cytoplasmic granules to the precursors of the germline. In Drosophila, the vasa gene has been shown to encode an essential component of these granules. While Vasa protein is directly targeted to the forming germ cells of Drosophila, Vasa protein expression in the germline of Xenopus and zebrafish is thought to be achieved by RNA localization.


RESULTS
To analyze whether the machinery responsible for RNA localization is conserved among lower vertebrates, we tested different vasa homologs for their ability to localize in Xenopus oocytes. Reporter transcripts fused to the vasa 3'UTR of zebrafish are recruited to the germ plasm of injected Xenopus oocytes, although the 3'UTR shows no clear sequence similarity to the Xenopus vasa-like DEADsouth 3'UTR. However, isolation, expression pattern analysis, and sequence inspection of vasa genes from different teleosts indicate that RNA localization correlates with the presence of several conserved regions in the 3'UTR. Introduction of reporter transcripts fused to different vasa 3'UTR deletions into Xenopus and zebrafish demonstrates that one of these conserved regions is sufficient for RNA localization in either species. Moreover, these regions target GFP translation to the germline of transgenic fish.


CONCLUSIONS
Our results suggest the existence of a common RNA localization machinery in lower vertebrates that uses a functionally conserved localization signal to target gene expression to the germline.
Knaut
Holger
H
Abteilung III/Genetik, Max Planck Institut für Entwicklungsbiologie, Tübingen, Germany. holger.knaut@tuebingen.mpg.de
Steinbeisser
Herbert
H
Schwarz
Heinz
H
Nüsslein-Volhard
Christiane
C
D020413:3' Untranslated Regions; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017124:Conserved Sequence; D053487:DEAD-box RNA Helicases; D019143:Evolution, Molecular; D005260:Female; D005399:Fishes; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D014176:Protein Biosynthesis; D012313:RNA / Q000378:metabolism; D020365:RNA Helicases / Q000235:genetics* / Q000378:metabolism; D014981:Xenopus / Q000235:genetics; D015027:Zebrafish / Q000235:genetics*; D029961:Zebrafish Proteins
D020413:3' Untranslated Regions; D008164:Luminescent Proteins; D029961:Zebrafish Proteins; D049452:Green Fluorescent Proteins; D012313:RNA; C498289:ddx4 protein, zebrafish; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases