We have analyzed the expression and intracellular distribution, during oogenesis and embryogenesis, of Vg1 RBP, a protein implicated in the intracellular localization of Vg1 mRNA to the vegetal cortex of Xenopus oocytes. Vg1 RBP (protein) colocalizes with Vg1 RNA at all stages of oogenesis. Vg1 RBP RNA, however, localizes to the animal pole during late oogenesis, and remains in the animal blastomeres and ectodermal precursors until its zygotic transcription is activated, around stage 12. Vg1 RBP mRNA then becomes expressed throughout the neural epithelium. Vg1 RBP mRNA expression is also detected in what appears to be neural crest cells undergoing delamination and lateral migration. By tailbud stages, Vg1 RBP expression is present in the branchial arches, otic vesicle, pronephros, and along the neural tube. To examine the expression pattern in different species, we cloned the zebrafish homolog of Vg1 RBP by using a highly homologous EST clone to screen an embryonic cDNA library. In situ hybridization reveals that Vg1 RBP RNA localizes early in oogenesis to the animal pole. Although Vg1 RBP RNA is detected in all blastomeres of the early embryo, the expression pattern in the one day old zebrafish embryo is almost identical to that of the equivalent stage Xenopus embryo. These results indicate that the zygotic expression pattern is similar in frogs and fish, and that there is a conserved zygotic expression of Vg1 RBP distinct from its expression in the oocyte. Copyright (C) 1999 Elsevier Science Ireland Ltd.
Bibliographical noteFunding Information:
We would like to thank Abraham Fainsod and his laboratory for their help with all aspects of the Xenopus embryo in situ hybridizations, J. Sommerville for anti-X p54 antibody, B. Appel and J. Eisen for the zebrafish cDNA library, C. Kalcheim for advice and a critical reading of the manuscript, and F. Mueller-Pillasch for communication of unpublished results. This work was supported in part by grants from the Israel Science Foundation (J.K. Yisraeli) and from the UK-Israel Science and Technology Research Fund (N. Standart and J.K. Yisraeli). The zebrafish Vg1 RBP sequence has been deposited in the GenBank under accession number AF161270.
- Neural crest
- RNA binding protein
- RNA localization
- Xenopus oocytes