Embryonic expression and nuclear localization of Xenopus homeobox (Xhox) gene products.

We have isolated a Xenopus genomic clone (Xhox-1) that contains two homeoboxes, at least one of which is highly conserved in vertebrates. Two transcripts are derived from Xhox-1 and these are present from early in development through swimming tadpole stages. A detailed analysis of one of the genes shows that it is expressed maternally and that transcription from the zygotic genome begins at mid-gastrulation. Examination of exogastrula shows that the expression of these genes does not depend on neural induction. We have determined the DNA sequence of a Xhox-1 cDNA and this allows us to predict the complete sequence of a vertebrate homeobox protein. Synthetic mRNAs made from this cDNA are translated efficiently in Xenopus oocytes where the homeobox protein localizes to the oocyte nucleus.