Posterior expression of a homeobox gene in early Xenopus embryos.

The homeobox containing transcript Xhox-36 is expressed exclusively in the posterior mesoderm and ectoderm of early Xenopus embryos. Therefore, the transcript shows region-specific rather than tissue-specific expression in the gastrula and neurula, a time when cells are becoming committed to defined fates. Exposure of early embryos to LiCl, which shifts posterior cells to more anterior fates, reduces the abundance of this posterior-specific transcript. In contrast, embryos ventralized by u.v. treatment express normal levels of the transcript, implying that expression of the gene is not absolutely linked to dorsal cell identity. The sequence of a full-length cDNA corresponding to this transcript predicts a homeodomain-containing protein of 209 amino acids.