Cephalic expression and molecular characterization of Xenopus En-2.

We have isolated and characterized cDNAs corresponding to the Xenopus En-2 gene. Comparison of amino acid sequences between the entire Xenopus En-2 and the Drosophila engrailed proteins confirms conservation of sequences inside as well as proximal to the homeobox and reveals a region of similarity towards the N terminus. Two transcripts encode the Xenopus En-2 protein. Both transcripts are regulated temporally in an identical fashion and are likely to be transcribed from two copies of the En-2 gene. We have also analyzed the distribution of the protein in the head tissue and in the dissected brain of tailbud stage embryos. In addition to the main band of expression at the midbrain-hindbrain boundary, we show that the protein is expressed in three novel areas: the mandibular arch, the optic tectum and the region of anterior pituitary.