CLONING, SEQUENCING AND EXPRESSION OF A NOVEL HOMEOBOX GENE AXNOX-1 FROM THE MEXICAN AXOLOTL

We have cloned and sequenced a cDNA containing a homeobox gene, AxNox- 1, from a stage 18 axolotl embryonic cDNA library which shows only mod erate levels of similarity to other known homeobox genes. The nucleoti de sequence of the cDNA has an open reading frame for 335 amino acids and besides the homeodomain, there is an acidic domain and a proline-r ich domain present in the protein. The transcripts for this gene are d etectable at stage 4 of embryonic development and, hence, there is a g ood possibility that the transcripts are maternally contributed. Expre ssion levels for AxNox-1 reach maximum levels by stage 12 of developme nt and thereafter decline to very low levels by stage 25. High levels of the transcript for AxNox-1 are later found in the brains of both ne otenous and metamorphosing adult axolotls. Low amounts of the message are also found to be present in a number of other organs that were tes ted. In situ hybridization studies on whole mounts and sections sugges t that this gene is expressed predominantly in neural tissue during de velopment. (C) 1998 Elsevier Science B.V. All rights reserved.