Evolution of Antp-Class Genes and Differential Expression of Hydra Hox/ParaHox Genes in Anterior Patterning

• Published in: Proceedings of the National Academy of Sciences - PNAS 2000-04, Vol.97 (9), p.4493-4498
• Main Authors: Gauchat, Dominique, Mazet, Francoise, Berney, Cedric, Schummer, Michel, Kreger, Sylvia, Pawlowski, Jan, Galliot, Brigitte
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Antennapedia Homeodomain Protein; Antp protein; Barx gene; Biological Sciences; Body Patterning - genetics; Cloning, Molecular; cnox-1 gene; cnox-2 gene; cnox-3 gene; Complementary DNA; Conserved Sequence; Dlx gene; DNA; Electrophoresis, Gel, Pulsed-Field; Emx gene; Evolution; Evolution, Molecular; Evx gene; Gels; Genes; Genes, Homeobox; Genomics; Head; Homeobox genes; Homeodomain Proteins - genetics; Hox protein; Hydra; Hydra - anatomy & histology; Hydra - classification; Hydra - genetics; Molecular Sequence Data; Msx gene; Multigene Family; NK-2 gene; Not gene; Nuclear Proteins; Phylogenetics; Phylogeny; Prh/Hex gene; Tlx gene; Transcription Factors - genetics; Zoology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.97.9.4493

The conservation of developmental functions exerted by Antp-class homeoproteins in protostomes and deuterostomes suggested that homologs with related functions are present in diploblastic animals. Our phylogenetic analyses showed that Antp-class home-odomains belong either to non-Hox or to Hox/paraHox families. Among the 13 non-Hox families, 9 have diploblastic homologs, Msx, Emx, Barx, Evx, Tlx, NK-2, and Prh/Hex, Not, and Dlx, reported here. Among the Hox/paraHox, poriferan sequences were not found, and the cnidarian sequences formed at least five distinct cnox families. Two are significantly related to the paraHox Gsx (cnox-2) and the mox (cnox-5) sequences, whereas three display some relatedness to the Hox paralog groups 1 (cnox-1), 9/10 (cnox-3) and the paraHox cdx (cnox-4). Intermediate Hox/paraHox genes (PG 3 to 8 and Iox) did not have clear cnidarian counterparts. In Hydra, cnox-1, cnox-2, and cnox-3 were not found chromosomally linked within a 150-kb range and displayed specific expression patterns in the adult head. During regeneration, cnox-1 was expressed as an early gene whatever the polarity, whereas cnox-2 was up-regulated later during head but not foot regeneration. Finally, cnox-3 expression was reestablished in the adult head once it was fully formed. These results suggest that the Hydra genes related to anterior Hox/paraHox genes are involved at different stages of apical differentiation. However, the positional information defining the oral/aboral axis in Hydra cannot be correlated strictly to that characterizing the anterior-posterior axis in vertebrates or arthropods.