Evolution of Antp-class genes and differential expression of Hydra Hox/paraHox genes in anterior patterning.
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 homeodomains 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 lox) 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.
Gauchat
D
D
Department of Zoology and Animal Biology, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
Mazet
F
F
Berney
C
C
Schummer
M
M
Kreger
S
S
Pawlowski
J
J
Galliot
B
B
D000595:Amino Acid Sequence; D000818:Animals; D051943:Antennapedia Homeodomain Protein; D019521:Body Patterning / Q000235:genetics*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D006829:Hydra / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins; D010802:Phylogeny; D014157:Transcription Factors / Q000235:genetics
D051943:Antennapedia Homeodomain Protein; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors