title: Gene and domain duplication in the chordate Otx gene family: insights from amphioxus Otx.
abstract: We report the genomic organization and deduced protein sequence of a cephalochordate member of the Otx homeobox gene family (AmphiOtx) and show its probable single-copy state in the genome. We also present molecular phylogenetic analysis indicating that there was single ancestral Otx gene in the first chordates which was duplicated in the vertebrate lineage after it had split from the lineage leading to the cephalochordates. Duplication of a C-terminal protein domain has occurred specifically in the vertebrate lineage, strengthening the case for a single Otx gene in an ancestral chordate whose gene structure has been retained in an extant cephalochordate. Comparative analysis of protein sequences and published gene expression patterns suggest that the ancestral chordate Otx gene had roles in patterning the anterior mesendoderm and central nervous system. These roles were elaborated following Otx gene duplication in vertebrates, accompanied by regulatory and structural divergence, particularly of Otx1 descendant genes.
authors.affiliation: School of Animal and Microbial Sciences, University of Reading, U.K.
authors.forename: N A
authors.initials: NA
authors.lastname: Williams
authors.forename: P W
authors.initials: PW
authors.lastname: Holland
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D002490:Central Nervous System / Q000254:growth & development; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins; D006801:Humans; D007438:Introns; D008648:Mesoderm; D008969:Molecular Sequence Data; D005810:Multigene Family; D009419:Nerve Tissue Proteins / Q000235:genetics*; D051857:Otx Transcription Factors; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors; D014714:Vertebrates / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D051857:Otx Transcription Factors; D015534:Trans-Activators; D014157:Transcription Factors