title: Comparative expression analysis of transcription factor genes in the endostyle of invertebrate chordates.
abstract: The endostyle of invertebrate chordates is a pharyngeal organ that is thought to be homologous with the follicular thyroid of vertebrates. Although thyroid-like features such as iodine-concentrating and peroxidase activities are located in the dorsolateral part of both ascidian and amphioxus endostyles, the structural organization and numbers of functional units are different. To estimate phylogenetic relationships of each functional zone with special reference to the evolution of the thyroid, we have investigated, in ascidian and amphioxus, the expression patterns of thyroid-related transcription factors such as TTF-2/FoxE4 and Pax2/5/8, as well as the forkhead transcription factors FoxQ1 and FoxA. Comparative gene expression analyses depicted an overall similarity between ascidians and amphioxus endostyles, while differences in expression patterns of these genes might be specifically related to the addition or elimination of a pair of glandular zones. Expressions of Ci-FoxE and BbFoxE4 suggest that the ancestral FoxE class might have been recruited for the formation of thyroid-like region in a possible common ancestor of chordates. Furthermore, coexpression of FoxE4, Pax2/5/8, and TPO in the dorsolateral part of both ascidian and amphioxus endostyles suggests that genetic basis of the thyroid function was already in place before the vertebrate lineage.
authors.affiliation: Department of Biology, Faculty of Science, Chiba University, Chiba, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Hiruta
authors.forename: Francoise
authors.initials: F
authors.lastname: Mazet
authors.forename: Kinya
authors.initials: K
authors.lastname: Yasui
authors.forename: Peijun
authors.initials: P
authors.lastname: Zhang
authors.forename: Michio
authors.initials: M
authors.lastname: Ogasawara
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002816:Chordata, Nonvertebrate / Q000033:anatomy & histology* / Q000235:genetics* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers / Q000235:genetics; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*; D014561:Urochordata / Q000033:anatomy & histology / Q000235:genetics
chemical_list: D005819:Genetic Markers; D012333:RNA, Messenger; D014157:Transcription Factors