title: Restricted expression of NADPH oxidase/peroxidase gene (Duox) in zone VII of the ascidian endostyle.
abstract: The ascidian Ciona intestinalis, a marine invertebrate chordate, is an emerging model system for developmental and evolutionary studies. The endostyle, one of the characteristic organs of ascidians, is a pharyngeal structure with iodine-concentrating and peroxidase activities and is therefore considered to be homologous to the follicular thyroid of higher vertebrates. We have previously reported that a limited part of the endostyle (zone VII) is marked by the expression of orthologs of the thyroid peroxidase (TPO) and thyroid transcription factor-2 (TTF-2/FoxE) genes. In this study, we have identified the Ciona homolog of NADPH oxidase/peroxidase (Duox), which provides hydrogen peroxide (H(2)O(2)) for iodine metabolism by TPO in the vertebrate thyroid. Expression patterns assessed by in situ hybridization have revealed that Ciona Duox (Ci-Duox) is predominantly expressed in the dorsal part of zone VII of the endostyle. Furthermore, two-color fluorescent in situ hybridization with Ci-Duox and Ciona TPO (CiTPO) has revealed that the ventral boundary of the Ci-Duox domain of expression is more dorsal than that of CiTPO. We have also characterized several genes, such as Ci-Fgf8/17/18, 5HT7, and Ci-NK4, which are predominantly expressed in the ventral part of zone VII, in a region complementary to the Ci-Duox expression domain. These observations suggest that, at the molecular level, zone VII has a complex organization that might have some impact on the specification of cell types and functions in this thyroid-equivalent element of the ascidian endostyle.
authors.affiliation: Department of Biology, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Hiruta
authors.forename: Francoise
authors.initials: F
authors.lastname: Mazet
authors.forename: Michio
authors.initials: M
authors.lastname: Ogasawara
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation; D017403:In Situ Hybridization; D008954:Models, Biological; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D013961:Thyroid Gland / Q000201:enzymology*; D014561:Urochordata / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics*
chemical_list: D010544:Peroxidases; D019255:NADPH Oxidases