title: Identification of gene expression indicators for thyroid axis disruption in a Xenopus laevis metamorphosis screening assay. Part 2. Effects on the tail and hindlimb.
abstract: Thyroid hormones (TH), thyroxine (T(4)) and 3,5,3'-triiodothyronine (T(3)), play crucial roles in regulation of growth, development and metabolism in vertebrates and are targets for endocrine disruptive agents. Perturbations in TH action can contribute to the development of disease states and the US Environmental Protection Agency is developing a high throughput screen using TH-dependent metamorphosis of the Xenopus laevis tadpole as an assay platform. Currently this methodology relies on external morphological endpoints and changes in central thyroid axis parameters. However, exposure-related changes in gene expression in TH-sensitive tissue types that occur over shorter time frames have the potential to augment this screen. Using a combination of cDNA array and real time quantitative polymerase chain reaction (QPCR) analyses, this study identifies molecular markers in tissues peripheral to the central thyroid axis. We examine the hindlimb and tail of tadpoles up to 96 h of continuous exposure to T(3), T(4), methimazole, propylthiouracil, or perchlorate. Several novel biomarker candidates are indicated that include transcripts encoding importin, RNA helicase II/Gu, and defender against death protein, DAD1. In combination with previously-identified biomarker candidates, these transcripts will greatly augment the predictive and diagnostic power of the Xenopus metamorphosis assay for perturbation of TH action.
authors.affiliation: Department of Biochemistry and Microbiology, PO Box 3055, Stn. CSC, University of Victoria, Victoria, British Columbia V8W 3P6, Canada. chelbing@uvic.ca
authors.forename: Caren C
authors.initials: CC
authors.lastname: Helbing
authors.forename: Lan
authors.initials: L
authors.lastname: Ji
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Bailey
authors.forename: Nik
authors.initials: N
authors.lastname: Veldhoen
authors.forename: Fang
authors.initials: F
authors.lastname: Zhang
authors.forename: Gary W
authors.initials: GW
authors.lastname: Holcombe
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Kosian
authors.forename: Joseph
authors.initials: J
authors.lastname: Tietge
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Korte
authors.forename: Sigmund J
authors.initials: SJ
authors.lastname: Degitz
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology*; D001681:Biological Assay; D004784:Environmental Monitoring / Q000379:methods; D020869:Gene Expression Profiling / Q000662:veterinary; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D006614:Hindlimb / Q000187:drug effects*; D028884:Karyopherins / Q000032:analysis / Q000096:biosynthesis; D007633:Keratins / Q000032:analysis / Q000096:biosynthesis; D008668:Metallothionein / Q000032:analysis / Q000096:biosynthesis; D008675:Metamorphosis, Biological / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis / Q000662:veterinary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013623:Tail / Q000187:drug effects*; D013961:Thyroid Gland / Q000187:drug effects; D013963:Thyroid Hormones / Q000819:agonists* / Q000502:physiology; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D013956:Antithyroid Agents; D028884:Karyopherins; D013963:Thyroid Hormones; D014284:Triiodothyronine; D007633:Keratins; D008668:Metallothionein; D013974:Thyroxine