Mechanisms of dioxin insensitivity in developing frogs

发育中的青蛙对二恶英不敏感的机制

• 批准号: 6806295
• 负责人: WADE H POWELL
• 金额: $ 18.37万
• 依托单位: KENYON COLLEGE
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6806295
• 关键词: Xenopus; aromatic hydrocarbon receptor; biological signal transduction; dioxins; embryo /fetus; embryo /fetus toxicology; environmental contamination; environmental exposure; environmental toxicology; gene induction /repression; genetic transcription; immature animal; protein structure function; receptor binding; receptor expression; receptor sensitivity; reporter genes; tissue /cell culture; transfection

DESCRIPTION (provided by applicant): Embryos of the African clawed frog, Xenopus laevis, represent a long-standing model of vertebrate development. They are also used in FETAX (Frog Embryos Teratogenesis Assay-Xenopus) and similar assays of the developmental toxicity of chemicals and environmental samples. 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) is a potent developmental toxicant in most vertebrates. However, frogs are generally insensitive to TCDD toxicity, especially at early life stages. Thus, FETAX and other frog embryo toxicity tests may be poorly suited for determining the developmental toxicity of samples containing dioxin-like compounds. This research seeks to delineate the molecular mechanisms underlying TCDD insensitivity in frogs, using X. laevis as a model system. During the previous grant period, we cloned cDNAs encoding two distinct X. laevis aryl hydrocarbon receptors, AHR1A and AHR1B both of which exhibit extraordinarily low affinity for TCDD in vitro and unusually late onset of detectable signaling activity during development. The proposed project will elucidate the functions of the two AHRs and the regulation of their activity in embryo and tadpole stages. Specifically, we will (1) Dissect the transcriptional properties of AHR1A and AHR1B in reporter gene assays using transiently transfected cells; (2) Determine the timing of onset of AHR protein expression and functional AHR signaling during development; (3) Determine the role of AHR Repressor protein in the attenuation of AHR signaling in early embryos, and (4) Compare TCDD-induced lethality and elimination rates in tadpoles and early embryos. Understanding the molecular mechanisms of TCDD insensitivity in different life stages is important for determining the human health relevance of frog embryo toxicity assays. Moreover, the unique features of frog AHR function and expression may provide a novel perspective on the relationship between AHR expression, AHR activity, mechanisms developmental TCDD toxicity, and the endogenous functions of AHRs during vertebrate development.

描述（由申请人提供）：非洲爪蟾（Xenopus laevis）的胚胎代表了脊椎动物发育的长期模型。 它们还用于FETAX（蛙胚胎致畸试验-非洲爪蟾）和化学品和环境样品发育毒性的类似试验。 2，3，7，8-四氯二苯并-对-二恶英（TCDD）是一种对脊椎动物发育有毒性的物质。 然而，青蛙通常对TCDD毒性不敏感，特别是在生命的早期阶段。 因此，FETAX和其他青蛙胚胎毒性试验可能不适合于确定含有二恶英类化合物的样品的发育毒性。 本研究旨在阐明青蛙对TCDD不敏感的分子机制，使用X。作为一个模型系统。 在上一个资助期，我们克隆了编码两个不同X。Lavis芳烃受体，AHR 1A和AHR 1B，这两种受体在体外对TCDD表现出非常低的亲和力，并且在发育过程中可检测到的信号传导活性的出现异常晚。 该项目将阐明这两种AHR的功能及其在胚胎和蝌蚪阶段的活性调节。 具体而言，我们将（1）在使用瞬时转染细胞的报告基因测定中剖析AHR 1A和AHR 1B的转录特性;（2）确定发育过程中AHR蛋白表达和功能性AHR信号传导的起始时间;（3）确定AHR阻遏蛋白在早期胚胎中AHR信号减弱中的作用，比较TCDD对蝌蚪和早期胚胎的致死率和消除率。 了解TCDD在不同生命阶段不敏感的分子机制对于确定青蛙胚胎毒性检测的人类健康相关性是重要的。 此外，青蛙AHR功能和表达的独特功能可能提供了一个新的视角，AHR表达，AHR活性，发育TCDD毒性机制之间的关系，以及AHR在脊椎动物发育过程中的内源性功能。