THYROID HORMONE RECEPTORS IN DEVELOPMENT

这位研究人员的长期研究目标是阐明 发育过程中甲状腺激素的作用机制(S)。 本研究的目的是研究TH受体。 在两栖类林蛙生命的发育阶段 周而复始。对于这些研究来说，这是一种独特的动物模型。增长， 发育和变态依赖于TH，并可由以下因素诱导 某些组织中的外源性TH和TH受体数量(位置/核)可以 增加了。越来越多的证据表明TH受体被编码 通过c-erba基因，以及编码TH结合蛋白的c-erba cDNA 是从哺乳动物和鸟类组织中分离出来的。其中一些混血儿 与蝌蚪组织的mRNAs。这些DNA将被用来评估 C-erba相关基因在蝌蚪和青蛙中存在的种类和大小 组织，并确定是否存在发育调节的 在生命过程中这些物种中的一个或多个的水平的变化 周而复始。这些变化与已知的 发育过程中的受体数量将支持一种假设，即c- Erba基因编码TH受体。为了确定蝌蚪c-erba基因是否 编码TH受体，从蝌蚪组织构建的cDNA文库将 用cdna探针筛选阳性克隆的cdna插入片段。 测序，并测定其蛋白质产物的性质。克隆人 含有编码TH结合蛋白的cDNA将被测试其 在内源性含量低的细胞中赋予或增强T3反应性的能力 TH受体。最后，将进行研究，以确定TH- 在发育中的蝌蚪中诱导受体数量的增加是由于 对相关基因转录的影响。 在人类发育过程中，TH不足会导致永久性的脑损伤， 它最严重的表现是克汀病。然而，这些机制 在此期间，对这一行动的监管得到了相对 很少受到关注，部分原因是进行这种操作的困难 对胚胎哺乳动物的研究。拟议的研究将利用一种卓越的 合适的动物模型来研究这些重要的生物过程。

The long range research goal of this investigator is to elucidate the mechanism(s) of action of the thyroid hormones (TH) during development. The aim of the research proposed herein is to investigate the TH receptor in the amphibian Rana catesbeiana during developmental phases of the life cycle. This is a unique animal model for these studies. Growth, development and metamorphosis are dependent on TH and can be induced by exogenous TH, and TH receptor number (sites/nucleus) in some tissues can be increased by TH. Evidence is accumulating that the TH receptor is encoded by a c-erbA gene, and c-erbA cDNAs which encode TH binding proteins have been isolated form mammalian and avian tissues. Some of these hybridize with tadpole tissue mRNAs. These cDNAs will be used to assess the number and size of c-erbA-related mRNA species present in tadpole and frog tissues, and to determine whether there are developmentally-regulated changes in the levels of one or more of these species during the life cycle. A positive correlation of such changes with the known changes in TH receptor number during development will support the hypothesis that a c- erbA gene encodes the TH receptor. To determine if tadpole c-erbA genes encode a TH receptor, cDNA libraries constructed from tadpole tissues will be screened with the cDNA probes, the cDNA inserts of positive clones sequenced, and the properties of their protein products determined. Clones containing cDNAs which encode TH binding proteins will be tested for their ability to confer or enhance T3 responsiveness in cells low in endogenous TH receptor. Finally, studies will be performed to determine if the TH- induced increase in receptor number in developing tadpoles is due to an effect on the transcription of the relevant gene. Insufficient TH during human development results in permanent brain damage, the most severe manifestation of which is cretinism. Yet the mechanisms and regulation of TH action during this period have received relatively little attention, due in part to the difficulties of conduction such studies in fetal mammals. The proposed studies will utilize an eminently suitable animal model to investigate these important biological processes.