PHYSIOLOGY OF THYROID HORMONE DEPENDENT GENE EXPRESSION

描述：（从申请人的摘要扫描）我们的实验室专注于 三碘甲状腺原氨酸（T3）稳态调节机制的研究超过25年， 年这个过程的关键是碘甲腺原氨酸的作用， - 脱碘酶，其共同起调节甲状腺素（T4）活化的作用， T4和T3的失活。本提案延续了这一主题。上 具体目标我们将继续我们的研究细胞类型的具体 负性甲状腺激素反应元件（nTRE）在人类 1型脱碘酶（DI）基因。该甲状腺受体（TR）结合序列还 以高亲和力结合新的JEG细胞转录因子（JTF）， 的特异性JTF增加含有该序列的基因的表达， APO-TRs增强了这种作用。T3消除了这种影响。使用DNA 亲和矩阵技术，我们将分离和鉴定这个新发现的 蛋白质，并确定TR如何与它合作，作为一个具体的例子， 甲状腺激素对基因表达的负调控机制。 甲状腺激素不受控制的快速失活导致甲状腺功能减退， 我们最近在患有大血管瘤的婴儿中发现了这种综合征。 婴儿血管瘤表达3型碘甲腺原氨酸脱碘酶（D3），其主要作用是 生理灭活剂13和14，水平高达8倍， 胎盘大的肿瘤比婴儿的肿瘤能更快地使T4和T3脱碘 甲状腺可以分泌它们。具体目标2将阐明 D3在这些肿瘤中的异位表达。我们将比较血管瘤衍生的 和正常人毛细血管内皮细胞来发现 激活与胎盘中类似的D3表达。具体目标三： 明确甲状腺功能正常的心脏对甲状腺激素的心肌反应机制。 甲状腺毒性状态，如发生在甲状腺功能亢进症患者中。我们有 开发了一种新的方法，诱导小鼠慢性心肌甲状腺毒症 通过使用其中2型碘甲腺原氨酸脱碘酶（D2）被驱动的转基因， 由α-MHC启动子控制我们将首先定义双重 增加cAMP反应毛喉素在心肌膜从这些 转基因小鼠我们还将记录基因表达的差异， 青年和老年人甲状腺功能正常和甲状腺功能亢进心肌之间的曲线 小鼠只有少数基因已被确定增加其表达 甲状腺功能正常和甲状腺功能亢进之间有显著差异。识别此类 心肌中的基因对于理解心肌中的 甲状腺功能亢进症患者T3过量对心脏的影响这些研究将 提供与基础和临床甲状腺生理学相关的新信息。

DESCRIPTION: (Scanned from the applicant's abstract) Our laboratory has focused on the mechanisms regulating triiodothyronine (T3) homeostasis for over 25 years. Critical to this process are the actions of the iodothyronine deiodinases which function in concert to regulate thyroxine (T4) activation and the inactivation of T4 and T3. This proposal continues this theme. In the first Specific Aim we will continue our investigations of a cell type specific negative thyroid hormone response element (nTRE) in the promoter of the human Type 1 deiodinase (Dl) gene. This thyroid receptor (TR) binding sequence also binds a novel JEG cell transcription factor (JTF) with high affinity and specificity. JTF increases expression of genes containing this sequence and this effect is enhanced by APO-TRs. T3 eliminates this effect. Using DNA affinity matrix techniques we will isolate and identify this newly discovered protein and determine how TR cooperates with it as an example of a specific mechanism for negative regulation of gene expression by thyroid hormone. Uncontrolled, rapid inactivation of thyroid hormone causes hypothyroidism in a syndrome which we recently identified in infants with large hemangiomas. Infantile hemangiomas express Type 3 iodothyronine deiodinase (D3), the major physiological inactivator of 13 and 14, at levels up to 8-fold that in placenta. Large tumors can deiodinate T4 and T3 more rapidly than the infant's thyroid can secrete them. Specific Aim 2 will elucidate the mechanism for ectopic expression of D3 in these tumors. We will compare hemangioma-derived and normal human capillary endothelial cells to discover pathways which could activate D3 expression analogous to those in placenta. Specific Aim III is to define the mechanism for the myocardial response of the euthyroid heart to the thyrotoxic state such as occurs in patients with hyperthyroidism. We have developed a novel method for inducing chronic myocardial thyrotoxicosis in mice by use of a transgene in which Type 2 iodothyronine deiodinase (D2) is driven by the alpha-MHC promoter. We will first define the mechanism for the two-fold increase in the cAMP response to forskolin in myocardial membranes from these transgenic mice. We will also document the differences n gene expression profiles between euthyroid and thyrotoxic myocardium from both young and old mice. Only a few genes have been identified which increase their expression significantly between the euthyroid and hyperthyroid state. Identifying such genes in the myocardium will be especially critical to the understanding of the effects of T3 excess on the heart in human hyperthyroidism. These studies will provide new information relevant to both basic and clinical thyroid physiology.