THYROID HORMONE CONTROL OF A GENE EXPRESSION NETWORK

两栖动物变态提供了一个很好的机会，研究激素如何控制基因表达网络的组织特异性和发育阶段特异性的方式。 在从幼蛙到成蛙的转变过程中，甲状腺激素控制着新的成蛙结构的生长和分化、成蛙现有结构的重塑、整个幼蛙器官的甲状腺激素溶解。 这些形态发生变化是由核甲状腺激素受体介导的基因表达变化引起的。 消减杂交和候选基因的方法已经确定了20和30之间的甲状腺激素诱导和抑制的基因在重吸收蝌蚪尾巴，一个例子，神经系统控制的程序性细胞死亡检查下游上午信号事件，最终在组织特异性生物反应。此外，目前的方法，如天然染色。 我们建议，以确定甲状腺激素激活的基因，是最后被诱导在这个基因表达级联的机制。 我们选择研究的基因编码分泌型基质金属蛋白酶，胶原酶-3，和细胞内细胞死亡诱导蛋白酶，半胱天冬酶-3。 胶原酶-3是死亡肌肉细胞中上调最强烈的基因。 我们将使用两种互补的方法来鉴定和表征这两个测序的Th应答元件和基础调节元件。候选调控序列的理想测试是它是否可以支持适当的体内转录调控。 因此，我们最近将在非洲爪蟾中开发转基因技术以筛选来自胶原酶-3和半胱天冬酶-3基因的最小基因组片段基因组DNA将筛选与早期诱导转录结合的序列与重要调控序列的结合将使用转基因蝌蚪在体内进行功能表征，利用从甲状腺激素与其受体结合到A概念诱导的时间的增益和增益诱导的基因表达级联，在所提出的工作中鉴定的分子标记可以应用于其他重要但复杂的生物学问题。 其中包括甲状腺激素对两栖动物四肢生长和分化的控制，当然还有类固醇和甲状腺激素对成年和发育中的哺乳动物基因网络的控制。

Amphibian metamorphosis presents an excellent opportunity to study how hormones control gene expression networks in a tissue-specific and development stage-specific manner. During the transition from the larval tadpole to the adult frog, thyroid hormone controls the growth and differentiation of new adult structures, the remodeling of existing structures for a an adult frog, thyroid hormone lysis of entire larval organs. These morphogenetic changes are caused by gene expression changes mediated by the nuclear thyroid hormone receptors. Subtractive hybridization and candidate gene approaches have identified between twenty and thirty thyroid hormone induced and repressed genes in the reabsorbing tadpole tail, an example of hormonally controlled programmed cell death examined the downstream am signaling events that culminate in tissue specific biological responses. Furthermore, current methods such native chrromatin. We propose to determine the mechanism of thyroid hormone activation of genes that are among the last to be induced in this gene expression cascade. The genes we have chosen to study encode a secreted matrix metalloproteinase, collagenase-3 , and an intra cellular cell death inducing protease, caspase-3. Collagenase- 3 is the most strongly up-regulated gene in dying muscle cells. We will use two complementary approaches to identify and characterize the Th- responsive and basal regulatory elements in these two sequenced. The ideal test of a candidate regulatory sequence is whether or not it can support appropriate transcriptional regulation in vivo. Thus, we will recently developed transenic technologies in Xenopus laevis to screen for the minimal genomic fragment genomic DNA from the collagenase-3 and caspase-3 genes will be screened for sequences that bind to early induced transcription bind to important regulatory sequences will be functionally characterized in vivo using transgenic tadpoles, employing both gain- and hormone-induced gene expression cascade from the time of thyroid hor more binding to its receptors to the induction of a concepts, and molecular markers identified during the proposed work can be applied to other important yet complex biological problems. These include thyroid hormone control of the growth and differentiation of the amphibian limbs, and certainly steroid and thyroid hormone control of gene networks in adult and developing mammals.