THYROID PHYSIOLOGY STUDIES OF INHERITED DISORDERS

描述(由申请人提供)：这项研究提案的广泛目标是通过研究关键调节过程中的遗传缺陷来促进对甲状腺生理学的理解。更具体地说，研究集中在通过研究由于单羧酸转运体(MCT8)、硒半胱氨酸插入序列结合蛋白(SBP2)和核TH受体(TR)或辅助因子基因突变而导致的细胞膜运输、代谢和作用缺陷引起的对TH敏感性降低的症状来调节甲状腺激素(TH)的作用。这些缺陷将通过三种方法进行研究，即临床(体内)、组织(体外)和动物(基因工程小鼠)，以补充和弥补每种缺陷固有的局限性。1)。临床研究将关联中枢和外周组织对给予活性TH，Ta及其前体甲状腺素(T，4)的反应，以确定器官和细胞特异性TH的运输和代谢。2)。患者的成纤维细胞在培养中繁殖，将用于直接检查碘甲腺原氨酸在细胞膜上的特定转运及其细胞内代谢。我们还将研究SBP2在硒蛋白合成层级中的作用。对成纤维细胞中TH作用的微阵列分析将有助于确定有和没有TRR基因突变的受试者的差异，以揭示在没有TRB基因突变的情况下TH耐药的病因并确定重要的辅助因素。3)。Mct8基因缺陷的小鼠将有助于深入研究导致人类MCT8缺陷表现的甲状腺和大脑异常。将测试行为和运动功能，并通过原位杂交和免疫组织化学检查中枢神经系统的形态。将调查甲状腺和精神运动障碍程度之间的差异，以确定它们是否存在因果联系。TH敏感性存在品系依赖差异的小鼠将有助于确定TH作用的假定修饰物。4)。将测试各种方法来恢复或减少Mct8缺乏症的精神运动缺陷。在胎儿发育的关键阶段，将给Mct8缺陷小鼠注射TH激素。与肌酸结合的TH将通过肌酸转运蛋白将激素输送到大脑，从而绕过TH转运蛋白缺陷。补硒将被用来试图提高SBP2缺陷中的硒蛋白水平。实际意义：临床研究将确定由这些基因缺陷引起的表型，建立基因测试的标准。及早识别突变将提供产前诊断和遗传咨询的基础，特别是在MCT8缺陷导致男性后代丧失能力的情况下。成功开发产前治疗将把受影响的男性从这一严重残疾中解救出来。对携带TRS突变的妇女所怀的未受影响的胎儿进行产前检测，将提供早期治疗的选择。

DESCRIPTION (provided by applicant): The broad objective of this research proposal is to advance understanding of thyroid physiology through study of genetic defects at key regulatory processes. More specifically, research is centered on the mediation of thyroid hormone (TH) effects by studying syndromes of reduced sensitivity to TH due to defects in cell membrane transport, metabolism and action caused by mutations in the MCT8 (monocarboxylate transporter), SBP2 (selenocysteine insertion sequence binding protein) and TR (nuclear TH receptor) or cofactors genes, respectively. These defects will be studied with a triple approach, clinical (in-vivo), tissue (in- vitro) and animal (genetically engineered mice) that complement and compensate for limitations inherent in each. 1). Clinical studies will correlate the central and peripheral tissue responses to the administration of the active TH, Ta and its precursor thyroxine (T,4) in order to determine organ and cell specific TH transport and metabolism. 2). Patient's fibroblasts, propagated in culture, will serve for the direct examination of iodothyronine specific transport across the cell membrane and their intracellular metabolism. The role of SBP2 in the hierarchy of selenoprotein synthesis will also be studied. Microarray analysis of TH action in fibroblasts will serve to identify differences in subjects with and without TRR gene mutations, in order to uncover the etiology of resistance to TH in the absence of TRB gene mutations and identify important cofactors. 3). Mice deficient in the Mct8 gene will serve to study in depth the thyroid and brain abnormalities responsible for the manifestations of MCT8 defects in man. Behavior and motor function will be tested, and central nervous system morphology will be examined by in-situ hybridization and immunohistochemistry. The discrepancy between the magnitude of thyroid and psychomotor disorders will be investigated to determine if they are causally linked. Mice with strain dependent differences in TH sensitivity will serve to identify putative modifiers of TH action. 4). Various means will be tested to revert or diminish the psychomotor defect of Mct8 deficiency. TH hormone will be given to Mct8 deficient mice at crucial stages of fetal development. TH conjugated to creatine will serve to deliver the hormone to brain through the creatine transporter, thus bypassing the TH transport defect. Selenium supplementation will be used in an attempt to increase the selenoprotein levels in SBP2 defects. Practical Significance: Clinical studies will characterize the phenotypes caused by these genetic defects, establishing criteria for genetic testing. Early identification of mutations will provide prenatal diagnosis and the basis for genetic counseling, particularly in MCT8 defects producing incapacitating illness in male offspring. Successful development of prenatal treatment would rescue affected males from this severe handicap. The prenatal detection of unaffected fetuses carried by women with TRS mutations will provide the option of early treatment.