Molecular biological analysis of signal transduction system through parathyroid hormone receptor. Evaluation of parathyroid hormone receptor in patients with pseudohypoparathyroidism.

假性甲状旁腺功能减退症(PHP)是一组对甲状旁腺激素(PTH)耐药的疾病，PHP1b被认为是由PTH受体异常引起的。为阐明PHP1b的发病机制，采用逆转录-偶联聚合酶链式反应(RT-PCR)、Northern印迹分析和直接测序等方法对PHP1b患者皮肤成纤维细胞中的PTH受体进行了分析。PHP1b患者皮肤成纤维细胞中PTH受体的表达水平低于正常对照组，而PTH受体的表达水平在PHP1b患者皮肤成纤维细胞中无突变。因此，为了阐明PHP1b患者PTH受体表达降低的机制，我们进一步克隆了人PTH受体基因的5‘端。我们发现在人类PTH受体基因的5‘端至少有两个启动子和三个未翻译的外显子，这些启动子和外显子是以组织特异性的方式使用的。然而，PHP1b患者这些启动子区域和未翻译外显子的DNA序列与正常对照没有差异。因此，有必要分析与人PTH受体启动子区域相互作用的核蛋白来阐明PHP1b的发病机制。

Pseudohypoparathyroidism (PHP) is a group of diseases characterized by resistance to parathyroid hormone (PTH) and PHP1b has been thought to be caused by abnormal PTH receptor. In order to clarify the pathogenesis of PHP1b, PTH receptor in skin fibroblasts from patients with PHP1b was analyzed by reverse-transcription coupled polymerase chain reaction (RT-PCR), Northern blot analysis and direct sequencing of the PCR products. Although no mutation was found in cDNA for PTH receptor in patients with PHP1b, the expression level of PTH receptor in skin fibroblasts from patients with PHP1b was lower than that from normal control. Therefore, to clarify the mechanism of the reduced expression of PTH receptor in patients with PHP1b, we next cloned the 5' end of human PTH receptor gene. We found that there are at least two promoters and three untranslated exons in the 5' end of human PTH receptor gene, and these promoters and exons are used in a tissue-specific manner. However, the DNA sequences in these promoter regions and untranslated exons from patients with PHP1b are not different from those of normal control. Therefore, it seems necessary to analyze the nuclear proteins that interact with the promoter region of human PTH receptor to elucidate the pathogenesis of PHP1b.