Research for the transcriptional regulation of Gsα protein gene

Gsα基因的转录调控受遗传和表观遗传机制的控制，并受组织特异性基因组印迹的影响。为了阐明这一机制，我们进行了实验和临床研究，以培养的人尿液中的肾小管上皮细胞为材料，用RT-PCR方法研究了GNAS1基因的等位基因特异性表达。尽管启动子区域有正常和异常的甲基化模式，但Gsα蛋白在这些细胞中以双等位方式表达，因此组织特异性基因组印迹需要GNAS1DNA甲基化和其他高分化状态下产生的反式作用因子。在14例散发性假性甲状旁腺功能减退症(PHP-Ib)患者中，GNAS1的3个启动子区(NESP55、AS、Exon1A)均缺失母体甲基化模式，且XLAS区域的甲基化模式各不相同。在这些病例中，有8例经Southern杂交检查发现XLAS区域所有位点的甲基化缺失，其中包括4例具有某些特定临床特征的病例，如智力低下。用亚硫酸氢盐聚合酶链式反应检测XL外显子5‘和3’侧翼区各CpG位点的甲基化状态。在PHP-Ib中未发现临床特征的特异性甲基化模式，CpG甲基化的等位基因邻接缺失。这些结果表明，其他区域的表观遗传异常是导致XLAS区域甲基化模式异常的原因。

The transcriptional regulation of Gsα gene (GNAS1) is under control of genetic and epigenetic mechanism and subjects to tissue-specific genomic imprinting. In order to clarify this mechanism, the experimental and clinical study was performed Allele-specific expression of GNAS1 mRNA was studied by RT-PCR using cultured tubular cells isolated from human urine which were considered to be proximal tubule origin. Despite both normal and abnormal methylation patterns in the promoter region, mRNA of Gsα protein was biallelically expressed in these cells, therefore tissue-specific genomic imprinting requires both DNA methylation in GNAS1 and other trans-acting factors produced in highly differentiated status. In all 14 cases with sporadic pseudohypoparathyroidism type Ib (PHP-Ib), the maternal methylation pattern was lost in three promoter regions (NESP55, AS, exon1A) of GNAS1 and the methylation pattern in XLas region was different in each case. Among these cases, eight showed loss of methylation in all sites in XLas region examined by Southern hybridization and included four cases with some specific clinical features like mental retardation. Methylation status of each CpG site in 5' and 3' flanking region of exon XL was examined by bisulfite PCR No specific methylation pattern for clinical features was shown and loss of allelic contiguity in CpG methylation was observed in PHP-Ib. These results suggest that the epigenetic abnormality in other region is responsible for the abnormal methylation pattern in XLas region.