Analysis of thyroxine-binding globulin (TBG) gene regulation and inherited TGB abnormalities

1. 日本人的完全TGB缺陷基因（TBG-CDJ）在395个密码子中有352个核苷酸缺失，导致c端22个氨基酸因移码和过早终止而截断。TBG-CDJ cDNA在COS-1细胞中表达。脉冲追踪实验显示TBG-CDJ保留在粗内质网中，导致血清中完全缺乏。基因筛选结果显示23个日本TBG-CD家族具有相同突变TBG-CDJ.2。在1例女性TBG-CD患者中发现x染色体失活异常。TBG- cdj与正常TBG等位基因杂合。后一个等位基因选择性失活。日本人部分TBG缺乏症（TBG- pdj）在密码子363处发生核苷酸替换，正常原体（CCT）被亮氨酸（CTT）取代。TBG-PDJ在COS-1细胞中表达。结果表明，TBG-PDJ的细胞内转运延迟是部分缺乏的原因。发现分子伴侣GRP78的诱导参与了转运障碍。PCR和hplc检测结果显示，一个遗传性TBG过量家族存在基因重复。分离并鉴定了人类和大鼠基因组TBG基因。对两个基因的启动子区域进行测序，并将其亚克隆到CAT或荧光素酶报告基因结构中。发现HNF-1（肝细胞核因子1）结合位点对基础和肝脏特异性表达具有重要意义。基因表达及血清。皮质酮对大鼠TBG有下调作用。

1. Complete TGB deficiency in Japanese(TBG-CDJ)has a nucleotide deletion at codon 352 among 395 resulting in the production of C-terminal 22 amino acid truncation due to a frameshift and premature termination. The cDNA of TBG-CDJ was expressed in COS-1 cells. Pulse chase experiment revealed TBG-CDJ was retained in the rough endoplasmic reticulum resulting in complete deficiency in serum.Gene screening showed 23 Japanese families with TBG-CD had a same mutation TBG-CDJ.2. Abnormality of X-chromosome inactivation was found in a female TBG-CD patient. She was heterozygous of TBG-CDJ and normal TBG alleles. The latter allele was selectively inactivated.3. Partial TBG deficiency in Japanese (TBG-PDJ) has a nucleotide substitution at codon 363 replacing normal pro (CCT) with leu (CTT). The TBG-PDJ was expressed in COS-1 cells. lt was revealed that delay of intracellular transport of TBG-PDJ was a cause of partial deficiency. Induction of GRP78, molecular chaperone, was found to participate the transport disorder.4. Gene duplication was shown in a hereditary TBG excess family by using PCR and HPLC.5. Human and rat genomic TBG genes were isolated and characterized. Promoter regions of both genes were sequenced and subcloned to CAT or luciferase reporter construct. HNF-1 (hepatocyte nuclear factor 1) binding site was found important fot basal and liver specific expression. Gene expression and serum. TBG were down regulated by corticosterone in rat.