先天性甲状腺功能减低症汉族儿童的促甲状腺素受体基因失活突变

Thyrotropin receptor gene inactivating mutation in Chinese children with congenital hypothyroidism

目的探讨汉族儿童促甲状腺素受体(TSHR)基因失活突变与先天性甲状腺功能减低症(cH)的相关性。方法(1)选择79例 CH 汉族儿童(亚临床甲减14例,年龄1～5.5岁,男8例,女6例;甲减65例,年龄1.5～6岁,男27例,女38例)为研究对象;100名正常儿童(男40例,女60例,年龄1～8岁)作为对照组。(2)采用 PCR 和 DNA 测序技术检测 TSHR 基因失活突变。结果(1)79例 CH 患儿中有1例发生复合杂合子突变,其突变位点为(Pro52Thr/Val689Gly)。1例发生杂合子突变,其突变位点为(Gly245Ser)。30例患儿在第10外显子2181位核苷酸处发生 C-G 转换(GAC-GAG),使727位密码子天冬氨酸被谷氨酸代替(Asp727Glu)。47例患儿在第7外显子561位核苷酸处发生 T-C 转换(AAT→AAC),相应的187位氨基酸(Asn)不发生改变。(2)33例正常对照儿童在第10外显子2181位核苷酸处发生 C-G 转换;50例正常对照儿童在第7外显子561位核苷酸处发生 T-C 转换(AAT→AAC)。结论浙江汉族 CH 患儿 TSHR 基因有3个杂合子突变位点:(Pro52Thr)、(Gly245Ser)、(Val689Gly),第10外显子2181位核苷酸处(GAC→GAG)及第7外显子561位核苷酸处(AAT→AAC)存在 TSHR 基因多态性。

Objective The inactivating mutation of thyrotropin receptor （TSHR） gene results in partial or complete insensitivity of thyrotropin （TSH） and dysfunction of the TSH-TSHR-cAMP cascade. Therefore, it may cause congenital hypothyroidism （CH）. Depending on the degree of impairment of TSHR function, patients can present with subclinical hypothyroidism at one extreme of the spectrum, or severe hypothyroidism at the other. This study aimed to understand the relation between inactivating mutations of TSHR gene and Chinese children with CH. Methods （1） Seventy-nine Chinese children with CH, including 14 subclinical hypothyroidism patients （8 boys and 6 girls, age 1-5.5 years ） and 65 hypothyroidism patients （27 boys and 38 girls, age 1.5-6 years） were enrolled in this study. Meanwhile, 100 normal children were enrolled as control, 40 were male and 60 were female. The age of the normal children were at a range of 1-8 years. （2） Total genomic DNA was extracted from peripheral blood leukoeytes of the 79 patients and 100 normal subjects. Exons 1-10 of TSHR gene were individually amplified by polymerase chain reaction （PCR） and mutations were detected by direct sequencing. Results （1） A compound heterozygous missense mutations （Pro52Thr/Va1689Gly） and a heterozygous missense mutation （Gly245Ser） were detected in 79 patients. The mutations of Pro52Thr and Gly245Ser were located within the extracellular domain of TSHR, while Va1689Gly was located within the intracellular domain of TSHR. In 30 patients the normal cytosine at position 2181 in exon 10 was replaced by a guanine（ GAC→GAG）, resulting in the replacement of Glu727 by Asp. In 47 patients, the normal thymidine at position 561 in exon 7 was replaced by a cytosine （AAT→AAC）. This substitution did not change the amino acid （Asn） at position 187. （2） In 33 normal children the normal cytosine at position 2181 in exon 10 was also replaced by a guanine（GAC→GAG） and in 50 normal children the normal thymidine at position 561 in exon 7 was replaced by a cytosine （AAT→AAC ）. Conclusions Three heterozygous missense mutations （Pro52Thr, Gly245Ser, Va1689Gly）of TSHR gene were firstly detected in Chinese children with CH. There was a polymorphism in exon 10 at nucleotide 2181 （GAC→GAG）and in exon 7 at nucleotide 561 （AAT→AAC） in TSHR gene. The inactivating mutation of TSHR gene is an infrequent pathogeny for CH.