Hishinuma A, Takamatsu J, Ohyama Y, Yokozawa T, Kanno Y, Kuma K, Yoshida S, Matsuura N, Ieiri T
Department of Clinical Pathology, Dokkyo University School of Medicine, Mibu, Tochigi, Japan.
J Clin Endocrinol Metab. 1999 Apr;84(4):1438-44. doi: 10.1210/jcem.84.4.5633.
We analyzed the thyroglobulin (Tg) gene of 2 unrelated patients with congenital goiter and the Tg gene of 2 siblings with the variant type of adenomatous goiter. The clinical characteristics of the patients with congenital goiter and the variant type of adenomatous goiter were very similar, except for serum Tg levels, which were less than 15 pmol/L in the patients with congenital goiter, but 117-181 pmol/L in the patients with the variant type of adenomatous goiter (normal, 15-50 pmol/L). The tissue content of Tg in the thyroid glands of all 4 patients was reduced at 0.9-3.8% of total protein (normal, 19-40%). The missense mutation C1263R was detected in the 2 unrelated patients with congenital goiter; the pedigree study showed an autosomal recessive pattern of inheritance. In the 2 siblings with the variant type of adenomatous goiter, the missense mutation C1995S was homozygously detected. In the Tg complementary DNA of 110 normal subjects, the allelic frequencies of the C1263R and C1995S mutations were each less than 0.5%. Also in the normal subjects were detected 35 nucleotide polymorphisms, the insertion of 3 nucleotides, and 1 alternative splicing, each of which was not associated with any specific thyroid disease. From these data, the molecular mechanism of the C1263R and C1995S mutations was elucidated. We first analyzed the carbohydrate residues of C1263R Tg and C1995S Tg. Sensitivity to treatment by endoglycosidase H suggests that C1263R Tg and C1995S Tg were retained in the endoplasmic reticulum (ER). Also, the presence of endoglycosidase H-resistant Tg as well as endoglycosidase H-sensitive Tg in the patients with the variant type of adenomatous goiter suggests that a fraction of C1995S Tg was transported to the Golgi and associated with the mildly increased serum Tg levels. Native PAGE and Western blot analysis with anti-Tg antibody showed that C1263R Tg and C1995S Tg form high mol wt aggregates in the ER. Our results suggest that missense mutations that replace cysteine with either arginine or serine cause an abnormal three-dimensional structure of Tg. Such misfolded Tg polypeptides are retained in the ER as high mol wt aggregates.
我们分析了2例先天性甲状腺肿的非亲缘患者的甲状腺球蛋白（Tg）基因以及2例患变型腺瘤样甲状腺肿的同胞的Tg基因。先天性甲状腺肿患者和变型腺瘤样甲状腺肿患者的临床特征非常相似，只是血清Tg水平有所不同，先天性甲状腺肿患者的血清Tg水平低于15 pmol/L，而变型腺瘤样甲状腺肿患者的血清Tg水平为117 - 181 pmol/L（正常范围为15 - 50 pmol/L）。所有4例患者甲状腺组织中Tg的含量均降低，占总蛋白的0.9% - 3.8%（正常范围为19% - 40%）。在2例先天性甲状腺肿的非亲缘患者中检测到错义突变C1263R；系谱研究显示为常染色体隐性遗传模式。在2例患变型腺瘤样甲状腺肿的同胞中，检测到纯合的错义突变C1995S。在110名正常受试者的Tg互补DNA中，C1263R和C1995S突变的等位基因频率均低于0.5%。在正常受试者中还检测到35种核苷酸多态性、3个核苷酸的插入以及1种可变剪接，这些均与任何特定的甲状腺疾病无关。根据这些数据，阐明了C1263R和C1995S突变的分子机制。我们首先分析了C1263R Tg和C1995S Tg的碳水化合物残基。对内切糖苷酶H处理的敏感性表明，C1263R Tg和C1995S Tg保留在内质网（ER）中。此外，变型腺瘤样甲状腺肿患者中存在对内切糖苷酶H有抗性的Tg以及对内切糖苷酶H敏感的Tg，这表明一部分C1995S Tg被转运至高尔基体，并与血清Tg水平的轻度升高有关。用抗Tg抗体进行的非变性聚丙烯酰胺凝胶电泳（Native PAGE）和蛋白质免疫印迹分析表明，C1263R Tg和C1995S Tg在内质网中形成高分子量聚集体。
