Maret Alexander, Ding Changlin, Kornfield Sara Levine, Levine Michael A
Division of Pediatric Endocrinology, University Hospital of Geneva, CH-1211 Geneva, Switzerland.
J Clin Endocrinol Metab. 2008 Apr;93(4):1426-32. doi: 10.1210/jc.2007-1783. Epub 2008 Jan 8.
Hypoparathyroidism is characterized by hypocalcemia, hyperphosphatemia, and absent or markedly reduced serum levels of intact PTH. The transcription factor GCM2 is critical for the development of parathyroid glands in mice and humans.
We sought to determine the prevalence of GCM2 gene mutations in patients with familial or sporadic forms of isolated hypoparathyroidism (IH).
We used PCR to analyze the promoter, the exons, and flanking intronic sequences in 10 IH families with 17 affected members and in 10 patients with sporadic IH. Wild-type and mutant GCM2 proteins were expressed in HEK293 cells and characterized.
We identified nine single nucleotide changes, three in the 5' untranslated region and six in exon 5, that led to nonsynonymous changes in the GCM2 protein (G203S, I227V, Y282D, N315D, Q330L, and M354V). Variant GCM2 proteins had normal size, nuclear localization, and transactivational function when expressed in HEK293 cells. Similar analyses of two previously described GCM2 missense mutations, R47L and G63S, revealed decreased nuclear expression and markedly reduced (5-20% of normal) transactivational activity. The variant alleles did not segregate with inheritance of IH, and many of the single nucleotide substitutions were present in DNA from unrelated normal subjects, suggesting that these base changes were polymorphisms.
Our study describes nine single nucleotide changes in the GCM2 gene that represent polymorphisms. Although GCM2 mutations appear to be an uncommon cause of IH, the wide variety of GCM2 polymorphisms suggests that variant alleles may have a role in determining parathyroid function.
甲状旁腺功能减退的特征是低钙血症、高磷血症以及血清中完整甲状旁腺激素（PTH）水平缺失或显著降低。转录因子GCM2对小鼠和人类甲状旁腺的发育至关重要。
我们试图确定家族性或散发性孤立性甲状旁腺功能减退（IH）患者中GCM2基因突变的发生率。
我们使用聚合酶链反应（PCR）分析了10个有17名受影响成员的IH家族以及10名散发性IH患者的启动子、外显子和侧翼内含子序列。野生型和突变型GCM2蛋白在人胚肾293（HEK293）细胞中表达并进行特性分析。
我们鉴定出9个单核苷酸变化，其中3个在5'非翻译区，6个在外显子5，这些变化导致GCM2蛋白发生非同义变化（G203S、I227V、Y282D、N315D、Q330L和M354V）。当在HEK293细胞中表达时，变异型GCM2蛋白具有正常大小、核定位和反式激活功能。对先前描述的两个GCM2错义突变R47L和G63S进行的类似分析显示，核表达降低且反式激活活性显著降低（为正常的5%-20%）。变异等位基因与IH的遗传不相关，并且许多单核苷酸替换存在于无关正常受试者的DNA中，这表明这些碱基变化是多态性。
我们的研究描述了GCM2基因中的9个单核苷酸变化，这些变化代表多态性。尽管GCM2突变似乎是IH的罕见病因，但GCM2多态性的多样性表明变异等位基因可能在决定甲状旁腺功能方面发挥作用。
