Studies Of Pseudohypoparathyroidism And Related Disorders

假性甲状旁腺功能减退症及相关疾病的研究

• 批准号: 8939572
• 负责人: Lee Weinstein
• 金额: $ 21.89万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8939572
• 关键词: Adult; Age; Alleles; Brain; Calcium; Cell Surface Receptors; Characteristics; Chondrocytes; Chromogranins; Clinical; Clinical Trials; Congenital Disorders; Cyclic AMP; DNA; DNA Methylation; Defect; Deletion Mutation; Development; Disease; Energy Metabolism; Epiphysial cartilage; Exons; Fathers; GNAS gene; GTP-Binding Protein alpha Subunits, Gs; Gene Mutation; Generations; Genes; Genetic; Goals; Gonadotropins; Growth; Gs alpha mutations; Heterotopic Ossification; Heterotrimeric GTP-Binding Proteins; Histones; Hormones; Human; Hypercalcemia; Hyperparathyroidism; Inherited; Insulin Resistance; Invaded; Knock-out; Knockout Mice; Lesion; Link; Messenger RNA; Metabolic; Methylation; Modeling; Molecular; Morbid Obesity; Mothers; Mus; Mutate; Mutation; Neuraxis; Neurosecretory Systems; Obesity; Operative Surgical Procedures; Osteoblasts; Paper; Parathyroid Neoplasms; Parathyroid gland; Pathogenesis; Patients; Protein Isoforms; Proteins; Proximal Kidney Tubules; Pseudohypoparathyroidism; Pseudopseudohypoparathyroidism; Publishing; Reporting; Resistance development; Second Messenger Systems; Signal Pathway; Signaling Molecule; Skin; Somatotropin-Releasing Hormone; Thyrotropin; Tissues; United States National Institutes of Health; Vitamin D Analog; base; calcification; clinical phenotype; glucose metabolism; hormone resistance; hormone sensitivity; imprint; mouse model; neurobehavioral; overexpression; paternal imprint; promoter; response; second messenger; sex; soft tissue; subcutaneous; transmission process

Albright hereditary osteodystrophy (AHO) is a congenital disorder resulting from autosomal dominant inheritance of heterozygous mutations in the GNAS gene which disrupt expression of the heterotrimeric G protein Gs-alpha. Gs-alpha is a ubiquitously expressed signaling molecule that is required for the intracellular generation of the second messenger molecule cyclic AMP in response to stimulation of hormone and other cell-surface receptors. Features of AHO include short stature, subcutaneous ossifications, brachydactyly, and neurobehavioral and developmental abnormalities. Patients who inherit the disease from their mother also develop resistance to multiple hormones which activate Gs-alpha signaling pathways (eg. parathyroid hormone PTH, thyroid stimulating hormone, gonadotropins, and growth hormone releasing hormone) as well as obesity, and this form of the disease is also known as pseudohypoparathyroidism type 1A (PHP1A). In contrast patients who inherit the disease from their father only develop features of AHO, and this is also referred to as pseudopseudohypoparathyroidism (PPHP). We and others have shown in mice and humans that Gs-alpha is imprinted in a tissue-specific manner. In some hormone target tissues Gs-alpha is expressed primarily from the maternal allele, and therefore maternal inheritance of Gs-alpha mutations results in hormone resistance while paternal inheritance of these same mutations does not. A few patients with similar mutations develop a severe form of ectopic ossification called progressive osseous heteroplasia (POH) in which the ossifications form cast-like plates and invade deeper soft tissues. While it has reported that POH only occurs when the mutation is inherited paternally, we have recently studied two cases in which POH resulted from maternal transmission. We have generated mice with Gs-alpha deficiency in chondrocytes or osteoblasts, which provides evidence that the Gs-alpha deficiency in growth plate chondrocytes is likely the direct cause of the short stature and brachydactyly observed in AHO. GNAS (Gnas in mice) is a very complicated imprinted gene with multiple gene products generated by several alternative promoters and first exons. NESP55 is a chromogranin-like protein that is maternally expressed while XL-alpha-s is a paternally expressed Gs-alpha isoform with a long amino-terminal extension. Both are primarily expressed in neuroendocrine tissues. We have shown that NESP imprinting is not established until postimplantation development. We identified another alternative first exon (exon 1A) that generates paternally expressed untranslated mRNAs and that is a maternal germline imprint mark. We have shown that this region has allele-specific differences in DNA and histone methylation. We also have shown that the Gs-alpha promoter and first exon also has allele-specific differences in histone methylation which correlates to its tissue-specific imprinting, even though this region does not undergo DNA methylation. We have shown that PHPIB (parathyroid hormone resistance in the absence of AHO) is virtually always associated with loss of maternal exon 1A imprinting. A detailed analysis of GNAS imprinting in PHP IB patients showed that familial cases tend to only have abnormal exon 1A imprinting associated with a deletion mutation within a closely-linked gene, while sporadic cases often have additional imprinting defects involving NESP and XL-alpha-s. We have generated exon 1A knockout mice, and show that this region is not required for Nesp and XL-alpha-s imprinting, but is required for tissue-specific Gs-alpha imprinting. Mice with paternal exon 1A deletion, which have Gs-alpha overexpression in renal proximal tubules due to loss of paternal Gs-alpha imprinting, have increased parathyroid hormone sensitivity with low circulating parathyroid hormone levels. We have also published a paper this past year showing that PHPIB patients who are inadequately treated with calcium and vitamin D analogs can develop tertiary hyperparathyroidism (autonomous parathyroid tumors leading to hypercalcemia) which need to be removed by surgery. Although obesity has been previously considered to be a general feature of AHO present in both PHP1A and PPHP patients, we have recently shown that obesity is a specific feature of PHP1A and therefore is a result of loss of Gs-alpha expression in one or more tissues due to the combined effects of maternal mutation and paternal imprinting. These clinical observations are consistent with findings in mice with germline Gs-alpha mutations showing that mice with maternal mutations develop severe obesity with lower energy expenditure and insulin resistance and that these effects are reversed by the presence of a paternal 1A deletion which reverses Gs-alpha imprinting (Z01-DK043313-03). Results in a brain-specific Gs-alpha knockout model suggest that this imprinting effect is localized to one or more regions in the central nervous system (Z01-DK043315-01). Based upon these observations we are presently conducting studies in the NIH Obesity/Clinical Phenotyping Center examining the metabolic characteristics of AHO and related patients in detail to better characterize the metabolic defect and gain understanding of its pathogenesis. Results to date show that adult PHP1A patients, similar to the mouse models, are more insulin resistant, even when compared to other subjects matched for age, sex, and degree of adiposity, indicating that these patients have a primary defect in glucose metabolism. In addition we have shown that mice with the equivalent genetic mutation can develop skin calcifications, although they are associated with fibrous lesions and not true ossifications.

奥尔布赖特遗传性骨营养不良（AHO）是由GNAS基因中杂合突变的常染色体显性遗传引起的先天性疾病，其破坏异源三聚体G蛋白Gs-alpha的表达。Gs-alpha是一种广泛表达的信号分子，其是响应激素和其他细胞表面受体的刺激而在细胞内产生第二信使分子环AMP所必需的。AHO的特征包括身材矮小、皮下骨化、短指、神经行为和发育异常。从母亲那里遗传这种疾病的患者也会对多种激素产生抗性，这些激素会激活Gs-alpha信号通路（例如甲状旁腺激素PTH、促甲状腺激素、促性腺激素和生长激素释放激素）以及肥胖，并且这种形式的疾病也被称为假性甲状旁腺功能减退1A型（PHP 1A）。相反，从父亲那里遗传疾病的患者只会发展出AHO的特征，这也被称为假性甲状旁腺功能减退症（PPHP）。我们和其他人已经在小鼠和人类身上证明，Gs-alpha是以组织特异性方式印记的。在一些激素靶组织中，Gs-alpha主要由母体等位基因表达，因此Gs-alpha突变的母体遗传导致激素抗性，而这些相同突变的父系遗传则不会。少数具有类似突变的患者发展为称为进行性骨异型增生（POH）的严重异位骨化，其中骨化形成铸件样板并侵入更深的软组织。虽然有报道说，POH只发生在突变是遗传父亲，我们最近研究了两个案件中，POH造成的母亲传播。我们已经产生了软骨细胞或成骨细胞中Gs-alpha缺乏的小鼠，这提供了生长板软骨细胞中Gs-alpha缺乏可能是AHO中观察到的身材矮小和短指（趾）畸形的直接原因的证据。 GNAS（Gnasinmice）是一种非常复杂的印迹基因，由多个不同的启动子和第一外显子产生多个基因产物。NESP 55是一种母系表达的嗜铬粒蛋白样蛋白，而XL-α-s是一种父系表达的具有长氨基末端延伸的Gs-α同种型。两者主要在神经内分泌组织中表达。我们已经表明，NESP印记是不成立，直到植入后的发展。我们确定了另一个替代第一外显子（外显子1A），产生父系表达的非翻译mRNA，这是一个母系生殖系印记标记。我们已经表明，该区域在DNA和组蛋白甲基化方面具有等位基因特异性差异。我们还表明，GS-α启动子和第一外显子也有等位基因特异性差异组蛋白甲基化相关的组织特异性印迹，即使这个区域不进行DNA甲基化。我们已经表明，PHPIB（甲状旁腺激素抵抗在AHO的情况下）几乎总是与母亲外显子1A印记的损失。对PHP IB患者GNAS印迹的详细分析表明，家族性病例往往仅具有与紧密连锁基因内的缺失突变相关的异常外显子1A印迹，而散发病例通常具有涉及NESP和XL-α-s的额外印迹缺陷。我们已经产生了外显子1A基因敲除小鼠，并表明，该区域是不需要的Nesp和XL-α-S印记，但需要组织特异性GS-α印记。具有父系外显子1A缺失的小鼠，由于父系Gs-alpha印迹的丧失而在肾近端小管中具有Gs-alpha过表达，其甲状旁腺激素敏感性增加，循环甲状旁腺激素水平降低。我们还在去年发表了一篇论文，表明PHPIB患者如果钙和维生素D类似物治疗不足，可能会发展为三级甲状旁腺功能亢进（导致高钙血症的自主性甲状旁腺肿瘤），需要通过手术切除。 尽管肥胖以前被认为是PHP 1A和PPHP患者中存在的AHO的一般特征，但我们最近表明肥胖是PHP 1A的特异性特征，因此是由于母体突变和父亲印记的综合作用导致一种或多种组织中Gs-alpha表达丧失的结果。这些临床观察结果与具有生殖系GS-α突变的小鼠中的发现一致，这些发现表明具有母体突变的小鼠发展为重度肥胖，能量消耗较低和胰岛素抵抗，并且这些效应通过存在逆转GS-α印记的父体1A缺失而逆转（Z 01-DK 043313 -03）。脑特异性Gs-alpha敲除模型的结果表明，这种印记效应定位于中枢神经系统的一个或多个区域（Z 01-DK 043315 -01）。基于这些观察，我们目前正在NIH肥胖/临床表型中心进行研究，详细检查AHO和相关患者的代谢特征，以更好地表征代谢缺陷并了解其发病机制。迄今为止的结果显示，与小鼠模型相似，成年PHP 1A患者的胰岛素抵抗程度更高，即使与年龄、性别和肥胖程度匹配的其他受试者相比，也是如此，这表明这些患者在葡萄糖代谢方面存在原发性缺陷。此外，我们已经证明，具有相同基因突变的小鼠可以发生皮肤钙化，尽管它们与纤维病变而不是真正的骨化有关。