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: 8553473
• 负责人: Lee Weinstein
• 金额: $ 17.29万
• 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/8553473
• 关键词: Adult; 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; Non-Insulin-Dependent Diabetes Mellitus; 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; hormone resistance; hormone sensitivity; imprint; mouse model; neurobehavioral; overexpression; paternal imprint; promoter; response; second messenger; 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 and more prone to type 2 diabetes. 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）是一种先天性疾病，是由于GNA基因中杂合突变的常染色体显性遗传而导致的，它破坏了异源三聚体G蛋白GS-Alpha的表达。 GS-Alpha是一种普遍表达的信号分子，对于刺激激素和其他细胞表面受体的刺激响应于第二信使分子循环AMP所需的细胞内生成所需的信号分子。 AHO的特征包括身材矮小，皮下骨质，臂dact骨以及神经行为和发育异常。从母亲那里继承该疾病的患者也会产生对多种激素的抵抗力，这些激素激活GS-Alpha信号传导途径（例如，甲状旁腺激素PTH，甲状腺刺激激素，促性腺激素和生长激素释放激素）以及肥胖的形式，以及这种形式，如Pseudy的形式。相比之下，从父亲那里继承该疾病的患者只会发展出AHO的特征，这也称为假甲状腺甲状腺功能低下（PPHP）。我们和其他人在小鼠和人类中表明，GS-Alpha以组织特异性的方式印记。在某些激素靶组织中，GS-α主要来自母体等位基因，因此母体的GS-Alpha突变遗传会导致激素耐药性，而这些相同突变的父亲遗传并非如此。一些具有相似突变的患者会形成一种严重的异位骨化形式，称为进行性骨杂质（POH），其中骨化形成铸造板并侵入更深的软组织。虽然它报告说只有在遗传遗传的突变遗传时才会发生POH，但我们最近研究了POH由母体传播产生的两种情况。我们已经在软骨细胞或成骨细胞中产生了患有GS-Alpha缺乏症的小鼠，该小鼠提供了证据，表明生长板软骨细胞中GS-Alpha缺乏症可能是aho中短身材的直接原因，并且在AHO中观察到了腕足。 GNA（小鼠中的GNA）是一个非常复杂的印迹基因，由多个替代启动子和第一外显子产生的多个基因产物。 Nesp55是一种类似染色体蛋白的蛋白，在XL-Alpha-S是一种含有长氨基末端延伸的父子表达的GS-Alpha同工型时，在母体表达。两者主要在神经内分泌组织中表达。我们已经表明，直到植入后发展才能建立NESP印迹。我们确定了另一个替代的第一外显子（外显子1a），该外显子（外显子1a）产生了亲子表达的未翻译mRNA，这是母体种系烙印。我们已经表明，该区域在DNA和组蛋白甲基化方面具有特异性差异。我们还表明，GS-Alpha启动子和第一个外显子在组蛋白甲基化方面也具有特异性差异，这与其组织特异性印迹相关，即使该区域不经历DNA甲基化。我们已经表明，PhPIB（在没有AHO的情况下甲状旁腺激素的抗性）几乎始终与母体外显子1a印记的丢失有关。对PHP IB患者印记的GNA的详细分析表明，家族病例往往只有与密切相关基因中的缺失突变相关的异常外显子1A烙印，而散发病例通常具有涉及NESP和XL-Alpha-S的其他杂物。我们已经产生了外显子1A敲除小鼠，并表明该区域不需要NESP和XL-Alpha-S烙印，但对于组织特异性的GS-Alpha印记所需。父亲外显子1A缺失的小鼠由于父亲​​GS-Alpha烙印而导致肾近端小管中具有GS-Alpha过表达，其甲状旁腺激素敏感性提高了，且循环中的副副激素水平较低。在过去的一年中，我们还发表了一篇论文，表明接受钙和维生素D类似物治疗不足的PHPIB患者可以发展三级甲状旁腺功能亢进症（自主性甲状旁腺肿瘤导致高钙血症），需要通过手术去除。 尽管以前已将肥胖症视为PHP1A和PPHP患者中AHO的一般特征，但我们最近表明肥胖是PHP1A的特定特征，因此是由于母体突变和父亲的印迹的组合作用而导致一个或多个组织中GS-Alpha表达的结果。这些临床观察结果与生殖线GS-Alpha突变的小鼠的发现一致，表明带有母体突变的小鼠会在能量消耗较低和胰岛素抵抗的情况下发展出严重的肥胖症，并且这些作用会因存在父亲1A的存在而逆转，从而逆转了GS-Alpha印记（Z01-DK01-DK0433333333333333-03）。结果导致大脑特异性的GS-Alpha敲除模型表明，这种印迹效应位于中枢神经系统中的一个或多个区域（Z01-DK043315-01）。基于这些观察结果，我们目前正在对NIH肥胖/临床表型中心进行研究，以详细研究AHO和相关患者的代谢特征，以更好地表征代谢缺陷并获得对其发病机理的了解。迄今为止的结果表明，与小鼠模型相似的成年PHP1A患者更耐胰岛素，更容易容易出现2型糖尿病。此外，我们已经表明，具有等效遗传突变的小鼠可以发展皮肤钙化，尽管它们与纤维损伤相关，而不是真正的骨质。