Molecular Genetics of Familial Tumoral Calcinosis

家族性肿瘤钙质沉着症的分子遗传学

• 批准号: 7455027
• 负责人: JOUNI UITTO
• 金额: $ 31.69万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-20 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7455027
• 关键词: Abbreviations; Ablation; Address; Affect; Biological; Calcinosis; Calcium; Calcium Pyrophosphate; Cells; Chromosome Mapping; Clinical; Complex; Crystal Formation; Data; Degenerative polyarthritis; Deposition; Development; Diphosphates; Disease; Doctor of Medicine; Enzymes; Equilibrium; Etiology; Evaluation; Familial disease; Fibroblasts; Future; Galactosyltransferases; Gene Mutation; Genes; Genetic; Genets; Genome; Glycoproteins; Golgi Apparatus; Health; Homeostasis; Hydrolase; Hyperostosis; In Vitro; Individual; Joints; Kidney; Maps; Metabolic Diseases; Molecular; Molecular Biology; Molecular Genetics; Mucins; Mus; Mutation; Pathogenesis; Patients; Peripheral; Phenotype; Post-Translational Protein Processing; Protein Glycosylation; Proteins; Reaction; Regulation; Research; Research Personnel; Reverse Transcription; Role; Serine; Serum; Syndrome; System; Threonine; Tissues; Transferase; Transgenic Mice; Transgenic Organisms; United States Dept. of Health and Human Services; Variant; base; calcification; calcium phosphate; embryonic stem cell; extracellular; fibroblast growth factor 23; genetic linkage; glycosylation; in vivo; inorganic phosphate; insight; lymphoblast; mouse model; novel therapeutics; nucleoside triphosphate; polypeptide; ppGalNAc-T; prevent; programs; protein function; prototype; research study; sodium phosphate; sodium-phosphate cotransporter proteins; sugar; symporter; tool; tumor

DESCRIPTION (provided by applicant): The molecular and cellular pathomechanisms of calcium crystal deposition disorders are complex and focus of intense scientific research due to the steadily growing health problems posed by osteoarthritis and other less common arthropathies and periarthropathies. We propose to characterize the molecular genetics of a rare autosomal recessive disorder, familial tumoral calcinosis (FTC), to identify new key players responsible for periarticular calcium and phosphate homeostasis. FTC, a severely debilitating metabolic disorder is characterized by massive periarticular calcium crystal depositions over large joints and, in a subset of patients, by elevated serum phosphate levels. We have recently demonstrated (Nat Genet 36:579-581, 2004) that this disorder is caused by mutations in GALNT3 encoding ppGalNAc-T3, one of 24 known polypeptide galactosyltransferases. These Golgi-associated biosynthetic enzymes are responsible for mucin type Oglycosylation, a prevalent form of posttranslational modification and glycoprotein synthesis, through transfer of GalNAc from the sugar donor UDP-GalNAc to serine and threonine residues. However, the pathological mechanisms leading to the development of basic calcium crystals and phosphate imbalance remain obscure. We hypothesize that ppGalNAc-T3 deficiency is associated with a decrease in extracellular inorganic pyrophosphate (ePPi), which at normal levels prevents basic calcium phosphate crystal depositions in joints and other tissues. Therefore, we propose to evaluate PPi balance, and expression and function of molecules that control ePPi, such as the ANK protein and the ectoenzyme nucleoside triphosphate pyrophosphate hydrolase PC-1 in primary fibroblast and transformed lymphoblast cultures of FTC patients. To illuminate potential target proteins of ppGalNAc-T3 that are involved in phosphate homeostasis, we will assess changes in the expression and function of phosphatonins, such as fibroblast growth factor 23, and kidney sodiumphosphate transporters. Moreover, there is evidence that FTC is genetically heterogeneous and another gene might be implicated in the etiology of FTC. We propose clinical and genetic linkage studies to identify the second FTC gene and assess the causal role of FTC gene mutations in disorders with overlapping phenotypes. The biological relevance of our in vitro findings in the context of the complex and redundant ppGalNAc T system in vivo will be addressed by developing a transgenic mouse model of FTC using targeted ablation of Galnt3. The phenotypic characterization of ppGalNAc-T3 deficient mice combined with pathophysiological in vitro and in vivo studies will provided new insight in the molecular biology of mucin-type O-glycosylation and its intriguing role in ectopic calcium crystal deposition disorders. The Galnt3-l- mouse model of FTC will be a valuable tool for future research studies exploring the specific targets of individual ppGalNAc transferases and their interactions, for studying the complex mechanisms leading to ectopic crystal deposition and potentially for exploring new therapeutic approaches.

描述（由申请人提供）：由于骨关节炎和其他不太常见的关节病和关节周围病引起的健康问题日益严重，钙晶体沉积障碍的分子和细胞病理机制很复杂，并且是密集科学研究的焦点。我们建议描述一种罕见的常染色体隐性遗传疾病——家族性肿瘤钙质沉着症（FTC）的分子遗传学特征，以确定负责关节周围钙和磷酸盐稳态的新关键参与者。 FTC 是一种严重使人衰弱的代谢性疾病，其特征是大关节周围大量钙晶体沉积，并且在部分患者中血清磷酸盐水平升高。我们最近已经证明(Nat Genet 36:579-581, 2004)这种疾病是由编码ppGalNAc-T3的GALNT3突变引起的，ppGalNAc-T3是24种已知的多肽半乳糖基转移酶之一。这些高尔基体相关生物合成酶通过将 GalNAc 从糖供体 UDP-GalNAc 转移到丝氨酸和苏氨酸残基，负责粘蛋白型 O 糖基化，这是翻译后修饰和糖蛋白合成的普遍形式。然而，导致碱性钙晶体形成和磷酸盐失衡的病理机制仍不清楚。 我们假设 ppGalNAc-T3 缺乏与细胞外无机焦磷酸盐 (ePPi) 减少有关，正常水平下的 ePPi 可以防止碱性磷酸钙晶体沉积在关节和其他组织中。因此，我们建议评估 FTC 患者原代成纤维细胞和转化淋巴母细胞培养物中的 PPi 平衡以及控制 ePPi 的分子（例如 ANK 蛋白和外酶核苷三磷酸焦磷酸水解酶 PC-1）的表达和功能。为了阐明参与磷酸盐稳态的 ppGalNAc-T3 的潜在靶蛋白，我们将评估磷酸钙的表达和功能的变化，例如成纤维细胞生长因子 23 和肾脏磷酸钠转运蛋白。此外，有证据表明 FTC 具有遗传异质性，并且另一个基因可能与 FTC 的病因有关。我们建议进行临床和遗传连锁研究，以确定第二个 FTC 基因，并评估 FTC 基因突变在具有重叠表型的疾病中的因果作用。我们的体外研究结果在体内复杂且冗余的 ppGalNAc T 系统背景下的生物学相关性将通过使用 Galnt3 的靶向消融开发 FTC 转基因小鼠模型来解决。 ppGalNAc-T3 缺陷小鼠的表型特征与病理生理学体外和体内研究相结合，将为粘蛋白型 O-糖基化的分子生物学及其在异位钙晶体沉积性疾病中的有趣作用提供新的见解。 FTC 的 Galnt3-l- 小鼠模型将成为未来研究的一个有价值的工具，用于探索单个 ppGalNAc 转移酶的特定靶点及其相互作用，用于研究导致异位晶体沉积的复杂机制，并有可能探索新的治疗方法。