Conditional Isolation of Fgf23 Activity

Fgf23 活性的条件分离

• 批准号: 8152113
• 负责人: KENNETH E WHITE
• 金额: $ 19.96万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-27 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8152113
• 关键词: Actins; Address; Alleles; Animal Testing; Animals; Biochemical; Calcinosis; Calvaria; Cell physiology; Cells; Chronic Kidney Failure; Clinical; Collagen; Coupled; Data; Development; Disease; Disease model; Endocrine System Diseases; Exons; Exposure to; FLP recombinase; Familial hypophosphatemic bone disease; Gene Expression Regulation; Genes; Genetic Recombination; Goals; Homeostasis; Hormones; Human; Hypophosphatemia; Image; In Vitro; Kidney; Kidney Failure; Knock-out; Lead; Maintenance; Messenger RNA; Metabolic Bone Diseases; Metabolism; Minerals; Missense Mutation; Modeling; Molecular; Mus; Mutation; Neomycin; Osteoblasts; Osteocytes; Partner in relationship; Patients; Physiology; Production; Proteins; Regulation; Research; Research Personnel; Resistance; Resources; Risk; Role; Secondary to; Serum; Signal Transduction; Site; Skeleton; Syndrome; System; Testing; Tissues; Transgenic Mice; Vascular calcification; Weaning; base; bone; cell type; dentin matrix protein 1; embryonic stem cell; extracellular; fibroblast growth factor 23; in vivo; innovation; inorganic phosphate; model development; mortality; mouse model; new therapeutic target; novel strategies; public health relevance; receptor; recombinase; response; skeletal; skeletal disorder; tool; wasting

DESCRIPTION (provided by applicant): Proper control of serum phosphate concentrations is required to maintain skeletal integrity. We previously identified missense mutations in Fibroblast growth factor-23 (FGF23) as the cause of autosomal dominant hypophosphatemic rickets (ADHR), characterized by hypophosphatemia secondary to isolated renal phosphate wasting and metabolic bone disease. We subsequently demonstrated that inactivating FGF23 mutations result in the mirror-image disorder to ADHR, familial tumoral calcinosis (TC), which is manifested by markedly elevated serum phosphate and often severe ectopic and vascular calcifications. Further, FGF23 is elevated in X-linked hypophosphatemic rickets (XLH) and increased circulating FGF23 is also associated with a 5-6 fold higher mortality risk in patients with chronic kidney disease (CKD). There are currently no cures, only maintenance treatments, for the aforementioned syndromes. Although much progress has been made towards understanding both basic and clinical aspects of phosphate metabolism, the fundamental mechanisms regulating Fgf23 at the level of the skeleton under normal conditions and in disease are unknown. FGF23 is expressed in osteoblasts and osteocytes, however the cell type(s) that 'sense' changes in serum phosphate to control production and secretion of this hormone are also unknown. Importantly, we recently determined that primary cultures of osteoblasts/osteocytes increase Fgf23 in response to PTH and to phosphate, which represents an innovative shift in the current models explaining Fgf23 regulation. In combination with the newly- proposed in vivo systems, the cultures provide a novel approach for testing cell-specific control of Fgf23. The available Fgf23 knock-out and transgenic mouse models have provided essential in vivo data regarding FGF23 bioactivity, including interactions with its co-receptor a-Klotho (KL), however there are several limitations, including that the Fgf23 global knock-out is severely compromised at weaning and dies at 8-10 weeks, and the transgenic mice uncontrollably over-express FGF23. Therefore, an Fgf23 conditional-null model is a necessary tool to explore the pathophysiologic effects of Fgf23 in a non-lethal state and for isolating its role in human disorders. These proposed studies will address the central hypothesis that: FGF23 is regulated in a cell-specific manner, which is altered in disease, through undertaking the following specific aims: 1) To develop a mouse that will carry an Fgf23 allele that can be specifically interrupted in the presence of Cre recombinase; and 2) To test for cell-specific regulation of Fgf23 utilizing the conditional-null Fgf23flox/flox mice. Successful development of an Fgf23 conditional-null animal will provide a unique and important resource for us and for other investigators. Most of the molecular mechanisms guiding Fgf23 production and regulation under normal circumstances and in disorders of mineral metabolism are unknown, therefore this model will permit testing of hypotheses that are otherwise not possible. PUBLIC HEALTH RELEVANCE: The regulation of serum phosphate concentrations is critical for normal skeletal formation and cellular function. Pathogenic disturbances in phosphate homeostasis involving Fibroblast growth factor-23 (FGF23), such as those in the Mendelian disorders autosomal dominant hypophosphatemic rickets (ADHR), X-linked hypophosphatemic rickets (XLH), autosomal recessive hypophosphatemic rickets (ARHR), and familial tumoral calcinosis (TC), or common disorders such as renal failure, lead to severe endocrine and skeletal disease. These disorders currently have inadequate treatments. We expect that development of an Fgf23 conditional-null animal will reveal new mechanisms involved in phosphate homeostasis, and will provide novel therapeutic targets.

描述（由申请人提供）：需要适当控制血清磷酸盐浓度以维持骨骼完整性。我们之前发现成纤维细胞生长因子 23 (FGF23) 的错义突变是常染色体显性低磷血症性佝偻病 (ADHR) 的原因，其特征是继发于孤立性肾磷酸盐消耗和代谢性骨病的低磷血症。我们随后证明，FGF23 失活突变会导致 ADHR 的镜像障碍，即家族性肿瘤钙质沉着症 (TC)，其表现为血清磷酸盐显着升高，并且常常出现严重的异位钙化和血管钙化。此外，FGF23 在 X 连锁低磷血症佝偻病 (XLH) 中升高，循环 FGF23 升高还与慢性肾病 (CKD) 患者死亡风险增加 5-6 倍相关。对于上述综合症，目前尚无治愈方法，只能进行维持治疗。尽管在了解磷酸盐代谢的基础和临床方面已经取得了很大进展，但在正常条件和疾病中在骨骼水平调节 Fgf23 的基本机制尚不清楚。 FGF23 在成骨细胞和骨细胞中表达，但是“感知”血清磷酸盐变化以控制这种激素的产生和分泌的细胞类型也是未知的。重要的是，我们最近确定，成骨细胞/骨细胞的原代培养物会响应 PTH 和磷酸盐而增加 Fgf23，这代表了解释 Fgf23 调节的当前模型的创新转变。与新提出的体内系统相结合，培养物提供了一种测试 Fgf23 细胞特异性控制的新方法。 现有的 Fgf23 敲除和转基因小鼠模型提供了有关 FGF23 生物活性的重要体内数据，包括与其共受体 a-Klotho (KL) 的相互作用，但存在一些局限性，包括 Fgf23 全局敲除严重影响断奶时受到损害并在 8-10 周时死亡，并且转基因小鼠无法控制地过度表达 FGF23。因此，Fgf23 条件无效模型是探索 Fgf23 在非致死状态下的病理生理作用以及分离其在人类疾病中的作用的必要工具。这些拟议的研究将解决以下中心假设：FGF23 以细胞特异性方式受到调节，这种方式在疾病中会发生变化，通过实现以下具体目标：1) 开发一种携带 Fgf23 等位基因的小鼠，该等位基因可以被特异性中断在 Cre 重组酶存在下； 2) 利用条件无效的 Fgf23flox/flox 小鼠测试 Fgf23 的细胞特异性调节。 Fgf23 条件无效动物的成功开发将为我们和其他研究人员提供独特且重要的资源。在正常情况下和矿物质代谢紊乱中指导 Fgf23 产生和调节的大多数分子机制都是未知的，因此该模型将允许测试否则不可能的假设。 公众健康相关性：血清磷酸盐浓度的调节对于正常的骨骼形成和细胞功能至关重要。涉及成纤维细胞生长因子 23 (FGF23) 的磷酸盐稳态的致病性紊乱，例如孟德尔疾病常染色体显性低磷血症性佝偻病 (ADHR)、X 连锁低磷性佝偻病 (XLH)、常染色体隐性低磷性佝偻病 (ARHR) 和家族性肿瘤钙质沉着症 (TC) 或肾衰竭等常见疾病会导致严重的内分泌和骨骼疾病。目前这些疾病的治疗方法不足。我们期望 Fgf23 条件无效动物的开发将揭示涉及磷酸盐稳态的新机制，并将提供新的治疗靶点。