FGF2 Isoforms in Bone and Phosphate Homeostasis

项目摘要 成纤维细胞生长因子23（Fibroblast Growth Factor 23，FGF 23）是人类病理性疾病中主要的磷酸盐调节因子 与骨矿化异常和肾性磷酸盐消耗（Pi）相关。然而，监管机构 FGF 23的产生，FGF 23诱导的Pi消耗和有缺陷的矿化的信号通路，不是 完全理解我们的研究支持成纤维细胞生长因子2的核亚型的重要作用 （FGF 2）在FGF 23产生和生物学功能中的作用。使用表达HMW同种型的新型小鼠模型， 成骨细胞谱系细胞（HMWTg）小鼠和选择性缺失HMW同种型的小鼠（HMWKO）小鼠 我们证明HMWTg小鼠血清和骨中FGF 23增加，侏儒症，骨减少， 骨密度（BMD）、骨软化、低磷酸盐血症和异常FGF 23/FGF受体/ klotho/MAPK 以及骨骼和肾脏中的Wnt信号。初步数据显示，HMWFGF 2亚型的消融 增加BMD，增加血清磷酸盐和显著降低FGF 23 mRNA。我们也 在Hyp小鼠（一种小鼠模型）中观察到成骨细胞/骨细胞核HMWFGF 2表达增加 X连锁低磷血症性佝偻病（XLH）我们也有令人兴奋的初步数据，高分子量异构体是 在来自XLH患者的B淋巴细胞中过表达，支持这些研究的临床相关性。我们 中心假设是HMWFGF 2：i）通过增加肾脏中的Pi稳态而在肾脏中起重要作用。 FGF 23在骨中的产生。ii）通过FGF 23依赖性和非依赖性调节骨基质矿化 方面的影响. iii）在Hyp小鼠中导致Pi消耗和有缺陷的基质矿化。目标1将决定 HMWFGF 2亚型在高分子量转基因小鼠肾脏Pi稳态中的作用：我们的工作假设 HMWFGF 2同种型增加了骨中FGF 23的产生，而内分泌FGF 23介导了骨中的异常生长。 肾脏中的FGFR/klotho/MAPK信号传导导致Pi消耗。目标2将评估HMWFGF 2的作用 同种型/FGF 23/FGFR和Wnt信号转导在成骨细胞分化和矿化中的作用。封锁的影响 将测定FGF 23、FGFR、MAPK/ERK和硬化蛋白对HMWTg小鼠中骨形成的影响。目标3将 检测HMWFGF 2敲除对Pi和骨稳态的功能影响，以及HMWFGF 2是否 在Hyp小鼠的异常Pi消耗和基质矿化缺陷中起重要作用。我们的假设是 HMWFGF 2亚型介导异常Pi稳态和骨矿化缺陷。检查 磷酸盐稳态，HMW-/-小鼠和Hyp小鼠的骨骼和肾脏表型， HMWFGF 2与野生型同窝仔将检验该假设。我们还将评估FGF/FGF受体， 下游的信号通路。建议的研究将大大提高我们对 HMWFGF 2亚型在Pi稳态和基质矿化中的作用， 对调节人类磷酸盐消耗过程的机制的基本见解 紊乱

Project Summary Fibroblast Growth Factor 23 (FGF23) is the major phosphate regulator in human pathologic disorders associated with abnormal bone mineralization and renal phosphate wasting (Pi). However the regulators of FGF23 production, the signal pathway(s) for FGF23 induced Pi wasting and defective mineralization are not fully understood. Our studies support an important role for the nuclear isoforms of Fibroblast Growth Factor 2 (FGF2) in FGF23 production and biologic function. Using novel mouse models expressing HMW isoforms in osteoblast lineage cells (HMWTg) mice, and mice with selective deletion of the HMW isoforms (HMWKO) mice we demonstrate that HMWTg mice have increased FGF23 in serum and bone, dwarfism, decreased bone mineral density (BMD), osteomalacia, hypophosphatemia, and abnormal FGF23/FGFReceptor/ klotho/MAPK and Wnt signaling in bone and kidney. Preliminary data shows that ablation of the HMWFGF2 isoforms increased BMD, increased serum phosphate and significantly reduced FGF23 mRNA in mice. We also observed increased expression of nuclear HMWFGF2 in osteoblasts/osteocytes in Hyp mice, a murine model of X-linked hypophosphatemic rickets (XLH). We also have exciting preliminary data that HMW isoforms are overexpressed in B-lymphocytes from a patient with XLH supporting clinical relevance of these studies. Our Central Hypotheses are that HMWFGF2: i) plays an important role in Pi homeostasis in kidney by increasing FGF23 production in bone. ii) regulates bone matrix mineralization via FGF23 dependent and independent effects. iii) contributes to Pi wasting and defective matrix mineralization in Hyp mice. Aim 1 will determine the role of HMWFGF2 isoforms in Pi homeostasis in the kidney of HMW transgenic mice: Our working hypothesis is that HMWFGF2 isoforms increase FGF23 production in bone and that endocrine FGF23 mediates abnormal FGFR/klotho/MAPK signaling in kidney that leads to Pi wasting. Aim 2 will assess the role of HMWFGF2 isoforms/FGF23/FGFR and Wnt signaling in osteoblast differentiation and mineralization. Effects of blockade of FGF23, FGFR, MAPK/ERK and sclerostin on bone formation in HMWTg mice will be determined. Aim 3 will examine functional effects of knockout of HMWFGF2 on Pi and bone homeostasis and whether HMWFGF2 is important in the abnormal Pi wasting and matrix mineralization defect in Hyp mice. Our working hypothesis is that HMWFGF2 isoforms mediate abnormal Pi homeostasis and defective bone mineralization. Examining phosphate homeostasis, the skeletal and kidney phenotypes of HMW-/- mice and Hyp mice with deletion of HMWFGF2 versus wild type littermates will test this hypothesis. We will also assess FGF/FGF Receptor and downstream signaling pathways in these mice. The proposed studies will greatly enhance our understanding of the role of HMWFGF2 isoforms in Pi homeostasis and matrix mineralization and may provide novel and fundamental insights into the mechanisms that regulate these processes in human phosphate wasting disorders.