Pathogenic Mechanisms of Craniometaphyseal Dysplasia

项目总结/摘要 研究罕见孟德尔疾病的致病机制不仅对确定治疗方法很重要， 这不仅有助于制定终身衰弱疾病的治疗策略，而且有助于了解基本的生物机制。在这 更新申请，我们提出了颅骺发育不良（CMD）的机制和转化研究， 一种研究不足的颅管状骨疾病，特征为颅面骨的终身进行性骨质增生 骨骼和长骨的异常形状。CMD中持续的骨累积可导致极度痛苦的 头痛、失明、耳聋和面瘫。严重的病例可能危及生命。CMD患者 当面部畸形需要矫正或严重时， 出现神经症状。进行性关节强直蛋白（ANKH）和连接蛋白43（Cx43）的突变 已被确定为常染色体显性和隐性CMD的原因。为了研究CMD，我们 已经产生了最先进的研究工具，其中包括携带CMD突变的小鼠模型， 具有或不具有CMD突变的人诱导多能干细胞（hiPSC）和骨吸收细胞 （破骨细胞）来源于这些hiPSC。在过去的资助期间，我们发现 的突变ANKH（人）/ANK（小鼠）蛋白，并研究了突变ANKH/ANK对 细胞骨架决定细胞的形状、大小和极性。我们还发现了差异表达的 CMD破骨细胞中的蛋白和突变ANK蛋白的优先结合伴侣。然而，CMD 发病机制尚未完全了解，潜在的治疗方法尚未探索。 我们的长期目标是利用我们的研究结果来确定潜在的治疗靶点，以减少或 防止颅面骨中的终身骨沉积。在未来的5年里，我们将使用动物模型， 分子和细胞的方法，我们已经开发出专注于机制的调查， 为将来的临床研究做准备。根据我们的初步数据和以前的出版物，我们提出三个 明确的目标。我们将研究CMD突变体ANK对破骨细胞细胞酸化的影响（Aim 1）， CMD中细胞骨架和能量代谢调节剂之间的双向调节（目的2）。 这些可能是导致CMD的突变ANK的新的显性功能。在目标3中，我们将确定生物标志物 可以用来监测患者和小鼠模型的疾病进展。我们还将评估轮班情况 在我们的模型系统中，生物标志物表达对实验治疗方案的响应。我们预计 拟议的研究将更深入地了解CMD的致病机制， 发现治疗的候选靶点。对应于疾病进展或治疗的生物标志物 疗效将是未来临床研究的基础。

Project Summary/Abstract Investigating pathogenic mechanisms for rare Mendelian disorders is important not only to identify therapeutic strategies for lifelong debilitating diseases but also to understand fundamental biological mechanisms. In this renewal application, we propose mechanistic and translational studies for craniometaphyseal dysplasia (CMD), an understudied craniotubular bone disorder characterized by lifelong progressing hyperostosis of craniofacial bones and abnormal shape of long bones. Continued bone accrual in CMD can lead to excruciating headaches, blindness, deafness, and facial palsy. Severe cases can be life-threatening. CMD patients are treated with repetitive, costly and risky surgeries when corrections of facial deformity are needed or severe neurological symptoms occur. Mutations in the progressive ankylosis protein (ANKH) and connexin 43 (Cx43) have been identified as causes for autosomal dominant and recessive CMD, respectively. To study CMD, we have generated state-of-the-art research tools, which include mouse models carrying CMD mutations, isogenic human induced pluripotent stem cells (hiPSCs) with or without CMD mutations, and bone resorbing cells (osteoclasts) derived from these hiPSCs. In the past funding period, we have discovered the rapid degradation of mutant ANKH(Human)/ANK(Mouse) protein and studied negative effects of mutant ANKH/ANK on the cytoskeleton, which determinates cell shape, size, and polarity. We also identified differentially expressed proteins in CMD osteoclasts and preferential binding partners for mutant ANK protein. However, CMD pathogenesis is not fully understood and potential therapeutics have not been explored. Our long-term goal is to utilize our research findings for identifying potential therapeutic targets to reduce or prevent the lifelong bone deposition in craniofacial bones. In the next 5 years, we will use animal models and molecular and cellular methodologies that we have developed to focus on mechanistic investigations and prepare for future clinical studies. Based on our preliminary data and previous publications we propose three specific aims. We will study the impact of CMD-mutant ANK on cellular acidification of osteoclasts (Aim 1) and on the bi-directional regulation between the cytoskeleton and an energy metabolism regulator in CMD (Aim 2). These are likely novel dominant functions of mutant ANK leading to CMD. In Aim 3 we will identify biomarkers that can be used to monitor the disease progression in patients and mouse models. We will also evaluate shifts in biomarker expression in response to experimental treatment regimen in our model systems. We expect that the proposed studies will give deeper insight into pathogenic mechanisms of CMD, knowledge needed to discover candidate targets for therapeutics. Biomarkers that correspond to disease progression or treatment efficacy will be the basis for future clinical studies.