低磷性佝偻病（HR）是儿童常见的代谢性骨病，尿磷重吸收减少，血磷降低，骨矿化障碍，致畸致残率高。多种基因突变可导致HR，其中PHEX基因突变占50%-70%，提示PHEX在磷代谢调节中发挥重要作用。然而PHEX调磷靶分子未明确，分子机制未完全阐明。课题组已收集41个低磷性佝偻病家系，突变分析发现PHEX基因突变33例，新突变17例；非PHEX基因突变8例，新突变6例。生物信息学及体外功能学研究显示：PHEX基因新发突变高度保守，可导致蛋白表达减少，活性降低或热稳定性减弱，使PHEX蛋白功能缺陷。在此基础上课题组将通过CRISPR-Cas9技术构建PHEX基因定点突变小鼠模型，首次将HR患者错义突变引入小鼠，通过蛋白质组学分析，识别PHEX作用底物，在分子、细胞和整体三个水平，体外和体内结合，明确PHEX在磷代谢调节中的作用及其调控途径和关键分子，为制订HR防治策略提供新思路。

Hypophosphatemic rickets (HR) is a common kind of metabolic osteopathy in children characterized by reduced urinary phosphorus reabsorption, hypophosphatemia, bone mineralization disorder and high incidence of teratogenesis. Multiple gene mutations are attributed to HR, among of which PHEX mutation accounts for 50%-70%, suggesting that PHEX plays an important role in the regulation of phosphorus metabolism. However, the substrate of PHEX in regulating phosphorus metabolism is still unclear, and the molecular mechanism of PHEX regulating phosphorus reabsorption has not been fully elucidated. We have collected 41 families with HR in a preliminary research and found 33 cases with PHEX mutation including 17 cases with novel mutations through a mutation analysis and 8 cases with non-PHEX mutation including 6 cases with novel mutations. Bioinformatics and in vitro functional genomics studies have shown that new mutations of PHEX were highly conserved and could lead to reduced protein expression, decreased activity or thermostability, consequently producing defective PHEX protein. Based on our previous study, this research will firstly introduce the missense mutation found in HR patients into the mice by generating a mouse model carrying a defined point mutation of PHEX via CRISPR-Cas9 system, identify PHEX’s substrate through proteomic analysis, and clarify the role of PHEX on the regulation of phosphorus metabolism and the underlying regulatory pathway, which will reveal the mechanisms of interaction between PHEX and other phosphorus regulatory factors and further provide new evidence for HR prevention and treatment strategies.