HPDL基因变异引起线粒体呼吸链氧化磷酸化功能缺陷导致线粒体病的机制研究

线粒体病严重影响儿童神经发育，其病死率、致残率极高，探寻其遗传学病因及发病机制意义重大。我们前期利用全基因组测序技术首次在2例临床拟诊断为线粒体病的患儿中发现HPDL基因存在复合杂合变异，进一步细胞实验证实HPDL基因参与线粒体氧呼吸功能的调控，且HPDL敲低会导致细胞中呼吸链复合体I、III、IV的蛋白含量减低，因此我们推测HPDL基因变异可能会影响线粒体呼吸链复合体质量控制系统，从而导致一种新的线粒体疾病。本课题将在前期基础上，通过蛋白晶体结构解析、酶活测定等方法阐明HPDL蛋白的理化性质，并基于HPDL敲除小鼠及细胞系，在体内外模型中探索HPDL基因变异导致线粒体病的表型特征和致病机制。HPDL基因目前尚未见与任何疾病的关联性报道，本项目的研究成果不仅可以扩大线粒体病的遗传学病因谱和发病机制，也可以为今后线粒体病的诊断、遗传咨询和治疗提供思路和理论依据，具有很强的科学价值和临床意义。

Mitochondrial disorders seriously affect neurodevelopment with high rate of mortality and disability. It is crucial to clarify the genetic etiologies and pathogenesis of mitochondrial disorders. Using the whole genome sequencing (WGS) technology, we found 2 patients with tentative diagnosis of mitochondrial disorder carried compound heterozygous variants of HPDL gene. Therefore, we speculated that variation of HPDL will lead to a new type of mitochondrial disorder. The result of cell experiments confirmed the involvement of HPDL in regulating process of oxygen mitochondrial respiratory. Further results confirmed the decreasing amount of respiratory chain complex I, III, IV in HPDL knockdown cells, suggesting the damaging effect of HPDL variations on mitochondrial respiratory chain complex quality control system. This study will explore the phenotypic characteristics and pathogenesis of mitochondrial disorder caused by HPDL variation, via in vivo and in vitro experiments, including resolving the crystal structure of 4-HPPD-L protein and constructing HPDL knockout mice and overexpressed/knockout cell lines. The variation of HPDL gene has not been reported to associate with any disease so far. The results of this project can not only expand the genetic etiology spectrum of mitochondrial disorders, but also provide new thoughts and theoretical basis for the development of early diagnosis, genetic counseling and clinical treatment of mitochondrial disorders in the future, with potential significance in clinical practical.