遗传性牙本质发育异常I型（DD-I）是一种严重牙本质发育不良导致牙齿自发脱落的常染色体显性遗传病，对其致病基因的阐明是临床诊治该病的基础，目前该病致病基因仍未找到。在我们的前期研究中，收集到一个包括14名患者的34人DD-I患病大家系，通过基于SNP芯片全基因组扫描和STR分析确证将该家系候选致病基因定位到了5号染色体上的一个区域，随后通过目标序列捕获测序和家系内共分离等克隆到了致病基因，为一个目前尚无功能研究报道的开放阅读框，经检测在牙齿相关细胞表达。本研究拟在前期研究的工作基础上，通过体内和体外的功能学实验进一步确认和研究该基因在DD-I致病中的作用机理及其病理生理学机制。本课题的完成将充分阐明遗传性DD-I疾病的致病基因及其发病机理，为DD-I型疾病的临床诊治、遗传咨询和预防提供实验和理论依据；同时，将为牙齿尤其是牙本质和牙根的生理发育机制及相关信号通路提供新的基础知识和研究线索。

Dentin Dysplasia type I (DD-I) is a genetic defect of dentin formation to result in the tooth exfoliating spontaneously, which is inherited as an autosomal dominant trait.The disease-caused gene cloning with DD-I is the basic for the recognition, diagnosis and treatment to DD-I. However, the exactly genetic contributor for DD-I has not been identified and the etiology of DD-I remains unclear.Based on one family cohort with 34 populations including 14 patients of DD-I, our previous study identified a risk region for DD-1 in Chromosome 5 through whole genome-wide SNP array and STR linkage analysis. Further screening by the target sequence capture sequencing, bioinformatics and co-segregation analyses revealed a missense mutation in an open reading frame (C5orfN) associated with DD-I，and the C5orfN was velidated to express in tooth cells. In the present study, the experiments in vivo and in vitro including cytology experiments, protein interaction, zebrafish experiments and transgenic mouse will be employed to validate the molecular function of C5orfN involving in the development and etiology of DD-I. The results will provide insight into the pathogenesis mechanism of DD-I, and further improve clinical diagnosis and treatment for DD-I disease.In addition, the research resuts will provide the new mechanism to the physiological development and the signal pathway of tooth,especially in dentin and root of tooth.

遗传性牙本质发育异常I型（DDI）是一种严重牙本质发育不良导致牙齿自发脱落的常染色体显性遗传病，对其致病基因的克隆是认识和诊治该病的根本基础。目前该病致病基因的寻找仍是一片空白，使之成了5类牙本质发育缺陷疾病研究的一个盲区。在本项目中，我们利用一个包括14名患者的34人DDI患病大家系，通过基于SNP芯片全基因组扫描和STR分析确证将该家系候选致病基因定位到了3号染色体上3p26.1–3p24.3，随后通过目标序列捕获测序和家系内共分离找到了SSUH2基因一个错义突变c.353C>A (P118Q)为该家系的致病突变。体外细胞水平研究表明该突变改变了SSUH2蛋白的高级结构，显著降低了其RNA和蛋白表达水平。进一步我们通过构建的基因敲入小鼠牙齿表型分析发现小鼠呈现出牙髓腔部分堵塞，同时影响了上调或下调了牙本质发育的部分关键基因如Dspp, Dmp1, Runx2, Pax9, Bmp2和Dlx2等的表达。此外，在斑马鱼中敲降ssuh2基因呈现出牙齿缺损的表型，而且通过拯救实验能恢复部分缺损的牙齿。通过上述体内和体外的功能学实验进一步确认了SSUH2基因在DDI疾病致病中的作用机理及其分子生物学机制。本课题的完成对遗传性DDI疾病的致病基因定位克隆和分子致病机理研究揭开新的篇章，为牙本质生理发育的分子机制提供新的理论基础，为DDI型疾病的临床诊治和预防提供实验和理论依据。