ABHD1基因在牙龈纤维瘤/过度增生中的致病作用研究

Gingival fibromatosis/overgrowth is characterized by benign and diffuse fibrous hyperplasia in gingival tissues, which can be inherited or drug-induced. However, the pathophysiology of gingival fibromatosis/gingival overgrowth is still unknown. Previous studies indicated that hereditary gingival fibromatosis shows highly genetic heterogeneity with many diffirent locations for the disease gene in genome. So far, only a frameshift mutation of SOS1 gene has been regarded as a possible cause responsible for gingival fibromatosis; however, most of other studies only reported the location without finding the disease genes. By using genome-wide linkage analysis, genome-wide copy number analysis, and whole exome sequencing, we revealed a stop-codon gain mutation of ABHD1 gene on chromosome 2 in an autosomal dominant hereditary gingival fibromatosis family. This mutation was perfectly co-segregated with the phenotype of patients with gingival fibromatosis and was not found in 400 normal controls; the mRNA expression of ABHD1 has been detected in human gingival tissues. Therefore, ABHD1 gene was identified as a novel and promising candidate gene of gingival fibromatosis. Based on our previous results, this study will confirm this gene responsible for gingival fibromatosis and further discuss the signal pathways of drug-induced gingival overgrowth by using molecular biology technique including primary cell culture and knockout mice model. The study will indentify a novel gene for gingival fibromatosis and explore the pathogenesis of gingival fibromatosis; at the same time, we will provide a new clue for the prevention of drug-induced gingival overgrowth.

牙龈纤维瘤/过度增生是一类以牙龈组织良性弥漫性纤维增生为临床表现的疾病，多由药物诱导产生，少数为家族遗传所致，发病机制尚不清。遗传性牙龈纤维瘤表现出高度遗传异质性，目前除SOS1基因移码突变被认为是可能致病原因外，其他多项研究只是定位报道。在我们前期工作中，通过对常染色体显性遗传牙龈纤维瘤家系进行全基因组连锁分析、全基因组拷贝数分析和全外显子组测序，发现2号染色体上的ABHD1基因存在无义突变并与患者表型完全共分离；并进一步在人牙龈组织中检测到ABHD1基因表达，高度提示其很可能为新的牙龈纤维瘤致病基因。本项目将在前期工作基础上，采用分子生物学技术在原代细胞培养和基因敲除小鼠水平验证ABHD1基因突变是牙龈纤维瘤病的致病原因；并进一步探讨其在药物诱导的牙龈过度增生中发生的信号通路。该研究将突破性地发现牙龈纤维瘤新致病基因，阐明牙龈纤维瘤发病机制；同时将为预防药物性牙龈增生提供新靶点和思路。

牙龈纤维瘤/过度增生（Gingival fibromatosis/overgrowth）是一类临床上表现为牙龈组织良性弥漫性纤维性增生的疾病，可由药物诱导产生，也可为遗传基因突变所致。目前报道的遗传性牙龈纤维瘤四个候选基因位点分别引起GINGF1-4。除GINGF1中SOS1基因被认为是具体的致病基因外，其他类型GINGF都是定位研究而没有发现明确致病基因。本研究是针对一个排除了SOS1基因突变的中国人群遗传性牙龈纤维瘤病家系进行的致病基因及机制研究。主要研究内容包括全基因组芯片扫描连锁分析，STR标记连锁验证、全基因组CNV拷贝数分析、高通量测序（包括WES、WGS以及三代长片段测序）以及转基因动物研究。研究结果提示：1.该遗传性牙龈纤维瘤病家系表型呈常染色体显性遗传，全基因组扫描结果是在2号、7号、8号染色上有Lod值>2的可能候选区域；STR连锁分析进一步验证了2号染色体上候选区域（Chr2：23.8M-31.5M），该区域是目前该疾病定位2号染色体上最小候选区域；2.患者全基因组CNV拷贝数分析未发现与疾病相关的异常拷贝数变异；3.患者WES、WGS以及三代高通量测序结果提示2号染色体上ABHD1的无义突变；这个候选位点与该疾病表型共分离。4.ABHD1基因敲除小鼠无与人类疾病类似表型。由于种系差异，虽然在小鼠中没有重现表型，不能完全排除ABHD1是人类遗传性牙龈纤维瘤的候选基因。另外在本项目的资助下，我们在收集了多个口腔科家族性遗传疾病，如以牙齿增多为显著特征的家系存在RUNX2基因的新突变；如单纯性少牙为特征核心家系发现PAX9新突变。这些研究丰富了口腔科遗传疾病的致病基因突变谱。