Identification of disease-susceptibility genes related to congenital missing or supernumerary tooth.

在患病同胞对分析和SNPs相关分析中，我们选择并诊断了多生牙或先天性缺失等牙数异常的患者，特别是患病同胞对及其血缘关系和正常对照人群。用荧光标记的基因标记试剂盒和患者血液样本进行与染色体有关的基因分型，进行受累同胞对分析。但我们无法鉴定出与先天性缺失或多生牙相关的疾病易感基因，于是我们采用了机械应力的方法，其中环境因素与遗传因素进行了对比。为了阐明生物对机械刺激的反应，我们在体内和体外进行了分子生物学分析。采用半定量逆转录-聚合酶链反应（RT-PCR）技术检测了咬合刺激减少后大鼠牙周组织中IL-1 mRNA的表达。另外，在对磨牙施加机械刺激后，IL-1 mRNA的表达增加。低幅度的机械拉伸应力的牛牙周膜细胞的柔性底培养板诱导增加I型胶原和核心蛋白聚糖mRNA的表达，而不改变碱性磷酸酶（ALP）活性的牙周膜细胞。对基质细胞系（ST 2）施加低强度的机械张应力可诱导Cbfa 1/Runx 2 mRNA表达和ALP活性增加，而不改变I型胶原mRNA的表达。

For affected sib-pair analysis and SNPs related analysis, we selected and diagnosed patients with anomaly in tooth number such as supernumerary tooth or congenital missing, especially affected sib-pair, their consanguinities and normal control people. Affected sib-pair analysis was performed by gene typing concerned with chromosomes using samples of patients bloods and a fluorescence-labeled gene marker kit. But we could not identify the disease-susceptibility genes related to congenital missing or supernumerary tooth.Then we adopted the mechanical stress one of which environmental factors contrasted to hereditary factors. In order to clarify the biological response to the mechanical stimuli, we investigated using the molecular biological analysis in vivo and in vitro. When the occlusal stimuli were reduced in rats, the expression of IL-1 mRNA was increased in their hypofunctional periodontium using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the expression of IL-1 mRNA was increased after the mechanical stimuli were adopted to their molars. Mechanical tensional stress of low magnitude to the bovine periodontal ligament cells on the flexible bottomed culture plate induced the increase of both type I collagen and decorin mRNA expression without changing alkaline phosphatase (ALP) activity in periodontal ligament cells. Mechanical tensional stress of low magnitude to the stromal cell line (ST2) induced the increase of Cbfa1/Runx2 mRNA expression and ALP activity without changing type I collagen mRNA expression.These results suggest the possibility that environmental factors such as mechanical stimuli might induce anomaly in tooth number.