线粒体DNA异质性高通量并行测序分析及其作为2型糖尿病分子标志物的研究

线粒体DNA异质性（heteroplasmy）是指同一个体或细胞中同时存在两种或两种以上类型的线粒体基因组。线粒体致病突变位点许多以异质性存在，但线粒体多态性位点异质性与疾病关系仍有争议。我们最近发现，T2DM外周血细胞的线粒体DNA中，位于ND2基因且定义N9a2c单体型的5471、5474、5498位点存在高度异质性，这是首次发现线粒体非致病位点与T2DM的相关。由于异质性存在比例差异，低比例异质性用常规测序很难发现，本研究将通过线粒体DNA捕获技术和高通量并行测序来分析异质性比例，发现低比例异质性人群并随访观察比例的动态变化；基于家系研究异质性的遗传规律，探讨与疾病发生的关系；并在细胞水平研究异质性对线粒体功能的影响，进一步确认与T2DM关系，为疾病早期诊断提供新型的分子标志物和检测技术，并深化T2DM机制研究。

Mitochondrial DNA heteroplasmy is the presence of a mixture of more than one type of mitochondrion genome within a cell or individual. Most of the mitochondrial DNA mutations are existed as heteroplasmy, whereas the relationship between heteroplasmy of mt DNA common variants and disease remains unclear. Recently, we found that three allels (5471,5474 and 5498) on mtDNA, located in ND2 gene, which define the haplogroup of N9a2c, are heteroplasmic with high frenquecny in the peripheral blood cells of T2DM. This is the first discovery of the correlation of the common variants to T2DM. Due to the variable heteroplasmic levels, the low frequency of heteroplasmic variants failed to be detected via conventional sequencing. In this study, we are intending to develop the approach to simultaneously determine mtDNA sequence and quantify the heteroplasmic level by mitochondrial DNA capture and massively parallel sequencing. The patients with low frequency will be followed up so that the dynamic changes could be examined. We also plan to investigate the inheritance pattern based on the family. The purpose of this study is to reveal the association of mtDNA heteroplasmic variants with T2DM and the effect on cellular mitochondrion function. Thus we can identify the novel type of molecular biomarker for T2DM.