结核分枝杆菌北京基因型菌株的微进化与致病性的研究

结核分枝杆菌具有潜伏感染的特点，潜伏期的长短反映了致病性的差异，而该特征的进化与宿主环境的演变密切相关。我国结核病主要由结核分枝杆菌北京基因型菌株所致。我们的研究表明R1亚型在北京基因型菌株中占绝对优势，并推算出该亚型起源和扩张年代在5-6千年前。该时期东亚人群已从旧石器过渡到新石器时代，人口数量大量增加。我们提出R1亚型菌株在进化过程中积累的特定遗传变异增强了其致病性使其成功地在高密度人群中传播和扩张的科学假设。本研究将选出代表性的R1亚型菌株进行全基因组测序，筛选出可能的遗传突变；经大样本临床菌株验证，鉴定出R1亚型特异的遗传变异；利用生物信息学方法分析遗传突变对基因功能的影响和多基因间的相互作用, 预测特定遗传变异导致R1亚型致病性增强的分子机制; 设计相关实验并利用细胞和小鼠感染模型验证提出的导致致病性增强的分子机制。本研究对揭示病原微生物微进化以适应宿主新环境的机制有重要意义。

Tuberculosis (TB) is still one of the leading causes of death in our country. The causative agent Mycobacterium tuberculosis (MTB) is an obligate human pathogen whose evolution is highly associated with human migration and development of human society. TB in China is mainly caused by Beijing family strains. Our previous genotyping data indicate a recently evolved sublineage R1 dominate in the population of Beijing family strains around China. The whole genome based dating suggest R1 sublineage originated and expanded at 5,000-6,000 years ago, during which the modern human in East Asia has transformed form Paleolithic Age to Neolithic Age. Due to the introduction of agriculture, the population size and density has greatly increased in the Neolithic Age. We hypothesize that R1 sublineage has acuminated specific mutations during its evolution, which allows R1 strains more successful in causing diseases and transmission in large human populations with high population density. The current study will firstly select representative R1 strains from pools of clinical isolates and sequence them; then, by whole genome comparison and further large scaled genotyping, we will identify R1 specific mutations (including point mutations, large or small indels); next, we will apply profound bioinformatics analysis to predict the potential functional effects of these mutations and multi-gene interactions, which may contribute to the dominant phenotype of R1 strains; at last, we will design functional experiment as well as cell and mouse infectious model to verify the molecular mechanism of pathogenesis of R1 sublineage. This study is of great significance to uncover the mechanism of human pathogen to adapt to changed host ecologies during the development of human society.