慢性乙型病毒性肝炎相关低频/罕见遗传变异和拷贝数目变异的第Ⅱ期研究

Chronic hepatitis B (CHB) is a polygenic, multifactorial disease. Genetic background plays an important role in the susceptibility to the disease. In the search of the susceptible genes, much efforts have been delivered into common genetic variations (frequency >5%). However it has been confirmed that less frequent/rare variations (frequency <5%) usually confers stronger phenotypic effects, but are extremely heterogeneous. This feature of the rare/less frequent alleles determined the selection of the candidates have to be performed in different phases of discovery groups.Our team is the first reported four less frequent/rare genetic variations associated with the susceptibility to the disease (Hepatology 2012;56:1661-1670)(impact factor 12.003). However the extreme heterogeneity of the less frequent/rare variations clearly shows that there are much more associated variations have not been unraveled. Modeling the progression of the international HapMap and the 1000 genome project by different phases, we propose to conduct the second phase of the project. We have further performed exom sequencing in another 49 CHB cases and 50 controls subjects, and the whole genome sequencing in 3 cases and 1 control. We selected 21 candidates less frequent/rare variations and 4 copy number variations. We have also further extended our cohort to 2,029 cases and 1,896 controls with the exclusion of individuals certain of having had HBV vaccine. We aim to identify more novel less frequent/rare variations and copy number variations associated with CHB. With the already proven strategies and techniques, also the experience obtained from the phase　I　study we anticipate that this phase of the project will yield good results, which will shed light on pathogenesis of CHB，and may have potential in medical practice.

慢性乙型病毒性肝炎（乙肝）是多基因复杂性疾病。宿主的遗传背景在乙肝的易感性上起重要作用。本课题组在乙肝相关遗传变异的第Ⅰ期研究中首先在国际上报导了4个相关的低频/罕见遗传变异（Hepatology 2012;56:1661-1670）（影响因子12.003）。现本课题组拟开展乙肝相关基因的第Ⅱ期研究。我们已对另外49例病例及另外50例对照进行了全外显子组测序；并对其中4例进行了全基因组测序；筛选了21个候选基因及4个候选拷贝数目变异,全为国际上尚未报导过的基因/拷贝数目变异。我们已收集到2029例病例，1896例未注射过乙肝疫苗或注射状态不明的对照。现拟在我们的cohort中进一步筛选乙肝相关低频/罕见遗传变异及拷贝数目变异。第Ⅱ期研究是我们第Ⅰ期研究的深入及延续，我们预期会获得好的进一步的结果，这些结果不仅会加深我们对乙肝发病机理的认识，并可能有有个体化治疗上的应用潜能。

慢性乙型病毒性肝炎（乙肝）是严重危害我国及其它发展中国家人口健康的大病，同时也是一项重要的全球性的公共卫生问题。受感染者的遗传背景对乙肝的发病，进展及预后有重大影响。在本项目及其前一项目中，集中研究了对表型有重大影响的罕见遗传变异。乙肝病毒受体是科学界找寻了近半个世纪的重要个体相关因子。虽然体外研究提示3种人体因子可能为乙肝病毒受体，但都难以在体内证实。我国李文辉教授课题组的体外研究显示人类的一种胆汁酸受体（NTCP）为乙肝病毒受体后，我们在乙肝病人中对编码这一受体的基因SLC10A1中的一个次要等位基因频率在中国北方人群中约4%以及在中国南方人群中约8%的变异进行了研究。我们的结果提供了基于人体研究NTCP就是乙肝病毒受体的强有力的证据。这一结果已被台湾岛内乙肝病人及其他相似研究证实。同时，我们的结果还显示这一受体基因p.Ser267Phe突变携带者有更强的抗乙肝病毒感染的能力及在感染后更低的肝衰竭的发生率。由于NTCP的生理功能是在胆汁酸的肝肠循环中向肝细胞转运胆汁酸，在乙肝病毒受体的研究之后，本课题组进一步对这一基因的p.Ser267Phe纯合性突变个体进行了研究，理论上该类个体在中国南方人群中的频率为0.64%。这一研究导致我们发现了一种以前未知的新型无症状的高胆汁酸血症。这一新型的高胆汁酸血症也有几个独立的研究证实。对这些纯合个体的深度医学评估显示这些纯合性突变的个体都有维生素D缺乏，且一部分人有类固醇激素的紊乱。这些研究不仅有科学上的意义，也对这些个体的健康评估个体化诊疗提供了指导意见。