用动物模型定位、克隆复杂性疾病的易感基因:以类风湿关节炎动物模型为范例

基于复杂性疾病的临床异质性,或称表型异质性;遗传异质性,或称位点异质性;多基因的微效作用;异位显性(epistasis);拟表型(phenocopy);环境因素的作用等特点,鉴定复杂性疾病的易感基因是一种艰巨有时难以完成的任务。近交系动物遗传背景清晰,动物实验可控制环境因素的干扰,以及转基因动物在研究基因功能中独特的作用,应用动物模型为筛选鉴定人类复杂性疾病的易感基因提供了不可替代的工具。以大鼠类风湿关节炎模型为例,定位克隆易感基因步骤包括:①选择亲代近交系,建立关节炎模型;②分离育种,连锁分析、确定数量性状位点(QTLs);③建立Congenic系、窄化QTL区域;④位置克隆基因;⑤易感基因的功能验证。我们应用这一策略从朴日斯烷(Pristane)诱导的关节炎大鼠模型中已筛选出十余个控制关节炎发生发展的非MHC基因位点,在此基础上克隆的Pia4基因被鉴定为是中性粒细胞胞浆因子1(Ncf1)。说明该研究策略是完全可行的,并且可能发现新的功能基因或已知基因的新功能。

Identification of susceptibility genes for complex diseases using animal models: rat arthritis models as a paradigm

To identify and clone susceptibility genes for complex diseases is a formidable task since the complex diseases manifest clinical or phenotype heterogeneity, genetic or locus heterogeneity, minor effect of multiple genes, epistasis, phenocopy and interaction between genes and environmental factors. Animal models for complex diseases provide an irreplaceable tool to identify the susceptibility genes in terms of the fact that inbred animals show a known genetic background, animal experiments are performed under a controllable environmental condition and transgenic animals have been widely using to verify gene function. Identification of susceptibility genes for complex diseases in animal model, here rat arthritis as an example, may include the following steps: ① selecting inbred animal strains and establishing disease models; ② segregating breeding in F2 animals and running linkage analysis to find QTLs; ③ producing a series of congenic strains to narrow down QTL region under help of STR or SNPs markers; ④ carrying out positional cloning of susceptibility genes, and ⑤ confirming the function of susceptibility genes. By using this strategy, we have found a dozen of susceptibility loci in different chromosomes and suscessfully identified Ncf1 as the gene located in Pia4 to regulate susceptibility to pristane induced arthritis (PIA) of rats. It suggests that the strategy is of feasibility to discover new functional genes or new function of known genes.