3型进行性家族性肝内胆汁淤积症（PFIC3）是ABCB4基因突变引起的罕见遗传性疾病。申请人在成人PFIC3临床队列中发现5个ABCB4错义突变（4个为新发现），经肝组织免疫组化、生物信息学分析提示这些突变均有致病性；针对较常见位点R788W构建慢病毒载体并感染HEK293细胞后可显著抑制胆碱磷脂分泌，也提示为致病突变。在此基础上，拟继续纳入PFIC3病例，并根据已发现的错义突变位点，分别构建含野生或突变ABCB4序列的慢病毒颗粒并感染HKE293细胞和HepG2细胞；构建含野生或突变序列的Abcb4表达载体并导入Mdr2-/-小鼠（Mdr2是小鼠的MDR3同源蛋白），借助细胞及动物模型研究不同错义突变对所编码MDR3蛋白表达和功能的影响。本研究将阐明ABCB4突变对PFIC3的致病性和机制，明确基因突变和临床表型间的相关性；并有助于将来建立符合国人突变位点的基因诊断方法。

Type 3 progressive familial intrahepatic cholestasis (PFIC3) is a rare hereditary disease caused by ABCB4 (ATP-binding cassette B4) gene mutations. We found 5 ABCB4 missense mutations in our adult PFIC3 clinical cohort (4 were newly discovered). Liver tissue multidrug resistance protein 3 (MDR3) immunohistochemistry, bioinformatics analysis both indicated that these mutations be pathogenic. We constructed lentiviral vector that contains one of R788W mutant ABCB4 DNA Sequence and infected HEK293 cells with the vector, and found that cell's ability of phosphatidylcholine secretion were significantly reduced, also suggesting that R788W be a pathogenic mutation. On this basis, we will continue to enrol PFIC3 cases for research. Lentiviral particles containing wild or mutant ABCB4 sequences according to the discovered missense mutation sites will be constructed and infect HEK293 cells and HepG2 cells. The plasmid vectors containing wild or mutated Abcb4 sequences will be constructed and introduced into Mdr2-/- mice (Mdr2 is a mouse MDR3 homologous protein). The effects of different missense mutations on MDR3 protein expression and function will be investigated by means of cell and animal models. This study will clarify the pathogenicity and mechanism of ABCB4 mutations on PFIC3, clarify the correlation between gene mutations and clinical phenotypes，and help to establish a genetic diagnosis method that conforms to the mutation site of Chinese people in the future.