Noe Johannes, Kullak-Ublick Gerd A, Jochum Wolfram, Stieger Bruno, Kerb Reinhold, Haberl Michael, Müllhaupt Beat, Meier Peter J, Pauli-Magnus Christiane
Division of Clinical Pharmacology and Toxicology, Department of Internal Medicine, University Hospital Zurich, Rämistrasse 100, E RAE 09, 8091 Zürich, Switzerland.
J Hepatol. 2005 Sep;43(3):536-43. doi: 10.1016/j.jhep.2005.05.020.
BACKGROUND/AIMS: Inherited dysfunction of the bile salt export pump BSEP (ABCB11) causes a progressive and a benign form of familial intrahepatic cholestasis, denominated as PFIC2 and BRIC2, respectively. We functionally characterized novel ABCB11 mutations encountered in two patients with a PFIC2 and a BRIC2 phenotype, respectively.
BSEP expression was determined in liver biopsies by immunohistochemistry. ABCB11 mutations were functionally characterized by taurocholate transport in SF9 cells transfected with human ABCB11.
The PFIC2 patient was compound heterozygous for a splicing mutation in intron 4 ((+3)A > C) combined with an early stop codon at position 930 (R930X), while the BRIC2 patient was compound heterozygous for two nonsynonymous mutations in exon 9 (E297G) and exon 12 (R432T), respectively. Hepatic BSEP expression was absent in PFIC2 and preserved in BRIC2. In BRIC2, taurocholate transport was decreased to 13% and 20% of reference levels for R432T and E297G, respectively.
The intron 4 (+3)A > C, R930X and R432T represent previously undescribed mutations of the ABCB11 gene that confer a PFIC2 and a BRIC2 phenotype, respectively. By combining functional in-vitro characterization with immunohistochemical detection of variant BSEP we provide direct evidence for the role of ABCB11 mutations in the pathogenesis of different forms of intrahepatic cholestasis.
背景/目的：胆汁盐输出泵BSEP（ABCB11）的遗传性功能障碍分别导致进行性和良性家族性肝内胆汁淤积，分别称为PFIC2和BRIC2。我们对分别患有PFIC2和BRIC2表型的两名患者中发现的新型ABCB11突变进行了功能特征分析。
通过免疫组织化学在肝活检中测定BSEP表达。通过在转染了人ABCB11的SF9细胞中进行牛磺胆酸盐转运来对ABCB11突变进行功能特征分析。
PFIC2患者为内含子4中的剪接突变（（+3）A>C）与第930位的早期终止密码子（R930X）的复合杂合子，而BRIC2患者分别为外显子9（E297G）和外显子12（R432T）中的两个非同义突变的复合杂合子。PFIC2患者肝脏中无BSEP表达，BRIC2患者中BSEP表达得以保留。在BRIC2患者中，R432T和E297G的牛磺胆酸盐转运分别降至参考水平的13%和20%。
内含子4（+3）A>C、R930X和R432T分别代表ABCB11基因以前未描述的突变，这些突变分别导致PFIC2和BRIC2表型。通过将体外功能特征分析与变异型BSEP的免疫组织化学检测相结合，我们为ABCB11突变在不同形式肝内胆汁淤积发病机制中的作用提供了直接证据。
