Severe Bile Salt Export Pump Deficiency: 82 Different ABCB11 Mutations in 109 Families

Background & Aims: Patients with severe bile salt export pump (BSEP) deficiency present as infants with progressive cholestatic liver disease. We characterized mutations of ABCB11 (encoding BSEP) in such patients and correlated genotypes with residual protein detection and risk of malignancy. Methods: Patients with intrahepatic cholestasis suggestive of BSEP deficiency were investigated by single-strand conformation polymorphism analysis and sequencing of ABCB11. Genotypes sorted by likely phenotypic severity were correlated with data on BSEP immunohistochemistry and clinical outcome. Results: Eighty-two different mutations (52 novel) were identified in 109 families (9 nonsense mutations, 10 small insertions and deletions, 15 splice-site changes, 3 whole-gene deletions, 45 missense changes). In 7 families, only a single heterozygous mutation was identified despite complete sequence analysis. Thirty-two percent of mutations occurred in >1 family, with E297G and/or D482G present in 58% of European families (52/89). On immunohistochemical analysis (88 patients), 93% had abnormal or absent BSEP staining. Expression varied most for E297G and D482G, with some BSEP detected in 45% of patients (19/42) with these mutations. Hepatocellular carcinoma or cholangiocarcinoma developed in 15% of patients (19/128). Two protein-truncating mutations conferred particular risk; 38% (8/21) of such patients developed malignancy versus 10% (11/107) with potentially less severe genotypes (relative risk, 3.7 [confidence limits, 1.7–8.1; P = .003]). Conclusions: With this study, >100 ABCB11 mutations are now identified. Immunohistochemically detectable BSEP is typically absent, or much reduced, in severe disease. BSEP deficiency confers risk of hepatobiliary malignancy. Close surveillance of BSEP-deficient patients retaining their native liver, particularly those carrying 2 null mutations, is essential. Background & Aims: Patients with severe bile salt export pump (BSEP) deficiency present as infants with progressive cholestatic liver disease. We characterized mutations of ABCB11 (encoding BSEP) in such patients and correlated genotypes with residual protein detection and risk of malignancy. Methods: Patients with intrahepatic cholestasis suggestive of BSEP deficiency were investigated by single-strand conformation polymorphism analysis and sequencing of ABCB11. Genotypes sorted by likely phenotypic severity were correlated with data on BSEP immunohistochemistry and clinical outcome. Results: Eighty-two different mutations (52 novel) were identified in 109 families (9 nonsense mutations, 10 small insertions and deletions, 15 splice-site changes, 3 whole-gene deletions, 45 missense changes). In 7 families, only a single heterozygous mutation was identified despite complete sequence analysis. Thirty-two percent of mutations occurred in >1 family, with E297G and/or D482G present in 58% of European families (52/89). On immunohistochemical analysis (88 patients), 93% had abnormal or absent BSEP staining. Expression varied most for E297G and D482G, with some BSEP detected in 45% of patients (19/42) with these mutations. Hepatocellular carcinoma or cholangiocarcinoma developed in 15% of patients (19/128). Two protein-truncating mutations conferred particular risk; 38% (8/21) of such patients developed malignancy versus 10% (11/107) with potentially less severe genotypes (relative risk, 3.7 [confidence limits, 1.7–8.1; P = .003]). Conclusions: With this study, >100 ABCB11 mutations are now identified. Immunohistochemically detectable BSEP is typically absent, or much reduced, in severe disease. BSEP deficiency confers risk of hepatobiliary malignancy. Close surveillance of BSEP-deficient patients retaining their native liver, particularly those carrying 2 null mutations, is essential. Bile salt export pump (BSEP) deficiency is caused by mutations in ABCB11.1Strautnieks S.S. Bull L.N. Knisely A.S. et al.A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis.Nat Genet. 1998; 20: 233-238Crossref PubMed Scopus (833) Google Scholar, 2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar The severity of BSEP deficiency varies from progressive early-onset1Strautnieks S.S. Bull L.N. 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Their collective estimated incidence in Western Europe is 1 in 50,000–70,000 births per year. BSEP, previously termed “sister of P-glycoprotein,”14Childs S. Yeh R.L. Georges E. et al.Identification of a sister gene to P-glycoprotein.Cancer Res. 1995; 55: 2029-2034PubMed Google Scholar is a member of the adenosine triphosphate–binding cassette (ABC) superfamily and P-glycoprotein/multidrug resistance (MDR/ABCB) subfamily of transporters.15Thompson R. Strautnieks S. BSEP: function and role in progressive familial intrahepatic cholestasis.Semin Liver Dis. 2001; 21: 545-550Crossref PubMed Scopus (110) Google Scholar, 16Stieger B. Meier Y. Meier P.J. The bile salt export pump.Pflugers Arch. 2007; 453: 611-620Crossref PubMed Scopus (180) Google Scholar BSEP, expressed at the hepatocyte canalicular membrane, is the major exporter of primary bile acids.17Gerloff T. Stieger B. Hagenbuch B. et al.The sister of P-glycoprotein represents the canalicular bile salt export pump of mammalian liver.J Biol Chem. 1998; 273: 10046-10050Crossref PubMed Scopus (808) Google Scholar, 18Byrne J.A. Strautnieks S.S. Mieli-Vergani G. et al.The human bile salt export pump: characterization of substrate specificity and identification of inhibitors.Gastroenterology. 2002; 123: 1649-1658Abstract Full Text Full Text PDF PubMed Scopus (283) Google Scholar, 19Noe J. Stieger B. Meier P.J. Functional expression of the canalicular bile salt export pump of human liver.Gastroenterology. 2002; 123: 1659-1666Abstract Full Text Full Text PDF PubMed Scopus (224) Google Scholar It actively transports conjugated bile salts into biliary canaliculi against extreme concentration gradients. Liver disease in BSEP deficiency is ascribed to failed secretion and intrahepatocytic accumulation of toxic bile salts. Patients with the progressive form present as infants with high serum bile salt levels, pruritus, malabsorption, failure to thrive, jaundice, and cholestasis. They develop fibrosis and end-stage liver disease before adulthood.20Whitington P.F. Freese D.K. Alonso E.M. et al.Clinical and biochemical findings in progressive familial intrahepatic cholestasis.J Pediatr Gastroenterol Nutr. 1994; 18: 134-141Crossref PubMed Scopus (233) Google Scholar, 21Bull L.N. Carlton V.E. Stricker N.L. et al.Genetic and morphological findings in progressive familial intrahepatic cholestasis (Byler disease [PFIC-1] and Byler syndrome): evidence for heterogeneity.Hepatology. 1997; 26: 155-164Crossref PubMed Scopus (229) Google Scholar, 22Shneider B.L. Progressive intrahepatic cholestasis: mechanisms, diagnosis and therapy.Pediatr Transplant. 2004; 8: 609-612Crossref PubMed Scopus (31) Google Scholar Partial external biliary diversion and ileal exclusion can relieve pruritus and, in some cases, slow disease progression.23Whitington P.F. Whitington G.L. Partial external diversion of bile for the treatment of intractable pruritus associated with intrahepatic cholestasis.Gastroenterology. 1988; 95: 130-136Abstract PubMed Google Scholar, 24Emond J.C. Whitington P.F. Selective surgical management of progressive familial intrahepatic cholestasis (Byler’s disease).J Pediatr Surg. 1995; 30: 1635-1641Abstract Full Text PDF PubMed Scopus (137) Google Scholar, 25Ismail H. Kalicinski P. Markiewicz M. et al.Treatment of progressive familial intrahepatic cholestasis: liver transplantation or partial external biliary diversion.Pediatr Transplant. 1999; 3: 219-224Crossref PubMed Scopus (97) Google Scholar, 26Kalicinski P.J. Ismail H. Jankowska I. et al.Surgical treatment of progressive familial intrahepatic cholestasis: comparison of partial external biliary diversion and ileal bypass.Eur J Pediatr Surg. 2003; 13: 307-311Crossref PubMed Scopus (98) Google Scholar, 27Kurbegov A.C. Setchell K.D. Haas J.E. et al.Biliary diversion for progressive familial intrahepatic cholestasis: improved liver morphology and bile acid profile.Gastroenterology. 2003; 125: 1227-1234Abstract Full Text Full Text PDF PubMed Scopus (99) Google Scholar However, most patients ultimately need orthotopic liver transplantation. We here present the mutations of ABCB11 in 109 families with severe BSEP deficiency. Families with progressive familial intrahepatic cholestasis were recruited through referral to King’s College London or the University of California, San Francisco. All procedures were conducted with informed consent as routine diagnostic investigations or under an institutional review board–approved protocol. Referrers supplied clinical data. No patient had elevated serum concentrations of γ-glutamyltransferase. Other causes of “neonatal hepatitis” were excluded, including primary disorders of bile acid synthesis in most cases. Families were defined as affected by “severe” progressive familial intrahepatic cholestasis and included in the study if at least one family member presented in infancy with cholestasis and low γ-glutamyltransferase that progressed, with clinical and biochemical markers of cholestasis persistently abnormal (absent surgical intervention). They were excluded if cholestasis ever resolved completely. Selection for likely BSEP deficiency was based on clinical and histologic data (specifically liver disease without the extrahepatic manifestations [pancreatitis, hearing loss, profound diarrhea] characteristic of familial intrahepatic cholestasis 1 deficiency and exhibiting giant cell hepatitis rather than bland cholestasis on histologic assessment21Bull L.N. Carlton V.E. Stricker N.L. et al.Genetic and morphological findings in progressive familial intrahepatic cholestasis (Byler disease [PFIC-1] and Byler syndrome): evidence for heterogeneity.Hepatology. 1997; 26: 155-164Crossref PubMed Scopus (229) Google Scholar). Where possible, BSEP immunohistochemical analysis (30%)2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar, 28Knisely A.S. Strautnieks S.S. Meier Y. et al.Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiency.Hepatology. 2006; 44: 478-486Crossref PubMed Scopus (282) Google Scholar, 29Scheimann A.O. Strautnieks S.S. Knisely A.S. et al.Mutations in bile salt export pump (ABCB11) in two children with progressive familial intrahepatic cholestasis and cholangiocarcinoma.J Pediatr. 2007; 150: 556-559Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar and/or microsatellite-based haplotype analysis13Bull L.N. van Eijk M.J. Pawlikowska L. et al.A gene encoding a P-type ATPase mutated in two forms of hereditary cholestasis.Nat Genet. 1998; 18: 219-224Crossref PubMed Scopus (602) Google Scholar, 30Strautnieks S.S. Kagalwalla A.F. Tanner M.S. et al.Locus heterogeneity in progressive familial intrahepatic cholestasis.J Med Genet. 1996; 33: 833-836Crossref PubMed Scopus (43) Google Scholar, 31Strautnieks S.S. Kagalwalla A.F. Tanner M.S. et al.Identification of a locus for progressive familial intrahepatic cholestasis PFIC2 on chromosome 2q24.Am J Hum Genet. 1997; 61: 630-633Abstract Full Text PDF PubMed Scopus (168) Google Scholar were used. The resultant subgroup was analyzed for ABCB11 mutations. A total of 109 families (data and/or biopsy material available for 132 individuals) met the inclusion criteria of genetically proven severe BSEP deficiency (Supplementary Table 1A, Supplementary Table 1B, Supplementary Table 1C, Supplementary Table 1D, Supplementary Table 1E; see supplementary material online at www.gastrojournal.org). Eighty-nine families were European (European, Australian, North American), and 20 were Central Asian/Arab, East Asian (Korean, Japanese, Chinese), South Asian (Indian, Pakistani), or African. BSEP immuno–staining was possible for 88 patients; clinical follow-up for malignancy was available in 128. In 7 families, clinical outcome and/or immunohistochemical results from a deceased sibling were included without mutational confirmation. In 5 families, only parental DNA was analyzed. We have previously reported single mutations in 8 families1Strautnieks S.S. Bull L.N. Knisely A.S. et al.A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis.Nat Genet. 1998; 20: 233-238Crossref PubMed Scopus (833) Google Scholar, 2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar, 32Chen F. Ananthanarayanan M. Emre S. et al.Progressive familial intrahepatic cholestasis, type 1, is associated with decreased farnesoid X receptor activity.Gastroenterology. 2004; 126: 756-764Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar; the second mutant allele is now identified in each. Clinical observations in 21 families have been reported previously.28Knisely A.S. Strautnieks S.S. Meier Y. et al.Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiency.Hepatology. 2006; 44: 478-486Crossref PubMed Scopus (282) Google Scholar, 29Scheimann A.O. Strautnieks S.S. Knisely A.S. et al.Mutations in bile salt export pump (ABCB11) in two children with progressive familial intrahepatic cholestasis and cholangiocarcinoma.J Pediatr. 2007; 150: 556-559Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar, 33Walkowiak J. Jankowska I. Pawlowska J. et al.Exocrine pancreatic function in children with progressive familial intrahepatic cholestasis type 2.J Pediatr Gastroenterol Nutr. 2006; 42: 416-418Crossref PubMed Scopus (17) Google Scholar These families are included to retain our population’s mutation profile. Family number used throughout the text refer to the listing in Supplementary Table 1A, Supplementary Table 1B, Supplementary Table 1C, Supplementary Table 1D, Supplementary Table 1E. The 1321–amino acid BSEP protein is encoded by ABCB11 on chromosome 2q24–31. ABCB11 spans a 108 kilobase genomic region and is composed of 27 coding exons and one 5′ untranslated exon (designated 1–28). ABCB11 complementary DNA sequence (AF091582; AF136523; NM_003742) and genomic structure1Strautnieks S.S. Bull L.N. Knisely A.S. et al.A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis.Nat Genet. 1998; 20: 233-238Crossref PubMed Scopus (833) Google Scholar are available (National Center for Biotechnology Information; http://www.ncbi.nlm.nih.gov/). Mutation nomenclature34den Dunnen J.T. Antonarakis S.E. Mutation nomenclature extensions and suggestions to describe complex mutations: a discussion.Hum Mutat. 2000; 15: 7-12Crossref PubMed Scopus (1503) Google Scholar follows Human Genome Variation Society recommendations (http://www.hgvs.org/mutnomen/). Previously reported mutations have been revised accordingly. Patients were initially screened by restriction endonuclease digestion for recurrent changes at mutation hot spots and, depending on ethnicity, for population-associated changes. ABCB11 exons subsequently underwent single-strand conformation polymorphism analysis in 44 patients followed by sequence analysis of exons with identified mobility changes. Latterly this was replaced by primary sequencing. All exons were sequenced until clearly damaging, or previously known, mutations were identified on both alleles. Samples with novel missense changes were sequenced throughout. Mutations were confirmed using freshly extracted DNA from affected individuals and parental DNA (as available). Missense changes were distinguished from polymorphisms by several criteria. First was their absence from ethnically matched control panels of at least 300 alleles (published,35Pauli-Magnus C. Kerb R. Fattinger K. et al.BSEP and MDR3 haplotype structure in healthy Caucasians, primary biliary cirrhosis and primary sclerosing cholangitis.Hepatology. 2004; 39: 779-791Crossref PubMed Scopus (153) Google Scholar, 36Pauli-Magnus C. Lang T. Meier Y. et al.Sequence analysis of bile salt export pump (ABCB11) and multidrug resistance p-glycoprotein 3 (ABCB4, MDR3) in patients with intrahepatic cholestasis of pregnancy.Pharmacogenetics. 2004; 14: 91-102Crossref PubMed Scopus (228) Google Scholar, 37Lang T. Haberl M. Jung D. et al.Genetic variability, haplotype structures and ethnic diversity of hepatic transporters MDR3 (ABCB4) and bile salt export pump (ABCB11).Drug Metab Dipos. 2006; 34: 1582-1599Crossref PubMed Scopus (86) Google Scholar, 38Lang C. Meier Y. Stieger B. et al.Mutations and polymorphisms in the bile salt export pump and the multidrug resistance protein 3 associated with drug-induced liver injury.Pharmacogenet Genomics. 2007; 17: 47-60Crossref PubMed Scopus (265) Google Scholar in public databases [http://pharmacogenetics.ucsf.edu/39Leabman M.K. Huang C.C. DeYoung J. et al.Natural variation in human membrane transporter genes reveals evolutionary and functional constraints.Proc Natl Acad Sci U S A. 2003; 100: 5896-5901Crossref PubMed Scopus (205) Google Scholar], or within this study). Also considered was conservation across BSEP orthologues and MDR/ABCB homologues. Finally, predicted functional effects and differences in physical and chemical properties were assessed. The Statistics Calculator was used (http://www.cebm.utoronto.ca/practise/ca/statscal/). χ2 testing assessed differences between groups. Using the same data and calculator, relative risk and 95% confidence limits were similarly calculated. Sections of formalin-fixed, paraffin-embedded liver, when available, were routinely stained and immunostained for BSEP using a polyclonal antibody raised in rabbit to the carboxy-terminal 21 amino acids of BSEP as previously described.19Noe J. Stieger B. Meier P.J. Functional expression of the canalicular bile salt export pump of human liver.Gastroenterology. 2002; 123: 1659-1666Abstract Full Text Full Text PDF PubMed Scopus (224) Google Scholar As a control for antigen preservation or protein expression deficiencies not specific to BSEP, parallel sections were immunostained for a structurally similar canalicular ABC transporter, multidrug resistance-associated protein 2, using a monoclonal antibody raised in mouse (Signet/Bioquote, York, England). Findings were evaluated by light microscopy as described.28Knisely A.S. Strautnieks S.S. Meier Y. et al.Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiency.Hepatology. 2006; 44: 478-486Crossref PubMed Scopus (282) Google Scholar, 29Scheimann A.O. Strautnieks S.S. Knisely A.S. et al.Mutations in bile salt export pump (ABCB11) in two children with progressive familial intrahepatic cholestasis and cholangiocarcinoma.J Pediatr. 2007; 150: 556-559Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar For 6 families, immunohistochemical protocols used were as described.2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar BSEP immunostaining was classified as normal, not detected, or abnormal, where abnormal refers to either reduced intensity or focal absence. Immunohistochemical analysis preceded genetic analysis in 30% of cases and followed it in the remainder. Abnormality was judged by 2 or more investigators, all blinded to genetic status. DNA was extracted from blood and tissue samples using standard protocols. Polymerase chain reaction (PCR) amplification was conducted using Taq DNA polymerase (New England Biolabs, Ipswich, MA) and Roche Fast Start PCR systems (Roche Diagnostics, Basel, Switzerland). Primer details are provided in Supplementary Table 2. Microsatellite marker haplotype analysis was conducted across the ABCB11 (2q24) and ATP8B1 (18q21) chromosomal regions in consanguineous families, or those with ≥2 affected children, to determine which gene was likely mutated. Marker loci were selected from genetic maps40Kruglyak L. The use of a genetic map of biallelic markers in linkage studies.Nat Genet. 1997; 17: 21-24Crossref PubMed Scopus (387) Google Scholar and developed from polymorphic repeats (Human Genome Mapping Project/Celera reference sequences; http://www.ncbi.nlm.nih.gov/). Primers were designed to allow multiplex analysis based on product size and fluorescent label (see Supplementary Table 3A, Supplementary Table 3B online at www.gastrojournal.org). Amplification products were separated on a 3100 Avant Genetic Analyser, data were analyzed using GeneMapper software (all Applied Biosystems, Foster City, CA), and haplotypes were constructed. Families with non-Mendelian segregation of mutations were investigated for deletions of the ABCB11 chromosomal region using microsatellite markers spanning 16.2 megabase of chromosome 2. Restriction endonuclease digestion was used to identify common or recurring changes rapidly and to screen ethnically matched control panels for novel changes. Enzymes were selected using NEBcutter V2.0 (http://tools.neb.com/NEBcutter2/index.php; New England Biolabs or Roche Diagnostics). The common mutations E297G, D482G, R575X, R1153C, and R1153H abolish HphI, FokI, FokI, BsrBI, and BsrBI sites, respectively, while G982R creates an AlwNI site. PCR-amplified exon digestion products underwent 3%–5% agarose gel electrophoresis (Supplementary Table 4). Single-strand conformation polymorphism analysis was conducted using 12.5% acrylamide GeneGel Excel nondenaturing gels on a GenePhor Electrophoresis system (all Amersham Biosciences, Little Chalfont, England), initially at 5°C and, if necessary for enhanced resolution, at 15°C. Single-strand conformation polymorphism patterns were visualized by DNA silver staining (Amersham Biosciences). Products larger than 150 base pairs were digested before analysis (as above). PCR products were purified using the High Pure PCR purification system (Roche Diagnostics) before direct sequence analysis using the version 3.1 Dye Terminator cycle sequencing kit (Applied Biosystems) and electrophoresis on a 3100 Avant Genetic Analyzer. Data were analyzed using Sequencher (Gene Codes, Ann Arbor, MI) or SeqScape (Applied Biosystems) software. Eighty-two different ABCB11 mutations were identified on 208 alleles in 109 families with severe BSEP deficiency (Table 1, Table 2, Table 3, Figure 1, and Supplementary Table 1A, Supplementary Table 1B, Supplementary Table 1C, Supplementary Table 1D, Supplementary Table 1E). Homozygosity, or compound heterozygosity, for ABCB11 mutations was completely concordant with disease expression in all families genotyped. Fifty-two mutations were novel. Eighteen previously reported severe mutations were not detected.1Strautnieks S.S. Bull L.N. Knisely A.S. et al.A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis.Nat Genet. 1998; 20: 233-238Crossref PubMed Scopus (833) Google Scholar, 2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar, 5Noe J. Kullak-Ublick G.A. Jochum W. et al.Impaired expression and function of the bile salt export pump due to three novel ABCB11 mutations in intrahepatic cholestasis.J Hepatol. 2005; 43: 536-543Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar, 44Chen H.L. Chang P.S. Hsu H.C. et al.FIC1 and BSEP defects in Taiwanese patients with chronic intrahepatic cholestasis with low gamma-glutamyltranspeptidase levels.J Pediatr. 2002; 140: 119-124Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar, 45Goto K. Sugiyama K. Sugiura T. et al.Bile salt export pump gene mutations in two Japanese patients with progressive familial intrahepatic cholestasis.J Pediatr Gastroenterol Nutr. 2003; 36: 647-650Crossref PubMed Scopus (34) Google Scholar, 46Jung C. Driancourt C. Baussan C. et al.Prenatal molecular diagnosis of inherited cholestatic diseases.J Pediatr Gastroenterol Nutr. 2007; 44: 453-458Crossref PubMed Scopus (35) Google Scholar, 47Liu C. Aronow B.J. Jegga A.G. et al.Novel resequencing chip customized to diagnose mutations in patients with inherited syndromes of intrahepatic cholestasis.Gastroenterology. 2007; 132: 119-126Abstract Full Text Full Text PDF PubMed Scopus (80) Google ScholarTable 1Nonsense Mutations, Deletions, and Insertions in ABCB11Nucleotide changeExonPredicted effectMutation typeCpG siteTotal no. of families in which identifiedFamilies in current studyEthnic originPrevious reports (reference no.)c.74C>A2p.Ser25XNonsenseNo118EU28Knisely A.S. Strautnieks S.S. Meier Y. et al.Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiency.Hepatology. 2006; 44: 478-486Crossref PubMed Scopus (282) Google Scholarc.379delA5p.Thr127HisfsX6Deletion31–3CA/ARc.1101_1102delAG11p.Val368ArgfsX27Deletion152EUc.1139delT11p.Leu380TrpfsX18Deletion113EUc.1145_1165del11p.Ala382_Ala388delDeletion214, 15EUc.1416T>A13p.Tyr472XNonsenseNo14CA/AR28Knisely A.S. Strautnieks S.S. Meier Y. et al.Hepatocellular carcinoma in ten children under five years of age with bile salt export pump deficiency.Hepatology. 2006; 44: 478-486Crossref PubMed Scopus (282) Google Scholarc.1558A>T14p.Arg520XNonsenseNo259, 81EUc.1583_1584delTA14p.Ile528SerfsX21Deletion253, 54EUc.1723C>T15p.Arg575XNonsenseYes612, 13, 17, 19, 37EU, EA1Strautnieks S.S. Bull L.N. Knisely A.S. et al.A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis.Nat Genet. 1998; 20: 233-238Crossref PubMed Scopus (833) Google Scholar, 2Jansen P.L. Strautnieks S.S. Jacquemin E. et al.Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis.Gastroenterology. 1999; 117: 1370-1379Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar, 32Chen F. Ananthanarayanan M. Emre S. et al.Progressive familial intrahepatic cholestasis, type 1, is associated with decreased farnesoid X receptor activity.Gastroenterology. 2004; 126: 756-764Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar, 45G