Single-nucleotide polymorphism analysis of the multidrug resistance protein 3 gene for the detection of clinical progression in Japanese patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a multifactorial disease in which genetic factors rather than environmental factors may predominantly contribute to the pathogenesis. In order to identify the genetic determinants of the disease severity and progression of PBC, we examined an association of seven tag single-nucleotide polymorphisms (SNPs) in the multidrug resistance protein 3 (MDR3/ABCB4) gene in 148 Japanese PBC patients and 150 age- and sex-matched healthy control subjects. SNPs were detected via polymerase chain reaction (PCR) restriction fragment length polymorphism and PCR direct DNA sequencing methods. Subsequently, haplotypes were constructed from three tag SNPs (rs31658, rs31672, and rs1149222) that were significantly associated with progression of PBC. Logistic regression analyses revealed that a Hap 2 haplotype and its homozygous diplotype, Hap 2/Hap 2, in MDR3 were closely associated with the susceptibility to jaundice-type progression of PBC [P = 0.004, odds ratio (OR) 3.93, 95% confidence interval (CI) 1.56-9.90 and P = 0.0003, OR 17.73, 95% CI 3.77-83.42, respectively]. Conversely, another haplotype, Hap 1, and its homozygous diplotype, Hap 1/Hap 1, were associated with the insusceptibility to the progression to late-stage PBC (P = 0.021, OR 0.55, 95% CI 0.33-0.91 and P = 0.011, OR 0.24, 95% CI 0.08-0.71, respectively). CONCLUSION: The present study is the first report of an association of MDR3 haplotypes and diplotypes with progression of PBC. The Hap 2/Hap 2 diplotype in MDR3 could therefore be potentially applied to DNA-based diagnosis in Japanese patients with PBC as a strong genetic biomarker for predicting the progression and prognosis of PBC.     

Duplication of MER115 on chromosome 4 in patients with primary biliary cirrhosis

Background: Primary biliary cirrhosis (PBC) is a complex disease with genetic and environmental influences. The disease is more prevalent in families with PBC and candidate gene case–control studies have linked PBC with DRB1^*08 human leucocyte antigen class II alleles. Aims: The goal of this study was to characterize a MER115 intergenic region on chromosome 4 as a putative genetic variant associated with PBC. Methods/Results: This region was incidentally identified during investigations to discover candidate microbial agents using representational difference analysis (RDA) with liver samples from patients with PBC and primary sclerosing cholangitis (PSC). blast search analysis of all the RDA products from the PBC liver revealed genomic sequences, whereas Escherichia coli, mycoplasma and hepatitis B virus DNA were found in the PSC liver. We identified one of the PBC RDA products as an ancestral repeat, referred to as MER115. Southern blot analysis with the PBC product uncovered a restriction fragment length polymorphism in PBC patients' liver. Southern blot hybridization signal showed increased signal intensity in PBC vs. control patients' DNA (P<0.005) and slot blot hybridization studies confirmed a copy number variation of the MER115 in hepatic DNA of PBC vs. control patients (P=0.02). Conclusions: Further comparative genetic studies will be required to determine the extent of genomic duplication associated with MER115 and provide data on the possible copy number variants of genes close to this intergenic region in patients with PBC.     

Linkage between a new splicing site mutation in the MDR3 alias ABCB4 gene and intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is defined as pruritus and elevated bile acid serum concentrations in late pregnancy. Splicing mutations have been described in the multidrug resistance p-glycoprotein 3 (MDR3, ABCB4) gene in up to 20% of ICP women. Pedigrees studied were not large enough for linkage analysis. Ninety-seven family members of a woman with proven ICP were asked about pruritus in earlier pregnancies, birth complications and symptomatic gallstone disease. The familial cholestasis type 1 (FIC1, ATP8B1) gene, bile salt export pump (BSEP, ABCB11) and MDR3 gene were analyzed in 55 relatives. We identified a dominant mode of inheritance with female restricted expression and a new intronic MDR3 mutation c.3486+5G>A resulting in a 54 bp (3465-3518) inframe deletion via cryptic splicing site activation. Linkage analysis of the ICP trait versus this intragenic MDR3 variant yielded a LOD score of 2.48. A Bayesian analysis involving MDR3, BSEP, FIC1 and an unknown locus gave a posterior probability of >0.9966 in favor of MDR3 as causative ICP locus. During the episode of ICP the median gamma-glutamyl transpeptidase (gamma-GT) activity was 10 U/l (95% CI, 6.9 to 14.7 U/l) in the index woman. Four stillbirths were reported in seven heterozygous women (22 pregnancies) and none in five women (14 pregnancies) without MDR3 mutation. Symptomatic gallstone disease was more prevalent in heterozygous relatives (7/21) than in relatives without the mutation (1/34), (P = 0.00341). CONCLUSION: This study demonstrates that splicing mutations in the MDR3 gene can cause ICP with normal gamma-GT and may be associated with stillbirths and gallstone disease.     

Hereditäre Defekte hepatobiliärer Transportproteine

Defects in transport proteins that are expressed at the hepatocyte canalicular membrane can cause severe impairment of hepatobiliary transport processes. Progressive familial intrahepatic cholestasis (PFIC) typically manifests in early childhood. Genetic variants in the aminophospholipid transporter FIC1 (ATP8B1 gene) cause PFIC1, characterized by elevated serum bile acids but normal or only mildly elevated gamma-GT levels. Benign recurrent intrahepatic cholestasis type 1 (BRIC1) is also caused by ATP8B1 mutations. Defects in the function of the bile salt efflux pump (BSEP; ABCB11) cause PFIC2 or BRIC2, depending on the degree of BSEP impairment. A common BSEP variant, the V444A polymorphism, is commonly found in various types of cholestatic liver injury, including drug-induced liver injury. Finally, dysfunction of the multidrug resistance gene product MDR3 (ABCB4) leads to PFIC3, characterized by low biliary phospholipids and high gamma-GT levels in serum due to bile duct injury. All three transporter genes are also associated with intrahepatic cholestasis of pregnancy. Treatment options include ursodeoxycholic acid for milder forms and liver transplantation for severe pediatric cases.     

Differenzialdiagnose Ikterus

Jaundice is the result of increased serum bilirubin levels. An initial differentiation of the underlying causes can be made by distinguishing increased conjugated and non-conjugated serum bilirubin and the findings of abdominal ultrasound examination. This combined approach enables a first classification into extrahepatic causes, hepatocellular dysfunction and intrahepatic and extrahepatic forms of cholestasis. In each diagnostic category of jaundice the differential diagnosis can be improved by additional imaging techniques comprising helical CT scanning, MRCP or ERCP, targeted laboratory tests and finally a liver biopsy. Specific difficult-to-diagnose cholestatic diseases include primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), autoimmune hepatitis PBC and PSC overlap syndromes, IgG4 cholangiopathy and familial deficiency of biliary transporters due to mutations in the ATP8B1, ABCB11, ABCB4 and Jag1 genes. Molecular genetic testing enables these familial conditions to be differentiated.     

Interindividual variability of canalicular ATP-binding-cassette (ABC)-transporter expression in human liver

Interindividual variability in hepatic canalicular transporter expression might predispose to the development of hepatic disorders such as acquired forms of intrahepatic cholestasis. We therefore investigated expression patterns of bile salt export pump (BSEP, ABCB11), multidrug resistance protein 3 (MDR3, ABCB4), multidrug resistance associated protein 2 (MRP2, ABCC2) and multidrug resistance protein 1 (MDR1, ABCB1) in healthy liver tissue of a white population. Protein expression levels were correlated with specific single nucleotide polymorphisms (SNPs) in the corresponding transporter genes. Hepatic protein expression levels from 110 individuals undergoing liver resection were assessed by Western blot analysis of liver plasma membranes enriched in canalicular marker enzymes. Each individual was genotyped for the following synonymous (s) and nonsynonymous (ns) SNPs: ABCB11: (ns:1457T>C and 2155A>G), ABCB4: (ns:3826A>G) and ABCC2 (ns:1286G>A,3600T>A and 4581G>A) and ABCB1 (ns:2677G>T/A and s:3435C>T). Transporter expression followed unimodal distribution. However, of all tested individuals 30% exhibited a high expression and 32% a low or very low expression phenotype for at least one of the four investigated transport proteins. Transporter expression levels did not correlate with age, sex, underlying liver disease, or presurgery medication. However, low BSEP expression was associated with the 1457C-allele in ABCB11 (P = .167) and high MRP2 expression was significantly correlated with the 3600A and 4581A ABCC2 variants (P = .006). In conclusion, the results demonstrate a considerable interindividual variability of canalicular transporter expression in normal liver. Furthermore, data suggest a polymorphic transporter expression pattern, which might constitute a risk factor for the development of acquired forms of cholestatic liver diseases.     

Apoptosis of biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND/AIMS: Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by inflammatory destruction of small bile ducts. Primary sclerosing cholangitis (PSC) is a different, presumed autoimmune cholestatic liver disease where the bile ducts are also destroyed. In this study, apoptosis and portal triad inflammation in liver tissue from patients with PBC is examined and compared to that from patients with PSC and patients with normal liver. METHODS: Explanted liver tissue from patients with PBC and PSC and normal liver from patients with metastases to liver were examined. The liver samples were stained for apoptosis using the terminal deoxynucleotidyl triphosphate (TdT)-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay. The biliary epithelial cells (BEC) were then scored on the basis of their TUNEL stain and the degree of periductal inflammation. RESULTS: In PBC, apoptosis of BEC, as detected by the TUNEL assay, was significantly increased in the presence of inflammation. Regardless of the presence or absence of inflammation, the small bile ducts in PBC liver tissue exhibited greater evidence of apoptosis than did similar ducts from PSC or control livers. CONCLUSION: These findings suggest that in PBC, unlike PSC, the apoptosis of BEC in PBC is secondary to the invasion of inflammatory cells.     

Antisense oligonucleotides rescue an intronic splicing variant in the ABCB11 gene that causes progressive familial intrahepatic cholestasis type 2

BackgroundProgressive familial intrahepatic cholestasis type 2 (PFIC2) is a rare disorder caused by variants in the ABCB11 gene encoding the bile salt export pump (BSEP). We investigated the molecular defect in a PFIC2 infant and rescued the splicing defect with antisense oligonucleotides (ASOs).MethodsWhole-exome sequencing (WES) revealed compound heterozygous variants in the ABCB11 gene in a PFIC2 patient. Liver biopsy was immunostained for BSEP. The splicing effect of the candidate variants was investigated by minigene assay. ASOs were designed to rescue aberrant splicing.ResultsA Chinese girl of two nonconsanguineous healthy parents suffered from low glutamyl transpeptidase cholestasis and showed no response to the ursodeoxycholic acid. WES revealed that the patient was compound heterozygous for two novel variants in the ABCB11 gene: c.76+29T>G and c.390–2A>G. Liver immunohistochemistry showed the absence of BSEP. The variant c.76+29T>G was confirmed to retain 42 bp in the mature mRNA. The variant c.390–2A>G was confirmed to cause exon 6 skipping. We designed two ASOs and identified one of them that efficiently induced pseudoexon exclusion.ConclusionWe reported two novel variants of the ABCB11 gene, c.76+29T>G and c.390-2A>G, in a PFIC2 infant, thereby expanding the genotype of PFIC2. Our findings provide evidence for ASOs as a therapeutic approach for PFIC2 patients carrying intronic variants.     

Impaired expression and function of the bile salt export pump due to three novel ABCB11 mutations in intrahepatic cholestasis

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. METHODS: BSEP expression was determined in liver biopsies by immunohistochemistry. ABCB11 mutations were functionally characterized by taurocholate transport in SF9 cells transfected with human ABCB11. RESULTS: 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. CONCLUSIONS: 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.     

Multidrug resistance 1 genotype and disposition of budesonide in early primary biliary cirrhosis.

BACKGROUND: Budesonide, which is a dual substrate of P-glycoprotein, the product of the multidrug resistance 1 (MDR1) gene, and cytochrome P450 3A (CYP3A) has been proposed for treatment of early primary biliary cirrhosis (PBC). Recently, MDR1 gene polymorphisms have been discussed as a potential cause of glucocorticoid resistance. We tested the hypothesis that MDR1 gene polymorphisms affect absorption of oral budesonide. METHODS: In 21 patients with histologically proven early-stage (I/II) PBC and nine healthy subjects, we evaluated the impact of MDR1 single nucleotide polymorphisms (2,677G>T,A and 3,435C>T) on disposition of a single oral dose of 3 mg budesonide. CYP3A5 gene polymorphisms (6,986A>G) were analyzed in parallel. RESULTS: In MDR1 2,677 GG and 3,435 CC genotypes, absorption and elimination of budesonide were not significantly different from those in corresponding homozygous variants. Peak plasma levels and areas under the plasma concentration time curves (AUC) of budesonide were not lower in MDR1 3,435 CC with putatively high intestinal expression of P-glycoprotein than in MDR1 3,435 TT. Interestingly, in two CYP3A5*1/*3 carriers with high enzyme activity, lower AUC was noted than in 28 CYP3A5*3/*3 carriers with a deficient enzyme. CONCLUSION: Common MDR1 gene polymorphisms do not affect disposition of budesonide in early PBC.     

Thyroid dysfunction in primary biliary cirrhosis,primary sclerosing cholangitis and non‐alcoholic fatty liver disease

Background/Aims: Primary biliary cirrhosis (PBC) is frequently associated with autoimmune diseases, including thyroid disease, although it is uncertain that this association is higher than in other liver diseases. Methods: We compared the prevalence and incidence of thyroid dysfunction (TD) in a series of patients with PBC (n=67) with patients with primary sclerosing cholangitis (PSC) (n=79) and non‐alcoholic fatty liver disease (NAFLD) (n=97) seen in a tertiary referral centre who had previously participated in clinical trials. Results: At initial evaluation, prevalence of TD in PBC was 13% compared with 11% in PSC (P=0.71) and 25% in NAFLD (P=0.08). Incidence of TD was 2.9 patients per 100 person‐years in PBC compared with 2.1 patients per 100 person‐years in PSC (P=0.57) and 1.8 patients per 100 person‐years in non‐alcoholic liver disease (P=0.45). Older age, female gender, biochemical abnormalities and concurrent autoimmune disorders were not predictive of the development of TD. Conclusions: TD was unexpectedly as common in patients with PBC as in patients with PSC and NAFLD, yet significantly more common than expected in the general population. Further investigation of thyroid disease in PSC and NAFLD is warranted.     

Changes in the expression and localization of hepatocellular transporters and radixin in primary biliary cirrhosis

BACKGROUND/AIMS: Expression and localization of human hepatocellular transporters and of radixin, cross-linking actin with some membrane transporters, may change in cholestatic liver diseases. METHODS: We investigated the uptake transporters OATP2 (SLC21A6), OATP8 (SLC21A8), and NTCP (SLC10A1), the export pumps MRP2 (ABCC2), MRP3 (ABCC3), MRP6 (ABCC6), and P-glycoproteins (ABCB1, ABCB4, ABCB11), and radixin, in non-icteric primary biliary cirrhosis (PBC stages I-III) and control human liver needle-biopsies using immunofluorescence microscopy and semi-quantitative RT-PCR. RESULTS: Expression and localization of all transporters were unchanged in PBC I-II. Immunostaining intensities of uptake transporters decreased in PBC III with a concomitant decrease in mRNA levels. Immunostaining intensities and mRNA levels of export pumps were similar in controls and PBC I-III, however, irregular MRP2 immunostaining suggested redistribution of MRP2 into intracellular structures in PBC III. Areas of irregular MRP2 immunostaining showed largely reduced radixin immunostaining, whereas normal hepatocytes had MRP2 and radixin confined to the canalicular membrane. Disrupted localization of radixin and MRP2 supports the concept that radixin contributes to the canalicular localization of MRP2. CONCLUSIONS: Down-regulation of uptake transporters may contribute to the impaired hepatobiliary elimination in advanced PBC, and partially altered localization of MRP2 may reflect the onset of changes leading to icteric PBC.     

Recurrence of primary sclerosing cholangitis after living donor liver transplantation.

BACKGROUND/AIMS: Cumulative experience in deceased donor liver transplantation for end-stage liver disease due to primary sclerosing cholangitis (PSC) suggests that liver transplantation is the treatment of choice with excellent results. Reports on the outcome of live donor liver transplantation (LDLT) for PSC, however, remain anecdotal. METHODS: The clinical course and genetic disposition of nine patients who underwent LDLT for PSC were analyzed. The median follow-up period was 3.5 years. RESULTS: Cumulated 5-year patient and graft survival rates were 90% and 71%, respectively. Recurrent PSC was diagnosed in four patients. Ratios of freedom from recurrent PSC at 1, 3, and 5 years were 100%, 73%, and 49%, respectively. The mean time to recurrence was 3.3 years. Excluding the one case with a biologically unrelated donor, recurrent PSC was diagnosed in 50% (4/8). None of the patients presented with the human leukocyte antigen-B8DR3 haplotype, which is associated with a higher susceptibility for developing PSC among the Caucasian population. Overall patient survival of LDLT for PSC seems to equal that of deceased donor liver transplantation. CONCLUSIONS: PSC might recur earlier at a higher ratio after LDLT. Further study with protocol cholangiogram and genetic considerations, including high resolution human leukocyte antigen haplotype analysis, is necessary.     

Depression in patients with primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND/AIMS: Former studies reported a high prevalence of depression in patients with primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). These studies hypothesized that the presence of depression could explain the fatigue experienced by these patients. METHODS: Our aim was to study the prevalence of depression in a Dutch population with PBC and PSC. In addition, to investigating the effects of using an additional diagnostic structured psychiatric interview, after screening with the Beck Depression Inventory (BDI), a self-report severity scale instrument used in former studies. Patients with PBC and PSC (n=92) completed the BDI. Patients with scores of 10 or higher (n=39) were interviewed using a structured psychiatric interview. Patients with scores lower than 10 were at random (30/53, 57%) also interviewed using a structured psychiatric interview. RESULTS: Of the 92 patients that were included 42% had depressive symptoms according to the BDI. However, of these patients only 3.7% had a depressive syndrome according to the DSM-IV criteria as assessed with the structured psychiatric interview. CONCLUSIONS: The prevalence of a depressive disorder in patients with PBC and PSC is not higher than in the general population. Fatigue in patients with PBC and PSC cannot be explained by depression.     

Bile salt export pump deficiency: A de novo mutation in a child compound heterozygous for ABCB11. Laboratory investigation to study pathogenic role and transmission of two novel ABCB11 mutations

Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous group of autosomal disorders. PFIC type 2 is due to mutation in ABCB11, the gene encoding the bile salt export pump (BSEP) protein. The aim of the study was to describe a child with a de novo mutation in a compound heterozygous for ABCB11 gene. We report a 1.7‐year‐old girl who presented with pruritus, jaundice and liver dysfunction of PFIC type 2. Immunohistochemistry and molecular analysis are described. Liver biopsy showed micronodular cirrhosis and immunohistochemical staining for BSEP, the protein encoded by ABCB11, displayed a patchy and faint reactivity. Molecular analysis revealed two novel mutations of ABCB11. We give details that one mutation is transmitted by the mother while the second one appears a de novo mutation as mutations or a potential mosaicism were ruled out in the natural father. We further speculate that the ABCB11 mutations do not prevent BSEP glycoprotein to be expressed at the canalicular pole of hepatocytes, but interfere with its ability to export bile salts. As in most instances, mutational analysis is performed following the histochemical demonstration of an undetectable BSEP on liver biopsy specimen. This case stresses that clinical PFIC with an attenuated rather than absent BSEP immunostaining can still be due to ABCB11 mutations presumably encoding a functionally deficient protein.     

Which patients with primary biliary cirrhosis or primary sclerosing cholangitis should undergo endoscopic screening for oesophageal varices detection?

BACKGROUND: Recent guidelines from an AASLD Single Topic Symposium suggest that patients with cirrhosis, including those with primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC), should be screened for oesophageal varices when the platelet count is <140,000/mm3. AIM: To determine the validity of these guidelines in clinical practice in patients with PBC or PSC. METHODS: Retrospective review of individuals undergoing screening upper endoscopy for oesophageal varices at a single centre. Oesophageal varices were reported as being present or absent. RESULTS: A total of 235 patients with chronic liver disease, including 86 patients with PBC (n=79) or PSC (n=7), 104 patients with chronic viral hepatitis, and 45 with non-alcoholic cirrhosis of differing aetiologies, underwent a single screening endoscopy between 1996 and 2001. Oesophageal varices were detected in 26 (30%) of the PBC/PSC group, 38 (37%) of the viral hepatitis group, and 21 (47%) of the "other" group. Applying multiple logistic regression analysis to the data in the group with PBC/PSC, platelets <200,000/mm3 (odds ratio (OR) 5.85 (95% confidence interval (CI) 1.79-19.23)), albumin <40 g/l (OR 6.02 (95% CI 1.78-20.41)), and serum bilirubin >20 micromol/l (OR 3.66 (95% CI 1.07-12.47)) were shown to be independent risk factors for oesophageal varices. Prothrombin time was unhelpful. The values at these cut offs were not useful in predicting oesophageal varices in the other groups. CONCLUSION: We conclude that current guidelines recommended by the AASLD Single Topic symposium are invalid in our cohort of patients with PBC and PSC. Patients with a platelet count <200,000/mm3, an albumin level <40 g/l, and a bilirubin level >20 micromol/l should be screened for oesophageal varices.     

Adhesion molecule expression in primary sclerosing cholangitis and primary biliary cirrhosis.

There are conflicting reports regarding intercellular adhesion molecule-1 (ICAM-1) expression in primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC). Expression of adhesion molecules ICAM-1, lymphocyte adhesion molecule-1 (LFA-1), vascular cell adhesion molecule (VCAM), and E-selectin was examined together with HLA-DR in 16 liver biopsy specimens showing PSC and 12 specimens showing PBC. These were compared with biopsy specimens showing large duct obstruction (n = 7), chronic active hepatitis (n = 4), alcoholic liver disease (n = 4), and normal liver histological results (n = 5). ICAM-1 was detected on biliary epithelium in five of seven PSC specimens of histological stage 3 or 4, but not in nine early PSC specimens or in specimens from disease controls. In PBC, ICAM-1 was positive on three of 12 cases, two stage 2, and one stage 3. Nine of 16 PSC specimens (three of nine early, six of seven late disease) and six of 10 PBC specimens (three early, three late disease) were positive for HLA-DR. LFA-1 stained infiltrating inflammatory cells in PSC, PBC, and disease controls. In conclusion, ICAM-1 expression on biliary epithelium in PSC occurs mainly in late stage disease and therefore may be secondary to previous events inducing inflammation rather than of primary pathogenic importance. ICAM-1 expression in PBC is less common and not clearly associated with a particular disorder. Previous reports of ICAM-1 prevalence may have been biased towards end stage, pre-transplantation biopsy specimens.     

A study of exons 14, 15, and 24 of the ABCB11 gene in Egyptian children with normal GGT cholestasis

Background and study aimsProgressive familial intrahepatic cholestasis type 2 (PFIC2) is a rare inherited disorder caused by mutation in the ATP-binding cassette subfamily B member 11 gene (ABCB11) that encodes the bile salt export pump (BSEP), which is the main transporter of bile acids from hepatocytes to the canalicular lumen. Defects in BSEP synthesis and/or function lead to reduced bile salt secretion followed by accumulation of bile salts in hepatocytes and hepatocellular damage. This study aimed to detect variations in exons 14, 15, and 24 of the ABCB11 gene in patients with suspected PFIC2 among a group of Egyptian infants and children with normal gamma-glutamyl transpeptidase (GGT) cholestasis.Patients and methodsThis observational case-control study was conducted on 13 children with suspected PFIC2 and 13 healthy subjects as controls. Genotyping of the ABCB11 gene was performed via DNA extraction followed by PCR amplification, purification, and then sequencing analysis of exons 14, 15, and 24 of the ABCB11 gene.ResultsThe study detected two single nucleotide variations, c.1638+ 32T > C (rs2241340) in exon 14 and c.3084A > G (p.Ala1028 = ) (rs497692) in exon 24 of the ABCB11 gene. No variations were identified in exon 15.ConclusionThe study revealed two benign variants involving exons 14 and 24 of the ABCB11 gene. Exons 14, 15, and 24 are not hot spots for common mutations in Egyptian PFIC2 patients. Further study of other exons of the ABCB11 gene is necessary to confirm the diagnosis of PFIC2.