Sequence analysis of bile salt export pump (ABCB11) and multidrug resistance p-glycoprotein 3 (ABCB4, MDR3) in patients with intrahepatic cholestasis of pregnancy

Abstract

Intrahepatic cholestasis of pregnancy (ICP) is a liver disorder associated with increased risk of intrauterine fetal death and prematurity. There is increasing evidence that genetically determined dysfunction in the canalicular ABC transporters bile salt export pump (BSEP, ABCB11) and multidrug resistance protein 3 (MDR3, ABCB4) might be risk factors for ICP development. This study aimed to (i). describe the extent of genetic variability in BSEP and MDR3 in ICP and (ii). identify new disease-causing mutations. Twenty-one women with ICP and 40 women with uneventful pregnancies were recruited between April 2001 and April 2003. Sequencing of BSEP and MDR3 spanned 8-10 kb per gene and comprised the promoter region and 100-350 bp of the flanking intronic region around each exon. DNA sequencing of polymerase chain reaction fragments was performed on an ABI3700 capillary sequencer. MDR3 promoter activity of promoter constructs carrying different ICP-specific mutations was studied using reporter assays. A total of 37 and 51 variant sites were detected in BSEP and MDR3, respectively. Three non-synonymous sites in codons for evolutionarily conserved amino acids were specific for the ICP collective (BSEP, N591S; MDR3, S320F and G762E). Furthermore, four ICP-specific splicing mutations were detected in MDR3 [intron 21, G(+1)A; intron 25, G(+5)C and C(-3)G; and intron 26, T(+2)A]. Activity of the mutated MDR3 promoter was similar to that observed for the wild-type promoter. Our data further support an involvement of MDR3 genetic variation in the pathogenesis of ICP, whereas analysis of BSEP sequence variation indicates that this gene is probably less important for the development of pregnancy-associated cholestasis.

Novel Resequencing Chip Customized to Diagnose Mutations in Patients With Inherited Syndromes of Intrahepatic Cholestasis

“…For example, although mutations in ATP8B1 and ABCB11 have been reported for subjects with severe forms of PFIC with low serum levels of gamma-glutamyltranspeptide (γGTP), specific mutations within each gene have also been associated with milder clinical phenotypes. 15,17,[24][25][26][27][28][29][30] Equally notable is the phenotypic pleomorphism of mutations in ABCB4, which ranges from high γGTP-PFIC (or PFIC3), to intrahepatic cholestasis of pregnancy, and gallstone formation, 19,25,[31][32][33][34][35][36] and an array of mutations in JAG1 in subjects with liver and/or non-hepatic malformations (e.g. : cardiovascular and renal defects).…”

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

“…Missense changes were distinguished from polymorphisms by several criteria. First was their absence from ethnically matched control panels of at least 300 alleles (published [35][36][37][38] , in public databases [http://pharmacogenetics.ucsf.edu/ 39 ], or within this study). Also considered was conservation across BSEP orthologues and MDR/ABCB homologues.…”

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

“…Interestingly, SNPs and mutations of ATP-binding cassette (ABC) transporters, such as bile salt export pump (BSEP, ABCB11) 21,22 and multidrug resistance protein 3 (MDR3, ABCB4) 23,24 have been associated with intrahepatic cholestasis of pregnancy (ICP). 25 However, there is no association between PBC onset and SNPs and haplotypes in BSEP and MDR3. 26 From a therapeutic perspective, most patients with PBC are treated with ursodeoxycholic acid (UDCA), 27,28 which slows the rate of progression of PBC in most patients and is highly effective in at least 25% to 30% of patients with PBC, leading to improvement in prognosis.…”

“…Mutations in MDR3 have been reported in patients with progressive familial intrahepatic cholestasis type 3 (PFIC3) with high serum ␥-glutamyltransferase activity, 41,42 intrahepatic cholestasis of pregnancy (ICP), 25,43,44 and "adolescent cholelithiasis with recurrent intrahepatic cholestasis of pregnancy followed by adulthood biliary cirrhosis". 44 Almost all mutations found in patients with PFIC3 and ICP were frame-shift mutations due to deletion or nonsense mutations, introducing stop codons downstream and leading to the production of inactive truncated proteins.…”

“…Interestingly, patients with PFIC3 and ICP, who had these frame-shift or nonsense mutations, showed similar clinical manifestations, such as inheritance, early onset in childhood, and clinical severity. 25,[41][42][43] On the other hand, the patient with "adolescent cholelithiasis with intrahepatic cholestasis of pregnancy followed by adulthood biliary cirrhosis" had a heterozygous missense mutation of MDR3 and showed less severe clinical manifestations with middle-aged onset. The relatively mild MDR3 dysfunction due to missense mutations allowed for a slower progression of biliary cirrhosis.…”