ABCB4 p.Thr775Met
| Predicted by SNAP2: | A: N (82%), C: N (82%), D: N (66%), E: N (66%), F: N (82%), G: N (82%), H: N (82%), I: N (78%), K: N (61%), L: N (82%), M: N (82%), N: N (87%), P: N (61%), Q: N (78%), R: N (66%), S: N (93%), V: N (82%), W: N (61%), Y: N (93%), |
| Predicted by PROVEAN: | A: N, C: N, D: D, E: D, F: D, G: D, H: D, I: N, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: N, V: N, W: D, Y: D, |
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[hide] Molecular characterization and structural implicat... Eur J Hum Genet. 2007 Dec;15(12):1230-8. Epub 2007 Aug 29. Degiorgio D, Colombo C, Seia M, Porcaro L, Costantino L, Zazzeron L, Bordo D, Coviello DA
Molecular characterization and structural implications of 25 new ABCB4 mutations in progressive familial intrahepatic cholestasis type 3 (PFIC3).
Eur J Hum Genet. 2007 Dec;15(12):1230-8. Epub 2007 Aug 29., [PMID:17726488]
Abstract [show]
Progressive familial intrahepatic cholestasis type 3 (PFIC3) is an autosomal-recessive disorder due to mutations in the ATP-binding cassette, subfamily B, member 4 gene (ABCB4). ABCB4 is the liver-specific membrane transporter of phosphatidylcholine, a major and exclusive component of mammalian bile. The disease is characterized by early onset of cholestasis with high serum gamma-glutamyltranspeptidase activity, which progresses into cirrhosis and liver failure before adulthood. Presently, about 20 distinct ABCB4 mutations associated to PFIC3 have been described. We report the molecular characterization of 68 PFIC3 index cases enrolled in a multicenter study, which represents the largest cohort of PFIC3 patients screened for ABCB4 mutations to date. We observed 31 mutated ABCB4 alleles in 18 index cases with 29 distinct mutations, 25 of which are novel. Despite the lack of structural information on the ABCB4 protein, the elucidation of the three-dimensional structure of bacterial homolog allows the three-dimensional model of ABCB4 to be built by homology modeling and the position of the mutated amino-acids in the protein tertiary structure to be located. In a significant fraction of the cases reported in this study, the mutation should result in substantial impairment of ABCB4 floppase activity. The results of this study provide evidence of the broad allelic heterogeneity of the disease, with causative mutations spread along 14 of the 27 coding exons, but with higher prevalence on exon 17 that, as recently shown for the closely related paralogous ABCB1 gene, could contain an evolutionary marker for mammalian ABCB4 genes in the seventh transmembrane segment.
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18 The two TMDs contain specific sites for substrate binding and translocation, whereas the two NBDs, which display a high degree of sequence similarity with the equivalent domain of ABC transporters, couple the energy obtained from ATP hydrolysis to substrate transport.8 The ICDs are deemed to be involved in mediating the coupling between NBD conformational changes and the reorientation of TM helices concomitant with substrate extrusion.9 The ABCB1 gene, one of the most extensively studied ABC transporters, is responsible for the human multidrug resistance phenotype that is a rapidly growing obstacle to the treatment of numerous infectious diseases, including human immunodeficiency10 and malaria.11 The properties of this transporter are also exploited in cancer pharmacological therapy where ABCB1 translocates the chemotherapeutic drugs and other molecules with a broad but defined specificity.12 A gene duplication of ABCB1 and additional mutations selected as advantageous have created in mammals the T715I G723E L724AfsX744 A737V G954S G762X T775M G126E S320F A840D OUT IN Linker region F357L L701P A364V NBD-NH2 terminal NBD-COOH terminal A1193T NH2 COOH 1 2 54 6 7 8 129 11 10 EC2EC1 ICD2 A250P Y279X A286V ICD1 R159X T175A ICD3 EC3 EC4 EC6EC5 ICD4 ICD6 ICD5 E888X Y403H V475A A511T E558K R590Q T593A M630V 3 S379KfsX413 P726T Figure 1 (a) Localization of the 29 mutations identified in this study in the ABCB4 protein, schematically represented in its domains.
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ABCB4 p.Thr775Met 17726488:18:1054
status: NEW84 There are no PFIC3 epidemiologic data available to date; however, knowing that the number of newborns in Italy has been on average 500 000/year in the last 14 years (http://demo.istat.it/), since we observed 18 patients with ABCB4-mutated alleles born within a 14-year period (with Table 2 Mutations identified in ABCB4 Type of mutationb Exons cDNA locusa Missense Frameshift or nonsense ABCB4-predicted domain GenBank accession numberc Exon 6 c.377G4A G126E TM2 DQ861346 Exon 6 c.523A4G T175A ICD1 Exon 6 c.475C4T R159X ICD1 DQ861347 Exon 8 c.748G4C A250P ICD2 DQ861349 Exon 9 c.837T4A Y279X ICD2 DQ861348 Exon 9 c.857C4T A286V ICD2 DQ861350 Exon 9 c.959C4T S320F TM5 Exon 10 c.1069T4C F357L ICD3 DQ861351 Exon 10 c.1091C4T A364V ICD3 DQ861352 Exon 11 c.1135_1136insAA S379KfsX413 ICD3 DQ861353 Exon 11 c.1207T4C Y403H NBD-NH2 A-loop EF035007 Exon 13 c.1424T4C V475A NBD-NH2 ter DQ861354 Exon 13 c.1531G4A A511T NBD-NH2 ter DQ861355 Exon 14 c.1672G4A E558K NBD-NH2 ter DQ861356 Exon 15 c.1769G4A R590Q NBD-NH2 ter Exon 15 c.1777A4G T593A NBD-NH2 ter DQ861357 Exon 15 c.1888A4G M630V NBD-NH2 ter DQ861358 Exon 17 c.2102T4C L701P Linker region DQ861359 Exon 17 c.2144C4T T715I TM7 DQ861360 Exon 17 c.2168G4A G723E TM7 DQ861361 Exon 17 c.2169_2170insG L724AfsX744 TM7 DQ861362 Exon 17 c.2176C4A P726T TM7 DQ861363 Exon 17 c.2210C4T A737V EC4 DQ861364 Exon 18 c.2284G4T G762X TM8 DQ861365 Exon 19 c.2324C4T T775M TM8 Exon 21 c.2519C4A A840D TM9 DQ861366 Exon 21 c.2662G4T E888X ICD5 DQ861367 Exon 23 c.2860G4A G954S TM11 DQ861368 Exon 27 c.3577G4A A1193T NBD-COOH ter DQ861369 a cDNA sequence is based on reference sequence GenBank NM_018849.
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ABCB4 p.Thr775Met 17726488:84:1404
status: NEW[hide] Sequence analysis of bile salt export pump (ABCB11... Pharmacogenetics. 2004 Feb;14(2):91-102. Pauli-Magnus C, Lang T, Meier Y, Zodan-Marin T, Jung D, Breymann C, Zimmermann R, Kenngott S, Beuers U, Reichel C, Kerb R, Penger A, Meier PJ, Kullak-Ublick GA
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 Feb;14(2):91-102., [PMID:15077010]
Abstract [show]
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.
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109 Non-synonymous changes newly observed as singletons or doubletons in our sample set coded for the following amino acid changes: S320F, E528D, G762E and T775M.
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ABCB4 p.Thr775Met 15077010:109:152
status: NEW142 Q R I K R I Q I D F H G I E H D T T E L H S I D D T L K I S E G I G D K R Q R K F F H A I L R G A V A G V T R I G G Q H L E K A Q K H L L G A E I F E YA R R T L I E G L S H A F K A H R D F H S H D Q D K H S T G A L A Q V Q G A T G T R L R S R H G A L L K R E I A E T A T S L T Q E R V Y H S E F L P Y R H S V Q K K I K D E L E A A G H E L A K A Y D A T Q G K K V Q E P I L I E A I S C Q Q R I A I E V V Q G L S L P A K L S H KL H A D T A L R T A K K A I H V V K E Y G K K F D A R V K Q Q R I L A P V F Q G G A V Q H T G H E Q H L K A A S C S S G V L L A Q L G I R H D G Y A G Q L S G G P R A H V P F G R S TT A D L L L I E I H A D L I Q I K Q A L L G V V H S F Y S L Q R E F L Q V T S K G K L H V Q H I D Q S V V E R V G D K H V V F H Y P V K E TE E D L A S T T I H R L S T A E S Y S D I D F K E L L L D G Q E A A K A A A V E L P K K Y F G H I T F E Y L A TE E V V K E S Q E R T C I V G D A L K R A H H I P I F A P L G V T K G L P K D Y F H D L E R H A T G H K P T S E L G I S S K F D G V T K T K K R K H I F R Y S D H Q L T L D K A A Q K A E G V F V D K G A T H F S S L S F H V H L L P K K H T R E E E F P I H A Y Y Y Y H T D S R G H K A I I E S K Q Q K C H I F VG P G D D A F R F C G H R F R D V G A HY L I V H G Y G H Q V F G I GE L H H P S G L G I A H A T T H G H S LFL G A G L A Y I A T L V L S P I I I G HT T V F H S I L F G A F I V G Q S A P C A F S LI L F L F I I S G F T F F L Q G F T F G F A T F V G H F V Y G S H L A F A A S Y Y L L I F I FV A F S P G L Q G I A H A T V C G A H L I A L I L S I S F H I Y A T L L L V F I A IS F G A V A LV H AG S S F G I T Q A F H Y F S Y A L L L V V A I I P V S A I V G A Q H G T G I I I S F I F V V YG I A H F Q Q F A G F I V G F I A K A Y E K D L S F A S L A E A R E A H E K G I K I K A ISAH I E E T D L D H R V T E H K K E S V K F Y V G D K A A T V A H R L S A L L EI K H P A H G H Q K S L D C L A Q V E A D F G A I V V Q G S H S S T Q H H S E F E L H R G R T T I A E E G EE H F L R S K R K L K H S Q H S T QQ QG ID A IVK K G G S L L E A T S Q D R I A I R Q P K I L L A H A V L A V E R G A G P K F D T L Q L E V A K K R I E Y A H A F H H T K D E V H C Y G R G I E E S V V G Q T S F L V P T I H L R E I Y D R H F H V I Q P Y L R Q D I I T G E D H D S T V Q L T G S G C G K S V K H L G K L V Q G S Q V T A R H V K I A V F S Y P S H D P H G E K L G K I S D H E KAGLHF QIIILS F S D I K P H H D I I D V P P V H A E L G D T E V F V I I A A G R A H A F A D P K V L K F H K T E H L R R S L Q T G A Q H IAL V I T S H A I G L L A A S H A V L V V V S Q H T F A A L S K E Y I K T175A E528D T775M R652G S Cytoplasm R T G762E S320F Extracellular K Fig. 2 Secondary structure of multidrug resistance protein 3 with non-synonymous coding region genetic variants.
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ABCB4 p.Thr775Met 15077010:142:2525
status: NEW[hide] Aspects of liver pathology in adult patients with ... Virchows Arch. 2012 Mar;460(3):291-8. Epub 2012 Feb 14. Wendum D, Barbu V, Rosmorduc O, Arrive L, Flejou JF, Poupon R
Aspects of liver pathology in adult patients with MDR3/ABCB4 gene mutations.
Virchows Arch. 2012 Mar;460(3):291-8. Epub 2012 Feb 14., [PMID:22331132]
Abstract [show]
The aims of this study were to describe the histological liver lesions in adult patients with MDR3/ ABCB4 mutation and to study the usefulness of MDR3 immunostaining as a diagnostic tool. All adult patients from our institution with an MDR3/ABCB4 mutation and a liver histology were included (n = 13). Eleven patients had a single heterozygous gene mutation and two patients had two heterozygous mutations. Two patients had no liver lesions. Eight patients had a mild ductular reaction and portal fibrosis. One patient had a few fibrous septa and two patients had biliary cirrhosis. In three cases intraductal lipid crystals were identified. Two patients had biliary fibroobliterative lesions with no sclerosing cholangitis on cholangiography. Biliary dysplasia was identified in hepatectomy specimens from two patients, one of whom developed an intrahepatic cholangiocarcinoma. One patient with biliary cirrhosis developed a hepatocellular carcinoma. MDR3 immunostainings performed on formalin-fixed paraffin-embedded sections showed a strong canalicular staining in all patients except in one. To conclude, the predominant histological features were ductular reaction with no or mild fibrosis without cholangitis. Liver lesions previously unreported in association with MDR3/ABCB4 gene mutations (biliary dysplasia, cholangiocarcinoma, small duct sclerosing cholangitis) were also found. Lipid crystals in bile ducts may be suggestive of MDR3/ABCB4 mutation. MDR3 immunostaining on formalin-fixed paraffin-embedded sections does not seem to be sensitive for the diagnosis of heterozygous MDR3/ABCB4 mutations.
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107 Location and nucleotide change Effect on protein Status of variant Mutation category 1 c.1328dup p.Arg444Glu fsX4, truncating Heterozygous Insertion 2 c.1584 G > C p.Glu528Asp Heterozygous Missense 3 c.101 C > T p.Thr34Met Heterozygous Missense 4 c.1553delT p.Leu518Tyr fsX16, truncating Heterozygous Deletion 5 c.139 C > G p.Arg 47 Gly Heterozygous Missense 6 c.1217 G > A p.Arg 406 Gln Heterozygous Missense c.140 G > A p.Arg47Gln Heterozygous, compound Missense 7 c.857 C > T p.Ala 286 Val Heterozygous Missense 8 c.2324 C > T p.Thr775Met Heterozygous Missense c.2836 G > A p.Ala946Thr Heterozygous Missense 9 c.523A > G p.Thr175Ala Heterozygous Missense 10 c.1005 + 5 G > A p.?
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ABCB4 p.Thr775Met 22331132:107:532
status: NEW106 Location and nucleotide change Effect on protein Status of variant Mutation category 1 c.1328dup p.Arg444Glu fsX4, truncating Heterozygous Insertion 2 c.1584 G > C p.Glu528Asp Heterozygous Missense 3 c.101 C > T p.Thr34Met Heterozygous Missense 4 c.1553delT p.Leu518Tyr fsX16, truncating Heterozygous Deletion 5 c.139 C > G p.Arg 47 Gly Heterozygous Missense 6 c.1217 G > A p.Arg 406 Gln Heterozygous Missense c.140 G > A p.Arg47Gln Heterozygous, compound Missense 7 c.857 C > T p.Ala 286 Val Heterozygous Missense 8 c.2324 C > T p.Thr775Met Heterozygous Missense c.2836 G > A p.Ala946Thr Heterozygous Missense 9 c.523A > G p.Thr175Ala Heterozygous Missense 10 c.1005 + 5 G > A p.?
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ABCB4 p.Thr775Met 22331132:106:532
status: NEW[hide] Clinical features and genotype-phenotype correlati... J Pediatr Gastroenterol Nutr. 2011 Jan;52(1):73-83. Colombo C, Vajro P, Degiorgio D, Coviello DA, Costantino L, Tornillo L, Motta V, Consonni D, Maggiore G
Clinical features and genotype-phenotype correlations in children with progressive familial intrahepatic cholestasis type 3 related to ABCB4 mutations.
J Pediatr Gastroenterol Nutr. 2011 Jan;52(1):73-83., [PMID:21119540]
Abstract [show]
OBJECTIVES: The aim of the study was to estimate the frequency of ABCB4 mutations among children with chronic intrahepatic cholestasis with elevated gamma-glutamyl-transpeptidase (gamma-GT) activity and to characterize the genotypes with respect to severity of symptoms, response to ursodeoxycholic acid therapy, and outcome. PATIENTS AND METHODS: Molecular analysis of ABCB4 in 133 Italian children was performed, and ABCB4 mutations were classified as disease-causing mutations or benign substitutions according to the prediction algorithm PolyPhen. RESULTS: : Twenty-eight patients were identified carrying 31 mutations (20 disease causing). Twenty patients carried 2 mutated alleles and 8 only 1. At presentation (1-204 months), 20 children were symptomatic with jaundice and/or pruritus, whereas in 8 biochemical cholestasis was a fortuitous finding. Cirrhosis developed in 15 and 6 progressed to terminal liver failure. Disease-causing mutations on both alleles were found to be associated with reduced liver expression of ABCB4 protein, lack of response to ursodeoxycholic acid therapy, and progression to cirrhosis and end-stage liver disease, whereas mild genotypes, including single heterozygous mutations, were generally associated with less severe disease and, often, absence of symptoms. CONCLUSIONS: ABCB4 mutations are responsible for a chronic liver disease in more than one-third of patients with chronic intrahepatic cholestasis and elevated gamma-GT activity. In patients with severe ABCB4 genotype, the disease is often progressive with risk of developing cirrhosis and liver failure during the first 2 decades of life. Patients with mild genotypes, including single heterozygous mutations, have variable expressions of liver disease that may be influenced by comorbidity factors and modulated by still unknown genetic modifiers.
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107 Nucleotidechange (effectonprotein) Predictionscoresby PolyPhenanalysis Nucleotidechange (effectonprotein) Predictionscoresby PolyPhenanalysis Referencefor eachgenotype 1[1-I]c.475C>T(p.R159X)XUnknownUnknown20 1[1-II]c.475C>T(p.R159X)XUnknownUnknownThisstudy 2[2-I]c.523A>G(p.T175A)0.774c.1069T>C(p.F357L)þc.2324C>T(p.T775M)1.079þ0.59720 3[3-I]c.1135_1136insAA(p.S379KfsX413)Xc.2102T>C(p.L701P)2.22620 4[4-I]c.2662G>T(p.E888X)Xc.748G>C(p.A250P)Rc.1888A>G(p.M630V)1.871R1.67720 5[5-I]c.959C>T(p.S320F)1.287c.857C>T(p.A286V)1.40820 6[6-I]c.377G>A(p.G126E)1.998c.1531G>A(p.A511T)2.1720 6[6-II]c.377G>A(p.G126E)1.998c.1531G>A(p.A511T)2.1720 7[7-I]c.2176C>A(p.P726T)2.086c.1769G>A(p.R590Q)þc.2284G>T(p.G762X)2.623RX20 8[8-1]c.1091C>T(p.A364V)1.343c.2210C>T(p.A737V)0.21720 9[9-I]c.1777A>G(p.T593A)2.044UnknownUnknown20 10[10-I]c.2144C>T(p.T715I)0.383UnknownUnknown20 11[11-I]c.2519C>A(p.A840D)1.803c.1424T>C(p.V475A)2.60320 12[12-I]c.1672G>A(p.E558K)2.486c.2168G>A(p.G723E)Rc.3577G>A(p.A1193T)1.548þ2.34120 12[12-II]c.1672G>A(p.E558K)2.486c.2168G>A(p.G723E)Rc.3577G>A(p.A1193T)1.548þ2.34120 13[13-I]c.2860G>A(p.G954S)0.245c.2860G>A(p.G954S)0.24520 14[14-I]c.523A>G(p.T175A)0.774UnknownUnknown20 15[15-I]c.959C>T(p.S320F)1.287c.837T>A(p.Y279X)X20 16[16-I]c.523A>G(p.T175A)0.774UnknownUnknown20 17[17-I]c.2169_2170insG(p.L724AfsX744)Xc.2169_2170insG(p.L724AfsX744)X20 17[17-II]c.2169_2170insG(p.L724AfsX744)Xc.2169_2170insG(p.L724AfsX744)X20 18[18-I]c.1207T>C(p.Y403H)2.798c.1207T>C(p.Y403H)2.79820 19[19-I]c.208G>C(p.G70R)þc.1769G>A(p.R590Q)1.497þ2.623c.959C>T(p.S320F)1.287Thisstudy 19[19-II]c.208G>C(p.G70R)þc.1769G>A(p.R590Q)1.497þ2.623c.959C>T(p.S320F)1.287Thisstudy 19[19-III]c.208G>C(p.G70R)þc.1769G>A(p.R590Q)1.497þ2.623c.959C>T(p.S320F)1.287Thisstudy 20[20-I]c.217C>G(p.L73V)0.489UnknownUnknown22,thisstudy 21[21-I]c.959C>T(p.S320F)1.287c.959C>T(p.S320F)1.28716,thisstudy 22[22-I]c.1207T>C(p.Y403H)2.798UnknownUnknownThisstudy Xidentifiesmutationsthatpredictprematureterminationoftranslation.PolyPhenpredictionwithPSICscoredifferencesbelow1.5definebenignsubstitutions;PSICscoredifferencesencompassing between1.5and2.0(bold)definesubstitutionspossiblydamaging,whereasabove2.0(underlined)definesubstitutionsprobablydamaging.
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ABCB4 p.Thr775Met 21119540:107:322
status: NEW[hide] ABCB4 gene mutations and single-nucleotide polymor... J Med Genet. 2009 Oct;46(10):711-5. Epub 2009 Jul 6. Bacq Y, Gendrot C, Perrotin F, Lefrou L, Chretien S, Vie-Buret V, Brechot MC, Andres CR
ABCB4 gene mutations and single-nucleotide polymorphisms in women with intrahepatic cholestasis of pregnancy.
J Med Genet. 2009 Oct;46(10):711-5. Epub 2009 Jul 6., [PMID:19584064]
Abstract [show]
AIM: To evaluate the nature and frequency of ATP-binding cassette subfamily B member 4 (ABCB4) gene variants in a series of French patients with intrahepatic cholestasis of pregnancy (ICP). METHODS: In this prospective study, the entire ABCB4 gene coding sequence was analysed by DNA sequencing in 50 unrelated women with ICP defined by pruritus and raised serum alanine aminotransferase activity or bile acid concentration, with recovery after delivery. Genomic variants detected in patients with ICP were sought in 107 control pregnant women. Patients with ICP and controls were of Caucasian origin. RESULTS: Eight genomic variants were observed. One nonsense mutation (p.Arg144Stop) and two missense mutations (p.Ser320Phe and p.Thr775Met) were revealed each in one heterozygous patient. A third missense mutation (p.Arg590Gln) was detected in three heterozygous patients and in two homozygous patients also homozygous for a particular haplotype of three single-nucleotide polymorphisms (c.175C>T, c.504T>C, c.711A>T). The chromosomal frequency of the p.Arg590Gln variant was significantly different between the ICP and control group (7.0% vs 0.5%; p = 0.0017; OR 16.03, 95% CI 1.94 to 132.16). An association was also found between allele T of the c.504T>C silent nucleotide polymorphism and ICP (68.0% vs 53.7%; p = 0.017; OR 1.83, 95% CI 1.08 to 3.11). The chromosomal frequency of the p.Arg652Gly variant did not differ between the ICP and control group (p = 0.40). CONCLUSIONS: This study shows that 16% of Caucasian patients with ICP bear ABCB4 gene mutations, and confirms the significant involvement of this gene in the pathogenesis of this complex disorder.
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5 One nonsense mutation (p.Arg144Stop) and two missense mutations (p.Ser320Phe and p.Thr775Met) were revealed each in one heterozygous patient. A third missense mutation (p.Arg590Gln) was detected in three heterozygous patients and in two homozygous patients also homozygous for a particular haplotype of three single-nucleotide polymorphisms (c.175C.T, c.504T.C, c.711A.T).
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ABCB4 p.Thr775Met 19584064:5:83
status: NEW51 A missense mutation (c.2324C.T, p.Thr775Met) was detected in exon 19 in one heterozygous patient and was absent in controls.
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ABCB4 p.Thr775Met 19584064:51:34
status: NEW66 The heterozygous nonsense mutation (p.Arg144Stop) detected in one patient has previously been reported by our group.14 Three missense mutations (p.Ser320Phe, p.Arg590Gln, p.Thr775Met) were detected in this study.
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ABCB4 p.Thr775Met 19584064:66:173
status: NEW74 Furthermore, Arg590 is well conserved during evolution (fig 1), and the missense mutation p.Arg590Gln is localised in the first ATP-binding domain of the ABCB4 protein, where it substitutes a basic amino acid for a Table 3 Allele frequencies of ABCB4 genomic variants in 50 patients with intrahepatic cholestasis of pregnancy (100 chromosomes) and 107 controls (214 chromosomes) Genomic variant Exon Allele identification ICP (n (%)) Controls (n (%)) p Value Deduced effect Protein domain c.175 C.T 4 C 86 (86) 180 (84.1) 0.66 Silent T 14 (14) 34 (15.9) c.462 C.T 6 C 99 (99) 214 (100) 0.14 p.Arg144Stop (nonsense) Intracytoplasmic first loopT 1 (1) 0 (0) c.504 T.C 6 T 68 (68) 115 (53.7) 0.017 Silent C 32 (32) 99 (46.3) c.711 A.T 8 A 86 (86) 176 (82.2) 0.40 Silent T 14 (14) 38 (17.8) c.959 C.T 9 C 99 (99) 214 (100) 0.14 p.Ser320Phe (missense) TM5 T 1 (1) 0 (0) c.1769 G.A 15 G 93 (93) 213 (99.5) 0.0017 p.Arg590Gln (missense) NBD1 A 7 (7) 1 (0.5) c.1954 A.G 16 A 97 (97) 202 (94.4) 0.40 p.Arg652Gly (missense) NBD1 G 3 (3) 12 (5.6) c.2324 C.T 19 C 99 (99) 214 (100) 0.32 p.Thr775Met (missense) TM8 T 1 (1) 0 (0) ICP, intrahepatic cholestasis of pregnancy; NBD, nucleotide-binding domain; TM, transmembrane domain; n, number of chromosomes.
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ABCB4 p.Thr775Met 19584064:74:1077
status: NEW77 The heterozygous status for the missense p.Thr775Met mutation that we found in one patient with ICP has been reported in a woman in a control group.16 A deleterious effect of the p.Thr775Met allele may, however, be possible because of its localisation in a transmembrane domain, which is important for substrate specificity.9 Thr775 is conserved in mammals, and a cysteine is present in fish (fig 1).
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ABCB4 p.Thr775Met 19584064:77:43
status: NEWX
ABCB4 p.Thr775Met 19584064:77:181
status: NEW78 The p.Thr775Met mutation leads to substitution of a small polar amino acid for a large non-polar one.
X
ABCB4 p.Thr775Met 19584064:78:6
status: NEW94 Indeed, 82% of Table 4 Characteristics of eight patients with intrahepatic cholestasis of pregnancy (ICP) exhibiting ABCB4 mutations Nature of mutation (exon) Age Onset of pruritus (weeks of gestation) Total bilirubin* (N = 17 mmol/l) ALT* (N = 35 U/l) Total bile acids* (N = 6 mmol/l) GGT* (N = 15 U/l) Biliary lithiasis p.Arg144Stop:R/X (6) 23 26 36 1280 120.9 63 No p.Ser320Phe:S/F (9) 37 30 22 437 128.7 16 No p.Arg590Gln:R/Q (15) 39 30 8 73 17.7 13 No p.Arg590Gln:R/Q (15) 28 34 21 134 17.7 119 No p.Arg590Gln:Q/Q (15) 33 35 33 137 26.0 37 No p.Arg590Gln:Q/Q (15) 37 30 15 204 6.1 19 No p.Arg590Gln:R/Q (15) 24 30 14 173 78.0 20 No p.Thr775Met:T/M (19) 35 36 17 144 36.2 26 No *Maximum values during one occurrence of ICP.
X
ABCB4 p.Thr775Met 19584064:94:639
status: NEW