ABCMdb

ABCG8 p.Arg50Cys

Predicted by SNAP2:	A: D (53%), C: D (71%), D: D (71%), E: N (53%), F: D (80%), G: D (63%), H: D (66%), I: D (66%), K: N (87%), L: D (53%), M: D (59%), N: N (78%), P: D (80%), Q: N (78%), S: N (66%), T: N (61%), V: D (66%), W: D (85%), Y: D (80%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, G: N, H: N, I: D, K: N, L: D, M: N, N: N, P: D, Q: N, S: N, T: N, V: D, W: D, Y: D,

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Publications
[hide] Stomatocytic haemolysis and macrothrombocytopenia ... Br J Haematol. 2005 Jul;130(2):297-309. Rees DC, Iolascon A, Carella M, O'marcaigh AS, Kendra JR, Jowitt SN, Wales JK, Vora A, Makris M, Manning N, Nicolaou A, Fisher J, Mann A, Machin SJ, Clayton PT, Gasparini P, Stewart GW
Stomatocytic haemolysis and macrothrombocytopenia (Mediterranean stomatocytosis/macrothrombocytopenia) is the haematological presentation of phytosterolaemia.
Br J Haematol. 2005 Jul;130(2):297-309., [PMID:16029460]

Abstract [show]
Phytosterolaemia (sitosterolaemia) is a recessively inherited metabolic condition in which the absorption of both cholesterol and plant-derived cholesterol-like molecules at the gut is unselective and unrestricted. In haematology, Mediterranean stomatocytosis or Mediterranean macrothrombocytopenia is a poorly understood haematological condition that combines stomatocytic haemolysis with the presence of very large platelets. Five pedigrees showing this haematology were identified. Gas chromatography mass spectrometry (GC-MS) showed that all of the patients with this highly specific haematology had grossly elevated levels of phytosterols in the blood, diagnostic of phytosterolaemia. All showed mutations in the ABCG5 and ABCG8 previously linked to phytosterolaemia. Three pedigrees showed five new mutations, while two pedigrees showed the common W361X mutation in ABCG8. We draw the following four conclusions: (i) that Mediterranean stomatocytosis/macrothrombocytopenia is caused by an excess of phytosterols in the blood; (ii) that phytosterolaemia, which does not respond to standard statin treatment, can be diagnosed via the distinctive haematology described here, even when the cholesterol is normal; (iii) that phytosterolaemia should be considered in the differential diagnosis of all patients with large platelets; and (iv) that the platelet size should be noted in patients with hypercholesterolaemia.

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No. Sentence Comment
174 Family Sitosterol level (lmol/l) ABCG5 ABCG8 A E77X (229G>T) A-I-2 44 m/n A-II-1 1471 m/m A-II-2 17 n/n A-II-3 57 n/n A-II-4 970 m/m A-II-5 625 m/m A-II-9 508 m/m B IVS11+3insT R50C (148C>T) E146X (436G>T), M622V (1864A>G) B-I-1 77 n/n m/n B-I-2 42 m/n n/n B-II-1 2230 m/n m/n B-II-2 2350 m/n m/n B-II-3 137 n/n m/n C Q604E (1810C>G) Q271X (811C>T) IV9-3insT IV8-1G/A C54Y (161G>A) C-I-1 114 m/n n/n m/n m/n C-I-2 29 m/m m/n n/n m/m C-II-1 2100 m/n m/n m/n m/n C-II-2 2580 m/n m/n m/n m/n D W361X (1083G>A) D-I-1 22 m/n D-II-1 715 m/m E W361X (1083G>A) E-I-1 23 m/n E-II-1 1844 m/m E-II-2 21 n/n Mutations are shown in bold and large font. Login to comment

[hide] A detailed Hapmap of the Sitosterolemia locus span... BMC Med Genet. 2006 Feb 28;7:13. Pandit B, Ahn GS, Hazard SE, Gordon D, Patel SB
A detailed Hapmap of the Sitosterolemia locus spanning 69 kb; differences between Caucasians and African-Americans.
BMC Med Genet. 2006 Feb 28;7:13., [PMID:16507104]

Abstract [show]
BACKGROUND: Sitosterolemia is an autosomal recessive disorder that maps to the sitosterolemia locus, STSL, on human chromosome 2p21. Two genes, ABCG5 and ABCG8, comprise the STSL and mutations in either cause sitosterolemia. ABCG5 and ABCG8 are thought to have evolved by gene duplication event and are arranged in a head-to-head configuration. We report here a detailed characterization of the STSL in Caucasian and African-American cohorts. METHODS: Caucasian and African-American DNA samples were genotypes for polymorphisms at the STSL locus and haplotype structures determined for this locus RESULTS: In the Caucasian population, 13 variant single nucleotide polymorphisms (SNPs) were identified and resulting in 24 different haplotypes, compared to 11 SNPs in African-Americans resulting in 40 haplotypes. Three polymorphisms in ABCG8 were unique to the Caucasian population (E238L, INT10-50 and G575R), whereas one variant (A259V) was unique to the African-American population. Allele frequencies of SNPs varied also between these populations. CONCLUSION: We confirmed that despite their close proximity to each other, significantly more variations are present in ABCG8 compared to ABCG5. Pairwise D' values showed wide ranges of variation, indicating some of the SNPs were in strong linkage disequilibrium (LD) and some were not. LD was more prevalent in Caucasians than in African-Americans, as would be expected. These data will be useful in analyzing the proposed role of STSL in processes ranging from responsiveness to cholesterol-lowering drugs to selective sterol absorption.

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144 A number of studies have been implicated this locus in disease (or physiologi- Table 4: Results of pair-wise LD analyses Population M1 M2 ChiSq Pval ∆2 D' Caucasian INT1-21 INT1-7 20.01 1E-05 0.545 0.866 5'UTR-19 INT1-7 9.61 0.002 0.256 0.594 Q604E INT1-7 7.14 0.008 0.239 0.489 T400K A632V 6.13 0.013 0.125 1.000 5'UTR-19 T400K 5.84 0.016 0.153 1.000 Q604E D19H 5.02 0.025 0.174 1.000 INT1-7 T400K 4.94 0.026 0.111 1.000 R50C D19H 4.79 0.029 0.234 0.484 INT1-21 T400K 4.45 0.035 0.153 1.000 E238L INT10-50 4.42 0.036 0.238 1.000 INT1-7 C54Y 4.41 0.036 0.138 0.739 5'UTR-19 C54Y 4.24 0.040 0.134 0.619 T400K INT10-50 3.92 0.048 0.040 1.000 5'UTR-19 A565A 3.86 0.049 0.127 1.000 Q604E INT1-21 3.66 0.056 0.128 0.420 INT10-50 A632V 3.29 0.070 0.132 0.641 5'UTR-19 INT1-21 2.86 0.091 0.071 0.267 C54Y T400K 2.74 0.098 0.082 0.433 African-American 5'UTR-19 T400K 11.01 9E-04 0.080 1.000 INT1-7 A565A 8.09 0.004 0.085 0.587 R50C D19H 6.96 0.008 0.205 1.000 T400K A565A 6.56 0.010 0.088 0.557 Q604E INT1-21 5.82 0.016 0.119 0.505 5'UTR-19 A565A 5.10 0.024 0.059 0.460 C54Y A565A 3.93 0.047 0.053 0.270 5'UTR-19 C54Y 3.49 0.062 0.047 0.481 R50C INT1-7 3.05 0.081 0.044 1.000 INT1-7 A632V 3.05 0.081 0.044 1.000 Q604E D19H 3.01 0.083 0.038 1.000 M1 = 1st marker in pair of SNPs, M2 = 2nd marker in pair of SNPs, ChiSq = Value of chi-square test of association, Pval = Two-sided P-value corresponding to chi-square value in ChiSq column assuming 1 degree of freedom. Login to comment
73 Among the unrelated parents (Caucasians) all the SNPs, except R50C were in Hardy-Weinberg Equilibrium (p > 0.005, χ Square test). Login to comment
100 Of note, for the non-synonymous SNPs, R50C and D19H showed some LD in both populations, though the Ch-square statistic was only moderate (Table 4). Login to comment

[hide] Genetic and functional identification of the likel... Hepatology. 2012 Aug 16. doi: 10.1002/hep.26009. von Kampen O, Buch S, Nothnagel M, Azocar L, Molina H, Brosch M, Erhart W, von Schonfels W, Egberts J, Seeger M, Arlt A, Balschun T, Franke A, Lerch MM, Mayerle J, Kratzer W, Boehm BO, Huse K, Schniewind B, Tiemann K, Jiang ZY, Han TQ, Mittal B, Srivastava A, Fenger M, Jorgensen T, Schirin-Sokhan R, Tonjes A, Wittenburg H, Stumvoll M, Kalthoff H, Lammert F, Tepel J, Puschel K, Becker T, Schreiber S, Platzer M, Volzke H, Krawczak M, Miquel JF, Schafmayer C, Hampe J
Genetic and functional identification of the likely causative variant for cholesterol gallstone disease at the ABCG5/8 lithogenic locus.
Hepatology. 2012 Aug 16. doi: 10.1002/hep.26009., [PMID:22898925]

Abstract [show]
BACKGROUND & AIMS: The sterolin locus (ABCG5/ABCG8) has been solidly shown to confer susceptibility for cholesterol gallstone disease in humans. Both the responsible variant and the molecular mechanism causing an increased incidence of gallstones in these patients have as yet not been identified. METHODS: Genetic mapping utilized patient samples from Germany (2808 cases, 2089 controls), Chile (680 cases, 442 controls), Denmark (366 cases, 766 controls), India (247 cases, 224 controls) and China (280 cases, 244 controls). Analysis of allelic imbalance in cDNA samples from human liver (N=22) was performed using pyrosequencing. Transiently transfected HEK293 cells were used for [3H]-cholesterol export assays, analysis of protein expression and localisation of allelic constructs. RESULTS: Through fine mapping in German and Chilean samples, a approximately 250kB disease-associated interval could be defined for this locus. Lack of allelic imbalance or allelic splicing of the ABCG5 and ABCG8 transcripts in human liver limited the search to coding SNPs. Subsequent mutation detection and genotyping yielded two disease-associated variants ABCG5-R50C (p=4.94x10(-9) ) and ABCG8-D19H (p=1.74x10(-10) ) in high pair-wise LD (r(2) =0.95). [3H]-cholesterol export assays of allelic constructs harbouring these genetic candidate variants demonstrated increased transport activity (3.2-fold, p=0.003) only for the ABCG8-19H variant, which was also superior in nested logistic regression models in German (p=0.018), Chilean (p=0.030) and Chinese (p=0.040) patient samples. CONCLUSION: This variant thus provides a molecular basis for biliary cholesterol hypersecretion as the mechanism for cholesterol gallstone formation thereby drawing a link between "post-genomic" and "pre-genomic" pathophysiological knowledge about this common complex disorder. (HEPATOLOGY 2012.).

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No. Sentence Comment
17 Subsequent mutation detection and genotyping yielded two disease-associated variants ABCG5-R50C (p=4.94×10-9 ) and ABCG8-D19H (p=1.74×10-10 ) in high pair-wise LD (r2 =0.95). Login to comment
47 The different versions of both transporters, defined by the respective alleles of R50C and D19H, were introduced by site-directed mutagenesis (QuickChange Lightning Site-Directed Mutagenesis Kit, Agilent Technologies, Santa Clara, CA, USA) according to the Page 10 manufacturer`s protocol. HEK cells were transfected using Effectene Transfection Reagent (Qiagen, Hilden, Germany) according to the manufacturer`s protocol. Login to comment
49 In brief, HEK cells transiently expressing different allelic variants of ABCG5-R50C and ABCG8-D19H were incubated in 24 well cell culture plates with 0.5 ml DMEM supplemented with 10 mM HEPES, pH 7.4, 30 mg/ml cholesterol, 0.5 mCi/ml [³H]-cholesterol and 0.2% fatty acid free BSA for 24 h. Login to comment
79 ABCG8-D19H and ABCG5-R50C are the only functional candidates in the disease interval Owing to the absence of allelic imbalance and allele-dependent splicing, disease mechanisms such as differential transcription efficiency (caused by promoter polymorphisms or variable intronic enhancers) as well as differential transcript structure or stability could be safely ruled out. Login to comment
84 ABCG8-D19H, but not ABCG5-R50C leads to increased cholesterol transport Of all coding SNPs investigated in the disease-associated region, only rs6756629 (ABCG5-R50C; ORallelic=1.96, 95% CI: 1.56-2.47) and rs11887534 (ABCG8-D19H; ORallelic=2.07, 95% CI: 1.65-2.60) were found to be significantly associated with cholelithiasis in our Page 14 mapping panel. Login to comment
98 ABCG8-D19H but not ABCG5-R50C captures the genetic risk across populations In addition to the functional experiments, nested logistic regression analyses were performed to evaluate statistically the causative role of individual variants in the disease-associated region. Login to comment
100 When ABCG5-R50C was included as a mandatory explanatory variable, ABCG8-D19H significantly improved the model fit (p=0.0175) thereby suggesting again that ABCG8-D19H is the major causative variant in the region. Login to comment
101 To confirm this result, rs6756629 (ABCG5-R50C) and rs11887534 (ABCG8-D19H) were also genotyped in additional case-controls samples of German, Chilean, Danish, Indian and Chinese origin (Table 2). Login to comment
103 In each of the samples, ABCG8-D19H consistently showed an equal or higher allelic odds ratio as compared to ABCG5-R50C, thereby supporting the above conclusion. Login to comment