Genetic and functional identification of the likely causative variant for cholesterol gallstone disease at the ABCG5/8 lithogenic locus.
The sterolin locus (ABCG5/ABCG8) confers 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. Genetic mapping utilized patient samples from Germany (2,808 cases, 2,089 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 complementary DNA (cDNA) samples from human liver (n = 22) was performed using pyrosequencing. Transiently transfected HEK293 cells were used for [(3) H]-cholesterol export assays, analysis of protein expression, and localization of allelic constructs. Through fine mapping in German and Chilean samples, an ∼250 kB 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 single nucleotide polymorphisms. 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 pairwise linkage disequilibrium (r(2) = 0.95). [(3) H]-cholesterol export assays of allelic constructs harboring 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.


CONCLUSIONS
This variant thus provides a molecular basis for biliary cholesterol hypersecretion as the mechanism for cholesterol gallstone formation, thereby drawing a link between "postgenomic" and "pregenomic" pathophysiological knowledge about this common complex disorder. (HEPATOLOGY 2012).
Department of Internal Medicine I, Hospital Schleswig-Holstein, Kiel, Germany.
Oliver
O
von Kampen
Stephan
S
Buch
Michael
M
Nothnagel
Lorena
L
Azocar
Hector
H
Molina
Mario
M
Brosch
Wiebke
W
Erhart
Witigo
W
von Schönfels
Jan
J
Egberts
Marcus
M
Seeger
Alexander
A
Arlt
Tobias
T
Balschun
Andre
A
Franke
Markus M
MM
Lerch
Julia
J
Mayerle
Wolfgang
W
Kratzer
Bernhard O
BO
Boehm
Klaus
K
Huse
Bodo
B
Schniewind
Katharina
K
Tiemann
Zhao-Yan
ZY
Jiang
Tian-Quan
TQ
Han
Balraj
B
Mittal
Anshika
A
Srivastava
Mogens
M
Fenger
Torben
T
Jørgensen
Ramin
R
Schirin-Sokhan
Anke
A
Tönjes
Henning
H
Wittenburg
Michael
M
Stumvoll
Holger
H
Kalthoff
Frank
F
Lammert
Jürgen
J
Tepel
Klaus
K
Puschel
Thomas
T
Becker
Stefan
S
Schreiber
Matthias
M
Platzer
Henry
H
Völzke
Michael
M
Krawczak
Juan Francisco
JF
Miquel
Clemens
C
Schafmayer
Jochen
J
Hampe
D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000483:Alleles; D017398:Alternative Splicing; D016022:Case-Control Studies; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D042882:Gallstones / Q000235:genetics* / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D006801:Humans; D015810:Linkage Disequilibrium; D008074:Lipoproteins / Q000235:genetics*
C416945:ABCG5 protein, human; C416946:ABCG8 protein, human; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D008074:Lipoproteins; D002784:Cholesterol