We recently identified 2 Lith genes that determine
cholesterol gallstone formation in C57L/J inbred mice, which show a
gallstone prevalence of approximately 80% on feeding 1.0%
cholesterol and 0.5%
cholic acid. The aim of this study was to explore if the same Lith loci contribute to the variation in
gallstone susceptibility in a new experimental cross. After 12 weeks of feeding the lithogenic diet to inbred mice of strains A/J and AKR/J as well as their F(1) progeny, we used microscopy of bile to assess
mucin accumulation, crystallization pathways, and stone formation. Backcross progeny (n = 225) were phenotyped and genotyped selectively for microsatellite markers spanning the genome. Quantitative trait loci (QTL) affecting
gallstone phenotypes were identified by linkage analysis. Both inbred strains showed accumulation of
mucin gel and
cholesterol supersaturation. However, only strain AKR developed
gallstones (prevalence of 20%), whereas strain A showed a stable liquid crystalline state and no stones. QTL analysis identified a
gallstone locus on chromosome 17 (Lith3). A second gene locus on chromosome 15 that controls
mucin accumulation harbors the
mucin gene Glycam1, which was shown to be expressed in gallbladder epithelia by immunohistochemistry.
Gallstone and
mucin loci colocalized with potential QTLs affecting the formation of
cholesterol crystals. In conclusion, QTL analysis identified specific gene loci determining
mucin accumulation,
cholesterol crystallization, and
gallstone formation. Characterization of the pathophysiologic roles of Lith3 and the new biliary
mucin gene Glycam1 might provide insights into primary defects of human
cholelithiasis and lead to new therapeutic strategies for prestone intervention.