Expression profiling suggests a regulatory role of gallbladder in lipid homeostasis

Aim: To examine expression profile of gallbladder using microarray and to investigate the role of gallbladder in lipid homeostasis. Methods: ³³P-labelled cDNA derived from total RNA of gallbladder tissue was hybridized to a cDNA array representing 17 000 cDNA clusters. Genes with intensities ≥2 and variation <0.33 between two samples were considered as positive signals with subtraction of background chosen from an area where no cDNA was spotted. The average gray level of two gallbladders was adopted to analyze its bioinformatics. Identified target genes were confirmed by touch-down polymerase chain reaction and sequencing. Results: A total of 11 047 genes expressed in normal gallbladder, which was more than that predicted by another author, and the first 10 genes highly expressed (high gray level in hybridization image), e.g. ARPC5 (2 225.88±90.46), LOC55972 (2 220.32±446.51) and SLC20A2 (1 865.21±98.02), were related to the function of smooth muscle contraction and material transport. Meanwhile, 149 lipid-related genes were expressed in the gallbladder, 89 of which were first identified (with gray level in hybridization image), e.g. FASN (11.42±2.62), APOD (92.61±8.90) and CYP21A2 (246.11±42.36), and they were involved in each step of lipid metabolism pathway. In addition, 19 of those 149 genes were gallstone candidate susceptibility genes (with gray level in hybridization image), e.g. HMGCR (10.98±0.31), NPC1 (34.88±12.12) and NRiH4 (16.8±0.65), which were previously thought to be expressed in the liver and/or intestine tissue only. Conclusion: Gallbladder expresses 11 047 genes and takes part in lipid homeostasis.