A new splicing site mutation of the ABCB4 gene in intrahepatic cholestasis of pregnancy with raised serum gamma-GT.

BACKGROUND: Intrahepatic cholestasis of pregnancy is a liver disorder with a multifactorial etiology characterized by maternal pruritus, abnormal liver function tests and increased fetal risk. The main biochemical finding is the increase in total serum bile acid concentrations. In a subgroup of women, the serum gamma-glutamyl transpeptidase level is also increased. There is evidence that dysfunction of the ABCB4 gene might play a role in intrahepatic cholestasis of pregnancy development. AIM: To investigate the role of the ABCB4 gene in Italian women with intrahepatic cholestasis of pregnancy and raised gamma-glutamyl transpeptidase by, analyzing the complete coding sequence and mRNA splicing products.
METHODS: Among 299 women with intrahepatic cholestasis of pregnancy, 10 showing raised gamma-glutamyl transpeptidase were enrolled in this study. DNA and RNA were extracted from peripheral blood mononuclear cells using standard procedures. The 27 coding exons and the promoter region were amplified by polymerase chain reaction and analyzed by sequencing. Reverse transcript-polymerase chain reaction analysis of ABCB4 mRNA and cDNA analysis were also performed.
RESULTS: A novel splicing mutation that causes a truncated protein of 249 amino acid was identified in a woman who had the highest serum levels of gamma-glutamyl transpeptidase, alkaline phosphatase, bile acids, and the highest pruritus score. We identified also one already described p.R590Q mutation in a woman who had significantly higher serum levels of alkaline phosphatase, aspartate, and alanine aminotransferase.
CONCLUSIONS: Our study demonstrates that splicing mutations in the ABCB4 gene can cause ICP in women with high gamma-glutamyl transpeptidase and thus a complete analysis of coding sequence and cDNA products is required.