Non-Coding Keratin Variants Associate with Liver Fibrosis Progression in Patients with Hemochromatosis

• Published in: PloS one Vol. 7; no. 3; p. e32669
• Main Authors: Strnad, Pavel, Kucukoglu, Ozlem, Lunova, Mariia, Guldiken, Nurdan, Lienau, Tim C., Stickel, Felix, Omary, M. Bishr
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 07.03.2012; Public Library of Science (PLoS)
• Subjects: Acids; Adult; Amino acids; Analysis; Animals; Biology; Chromatography; Chronic infection; Cirrhosis; Deoxyribonucleic acid; Development and progression; Disease Progression; DNA; DNA sequencing; Female; Fibrosis; Gene sequencing; Genetic aspects; Genomics; Genotype; Health aspects; Hemochromatosis; Hemochromatosis - genetics; Hemochromatosis Protein; Hepatitis; Hepatitis C; Hepatocytes; Hepatocytes - metabolism; Hepatocytes - pathology; High performance liquid chromatography; Histocompatibility Antigens Class I - genetics; Humans; Infection; Interferon; Introns; Iron; Iron - metabolism; Iron - toxicity; Keratin; Keratin-18 - genetics; Keratin-8 - genetics; Liquid chromatography; Liver; Liver cirrhosis; Liver Cirrhosis - genetics; Liver diseases; Male; Medical research; Medicine; Membrane Proteins - genetics; Mice; Mice, Transgenic; Middle Aged; Mutation; Open Reading Frames; Patients; Primary biliary cirrhosis; Proteins; Rodents; Toxicity; Transgenic mice; United States > US; Michigan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0032669

Keratins 8 and 18 (K8/K18) are intermediate filament proteins that protect the liver from various forms of injury. Exonic K8/K18 variants associate with adverse outcome in acute liver failure and with liver fibrosis progression in patients with chronic hepatitis C infection or primary biliary cirrhosis. Given the association of K8/K18 variants with end-stage liver disease and progression in several chronic liver disorders, we studied the importance of keratin variants in patients with hemochromatosis. The entire K8/K18 exonic regions were analyzed in 162 hemochromatosis patients carrying homozygous C282Y HFE (hemochromatosis gene) mutations. 234 liver-healthy subjects were used as controls. Exonic regions were PCR-amplified and analyzed using denaturing high-performance liquid chromatography and DNA sequencing. Previously-generated transgenic mice overexpressing K8 G62C were studied for their susceptibility to iron overload. Susceptibility to iron toxicity of primary hepatocytes that express K8 wild-type and G62C was also assessed. We identified amino-acid-altering keratin heterozygous variants in 10 of 162 hemochromatosis patients (6.2%) and non-coding heterozygous variants in 6 additional patients (3.7%). Two novel K8 variants (Q169E/R275W) were found. K8 R341H was the most common amino-acid altering variant (4 patients), and exclusively associated with an intronic KRT8 IVS7+10delC deletion. Intronic, but not amino-acid-altering variants associated with the development of liver fibrosis. In mice, or ex vivo, the K8 G62C variant did not affect iron-accumulation in response to iron-rich diet or the extent of iron-induced hepatocellular injury. In patients with hemochromatosis, intronic but not exonic K8/K18 variants associate with liver fibrosis development.