title: Non-coding keratin variants associate with liver fibrosis progression in patients with hemochromatosis.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  In patients with hemochromatosis, intronic but not exonic K8/K18 variants associate with liver fibrosis development.
authors.affiliation: Department of Internal Medicine I, University Medical Center Ulm, Ulm, Germany. pavel.strnad@uniklinik-ulm.de
authors.forename: Pavel
authors.initials: P
authors.lastname: Strnad
authors.forename: Ozlem
authors.initials: O
authors.lastname: Kucukoglu
authors.forename: Mariia
authors.initials: M
authors.lastname: Lunova
authors.forename: Nurdan
authors.initials: N
authors.lastname: Guldiken
authors.forename: Tim C
authors.initials: TC
authors.lastname: Lienau
authors.forename: Felix
authors.initials: F
authors.lastname: Stickel
authors.forename: M Bishr
authors.initials: MB
authors.lastname: Omary
mesh_terms: D000328:Adult; D000818:Animals; D018450:Disease Progression; D005260:Female; D005838:Genotype; D006432:Hemochromatosis / Q000235:genetics*; D000071020:Hemochromatosis Protein; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D006801:Humans; D007438:Introns; D007501:Iron / Q000378:metabolism / Q000633:toxicity; D053538:Keratin-18 / Q000235:genetics*; D053533:Keratin-8 / Q000235:genetics*; D008103:Liver Cirrhosis / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008875:Middle Aged; D009154:Mutation; D016366:Open Reading Frames
chemical_list: C103673:HFE protein, human; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D053538:Keratin-18; D053533:Keratin-8; D008565:Membrane Proteins; D007501:Iron