Prevalence of genetic variants of keratins 8 and 18 in patients with drug-induced liver injury.
BACKGROUND
Keratin 8 and 18 (K8/K18) cytoskeletal proteins protect hepatocytes from undergoing apoptosis and their mutations predispose to adverse outcomes in acute liver failure (ALF). All known K8/K18 variants occur at relatively non-conserved residues and do not cause keratin cytoskeleton reorganization, whereas epidermal keratin-conserved residue mutations disrupt the keratin cytoskeleton and cause severe skin disease. The aim of our study was to identify keratin variants in idiosyncratic drug-induced liver injury (DILI).


METHODS
Genomic DNA was isolated from 800 patients enrolled in an ongoing US multicenter study, with DILI attributed to a wide range of drugs. Specific K8/K18 exonic regions were PCR-amplified and screened by denaturing HPLC followed by DNA sequencing. The functional impact of keratin variants was assessed using cell transfection and immune staining.


RESULTS
Heterozygous and compound amino acid-altering K8/K18 variants were identified in 86 DILI patients and non-coding variants in 15 subjects. Five novel amino acid-altering (K8 Lys393Arg, K8 Ala351Val, K8 Ala358Val, K8 Ile346Val, K18 Asp89His) and two non-coding variants were observed. Several variants segregated with specific ethnic backgrounds but were found at similar frequencies in DILI subjects and ethnically matched population controls. Notably, variants in highly conserved residues of K8 Lys393Arg (ezetimibe/simvastatin-related) and K18 Asp89His (isoniazid-related) were found in patients with fatal DILI. These novel variants also led to keratin network disruption in transfected cells.


CONCLUSIONS
Novel K8/K18 cytoskeleton-disrupting variants were identified in two patients and segregated with fatal DILI. Other non-cytoskeleton-disrupting keratin variants did not preferentially associate with DILI.
Department of Internal Medicine III and IZKF, University Hospital Aachen, RWTH Aachen, Pauwelsstrasse 30, D-52074, Aachen, Germany. valentyn.usachov@uni-ulm.de.|Department of Internal Medicine I, University Medical Center Ulm, Ulm, Germany. valentyn.usachov@uni-ulm.de.
Valentyn
V
Usachov
Division of Pharmacotherapy and Experimental Therapeutics, Center for Pharmacogenomics and Individualized Therapy, UNC Eshelman School of Pharmacy, UNC Hamner Institute for Drug Safety Sciences, University of North Carolina, Chapel Hill, NC, USA. thomas.urban@unc.edu.
Thomas J
TJ
Urban
Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI, USA. rfontana@med.umich.edu.
Robert J
RJ
Fontana
Department of Internal Medicine III and IZKF, University Hospital Aachen, RWTH Aachen, Pauwelsstrasse 30, D-52074, Aachen, Germany. annika.gross@googlemail.com.
Annika
A
Gross
Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA. sapnai@umich.edu.
Sapna
S
Iyer
Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA. mbishr@med.umich.edu.
M Bishr
MB
Omary
Department of Internal Medicine III and IZKF, University Hospital Aachen, RWTH Aachen, Pauwelsstrasse 30, D-52074, Aachen, Germany. pstrnad@ukaachen.de.
Pavel
P
Strnad
D056486:Chemical and Drug Induced Liver Injury / Q000453:epidemiology / Q000235:genetics; D004198:Disease Susceptibility; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D053538:Keratin-18 / Q000235:genetics*; D053533:Keratin-8 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D015995:Prevalence; D014481:United States / Q000453:epidemiology
C488421:KRT18 protein, human; C426203:KRT8 protein, human; D053538:Keratin-18; D053533:Keratin-8