title: Exome sequencing in HFE C282Y homozygous men with extreme phenotypes identifies a GNPAT variant associated with severe iron overload.
abstract: To identify polymorphisms associated with variability of iron overload severity in HFE-associated hemochromatosis, we performed exome sequencing of DNA from 35 male HFE C282Y homozygotes with either markedly increased iron stores (n = 22; cases) or with normal or mildly increased iron stores (n = 13; controls). The 35 participants, residents of the United States, Canada, and Australia, reported no or light alcohol consumption. Sequencing data included 82,068 single-nucleotide variants, and 10,337 genes were tested for a difference between cases and controls. A variant in the GNPAT gene showed the most significant association with severe iron overload (P = 3 × 10(-6) ; P = 0.033 by the likelihood ratio test after correction for multiple comparisons). Sixteen of twenty-two participants with severe iron overload had glyceronephosphate O-acyltransferase (GNPAT) polymorphism p.D519G (rs11558492; 15 heterozygotes, one homozygote). No control participant had this polymorphism. To examine functional consequences of GNPAT deficiency, we performed small interfering RNA-based knockdown of GNPAT in the human liver-derived cell line, HepG2/C3A. This knockdown resulted in a >17-fold decrease in expression of the messenger RNA encoding the iron-regulatory hormone, hepcidin.
  
  
  CONCLUSIONS
  GNPAT p.D519G is associated with a high-iron phenotype in HFE C282Y homozygotes and may participate in hepcidin regulation.
authors.affiliation: Department of Epidemiology, University of California, Irvine, CA.
authors.forename: Christine E
authors.initials: CE
authors.lastname: McLaren
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, WA.
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Emond
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.|Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia.
authors.forename: V Nathan
authors.initials: VN
authors.lastname: Subramaniam
authors.affiliation: Rochester General Hospital, Rochester, NY.
authors.forename: Pradyumna D
authors.initials: PD
authors.lastname: Phatak
authors.affiliation: Southern Iron Disorders Center, Birmingham, AL.
authors.forename: James C
authors.initials: JC
authors.lastname: Barton
authors.affiliation: Department of Medicine, London Health Sciences Center, London, Ontario, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Adams
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.|Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia.
authors.forename: Justin B
authors.initials: JB
authors.lastname: Goh
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: McDonald
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.|Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia.|Royal Brisbane & Women's Hospital, Brisbane, Australia.
authors.forename: Lawrie W
authors.initials: LW
authors.lastname: Powell
authors.affiliation: Center for MEGA Epidemiology, The University of Melbourne, Melbourne, Australia.
authors.forename: Lyle C
authors.initials: LC
authors.lastname: Gurrin
authors.affiliation: Murdoch Childrens Research Institute, Melbourne, Australia.
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Allen
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, WA.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Nickerson
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, WA.
authors.forename: Tin
authors.initials: T
authors.lastname: Louie
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.|Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia.
authors.forename: Grant A
authors.initials: GA
authors.lastname: Ramm
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.|School of Medicine and School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, Australia.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Anderson
authors.affiliation: Department of Veterans Affairs Long Beach Healthcare System, Long Beach, CA.|Division of Hematology/Oncology, Department of Medicine, University of California, Irvine, CA.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: McLaren
mesh_terms: D000217:Acyltransferases / Q000235:genetics*; D000483:Alleles; D000704:Analysis of Variance; D015153:Blotting, Western; D016022:Case-Control Studies; D059472:Exome / Q000235:genetics / Q000502:physiology; D005293:Ferritins / Q000097:blood; D014644:Genetic Variation; D006432:Hemochromatosis / Q000235:genetics* / Q000503:physiopathology; D000071020:Hemochromatosis Protein; D056945:Hep G2 Cells; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D019190:Iron Overload / Q000235:genetics* / Q000503:physiopathology; D008103:Liver Cirrhosis / Q000235:genetics / Q000503:physiopathology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D010641:Phenotype; D017354:Point Mutation; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D020539:Sequence Analysis, Protein; D012720:Severity of Illness Index
chemical_list: C103673:HFE protein, human; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D005293:Ferritins; D000217:Acyltransferases; C020051:glycerone-phosphate O-acyltransferase