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NADPH oxidase complex and IBD candidate gene studies: identification of a rare variant in NCF2 that results in reduced binding to RAC2
  1. Aleixo M Muise1,2,3,
  2. Wei Xu4,5,
  3. Cong-Hui Guo2,
  4. Thomas D Walters1,
  5. Victorien M Wolters1,
  6. Ramzi Fattouh2,
  7. Grace Y Lam2,
  8. Pingzhao Hu6,
  9. Ryan Murchie2,
  10. Mary Sherlock1,
  11. Juan Cristóbal Gana7,
  12. NEOPICS*,
  13. Richard K Russell8,
  14. Michael Glogauer9,
  15. Richard H Duerr10 11,
  16. Judy H Cho12,
  17. Charlie W Lees13,
  18. Jack Satsangi13,
  19. David C Wilson14,
  20. Andrew D Paterson5,6,
  21. Anne M Griffiths1,
  22. Mark S Silverberg15,
  23. John H Brumell2,3,16
  1. 1Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
  2. 2Program in Cell Biology, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
  3. 3Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
  4. 4Princess Margaret Hospital, Toronto, Ontario, Canada
  5. 5Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  6. 6The Centre for Applied Genomics and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
  7. 7Division of Pediatrics; Gastroenterology, Hepatology and Nutrition Unit, Pontificia Universidad Católica de Chile, Chile
  8. 8Department of Paediatric Gastroenterology, Royal Hospital for Sick Children, Glasgow
  9. 9Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
  10. 10Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, USA
  11. 11Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA
  12. 12Inflammatory Bowel Disease Centre, Departments of Medicine and Genetics, Yale University, New Haven, Connecticut, USA
  13. 13Department of Gastroenterology, Western General Hospital, University of Edinburgh, Edinburgh, UK
  14. 14Child Life and Health, Department of Pediatrics, University of Edinburgh, Edinburgh, UK
  15. 15Mount Sinai Hospital Inflammatory Bowel Disease Group, Zane Cohen Centre for Digestive Diseases, University of Toronto, Toronto, Ontario, Canada
  16. 16Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to Dr Aleixo Muise, Division of Gastroenterology, Program in Cell Biology, Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada; aleixo.muise{at}utoronto.ca

Abstract

Objective The NOX2 NADPH oxidase complex produces reactive oxygen species and plays a critical role in the killing of microbes by phagocytes. Genetic mutations in genes encoding components of the complex result in both X-linked and autosomal recessive forms of chronic granulomatous disease (CGD). Patients with CGD often develop intestinal inflammation that is histologically similar to Crohn's colitis, suggesting a common aetiology for both diseases. The aim of this study is to determine if polymorphisms in NOX2 NADPH oxidase complex genes that do not cause CGD are associated with the development of inflammatory bowel disease (IBD).

Methods Direct sequencing and candidate gene approaches were used to identify susceptibility loci in NADPH oxidase complex genes. Functional studies were carried out on identified variants. Novel findings were replicated in independent cohorts.

Results Sequence analysis identified a novel missense variant in the neutrophil cytosolic factor 2 (NCF2) gene that is associated with very early onset IBD (VEO-IBD) and subsequently found in 4% of patients with VEO-IBD compared with 0.2% of controls (p=1.3×10−5, OR 23.8 (95% CI 3.9 to 142.5); Fisher exact test). This variant reduced binding of the NCF2 gene product p67phox to RAC2. This study found a novel genetic association of RAC2 with Crohn's disease (CD) and replicated the previously reported association of NCF4 with ileal CD.

Conclusion These studies suggest that the rare novel p67phox variant results in partial inhibition of oxidase function and are associated with CD in a subgroup of patients with VEO-IBD; and suggest that components of the NADPH oxidase complex are associated with CD.

  • IBD
  • inflammatory bowel disease
  • Crohn's Disease chronic granulomatous disease
  • reactive oxygen species
  • NADPH oxidase complex
  • intestinal barrier function
  • coeliac disease
  • liver
  • portal hypertension
  • genetics
  • crohns colitis
  • crohns disease
  • IBD—genetics
  • gene expression
  • immunology
  • infliximab
  • enteral nutrition
  • paediatric gastroenterology
  • azathioprine
  • IBD clinical
  • chronic ulcerative colitis
  • antinutrophil cytoplasmic autoantibodies
  • genotype
  • genetic testing
  • genetic polymorphisms
  • bacterial pathogenesis
  • cell biology
  • cellular immunity
  • salmonella

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Footnotes

  • MSS and JHB contributed equally.

  • * Canadian National Early Onset IBD Cohort Study (NEOPICS): see online supplement for details.

  • Funding AMM is supported by a transition award from the Crohn's and Colitis Foundation of Canada (CCFC)/Canadian Association of Gastroenterology (CAG)/Canadian Institute for Health Research (CIHR), a Canadian Child Health Clinician Scientist Program (Strategic Training Initiatives in Health Research Program—CIHR) Award, an Early Researcher Award from the Ontario Ministry of Research and Innovation and a CDHNF/NASPGHAN George Ferry Young Investigator Development Award. DCW is the holder of a Medical Research Council Patient Cohorts Research Initiative award (G0800675). Financial assistance was also provided by the Wellcome Trust Programme Grant (072789/Z/03/Z), Action Medical Research, the Chief Scientist Office of the Scottish Government Health Department and the GI/Nutrition Research Fund, Child Life and Health, University of Edinburgh. RHD is supported by NIH/NIDDK grant (DK062420). ADP holds a Canada Research Chair in Genetics of Complex Diseases. MSS is supported by the Gale and Graham Wright Research Chair in Digestive Diseases at Mount Sinai Hospital and funding from CCFC and NIH/NIDDK (DK-06-2423). JHB holds an Investigator in the Pathogenesis of Infectious Disease Award from the Burroughs Wellcome Fund. Funding was provided by a CIHR operating grant (MOP97756) to AMM and JHB.

  • Competing interests None.

  • Ethics approval Hospital for Sick Children REB.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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  • PostScript
    R Somasundaram J J Deuring C J van der Woude M P Peppelenbosch G M Fuhler
  • PostScript
    Aleixo M Muise Ramzi Fattouh Grace Y Lam Sandeep Dhillon John H Brumell
  • Corrections
    BMJ Publishing Group Ltd and British Society of Gastroenterology