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Basic and translational research
Extended report
Association of IRF5 polymorphisms with activation of the interferon α pathway
  1. Ornella J Rullo1,
  2. Jennifer M P Woo1,
  3. Hui Wu2,
  4. Alice D C Hoftman3,
  5. Paul Maranian2,
  6. Brittany A Brahn2,
  7. Deborah McCurdy1,
  8. Rita M Cantor4,
  9. Betty P Tsao2
  1. 1Division of Pediatric Rheumatology, David Geffen School of Medicine, University of California-Los Angeles, California, USA
  2. 2Division of Rheumatology-Medicine, University of California-Los Angeles, California, USA
  3. 3Division of Pediatric Rheumatology, Children's Hospital of Orange County, Orange, California, USA
  4. 4Department of Human Genetics, University of California-Los Angeles, California, USA
  1. Correspondence to Dr O J Rullo, Division of Pediatric Rheumatology, Mattel Children's Hospital UCLA, 10833 Le Conte Avenue, Room 12-430 MDCC, Los Angeles, CA 90095, USA; orullo{at}mednet.ucla.edu

Abstract

Objective The genetic association of interferon regulatory factor 5 (IRF5) with systemic lupus erythematosus (SLE) susceptibility has been convincingly established. To gain understanding of the effect of IRF5 variation in individuals without SLE, a study was undertaken to examine whether such genetic variation predisposes to activation of the interferon α (IFNα) pathway.

Methods Using a computer simulated approach, 14 single nucleotide polymorphisms (SNPs) and haplotypes of IRF5 were tested for association with mRNA expression levels of IRF5, IFNα and IFN-inducible genes and chemokines in lymphoblastoid cell lines (LCLs) from individuals of European (CEU), Han Chinese (CHB), Japanese (JPT) and Yoruba Nigerian (YRI) backgrounds. IFN-inducible gene expression was assessed in LCLs from children with SLE in the presence and absence of IFNα stimulation.

Results The major alleles of IRF5 rs13242262 and rs2280714 were associated with increased IRF5 mRNA expression levels in the CEU, CHB+JPT and YRI samples. The minor allele of IRF5 rs10488631 was associated with increased IRF5, IFNα and IFN-inducible chemokine expression in CEU (pc=0.0005, 0.01 and 0.04, respectively). A haplotype containing these risk alleles of rs13242262, rs10488631 and rs2280714 was associated with increased IRF5, IFNα and IFN-inducible chemokine expression in CEU LCLs. In vitro studies showed specific activation of IFN-inducible genes in LCLs by IFNα.

Conclusions SNPs of IRF5 in healthy individuals of a number of ethnic groups were associated with increased mRNA expression of IRF5. In European-derived individuals, an IRF5 haplotype was associated with increased IRF5, IFNα and IFN-inducible chemokine expression. Identifying individuals genetically predisposed to increased IFN-inducible gene and chemokine expression may allow early detection of risk for SLE.

http://dx.doi.org/10.1136/ard.2009.118315

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    Footnotes

    • Ethics approval This study was conducted with the approval of the UCLA Institutional Review Board.

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