A functional RANKL polymorphism associated with younger age at onset of rheumatoid arthritis

Arthritis Rheum. 2010 Oct;62(10):2864-75. doi: 10.1002/art.27589.

Abstract

Objective: We previously observed the association of the co-occurrence of the HLA-DRB1 shared epitope (SE) and RANKL single-nucleotide polymorphisms (SNPs) with younger age at the onset of rheumatoid arthritis (RA) in 182 rheumatoid factor (RF)-positive European American patients with early-onset RA. The aim of this study was to fine-map the 48-kb RANKL region in the extended cohort of 210 European American RF-positive patients with early RA, to seek replication of RA-associated SNPs in additional RA cohorts of 501 European Americans and 298 African Americans, and to explore the functional consequences of RA-associated SNPs.

Methods: SNP genotyping was conducted using pyrosequencing or TaqMan polymerase chain reaction (PCR) assays. Associations of rs7984870 with RANKL expression in plasma, peripheral blood mononuclear cells, and isolated T cells were quantified using enzyme-linked immunosorbent assay and reverse transcription-PCR. Site-directed mutagenesis of rs7984870 within the 2-kb RANKL promoter was performed to drive the luciferase reporter gene in osteoblast and stromal cell lines. Interaction of DNA and protein was determined by electrophoretic mobility shift assay.

Results: A single promoter SNP, rs7984870, was consistently significantly associated with earlier age at the onset of RA in 3 independent seropositive (RF or anti-cyclic citrullinated peptide antibody) RA cohorts but not in seronegative RA patients. The C risk allele of rs7984870 conferred 2-fold higher plasma RANKL levels in RF-positive patients with RA, significantly elevated RANKL messenger RNA expression in activated normal T cells, and increased promoter activity after stimulation in vitro via differential binding to the transcription factor SOX5.

Conclusion: The RANKL promoter allele that increased transcription levels upon stimulation might promote interaction between activated T cells and dendritic cells, predisposing to a younger age at the onset of RA in seropositive European American and African American patients.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • African Americans / genetics
  • Age of Onset
  • Arthritis, Rheumatoid / ethnology
  • Arthritis, Rheumatoid / genetics*
  • European Continental Ancestry Group / genetics
  • Female
  • Genetic Predisposition to Disease / ethnology
  • Genetic Predisposition to Disease / genetics
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Polymorphism, Single Nucleotide*
  • Promoter Regions, Genetic / genetics*
  • RANK Ligand / blood
  • RANK Ligand / genetics*
  • RNA, Messenger / metabolism
  • SOXD Transcription Factors / physiology

Substances

  • RANK Ligand
  • RNA, Messenger
  • SOX5 protein, human
  • SOXD Transcription Factors
  • TNFSF11 protein, human