Genome-wide association study in an admixed case series reveals IL12A as a new candidate in Behçet disease

Jasper H Kappen, Carolina Medina-Gomez, P Martin van Hagen, Lisette Stolk, Karol Estrada, Fernando Rivadeneira, Andre G Uitterlinden, Miles R Stanford, Eldat Ben-Chetrit, Graham R Wallace, Merih Soylu, Jan A M van Laar

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INTRODUCTION: The etiology of Behçet's disease (BD) is unknown, but widely considered an excessive T-cell mediated inflammatory response in a genetically susceptible host. Recent genome-wide association studies (GWAS) have shown limited number of novel loci-associations. The rarity and unequal distribution of the disease prevalence amongst different ethnic backgrounds have hampered the use of GWAS in cohorts of mixed ethnicity and sufficient sample size. However, novel statistical approaches have now enabled GWAS in admixed cohorts.

METHODS: We ran a GWAS on 336 BD cases and 5,843 controls. The cases consisted of Western Europeans, Middle Eastern and Turkish individuals. Participants from the Generation R study, a multiethnic birth cohort in Rotterdam, The Netherlands were used as controls. All samples were genotyped and data was combined. Linear regression models were corrected for population stratification using Genomic Principal Components and Linear Mixed Modelling. Meta-analysis was performed on selected results previously published.

RESULTS: We identified SNPs associated at genome-wide significant level mapping to the 6p21.33 (HLA) region. In addition to this known signal two potential novel associations on chromosomes 6 and 18 were identified, yet with low minor allele frequencies. Extended meta-analysis reveal a GWS association with the IL12A variant rs17810546 on chromosome 3.

DISCUSSION: We demonstrate that new statistical techniques enable GWAS analyses in a limited sized cohort of mixed ethnicity. After implementation, we confirmed the central role of the HLA region in the disease and identified new regions of interest. Moreover, we validated the association of a variant in the IL2A gene by meta-analysis with previous work. These findings enhance our knowledge of genetic associations and BD, and provide further justification for pursuing collective initiatives in genetic studies given the low prevalence of this and other rare diseases.

Original languageEnglish
Article numbere0119085
Number of pages13
JournalPLoS ONE
Issue number3
Publication statusPublished - 23 Mar 2015


  • Adolescent
  • Adult
  • Aged
  • Behcet Syndrome
  • Cohort Studies
  • Female
  • Genetic Predisposition to Disease
  • Genome-Wide Association Study
  • Humans
  • Interleukin-12 Subunit p35
  • Male
  • Meta-Analysis as Topic
  • Middle Aged
  • Phenotype
  • Polymorphism, Single Nucleotide
  • Young Adult


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