A polymorphism in the promoter region of the CD86 (B7.2) gene is associated with systemic sclerosis

Authors


K. I. Welsh, Clinical Genomics Group, National Heart and Lung Institute, Imperial College London, London, UK. Tel: 0207-351-8354; Fax: 0207-351-8336; E-mail: k.welsh@imperial.ac.uk

Summary

Systemic sclerosis (SSc) is a connective tissue disease of unknown aetiology characterized by fibrosis of the skin and internal organs, vascular abnormalities and humoral autoimmunity. Strong T-cell-dependent autoantibody and HLA associations are found in SSc subsets. The co-stimulatory molecule, CD86, expressed by antigen-presenting cells, plays a crucial role in priming naïve lymphocytes. We hypothesized that SSc, or one of the disease subsets, could be associated with single-nucleotide polymorphisms of the CD86 gene. Using sequence specific primer-polymerase chain reaction (SSP-PCR) methodology, we assessed four CD86 polymorphisms in 221 patients with SSc and 227 healthy control subjects from the UK. Haplotypes were constructed by inference and confirmed using PHASE algorithm. We found a strong association between SSc and a specific haplotype (haplotype 5), which was more prevalent in patients than in controls (29% vs 15%, OR = 2.3, χ2 = 12, P = 0.0005). This association could be attributed to the novel −3479 promoter polymorphism; a significant difference was observed in the distribution of the CD86 −3479 G allele in patients with SSc compared to controls (43.7% vs. 32.4%, OR = 1.7, χ2 = 12.1, P = 0.0005). TRANSFAC analyses suggest that the CD86-3479T allele contains putative GATA and TBP sites, whereas G allele does not. We assessed the relative DNA protein-binding activity of the −3479 polymorphism in vitro using electromobility gel shift assays (EMSA), which showed that the −3479G allele has less binding affinity compared to the T allele for nuclear proteins. These findings highlight the importance of co-stimulatory pathways in SSc pathogenesis.

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