A candidate gene study identifies a haplotype of CD2 as novel susceptibility factor for systemic sclerosis

Objective. Systemic sclerosis (SSc) is a rare autoimmune disease (AID) with a complex genetic aetiology. Evidence for a shared pathogenesis across AIDs is given by the well-known pleiotropism of autoimmune genes. Recently, several unbiased approaches have identified an association between polymorphisms of the CD2 gene, and rheumatoid arthritis (RA) susceptibility. The objective of this study was to investigate whether CD2 polymorphisms are associated with SSc. Methods. Two SNPs of CD2, rs624988 and rs798036, were genotyped in a total of 1,786 SSc patients and 2,360 healthy individuals from two European populations (France and Italy). Meta analyses were performed to assess whether an association exists between CD2 polymorphisms or haplotypes and SSc or its main subtypes. Results. The combined analyses revealed an association between the rs624988 A allele and SSc susceptibility: p(adj)=0.023, OR=1.14 (95%CI 1.04-1.25). Single marker analysis did not reveal any association between rs798036 and SSc. Haplotype analysis identified that the A-T haplotype, previously described in RA, was associated with higher susceptibility for SSc (p(adj)=0.029, OR=1.14, 95%CI 1.04-1.25) and with the positive anticentromere antibody sub-group of SSc patients (p(adj)=0.009, OR=1 95%CI 1.07-1.32). Genotype-mRNA expression correlations revealed that the CD2 risk haplotype was associated with decreased CD2 mRNA expression in SSc patients. Conclusion. Our study establishes CD2 as a new susceptibility factor for SSc, in a European Caucasian population, confirming the sharing of autoimmune risk factors by SSc and RA