A candidate gene study reveals association between a variant of the SRp55 splicing factor gene and systemic sclerosis

To examine the possible implication of the mRNA-binding protein serine/arginine protein 55 (SRp55, also known as SRSF6) rs2235611 single nucleotide polymorphism (SNP) in the genetic predisposition to systemic sclerosis (SSc) susceptibility and clinical phenotype. A total population of 872 white Italian individuals (414 SSc patients, 458 controls) was studied. SSc patients were assessed for limited and diffuse cutaneous subsets and the presence of autoantibodies, interstitial lung disease (ILD), and nailfold videocapillaroscopy (NVC) abnormalities. The SRp55 rs2235611 SNP was genotyped by TaqMan real-time PCR. SRp55 rs2235611 genotype distribution and allele frequency were similar in SSc and healthy controls, though a trend toward significance was observed for genotype distribution (p=0.07). The SRp55 rs2235611 AA genotype significantly influenced the predisposition to SSc (p= 0.03). The SRp55 rs2235611 A minor allele and AA genotype showed a significant risk association with susceptibility to SSc-related ILD (A allele: p=0.046; AA genotype: p=0.007). A significant association of the AA genotype with SSc late NVC pattern was also found (p=0.006). After Bonferroni correction for multiple comparisons, the risk association of the SRp55 rs2235611 AA genotype with SSc-related ILD and late NVC pattern remained significant (padj=0.049 and padj=0.042, respectively). The SRp55 rs2235611 AA genotype significantly influences the susceptibility to SSc, and specifically associates with the presence of SSc-related ILD and late NVC pattern. Further in-depth studies on the SRp55 gene locus will hopefully contribute to extend our knowledge of the genetic predisposition to major SSc-related manifestations such as pulmonary fibrosis and peripheral microvasculopathy.