Association of TLR7 copy number variation with susceptibility to childhood-onset systemic lupus erythematosus in Mexican population

Abstract

Objective Variations in gene copy number (CNV) have been recognised as a hereditable source of susceptibility in human complex diseases. Recent studies have shown that Tlr7 gene dosage has a significant contribution in the autoimmune-enhancing effect in mouse models of systemic lupus erythematosus (SLE). A study was therefore performed to investigate whether CNVs in TLR7 contribute to the genetic component of childhood-onset SLE. Methods A case–control association study was performed in 328 Mexican children with SLE and 403 healthy controls. Determination of CNVs of TLR7 was achieved by real-time PCR using the ΔΔCt method. Expression levels of TLR7 and interferon α (IFNα) were determined in 23 patients. In addition, a stratification analysis was performed to investigate the association of TLR7 gene copy number (CN) with lupus nephritis. Results A significant increase was found in the relative TLR7 gene CN in females patients with SLE compared with female controls (p1 copy of TLR7 than in female patients with >2 copies (OR 3.07, pTLR7 mRNA levels correlated significantly with TLR7 CN and with IFNα mRNA levels. Conclusion These results show that an increase in TLR7 CN is a risk factor for childhood-onset SLE and provide new evidence for a role for X-linked gene dosage in SLE susceptibility. There is also evidence to suggest that TLR7 may be involved in the pathogenesis of SLE through the induction of IFNα.