Preferential association of a functional variant in complement receptor 2 with antibodies to double-stranded DNA.
Zhao J., Giles BM., Taylor RL., Yette GA., Lough KM., Ng HL., Abraham LJ., Wu H., Kelly JA., Glenn SB., Adler AJ., Williams AH., Comeau ME., Ziegler JT., Marion M., Alarcón-Riquelme ME., BIOLUPUS and GENLES Networks None., Alarcón GS., Anaya J-M., Bae S-C., Kim D., Lee H-S., Criswell LA., Freedman BI., Gilkeson GS., Guthridge JM., Jacob CO., James JA., Kamen DL., Merrill JT., Sivils KM., Niewold TB., Petri MA., Ramsey-Goldman R., Reveille JD., Scofield RH., Stevens AM., Vilá LM., Vyse TJ., Kaufman KM., Harley JB., Langefeld CD., Gaffney PM., Brown EE., Edberg JC., Kimberly RP., Ulgiati D., Tsao BP., Boackle SA.
OBJECTIVES: Systemic lupus erythematosus (SLE; OMIM 152700) is characterised by the production of antibodies to nuclear antigens. We previously identified variants in complement receptor 2 (CR2/CD21) that were associated with decreased risk of SLE. This study aimed to identify the causal variant for this association. METHODS: Genotyped and imputed genetic variants spanning CR2 were assessed for association with SLE in 15 750 case-control subjects from four ancestral groups. Allele-specific functional effects of associated variants were determined using quantitative real-time PCR, quantitative flow cytometry, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-PCR. RESULTS: The strongest association signal was detected at rs1876453 in intron 1 of CR2 (pmeta=4.2×10(-4), OR 0.85), specifically when subjects were stratified based on the presence of dsDNA autoantibodies (case-control pmeta=7.6×10(-7), OR 0.71; case-only pmeta=1.9×10(-4), OR 0.75). Although allele-specific effects on B cell CR2 mRNA or protein levels were not identified, levels of complement receptor 1 (CR1/CD35) mRNA and protein were significantly higher on B cells of subjects harbouring the minor allele (p=0.0248 and p=0.0006, respectively). The minor allele altered the formation of several DNA protein complexes by EMSA, including one containing CCCTC-binding factor (CTCF), an effect that was confirmed by ChIP-PCR. CONCLUSIONS: These data suggest that rs1876453 in CR2 has long-range effects on gene regulation that decrease susceptibility to lupus. Since the minor allele at rs1876453 is preferentially associated with reduced risk of the highly specific dsDNA autoantibodies that are present in preclinical, active and severe lupus, understanding its mechanisms will have important therapeutic implications.