Ethnic specificity of lupus-associated loci identified in a genome-wide association study in Korean women

Objectives

To identify novel genetic candidates for systemic lupus erythematosus (SLE) in the Korean population, and to validate the risk loci for SLE identified in previous genome-wide association studies (GWAS).

Methods

We performed a GWAS in 400 Korean female SLE patients and 445 controls. Selected single-nucleotide polymorphisms (SNP) were then replicated in an independent cohort of 385 SLE patients and 583 controls (replication cohort 1), and in a further 811 SLE patients and 1502 controls (replication cohort 2).

Results

In the GWAS phase, rs9275428 located near HLA-DQB1 showed the strongest association with SLE (OR 0.50, false discovery rate (FDR) p=3.07×10⁻⁶). Although no loci reached genome-wide significance outside major histocompatibility complex (MHC), C8orf13-BLK, STAT4, CSMD1, DIAPH3, GLDC and TNFSF4 showed FDR p < 0.05. Our results suggest that STAT4, BLK, IRF5, PTTG1-miR-146a, UBE2L3 and TNFAIP3 are shared susceptibility loci among Caucasians and Asians, while ETS1, IKZF1, SLC15A4 are likely to be Asian-specific loci. In a combined analysis of 1596 SLE patients and 2540 controls for selected 22 candidate SNP, STAT4 and BLK as positive controls showed a strong association with SLE (FDR p=9.85×10⁻¹³ and 2.28×10⁻⁸, respectively). Of these, 16 candidates (PEX5L, TRAJ50, MYO18B, SOS1, ARHGAP26, SMURF1, CADPS, HAND1, FAM78B, DIAPH3, TBL1XR1, CSMD1, ZBTB20, C3orf21, HIPK1 and AP001042.1) showed only nominal significance (7.05×10⁻⁴≤FDR p≤4.38×10⁻²).

Conclusions

There are similarities and differences in genetic susceptibility for SLE between Caucasian and Asian ethnic groups. Although 16 putative novel loci for SLE have been suggested in the Korean population, further research on a larger sample is required to discriminate truth from error.