Association of BANK1 and TNFSF4 with systemic lupus erythematosus in Hong Kong Chinese

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. Recently, single nucleotide polymorphisms (SNPs) in BANK1 and TNFSF4 have been shown to be associated with SLE in Caucasian populations, but it is not known whether they are also involved in the disease in other ethnic groups. Recent data from our genome-wide association study (GWAS) for 314 SLE cases and 920 controls collected in Hong Kong identified SNPs in and around BANK1 and TNFSF4 to be associated with SLE risk. On the basis of the results of the reported studies and our GWAS, SNPs were selected for further genotyping in 949 SLE patients (overlapping with the 314 cases in our GWAS) and non-overlapping 1042 healthy controls. We confirmed the associations of BANK1 and TNFSF4 with SLE in Chinese (BANK1, rs3733197, odds ratio (OR) = 0.84, P = 0.021; BANK1, rs17266594, OR = 0.61, P = 4.67 × 10^-9; TNFSF4, rs844648, OR = 1.22, P = 2.47 × 10^-3; TNFSF4, rs2205960, OR = 1.30, P = 2.41 × 10^-4). Another SNP located in intron 1 of BANK1, rs4522865, was separately replicated by Sequenom in 360 cases and 360 controls and was also confirmed to be associated with SLE (OR = 0.725, P = 2.93 × 10^-3). Logistic regression analysis showed that rs3733197 (A383T in ankyrin domain) and rs17266594 (a branch point-site SNP) from BANK1 had independent contributions towards the disease association (P=0.037 and 6.63 × 10^-8, respectively). In TNFSF4, rs2205960 was associated with SLE independently from the effect of rs844648 (P = 6.26 × 10^-3), but not vice versa (P = 0.55). These findings suggest that multiple independent genetic variants may be present within the gene locus, which exert their effects on SLE pathogenesis through different mechanisms.