We have performed a large-scale replication study based on our previous genome-wide association study (GWAS) of SLE in the Chinese Han population to further explore additional genetic variants affecting susceptibility to SLE.
Thirty-eight single nucleotide polymorphisms from our GWAS were genotyped in two additional Chinese Han cohorts (total 3152 cases and 7050 controls) using the Sequenom Massarray system. Association analyses were performed using logistic regression with gender or sample cohorts as a covariate.
Association evidence for rs16972959 (PRKCB at 16p11.2) and rs12676482 (8p11.21) with SLE was replicated independently in both replication cohorts (P < 0.05), showing high significance for SLE in combined all 4199 cases and 8255 controls of Chinese Han [rs16972959: odds ratio (OR) = 0.81; 95% CI 0.76, 0.87; P(combined) = 1.35 × 10(-9); rs12676482: OR = 1.26; 95% CI 1.15, 1.38; P(combined) = 6.68 × 10(-7)). PRKCB is related to the established SLE immune-related pathway (NF-κB) and 8p11.21 contains important candidate genes such as IKBKB and DKK4. IKBKB is a critical component of NF-κB and DKK4 is an inhibitor of canonical Wnt signalling pathway. Interestingly, PRKCB is required for recruiting IKBKB into lipid rafts, up-regulating NF-κB-dependent survival signal.
Our findings provided novel insights into the genetic architecture of SLE and emphasized the contribution of multiple variants of modest effect. Further study focused on PRKCB, 8p11.21, should advance our understanding on the pathogenesis of SLE.
"In a large-scale replication study based upon a previous genome-wide association study (GWAS) of SLE in the Han Chinese population, association evidence for rs12676482 with systemic lupus erythematosus (SLE) was replicated independently in two large cohorts (Sheng et al., 2011). The significance of this lies in the fact that rs12676842 is a SNP in the noncoding region adjacent to the POLB gene on 8p11.21. "
[Show abstract][Hide abstract] ABSTRACT: A replication study of a previous genome-wide association study (GWAS) suggested that a SNP linked to the POLB gene is associated with systemic lupus erythematosus (SLE). This SNP is correlated with decreased expression of Pol β, a key enzyme in the base excision repair (BER) pathway. To determine whether decreased Pol β activity results in SLE, we constructed a mouse model of POLB that encodes an enzyme with slow DNA polymerase activity. We show that mice expressing this hypomorphic POLB allele develop an autoimmune pathology that strongly resembles SLE. Of note, the mutant mice have shorter immunoglobulin heavy-chain junctions and somatic hypermutation is dramatically increased. These results demonstrate that decreased Pol β activity during the generation of immune diversity leads to lupus-like disease in mice, and suggest that decreased expression of Pol β in humans is an underlying cause of SLE.
[Show abstract][Hide abstract] ABSTRACT: We performed a genome-wide association study with 706 individuals with leprosy and 5,581 control individuals and replicated the top 24 SNPs in three independent replication samples, including a total of 3,301 individuals with leprosy and 5,299 control individuals from China. Two loci not previously associated with the disease were identified with genome-wide significance: rs2275606 (combined P = 3.94 × 10(-14), OR = 1.30) on 6q24.3 and rs3762318 (combined P = 3.27 × 10(-11), OR = 0.69) on 1p31.3. These associations implicate IL23R and RAB32 as new susceptibility genes for leprosy. Furthermore, we identified evidence of interaction between the NOD2 and RIPK2 loci, which is consistent with the biological association of the proteins encoded by these genes (NOD2-RIPK2 complex) in activating the NF-κB pathway as a part of the host defense response to infection. Our findings have expanded the biological functions of IL23R by uncovering its involvement in infectious disease susceptibility and suggest a potential involvement of autophagocytosis in leprosy pathogenesis. The IL23R association supports previous observations of the marked overlap of susceptibility genes for leprosy and Crohn's disease, implying common pathogenesis mechanisms.
[Show abstract][Hide abstract] ABSTRACT: Autoimmune diseases now include over 100 conditions and are estimated to affect over 20 million people in the United States or 5% of the world population with numerous geographical differences coined as geoepidemiology. Further, concordance rates in monozygotic twins are significantly higher compared to dizygotic sets while being significantly below 50% for most autoimmune diseases. These lines of evidence suggest that additional mechanisms are needed to link the individual susceptibility with the proposed chemical and infectious factors in the environment. Epigenetics may well constitute this missing link to include DNA methylation, histone changes, and microRNA which contribute to the epigenome characterizing specific diseases. Importantly, these epigenetic changes may be ideal targets for new personalized treatments as suggested by data in cancer. A number of chemical and physical factors, along with proposed infectious agents or aging, are involved in the etiopathogenesis of autoimmune diseases through epigenetic changes. The most prominent evidence on the association between environment and autoimmunity has been reported in systemic lupus erythematosus, but similar mechanisms were proposed in rheumatoid arthritis, systemic sclerosis, and type 1 diabetes.
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