| Rheumatoid arthritis （RA）is caused by coefficient of genetic and environmentalfactors. Recent studies found that genetic factors in a large amount lead to rheumatoidarthritis.RA and psoriatic arthritis (PsA) were autoimmune diseases and a variety ofcytokines participated in the pathomechanism of the two diseases[2]. RA, PsA andankylosing spondylitis（AS）all were accompanied by articular destruction of bone andcartilage tissue.The psoriasis susceptibility1candidate1(PSORS1C1, formerly SEEK1) gene islocated127kb telomeric to the HLA-C locus on chromosome6p21.3. The locus mainlyconfers susceptibility to psoriasis (PS) in many populations[3-7]. About10-30%of peoplewith psoriasis have PsA, an inflammatory rheumatic disorder of unknown etiology[8-10].PSORS1C1is also reported to be associated with psoriatic arthritis in the Newfoundlandfounder population[11]. Basing on what RA and PsA diseases have in common, this studypredict that PSORS1C1gene is associated with susceptibility to RA disease.In this study, we genotyped tagSNPs across PSORS1C1region. To our knowledge,this is the first study to examine the potential association of PSORS1C1genepolymorphism with RA.Corneodesmosin(CDSN) gene, which is located in the major histocompatibilitycomplex (MHC) class I region, also harbors in the5’-UTR of PSORS1C1, encodescorneodesmosin protein. Polymorphism of PSORS1C1gene may also affect theexpression of CDSN protein. Aiming to detect the influence of PSORS1C1gene for RApatients, PSORS1C1and CDSN expression in synovial tissues from RA patients were investigated using western blot. PSORS1C1and CDSN expression in serum of RApatients were investigated using ELISA.Objective: By analysising allele/genotype freqences of tagSNPs across PSORS1C1region to determine whether PSORS1C1gene is associated with rheumatoid arthritis;Also analysising PSORS1C1and CDSN protein expression in serum and synovial tissueof RA patients, to provide a basis for further study of the pathogenesis of RA.Methods:1.The tagSNPs across PSORS1C1were genotyped using acustom-designed Illumina96-SNP VeraCode microarray (Illumina). Peripheral bloodsamples were collected from patients with RA (97female, mean age50.2±10.93) andhealthy control (90female，mean age46.3±12.46). TagSNPs across the PSORS1C1genewere determined by searching the HapMap database. Only SNPs with minor allelefrequency (MAF) greater than5%with a pair-wise r2≥0.8were considered. CandidateSNPs were submitted to the Illumina for a design score.2.To confirm microarray results, TaqMan SNP genotyping assays were used togenotype in a cohort of384patients with RA (293female, mean age52.2±12.04), and288healthy controls (132female，mean age63.5±11.79). These people were differentwith the sample used in experiments for the Illumina microarray.3.Western blot was used to measure the expression levels of PSOROS1C1and CDSN inthe synovial tissues of patients with7RA patients（5female，51±13.20）、7OA patients（4female，mean age53±12.23）and5AS patients（3female，mean age43±21.11）.4.A sandwich ELISA was used to measure the levels of PSOROS1C1and CDSN in theserum of RA patients（17female, mean age62±10.34)，AS（5female，mean age46±11.44）, PS（7female，mean age34±15.46)and healthy control（20female，meanage41±12.56）.Results：1.150cases of rheumatoid arthritis (97women, mean age age of50.2 ±10.93) and150cases of healthy control (97women, average age age of50.2±12.46)were used in Illumina genotyping analysis. Illumina gene chip filtered out rs3130983,rs3778638and rs4959053these3meaningful tagSNPs site across PSORS1C1.2. TaqMan genotyping results showed the allele and genotype frequencies of the threeSNPs did not deviate from Hardy-Weinberg equilibrium in controls. The allele andgenotype frequencies of SNP rs3778638and rs4959053demonstrated statisticallysignificant evidence for an association with RA (P<0.05). SNP genotype frequence ofrs3778638is associated with susceptibility to RA disease significantly.(P<0.05).3. Western Blot showed that expression of PSORS1C1in RA synovial tissue weresignificantly higher than OA patients(P=0.007). PSORS1C1expression in AS synovialtissue didn’t showed difference with OA patients.(P>0.05). CDSN expression in synovialtissues of RA, OA and AS patients showed no significant difference (P>0.05).4. ELISA analysis showed that expression of PSORS1C1in serum of RA patientssubstantially higher than healthy control group (P=0.00001), PSORS1C1and CDSNexpression level in serum of PS, AS patients showed no significant difference withhealthy controls (P>0.05).Conclusion: This study showed allele/genotype frequencies of rs3130983and rs4959053in RA patients were different with control group(p<0.05), genotype frequencies ofrs3778638also showed difference between RA patients and healthy control aswell(p<0.05).This confirmed that polymorphism of PSORS1C1gene were associatedwith susceptibility to RA disease. The expression of PSORS1C1protein in synovialtissue and serum of RA patients showed significant difference compared with OApatients(P<0.05).This demonstrated that PSORS1C1may participated in pathologicalchanges of synovial tissues, or through other unknow pathway inffecting RA diseaseoccurrence or development. Therefore, this study suggests PSORS1C1gene have astrong association with RA. PSORS1C1protein may be involved in the pathogenesis ofRA disease,while the specific mechanism remains to be further studied. |
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