| Introduction: Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease, characterized by a diverse array of autoantibody production, complement activation, immune complex deposition, tissues and organs damage influenced by both genetic and environmental factors. It can affect multiple systems and organs of the body and it is difficulty to give clinical diagnosis and treatment because of diverse clinical manifestations and differences between the patients. SLE affects predominantly in women (prevalence ratio of women to men is 9 to 1) and particularly during childbearing years. The pathogenesis of SLE has not yet been fully elucidated. It was concluded that genetic and environmental factors lead to the occurrence of the disease. There are marked disparities in incidence and prevalence of SLE patients worldwide, which varies in different ethnic and geographical populations. The prevalence of SLE ranges from 31 to 70 cases per 100,000 persons among Chinese and 7 to 71 in European populations. The ethnic and genetic heterogeneity may contribute to the complexity of its clinical manifestation.Copy number variation (CNV) and single nucleotide polymorphism (SNP) are two important human variations of human diversity in the genetic basis. At present, tag SNPs-based analysis of genome-wide association studies(GWAS)in European and Asian populations have identified more than thirty robust susceptibility genes and/or loci. However, susceptibility genes that were identified by SNP-GWAS can only explain a small part of the relative risk of disease, and interpretate of 2% to 15% disease pathogen. Even if more large-scale, large sample size been analyzed, they will still not explain all the main reason of genetic risk factors. After the boom of SNP-GWAS, many research institutions concerned that how to further identified the residual value data of SNP chip. CNV analysis is part of the late GWAS using microarray data. We found uncertain results of CNV through illumine-610 chip platform, which result in stagnation of leaning CNV using the platform. In order to further understand and analysis of CNV, we have analyzed C4 CNV which strong correlation with SLE though candidate gene approach.Many progresses in the area of CNV allow us to re-examine the necessity and feasibility studies beween the clinical phenotype and disease CNP. Recently, it was found that the number of susceptibility genes in many different populations of SLE patients through SLE GWAS study. The study not only provide direct evidence for genetic factors in SLE, but also learn the the pathogenesis of SLE from level of the genome, which provides an important clues to learn SLE. Furthermore, the studies of the genotype-phenotype on the SLE have emerged, the results not only implied that SLE is a heterogeneous disease, but also demonstrated that genetic factors have an important role in the pathogenesis of SLE. The correlation of gene copy number variations and disease phenotype indicates that gene copy number related to disease clinical phenotype. Here, we performed the analysis to explore the relationships between clinical phenotype and gene copy number variations in Chinese Han population, it is important to further explore the C4 copy number variation in the pathogenesis of SLE and further clarify the role of the pathogenesis of systemic lupus erythematosus.Object: 1) To find the distribution status of C4 gene copy number (C4GCNs) in the Chinese Han population. 2) To analyze the correlation with SLE in the Chinese Han population. 3)To investigate their relationships of C4 gene copy number variation with disease clinical phenotypes, to further clarify susceptibility genes underline the pathogenesis of SLE , then to establish the appropriate animal models and confirm the association with specific phenotypes which providing evidence from functional studies.Methods: First, we recruited all samples of SLE patients and controls from two hospitals (1099 cases and 1254 cases of SLE patients with normal controls) in this study, which according to the same standards for collection, TaqMan quantitative PCR (TaqMan-based qRT-PCR) were to performed to identified C4 GCNs the distribution status in the normal population and correlation analysis with SLE population. Second, we performed case-only analyses (e.g. presence of arthritis versus no arthritis) to identify which subphenotypes were associated with gene copy number. Then, we also performed subphenotype-control analyses (e.g. presence of arthritis or negative of arthritis versus health controls) to examine the risk conferred by the gene copy number on different subtypes of SLE. Furthermore, we performed case-only analyses (e.g. presence of arthritis versus no arthritis) to identify which subphenotypes were associated with gene copy number. P values were estimated using SPSS11.0 software, which below 0.05 were considered to be statistically significant.Results: 1) The results showed that the GCN varied from 2 to 8 for total C4, from 0 to 6 for C4A, and from 0 to 5 for C4B in the normal population. Two copies of C4A are the most common counts of GCN. The distribution of C4A copy number: the frequency of <2 copy number is 7.25%; 2 copy number is 69.71 %; > 2 copy number is 23.04%, the distribution of C4B copy number: the frequency of <2 copy number is 20.16%; 2 copy number is 66.43 %;> 2 copy number is 13.41%. Four copies of total C4 is 63.56%, of which 2C4A-2C4B is about 51.94%.2) It was found that the distribution of C4 gene copy number in SLE patients. The frequencies of two copies of C4A(69.71%) and C4B(66.43%)genes are in the majority. The C4A GCN distribution is skewed towards the side of high copy number (<2, 13.10%; 2, 67.10 %;> 2, 19.81%), C4B GCN distribution is skewed towards the low side of copy number (<2, 13.10%; 2, 63.42 %;> 2, 19.81). Compared with the control sample analysis, low C4A GCN (<2) is a risk factor in SLE patients (P = 1.97×10-5; OR: 1.93; CL: 1.42-2 .62), higher C4A GCN (> 2) is no significant differences (P = 0.08). However, C4B is not clearly related to SLE. Low copy number (<4) for the risk factor in patients with SLE (P = 8.69×10-3; OR: 1.38; 95%CL: 1.09-1 .76); high copy number (> 4) is a protective factor for SLE (P = 0.04; OR: 0.79; 95% CL: 0.63-0.99). Furthermore, there was significantly increase or decrease in the frequencies of the C4 GCN due to the variations of C4A but not C4B in SLE cases. 3) Significant associations were found for C4A gene copy number variation with arthritis (P = 6.05×10-3), we examine the risks conferred by the C4A gene copy number on different subtypes of SLE; Significant associations were not found for C4 gene copy number variation with any clinical phenotype, however, we examine the risks conferred by C4 gene copy number on different subtypes of SLE.Conclusion: This study not only unfolds C4 GCNs in the Chinese normal population, but also validates that the C4 gene copy number was associated with SLE, and also identified that C4GCNs play an important role in the pathogenesis of SLE. Compared with the C4GCNs in European populations of SLE, we found that the susceptibility of copy number variation to SLE is difference in different ethnic, and the genetic heterogeneity of SLE susceptibility may play an important role. Through further analysis the clinical features, our study suggested that C4 gene copy number might be associated with arthritis, and C4 and C4A gene copy number play important roles in the development of SLE in Chinese Han population, which can conferred the risks on clinical features.The study will not only deepen our understanding of the genetic basis of the CNV, but also provide for the future mechanism to SLE. |
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