The genetics of systemic lupus erythematosus: putting the pieces together

Polygenic Risk Score Predicts Earlier-Onset Adult Systemic Lupus Erythematosus and First-Year Renal Diseases in a Taiwanese Cohort

OBJECTIVES

This study aimed to develop a predictive model using polygenic risk score (PRS) to forecast renal outcomes for adult systemic lupus erythematosus (SLE) in a Taiwanese population.

METHODS

Patients with SLE (n=2782) and matched non-SLE controls (n=11 128) were genotyped using Genome-Wide TWB 2.0 single-nucleotide polymorphism (SNP) array. PRS models (C+T, LDpred2, Lassosum, PRSice-2, PRS-continuous shrinkage (CS)) were constructed for predicting SLE susceptibility. Logistic regression was assessed for C+T-based PRS association with renal involvement in patients with SLE.

RESULTS

In the training set, C+T-based SLE-PRS, only incorporating 27 SNPs, outperformed other models with area under the curve (AUC) values of 0.629, surpassing Lassosum (AUC=0.621), PRSice-2 (AUC=0.615), LDpred2 (AUC=0.609) and PRS-CS (AUC=0.602). Additionally, C+T-based SLE-PRS demonstrated consistent predictive capacity in the testing set (AUC=0.620). Individuals in the highest quartile exhibited earlier SLE onset (39.06 vs 44.22 years, p<0.01), higher Systemic Lupus Erythematosus Disease Activity Index scores (3.00 vs 2.37, p=0.04), elevated risks of renal involvement within the first year of SLE diagnosis, including WHO class III-IV lupus nephritis (OR 2.36, 95% CI 1.47 to 3.80, p<0.01), estimated glomerular filtration rate <60 mL/min/1.73m2 (OR 1.49, 95% CI 1.18 to 1.89, p<0.01) and urine protein-to-creatinine ratio >150 mg/day (OR 2.07, 95% CI 1.49 to 2.89, p<0.01), along with increased seropositivity risks, compared with those in the lowest quartile. Furthermore, among patients with SLE with onset before 50 years, the highest PRS quartile was significantly associated with more serious renal diseases within the first year of SLE diagnosis.

CONCLUSIONS

PRS of SLE is associated with earlier onset, renal involvement within the first year of SLE diagnosis and seropositivity in Taiwanese patients. Integrating PRS with clinical decision-making may enhance lupus nephritis screening and early treatment to improve renal outcomes in patients with SLE.

Toll-like receptor 5 and Toll-like receptor 9 single nucleotide polymorphisms and risk of systemic lupus erythematosus and nephritis in Egyptian patients

Background

Toll-like (TLRs) play a crucial role in both adaptive and innate immunity. The aim of the present study was to assess the association of TLR5-rs5744168, TLR9-rs187084, and TLR9-rs352140 single nucleotide polymorphisms (SNPs) with susceptibility to systemic lupus erythematosus (SLE) and lupus nephritis (LN) in Egyptian patients.

Results

The C allele and homozygous CC genotype of the TLR9-rs352140 in co-dominant and recessive models were more prevalent in SLE patients than controls (P = 0.047, P = 0.017, and P = 0.005 respectively). In contrast, allelic and genotyping distribution of TLR5-rs5744168 and TLR9-rs187084 SNPs showed no association with the risk of SLE. The T allele of the TLR5-rs5744168 was more prevalent in LN patients than controls (P = 0.021). The homozygous TT genotype of TLR5-rs5744168 SNP was more prevalent in LN patients in the co-dominant and the recessive models than controls (P = 0.036 and P = 0.011 respectively). The C allele of the TLR9-rs352140 was more prevalent in LN patients than controls (P = 0.015). The homozygous CC genotype of the TLR9-rs352140 SNP was more prevalent in LN than controls in co-dominant and recessive models (P = 0.002 and P < 0.001). In the recessive model of the TLR5-rs5744168 SNP, the TT genotype was found in 3.2% of the SLE patients while none of the SLE patients without LN or controls had TT genotype (P = 0.036). Also, in the recessive model of the TLR9-rs352140 SNP, the CC genotype was significantly more frequent in SLE patients with LN than without LN (44.4% vs 29.9%, P = 0.045).

Conclusion

Our results support the potential role of TLR5-rs5744168 SNP and TLR9-rs3532140 SNP not only in increasing the risk for development of SLE, but also in increasing the risk of LN in SLE patients among the Egyptian population.

Association between complement gene polymorphisms and systemic lupus erythematosus: a systematic review and meta-analysis

Complement dysfunction results in impaired ability in clearing apoptotic cell debris that may stimulate autoantibody production in systemic lupus erythematosus (SLE). Herein, we provided a comprehensive search to find and meta-analyze any complement gene polymorphisms associated with SLE. The ITGAM, C1q, and MBL gene polymorphisms were included in this meta-analysis to reveal the exact association with SLE risk. Electronic databases, including Scopus, PubMed, and Google Scholar, were searched to find studies investigating the ITGAM, C1q, and MBL gene polymorphisms and SLE risk in different populations. The pooled odds ratio (OR) and its corresponding 95% confidence interval (CI) were used to analyze the association between ITGAM, C1q, and MBL gene polymorphisms and susceptibility to SLE. According to inclusion criteria, a total of 24 studies, comprising 4 studies for C1QA rs292001, 5 studies for C1QA rs172378, 9 studies for ITGAM rs1143679, 8 studies for MBL rs1800450, 3 studies for MBL2 rs1800451, and 3 studies for MBL2 rs5030737, were included in the final meta-analysis. A significant positive association was found between rs1143679 and SLE risk, while rs1800451 significantly associated with decreased SLE susceptibility. In summary, ITGAM gene rs1143679 SNP and MBL gene rs1800451 SNP were positively and negatively associated with SLE risk, respectively.

C1QTNF4 gene p.His198Gln mutation is correlated with early-onset systemic lupus erythematosus in Iranian patients

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease with multifactorial etiology. Several studies show that genetic factors have an important part in the incidence of SLE. The C1QTNF4 gene is involved in the regulation of the inflammatory pathways by pro-inflammatory function. In the present study, we have evaluated the association between C1QTNF4 gene p.His198Gln mutation and risk of SLE.

METHODS

Forty SLE patients and 40 control subjects were recruited in this case-control study. Genotyping of C1QTNF4 p.His198Gln mutation was performed using real-time polymerase chain reaction high resolution melting method.

RESULTS

We found a significant association between this mutation (GG + GC) with the risk of SLE (odds ratio = 6.33, 95% CI = 1.28-31.11). Furthermore, we observed that in the patient group, this mutation leads to early-onset SLE (19.7 ± 4.34 years for mutation carriers compared to 27.7 ± 11.4 years for wild type carriers; P = .003).

CONCLUSION

Our results suggest that this mutation (p.His198Gln) potentially has an important role in SLE risk in the Iranian population.

Retroviruses in the pathogenesis of systemic lupus erythematosus: Are they potential therapeutic targets?

The pathogenesis of systemic lupus erythematosus (SLE) is characterised by the hyper-activation of immunologic pathways related to the antiviral response. Exogenous and endogenous retroviruses, by integrating their DNA templates in the host cell genome, may epigenetically control the transcription of genes involved in the immune response. Furthermore, their nucleic acids or neo-synthesized proteins could stimulate the sensor molecules placed upstream the inflammatory cascade. Exogenous retroviruses, like human immunodeficiency virus, have been associated to SLE-like manifestations or to a fair SLE diagnosis. In addition, there is some evidence confirming a pathogenic role of human endogenous retroviruses in SLE. In line with these data, the use of antiretroviral agents could represent an attractive opportunity in the future therapeutic algorithms of this disease, but studies are still missing.

The Role of MECP2 and CCR5 Polymorphisms on the Development and Course of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic and systemic autoimmune disease. SLE is described by production of autoantibodies and causes damage of many organs. T-cells play a crucial role in SLE pathogenesis. T-cells intensify inflammation through a number of processes, which leads to autoimmunization. CCR5 and MECP2 genes are linked with T-cells and pathogenesis of SLE. Polymorphisms in these genes are related with the prognostic factors of risk of disease onset and disease severity. The aim of this study was to estimate the influence of polymorphisms in MECP2 and CCR5 genes on the development and course of systemic lupus erythematosus. We examined 137 SLE patients and 604 healthy controls. We studied polymorphisms for CCR5 gene: rs333 and for MECP2: rs2075596, rs1734787, rs17435, and rs2239464. We genotyped our MECP2 samples and we performed a restriction fragment length polymorphism (RFLP) analysis for CCR5 samples. We showed a risk factor for allele T in rs17435 and for allele A in rs2075596 in MECP2. We noticed that MECP2 rs2075596 G/A, rs1734787 C/A, rs17435 A/T, and rs2239464 G/A polymorphisms are more prevalent in SLE patients than in healthy controls. We believe that above-mentioned MECP2 polymorphisms can be considered as SLE susceptibility factor.

Serum/plasma homocysteine levels in patients with systemic lupus erythematosus: a systematic review and meta-analysis

Published studies have shown contradictory results in the association of serum/plasma levels of homocysteine (HCY) with systemic lupus erythematosus (SLE). This study is to systematically evaluate the association of serum/plasma HCY levels in SLE. A search was done using PubMed, Embase, Web of Science, and ScienceDirect databases up to 7 April 2019. Thirty-six articles including 2919 SLE patients and 3120 healthy controls were finally included in this meta-analysis. The HCY levels were significantly higher in SLE patients than in healthy controls (P < 0.001). The subgroup analysis revealed that Asian, African, Arab, Mixed, White and others as well as ages (< 35 and ≥ 35) had significant higher HCY levels in SLE patients than in the healthy controls. The study indicated that patients with disease activity index scores < 8 (P < 0.001) and ≥ 8 (P = 0.003) of SLE had significant higher HCY levels as compared with the healthy controls. It was also revealed that disease duration in SLE patients for < 10 and ≥ 10 years (P < 0.001) had significant higher HCY levels as compared with the healthy controls. A significant higher HCY level for body mass index (< 23 and ≥ 23) was found as well as measurement type in SLE patients than healthy controls. This meta-analysis demonstrated higher HCY levels in patients with SLE than healthy controls, suggesting a possible role of HCY in the disease.Key Points• Homocysteine (HCY) is closely related to the mechanisms of systemic lupus erythematosus (SLE).• This study reveals a significant correlation between HCY levels and the various indexes of disease activity.• This study reveals that medication may influence HCY levels in SLE.• This study also discovers that the subgroup analysis of all the factors influences the HCY levels in SLE patients.

Effects of Major Epigenetic Factors on Systemic Lupus Erythematosus

The pathogenesis of systemic lupus erythematosus (SLE) is influenced by both genetic factors and epigenetic modifications; the latter is a result of exposure to various environmental factors. Epigenetic modifications affect gene expression and alter cellular functions without modifying the genomic sequences. CpG-DNA methylation, histone modifications, and miRNAs are the main epigenetic factors of gene regulation. In SLE, global and gene-specific DNA methylation changes have been demonstrated to occur in CD4+ T-cells. Moreover, histone acetylation and deacetylation inhibitors reverse the expression of multiple genes involved in SLE, indicating histone modification in SLE. Autoreactive T-cells and B-cells have been shown to alter the patterns of epigenetic changes in SLE patients. Understanding the molecular mechanisms involved in the pathogenesis of SLE is critical for the introduction of effective, target-directed and tolerated therapies. In this review, we summarize the recent findings that highlight the importance of epigenetic modifications and their mechanisms in SLE.

Systemic lupus erythematosus with and without a family history: a meta-analysis

Objective The objective of this paper is to investigate the association of clinical manifestations and laboratory parameters between familial systemic lupus erythematosus (SLE) and sporadic SLE. Methods All relevant literature was retrieved from the PubMed, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI) databases. The qualities of these studies were evaluated using a modified version of the Newcastle-Ottawa scale. The characteristics and clinical manifestations of involved individuals were extracted from each study. Pooled odds ratio (OR) was calculated using the random effects-method, and the heterogeneity between studies was quantified using the I² statistic. Results Of 330 studies identified by the search strategy, six were included in this review. In total, 733 cases were familial SLE and 1405 were sporadic SLE. Analysis revealed that photosensitivity, nephritis and thrombocytopenia were negatively associated with familial SLE, with OR (95% CI) values of 0.73 (0.60-0.89), 0.72 (0.59-0.88) and 0.75 (0.57-0.98), respectively. Conclusions Photosensitivity, thrombocytopenia and renal involvement could be more common in non-familial SLE, which should be further confirmed by well-designed studies with large populations.

TLR9 polymorphisms and systemic lupus erythematosus risk: an update meta-analysis study

It has been reported that the Toll-like receptor 9 (TLR9) gene polymorphisms may be associated with systemic lupus erythematosus (SLE) risk. However, some studies yielded conflicting results. Therefore, a comprehensive meta-analysis was performed to assess the precise association between TLR9 polymorphisms and SLE susceptibility. We performed a systematic search in PubMed, Embase (Ovid), China National Knowledge Internet, and Wanfang databases up to July 15, 2015. Odds ratio (OR) and 95 % confidence interval (CI) were used to pool the effect size. Statistical analyses were performed with STATA 11.0 software. In total, 21 studies from nineteen articles with 10,273 subjects were included in this meta-analysis. The overall results suggested that there was a statistically significant association between TLR9 rs187084 polymorphism and SLE risk observed in recessive model (TT vs. TC + CC: OR 1.17, 95 % CI 1.05-1.30, P = 0.005), codominant model (TT vs. CC: OR 1.22, 95 % CI 1.03-1.43, P = 0.019), and allele model (T vs. C: OR 1.15, 95 % CI 1.02-1.30, P = 0.020) in Asians. However, we found that there may be no significant association between the other three TLR9 polymorphisms and SLE risk in either Asians or non-Asians. In conclusion, the meta-analysis results suggested that TLR9 rs187084 polymorphism may increase the risk of SLE in Asians. However, no significant association between TLR9 SNPs (rs352139, rs352140, and rs5743836) and SLE risk was identified.

Clinical significance of anti-C1q antibodies in SLE

Lupus nephritis (LN) is a severe and frequent complication of systemic lupus erythematosus (SLE). Untreated cases very often lead to patients’ death; therefore, it is important to use markers sensitive and specific enough for the diagnosis and subsequent monitoring of nephritis. Autoantibodies against double-stranded DNA (anti-dsDNA) are believed to play a major role in SLE in general and so their significance in prediction and monitoring of glomerular inflammation is low. For prediction of renal flares and effective, well-timed therapy, it is required to have an appropriate marker available. In our study, we have tested sera of 85 SLE patients with or without LN. The criterion for LN determination was the degree of proteinuria (persistent proteinuria > 0.5 g/day, according to ACR criteria for LN). Disease activity was described by SLE disease index (SLEDAI) score, renal functions were stated according to British Isles Lupus Assessment Group score. There were anti-C1q, total anti-dsDNA and high-avidity anti-dsDNA detected in the patients’ sera. We did not find any significant difference in average SLEDAI value between patients with renal and non-renal organ complications. Positivity of anti-C1q was more frequent in patients with nephritis than in those without any history of renal disease (58.3 vs. 39.1%). Higher prevalence of these antibodies was evident in patients with clinically active LN than in those without renal improvement (73.1 vs. 39.1%). When comparing anti-C1q with antibodies against structures of DNA, significant differences were found in case of high avidity anti-dsDNA. Our results have confirmed the studies showing that anti-C1q antibodies could serve as a reliable serological marker of LN activity along with other laboratory tests. Detection of anti-C1q together with high avidity anti-dsDNA antibodies seems to be a good algorithm for the prediction of possible renal flares in SLE patients.

Relation between HLA typing and clinical presentations in Systemic Lupus Erythematosus patients in Al-Qassim region, Saudi Arabia

BACKGROUND

Systemic lupus erythematosus (SLE) is a disease with diverse clinical presentations due to interaction between genetic and environmental factors. SLE is associated worldwide with polymorphisms at various loci, including the major histocompatibility complex (MHC), although inconsistencies exist among these studies.

AIMS

This study was carried out to investigate, the association of HLA-DRB1, DRB3, DRB4, DRB5, and DQB1 alleles in SLE patients and clinical presentations at Qassim, Saudi Arabia.

METHODS

Fifty one patients with SLE-84.3% of whom had kidney involvement were studied in a case control study for HLA-DRB1, DRB3, DRB4, DRB5, and DQB1.

RESULTS

It was found that DRB3 is a protective gene among Saudi's against SLE, HLA DRB3, HLA DRB1*11 frequency was increased in patients with serositis with a p value of (0.004), (0.047) respectively, increased frequency of HLA DQB1*3 among SLE patients with skin manifestations with a p value of (0.041), the frequency of HLA DRB1*15 alleles was increased among SLE patients with nephritis with a p value of (0.029), the frequency of HLA DRB1*11 among those with hematological manifestations with a p value of (0.03) and the frequency DRB1*10 was found to be increased among SLE patients with neurological manifestations with a p value of (0.002).

CONCLUSION

In contradistinction to what have been found among other populations DRB3 is a protective gene among Saudi's against SLE. No evidence for a role of the HLA-DRB1, DRB4, DRB5, DQB1 alleles. There was an increased HLA DRB3 frequency with serositis, DQB1*3 skin manifestations, HLA DRB1*15 with nephritis, DRB1*10 with hematological manifestations and DRB1*11 with neurological manifestations.

Diet influences expression of autoimmune-associated genes and disease severity by epigenetic mechanisms in a transgenic mouse model of lupus

OBJECTIVE

Lupus flares occur when genetically predisposed individuals encounter appropriate environmental agents. Current evidence indicates that the environment contributes by inhibiting T cell DNA methylation, causing overexpression of normally silenced genes. DNA methylation depends on both dietary transmethylation micronutrients and ERK-regulated DNA methyltransferase 1 (DNMT-1) levels. We used transgenic mice to study the effect of interactions between diet, DNMT-1 levels, and genetic predisposition on the development and severity of lupus.

METHODS

A doxycycline-inducible ERK defect was bred into lupus-resistant (C57BL/6) and lupus-susceptible (C57BL/6 × SJL) mouse strains. Doxycycline-treated mice were fed a standard commercial diet for 18 weeks and then switched to a transmethylation micronutrient-supplemented (MS) or -restricted (MR) diet. Disease severity was assessed by examining anti-double-stranded DNA (anti-dsDNA) antibody levels, the presence of proteinuria and hematuria, and by histopathologic analysis of kidney tissues. Pyrosequencing was used to determine micronutrient effects on DNA methylation.

RESULTS

Doxycycline induced modest levels of anti-dsDNA antibodies in C57BL/6 mice and higher levels in C57BL/6 × SJL mice. Doxycycline-treated C57BL/6 × SJL mice developed hematuria and glomerulonephritis on the MR and standard diets but not the MS diet. In contrast, C57BL/6 mice developed kidney disease only on the MR diet. Decreasing ERK signaling and methyl donors also caused demethylation and overexpression of the CD40lg gene in female mice, consistent with demethylation of the second X chromosome. Both the dietary methyl donor content and the duration of treatment influenced methylation and expression of the CD40lg gene.

CONCLUSION

Dietary micronutrients that affect DNA methylation can exacerbate or ameliorate disease in this transgenic murine lupus model, and contribute to lupus susceptibility and severity through genetic-epigenetic interactions.

Autoantibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with multigenic inheritance and various environmental factors implicated in its aetiopathogenesis. Despite the multiple mechanisms involved in the aetiology of SLE being elusive, recent studies have made progress in our understanding of the pathogenic mechanisms via abnormal regulation of cell-mediated and humoral immunity that lead to tissue damage. The heterogeneity of the clinical manifestations probably reflects the complexity of the disease pathogenesis itself. The immune system in SLE is characterised by a complex interplay between overactive B cells, abnormally activated T cells and antigen-presenting cells. This interplay leads to the production of an array of inflammatory cytokines, apoptotic cells, diverse autoantibodies and immune complexes that in turn activate effector cells and the complement system, leading to tissue injury and damage which are the hallmarks of the clinical manifestations. SLE patients have dysregulation of inflammatory cytokines, chemokines and immune response-related genes, as well as of the genes involved in apoptosis, signal transduction and the cell cycle.

Environmental exposure, estrogen and two X chromosomes are required for disease development in an epigenetic model of lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease primarily afflicting women. The reason for the gender bias is unclear, but genetic susceptibility, estrogen and environmental agents appear to play significant roles in SLE pathogenesis. Environmental agents can contribute to lupus susceptibility through epigenetic mechanisms. We used (C57BL/6xSJL)F1 mice transgenic for a dominant-negative MEK (dnMEK) that was previously shown to be inducibly and selectively expressed in T cells. In this model, induction of the dnMEK by doxycycline treatment suppresses T cell ERK signaling, decreasing DNA-methyltransferase expression and resulting in DNA demethylation, overexpression of immune genes Itgal (CD11a) and Tnfsf7 (CD70), and anti-dsDNA antibody. To examine the role of gender and estrogen in this model, male and female transgenic mice were neutered and implanted with time-release pellets delivering placebo or estrogen. Doxycycline induced IgG anti-dsDNA antibodies in intact and neutered, placebo-treated control female but not male transgenic mice. Glomerular IgG deposits were also found in the kidneys of female but not male transgenic mice, and not in the absence of doxycycline. Estrogen enhanced anti-dsDNA IgG antibodies only in transgenic, ERK-impaired female mice. Decreased ERK activation also resulted in overexpression and demethylation of the X-linked methylation-sensitive gene CD40lg in female but not male mice, consistent with demethylation of the second X chromosome in the females. The results show that both estrogen and female gender contribute to the female predisposition in lupus susceptibility through hormonal and epigenetic X-chromosome effects and through suppression of ERK signaling by environmental agents.

A naturally occurring variant in human TLR9, P99L, is associated with loss of CpG oligonucleotide responsiveness

The innate immune system employs Toll-like receptors (TLRs) for the detection of invading microorganisms based on distinct molecular patterns. For example, TLR9 is activated by microbial DNA and also by short therapeutic CpG-containing oligonucleotides (CpG-ODN). TLR9 activation leads to the production of interferons and the priming of humoral adaptive immune responses. Unfortunately, the principles of ligand recognition by TLR9 are poorly understood, and genetic variants of TLR9, which may affect its function, have not been characterized systematically on the molecular level. We therefore sought to functionally characterize reported single nucleotide polymorphisms of TLR9 in the HEK293 model system. We discovered that two variants, P99L and M400I, are associated with altered receptor function regarding NF-κB activation and cytokine induction. Our investigations show that for the most functionally impaired variant, P99L, the ability to respond to physiological and therapeutic TLR9 ligands is severely compromised. However, CpG-ODN binding is normal. CpG-ODN recognition by TLR9 thus appears to involve two separate events, CpG-ODN binding and sensing. Our studies highlight Pro-99 as a residue important for the latter process. In genotyping studies, we confirmed that both M400I (rs41308230) and P99L (rs5743844) are relatively rare variants of TLR9. Our data add rs41308230 and rs5743844 to the list of functionally important TLR variants and warrant further research into their relevance for infectious disease susceptibility or responsiveness to CpG-ODN-based therapies.

Spontaneous lupus-like syndrome in HLA-DQ2 transgenic mice with a mixed genetic background

To investigate the role of HLA-DQ2 in the pathogenesis of associated immune disorders, we generated transgenic mice that expressed HLA-DQ2 in the absence of endogenous murine class II molecules (AE(0)DQ2). These AE(0)DQ2 mice with a mixed genetic background spontaneously developed skin lesions on their ears, whereas control AE(0)DQ6 genotype control mice (also with a mixed genetic background) did not. The skin lesions were characterized by deep subepidermal blistering with hydropic degeneration and lymphoid infiltration in the subepidermal area as determined by histopathology. Immunofluorescence analysis revealed thick band-like granular deposition of IgG, IgM, and a thin band of IgA deposition along the basement membrane. AE(0)DQ2 mice also developed significant and progressive hematuria and proteinuria as compared with the AE(0)DQ6 mice (p < 0.05). Histopathology showed immune complex deposits in the glomeruli of AE(0)DQ2 mice. Immunofluorescence analysis showed progressive mesangial and capillary wall deposition of IgA, IgM, IgG and C1q in the kidney. With electron microscopy, the deposits showed a 'fingerprint' substructure; and tubuloreticular structures were identified within endothelial cells. Conversely, these changes were not observed in AE(0)DQ6 mice. Serum anti-double stranded (ds)DNA IgM and IgG levels were also significantly elevated among AE(0)DQ2 mice compared with AE(0)DQ6 mice (p < 0.001). In conclusion, AE(0)DQ2 mice spontaneously develop an autoimmune lupus-like syndrome and are useful model for this disease. It remains to be determined whether genetic admixture played a role in the development of this systemic lupus erythematosus-like syndrome in HLA-DQ2 transgenic mice. Lupus (2010) 19, 815-829.

Fcgamma receptor IIB and IIIB polymorphisms and susceptibility to systemic lupus erythematosus and lupus nephritis: a meta-analysis

The aim of this study was to explore whether polymorphisms of the Fcgamma receptors (FcgammaRs) IIB T/I232 and FcgammaRIIIB NA1/NA2, confer susceptibility to systemic lupus erythematosus (SLE) and lupus nephritis (LN). The authors conducted a meta-analysis on associations between the FcgammaRIIB T/I232 and FcgammaRIIIB NA1/NA2 polymorphisms and SLE and LN susceptibility as determined using 1) allele contrast, 2) recessive, 3) dominant models and 4) contrast of homozygotes. A total of 16 separate comparisons were considered, consisting of 2887 SLE patients and 3105 controls. Meta-analysis of the FcgammaRIIB T/I232 polymorphism showed a significant association between the FcgammaRIIB T allele and the risk of developing SLE compared with the FcgammaRIIB I allele (OR = 1.207, 95% CI = 1.061-1.373, P = 0.004). In subjects of Asian descent, a significant association was observed between the FcgammaRIIB T allele and SLE (OR = 1.332, 95% CI 1.138-1.558, P < 0.001). However, in Europeans no such association was found. In contrast, no association was found between SLE or LN and the FcgammaRIIIB NA1/NA2 polymorphism in all subjects, or in European and Asian populations. This meta-analysis shows that the FcgammaRIIB T/I232 polymorphism confers susceptibility to SLE, especially in Asian-derived populations.

Replication of recently identified systemic lupus erythematosus genetic associations: a case-control study

Introduction

We aimed to replicate association of newly identified systemic lupus erythematosus (SLE) loci.

Methods

We selected the most associated SNP in 10 SLE loci. These 10 SNPs were analysed in 1,579 patients with SLE and 1,726 controls of European origin by single-base extension. Comparison of allele frequencies between cases and controls was done with the Mantel–Haenszel approach to account for heterogeneity between sample collections.

Results

A previously controversial association with a SNP in the TYK2 gene was replicated (odds ratio (OR) = 0.79, P = 2.5 × 10-⁵), as well as association with the X chromosome MECP2 gene (OR = 1.26, P = 0.00085 in women), which had only been reported in a single study, and association with four other loci, 1q25.1 (OR = 0.81, P = 0.0001), PXK (OR = 1.19, P = 0.0038), BANK1 (OR = 0.83, P = 0.006) and KIAA1542 (OR = 0.84, P = 0.001), which have been identified in a genome-wide association study, but not found in any other study. All these replications showed the same disease-associated allele as originally reported. No association was found with the LY9 SNP, which had been reported in a single study.

Conclusions

Our results confirm nine SLE loci. For six of them, TYK2, MECP2, 1q25.1, PXK, BANK1 and KIAA1542, this replication is important. The other three loci, ITGAM, STAT4 and C8orf13-BLK, were already clearly confirmed. Our results also suggest that MECP2 association has no influence in the sex bias of SLE, contrary to what has been proposed. In addition, none of the other associations seems important in this respect.

Clinicopathological characteristics of familial SLE patients with lupus nephritis

This study aimed to analyze the clinicopathological characteristics of familial SLE patients with lupus nephritis (LN). A total of 136 Chinese patients with lupus nephritis diagnosed by renal biopsy, including 34 familial patients and 102 sporadic cases, were recruited. Their demographic information, age of onset, disease duration, clinical features, laboratory data and histological manifestations were compared. The first-degree relatives (17 sibling cases and eight parent-offspring cases) of familial SLE patients were primarily affected. The prevalence of fever, rash and arthritis in familial subjects was higher than that in sporadic subjects. Familial patients had lower platelet counts and higher low-density lipoprotein. In familial patients, class V lupus nephritis was less common. After adjusted with the Benjamini and Hochberg procedure, however, fever was the only feature occurring significantly and more frequently in familial patients (58.8% vs 26.5%, P = 0.001). Moreover, SLEDAI and other clinicopathological features did not differ significantly between the two groups. Multivariate analysis showed that a higher prevalence of fever was an independent predictor of familial SLE. Most clinicopathological features in familial SLE patients were not significantly different from those in sporadic patients; the severity of LN in familial SLE patients was similar to that of sporadic cases. Thus, familial SLE may not be a different clinical entity.

Association study of a single nucleotide polymorphism in the exon 2 region of toll-like receptor 9 (TLR9) gene with susceptibility to systemic lupus erythematosus among Chinese

Toll-like receptor 9 (TLR9) plays an important role in the induction and regulation of the innate immune system or adaptive immune responses. Genetic variations within human TLR9 have been reported to be associated with a range of immune-related diseases, such as asthma, systemic lupus erythematosus (SLE) and so on. Family-based association analysis was performed to further investigate whether a single nucleotide polymorphism (rs352140) in the exon 2 region of TLR9 gene is associated with susceptibility to SLE in a Chinese population. A total of 77 patients with SLE from 74 nuclear families, aged from 12 to 63 years, were enrolled according to 1997 criteria of American College of Rheumatology (ACR), 211 family members of these patients were also included. Genotyping was performed by PCR-restriction fragment length polymorphism (PCR-RFLP) assay. Among 77 patients with SLE, the CC, CT and TT genetype frequencies of the SNP (rs352140) were 20.8, 61.0 and 18.2%, respectively. Single loci analysis suggested that the T allele at position of rs352140 was significantly associated with the susceptibility to SLE (Z = 2.357, P = 0.018402) in dominant model, but not in additive or recessive model. Genetype analysis showed that individuals with CT genetype had greater susceptibility to SLE than those without (Z = 2.004, P = 0.045067). Our study suggests that a single nucleotide polymorphism (rs352140) in the exon 2 region of TLR9 gene may be a susceptibility factor for SLE in Chinese population.

The genetics of SLE: an update in the light of genome-wide association studies

Understanding the pathogenesis of SLE remains a considerable challenge. Multiple abnormalities of both the innate and adaptive immune system have been described and, furthermore, immunological dysfunction precedes clinical presentation by many years. There is a strong genetic basis to SLE, which means that genetic studies can play a key role in furthering our understanding of this disease. Since susceptibility variants are present from birth and are unaffected by the course of the disease, or by its treatment, genetic analysis is, perhaps uniquely, capable of identifying fundamental, causative, disease mechanisms. Over the last 12 months, there has been a staggering increase in our understanding of SLE genetics. We have seen the identification of new and important SLE susceptibility genes through candidate gene studies, and we have seen the publication of two whole-genome association analyses. The 'hypothesis free' whole-genome studies have provided additional evidence in support of a number of existing susceptibility genes and have identified novel gene candidates. In this article, we review the current SLE genetics literature in the light of these recent advances and we discuss our current understanding of the functional role of the key susceptibility genes. By considering how these genes fall into clusters with shared function we can begin to understand how dysregulation at a number of key immunological steps may predispose to the development of SLE.

Fc receptor genes and the systemic lupus erythematosus diathesis

Fc receptors represent a distinct group of hematopoeitic cell surface glycoproteins that have a characterized role in affecting the efficiency of the mononuclear phagocyte system to clear IgG immune complexes. Functional genetic variations in this family of receptors have been identified as heritable susceptibility factors for SLE and lupus nephritis across diverse populations. In this review, we describe the roles of the classical Fc receptors for IgG (Fc gamma) and non-classical Fc-like receptors (FCR1-FCRL6L), Fc receptors for IgE (Fc epsilon RI) and IgA and IgM (Fc alpha/mu R) in SLE diathesis. The combined effects of these genes on SLE pathogenesis, either via linkage disequilibrium or epistasis with additional genetic or environmental factors, provide a challenge for future investigations. The pursuit of a polygenic SLE-profile that includes longitudinal evaluations of SLE and markers involved in the protean clinical manifestations associated with SLE will facilitate our understanding of the cascade of inflammatory events associated with the diathesis.

Risks and relative risks of Wegener's granulomatosis among close relatives of patients with the disease

OBJECTIVE

The etiology of Wegener's granulomatosis (WG) supposedly involves interplay between genetic susceptibility and environmental triggers. However, little is known about whether WG actually clusters in families. Information on the degree of familial aggregation in WG is of clinical relevance, because patients with WG often want to know whether their diagnosis puts their closest relatives at increased risk of the disease. The aim of this study was to investigate the risk of WG in relatives of patients with WG.

METHODS

Using Swedish nationwide registers on morbidity, family structure, and vital status, we compared the occurrence of WG (register-based plus chart review) among 6,670 first-degree relatives and 428 spouses of 1,944 Swedish patients with WG with the occurrence among 68,994 first-degree relatives and 4,812 spouses of 19,655 control subjects from the general population. Relative risks were estimated using the Cox proportional hazards regression model.

RESULTS

Two of the 6,670 first-degree relatives of patients with WG and 13 of the 68,994 first-degree relatives of their population controls had WG, resulting in a relative risk of 1.56 (95% confidence interval 0.35-6.90). None of the 428 spouses of patients had WG.

CONCLUSION

In absolute terms, the occurrence of WG among close biologic and nonbiologic relatives of patients with WG is low. In terms of relative risk, our results provide strong evidence against a pronounced increase in familial risk such as that noted for systemic lupus erythematosus, irritable bowel disease, and multiple sclerosis but are compatible with familial aggregation of a magnitude similar to that for rheumatoid arthritis.

Familial lupus and antiphospholipid syndrome

The occurrence of systemic lupus erythematosus (SLE) in several members of a family has spurred intense efforts to identify susceptibility genes predisposing to the disease. As a result, a number of candidate association genes in different ethnic groups have been identified, and some genes have been linked to specific lupus manifestations. Particularly where familial disease occurs in childhood, and especially when it occurs prior to puberty, complement deficiencies and other immunologic defects should be explored. Evidence of other forms of autoimmunity, including autoimmune thyroiditis and antiphospholipid syndrome (APS), is common in families with SLE. Familial APS is uncommon in the absence of other thrombophilic defects, but occasionally is seen with apparent autosomal dominant inheritance. Thus far, no firm gene associations have been identified for APS, in part because of the rarity of multiplex families to study. A search for other familial causes of thrombotic disease should be performed when APS occurs in more than one family member.

Current status of lupus genetics

Over the past 40 years more than 100 genetic risk factors have been defined in systemic lupus erythematosus through a combination of case studies, linkage analyses of multiplex families, and case-control analyses of single genes. Multiple investigators have examined patient cohorts gathered from around the world, and although we doubt that all of the reported associations will be replicated, we have probably already discovered many of the genes that are important in lupus pathogenesis, including those encoding human leukocyte antigen-DR, Fcγ receptor 3A, protein tyrosine phosphatase nonreceptor 22, cytotoxic T lymphocyte associated antigen 4, and mannose-binding lectin. In this review we will present what is known, what is disputed, and what remains to be discovered in the world of lupus genetics.

Differential expression in lupus-associated IL-10 promoter single-nucleotide polymorphisms is mediated by poly(ADP-ribose) polymerase-1

Systemic lupus erythematosus (SLE) is a complex, multifactorial autoimmune disease characterized by the dysregulation of T and B cells that leads to hyperactivity of B cells and production of autoantibodies, and involves both environmental and genetic factors. Interleukin-10 (IL-10) is a candidate susceptibility gene in SLE. In particular, three IL-10 promoter single-nucleotide polymorphisms (SNPs; -1082A/G, -819T/C and -592A/C) are strongly associated with the pathogenesis of SLE. We found that the homozygous GCC haplotype linked to greater SLE severity confers higher IL-10 gene transcriptional activity than the ATA haplotype in macrophages that encounter apoptotic cells, because of the differential DNA binding to the -592 SNP by a nuclear protein uniquely induced by apoptotic cells. We identified this protein as poly(ADP-ribose) polymerase-1, confirmed its physiological role and characterized its molecular properties in modulating IL-10 production during phagocytosis of apoptotic cells. This study unveils a novel direct link between DNA damage repair/apoptosis pathways and IL-10-mediated immune regulation.

Altered Expression of Fc and Complement Receptors on B Cells in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by B cell hyper-reactivity, autoantibody production, immune complex (IC) deposition, and multiple organ damage. The contribution of IC and B cell-mediated changes in the pathogenesis of SLE is well established, however, the exact role of IC-binding receptors expressed on B cells, Fcgamma receptors, and complement receptors CR1 and CR2 in these pathological processes is unclear. Development of lupus-like symptoms in mice defective for the inhibitory Fc-gammaRIIb and genetic association of certain FcgammaR genes with SLE demonstrate a significant role for these receptors but reports indicating alterations of Fcgamma or complement receptor-mediated B cell functions in human SLE are relatively few. The present review highlights a selected set of data including our own discussing the significance of animal models, genetics, and functional alterations of these IC-binding receptors in the etiopathogenesis of SLE.

Reversal of autoimmune disease in lupus-prone New Zealand black/New Zealand white mice by nonmyeloablative transplantation of purified allogeneic hematopoietic stem cells

Patients with severe systemic lupus erythematosus (SLE) refractory to conventional treatment are candidates for autologous hematopoietic stem cell (HSC) transplantation if the intent is to reset the immunologic clock. These patients might be candidates for allotransplantation with (SLE)-resistant major histocompatibility complex (MHC) haplotype-matched HSC if partial or complete replacement of an autoimmune-prone system is the intent. Using lupus-prone New Zealand black x New Zealand white (NZBW) mice, we investigated the use of highly enriched, haplomismatched, allogeneic HSC to prevent development of or to treat established autoimmune pathology. Young NZBW mice receiving purified allogeneic HSC transplants had improved survival, decreased proteinuria, circulating immune complexes, and autoantibodies to nuclear antigens than did untreated mice or mice given NZBW HSCs. NZBW mice with established lupus-like disease that received nonmyeloablative conditioning and transplants of (MHC) haplomismatched allogeneic HSCs also had greatly increased overall survival. Mice that received transplants exhibited stabilization or reversal of their lupus symptoms; stabilized or decreased proteinuria, and a lower frequency of elevated circulating immune complexes or autoantibodies than did control mice. Induction of durable mixed chimerism by transplantation of purified allogeneic HSCs after nonmyeloablative conditioning has the potential to reverse symptoms of established NZBW lupus.

Cutaneous lupus erythematosus: understanding of clinical features, genetic basis, and pathobiology of disease guides therapeutic strategies

Cutaneous features of the protean disease lupus erythematous (LE) constitute 4 of 11 diagnostic criteria for systemic lupus erythematosus (SLE) and are exhibited by approximately 3/4 of patients during the course of their disease. Because the pathogenesis of LE is multifactorial and polygenic, many of the details of the pathogenesis remain unclear. We review here the clinical features of cutaneous lupus and recent genetic data that elucidate potential candidate genes for both cutaneous lupus erythematosus (CLE) and SLE. We discuss advances in elucidating the autoimmune pathogenesis of CLE and SLE. Furthermore, promising experimental therapies based on these advances are reviewed in the context of B cell directed therapies, T cell directed therapies, disruption of B and T cell interactions, cytokine directed therapies and finally, end-effector targeted therapies.

Effect of glutathione S-transferase polymorphisms and proximity to hazardous waste sites on time to systemic lupus erythematosus diagnosis: results from the Roxbury lupus project

OBJECTIVE

The high prevalence of systemic lupus erythematosus (SLE) among African American women may be due to environmental exposures, genetic factors, or a combination of factors. Our goal was to assess association of residential proximity to hazardous waste sites and genetic variation in 3 glutathione Stransferase (GST) genes (GSTM1, GSTT1, and GSTP1) with age at diagnosis of SLE.

METHODS

Residential histories were obtained by interviewing 93 SLE patients from 3 predominantly African American neighborhoods in Boston. Residential addresses and locations of 416 hazardous waste sites in the study area were geocoded using ArcView software. Time-varying Cox models were used to study the effect of residential proximity to hazardous sites, GST genotype, and interaction between genotype and exposure in determining age at diagnosis.

RESULTS

The prevalence of SLE among African American women in these neighborhoods was 3.56 SLE cases per 1,000. Homozygosity for GSTM1-null and GSTP1 Ile105Val in combination was associated with earlier SLE diagnosis (P = 0.03), but there was no association with proximity to 416 hazardous sites. Available data on specific site contaminants suggested that, at a subset of 67 sites, there was higher potential risk for exposure to volatile organic compounds (P < 0.05 with Bonferroni correction). GST genotypes had a significant interaction with proximity (P = 0.03) in analyses limited to these sites.

CONCLUSION

There was no independent association between residential proximity to hazardous waste sites and the risk of earlier SLE diagnosis in this urban population. However, analysis of a limited number of sites indicated that the risk of earlier SLE associated with proximity to hazardous sites might be modulated by GST polymorphisms.

Know thy neighbor: a survey of diseases and complex syndromes that map to chromosomal regions encoding TRP channels

On the basis of their ever-expanding roles, not only in sensory signaling but also in a plethora of other, often Ca(2+)-mediated actions in cell and whole body homeostasis, it is suggested that mutations in TRP channel genes not only cause disease states but also contribute in more subtle ways to simple and complex diseases. A survey is therefore presented of diseases and syndromes that map to one or multiple chromosomal loci containing TRP channel genes. A visual map of the chromosomal locations of TRP channel genes in man and mouse is also presented.

Clinical, serologic, and genetic profiles of patients with associated Sjögren's syndrome and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS) can coexist in patients. The aim of this study was to investigate the clinical, laboratory, and serologic features of the association of the two diseases. Data from 56 patients having both SS and SLE were analyzed, with special emphasis on their clinical, laboratory, and serologic features. Data from 50 patients with SLE and 50 patients with SS served as control subjects. The mean age in SS-SLE group was lower than in patients with SS but higher than patients with SLE. When SLE and SS were associated, presence of rheumatoid factor was less frequent, whereas anti-Ro/SS-A, anti-La/SS-B, antinuclear, anti-DNA, and antiphospholipid autoantibodies appeared more often. Antiphospholipid syndrome, anemia, leucopenia, and lymphopenia were more frequent in the associated disease than in patients with SS alone. In SS-SLE patients, pulmonary, renal, skin, central nervous system involvement, and serositis occurred more often than in patients with SS alone. Thyroiditis, autoantibodies to Ro/SS-A, La/SS-B and ds-DNA was more frequent in the SS-SLE group than in patients with SLE. Genetic background of the patients did not differ significantly. In conclusion, characteristic clinical, laboratory and serologic features distinguish between the association of SS and SLE and the primary forms of these two diseases.

Unraveling the genetics of systemic lupus erythematosus

The capacity to locate polymorphisms on a virtually complete map of the human genome coupled with the ability to accurately evaluate large numbers (by historical standards) of genetic markers has led to gene identification in complex diseases, such as systemic lupus erythematosus (SLE or lupus). While this is a phenotype with enormous clinical variation, the twin studies and the observed familial aggregation, along with the genetic effects now known, suggest a strong genetic component. Unlike type 1 diabetes, lupus genetics is not dominated by the powerful effect of a single locus. Instead, there are at least six known genetic association effects in lupus of smaller magnitude (odds ratio <2), and at least 17 robust linkages (established and arguably confirmed independently) defining potentially responsible genes that largely remain to be discovered. The more convincing genetic associations include the human leukocyte antigen region (with multiple genes), C1q, PTPN22, PDCD1, Fc receptor-like 3, FcgammaRIIA, FcgammaRIIIA, interferon regulatory factor 5, and others. How they contribute to disease risk remains yet to be clarified, beyond the obvious speculation derived from what has previously been learned about these genes. Certainly, they are expected to contribute to lupus risk independently and in combination with each other, with genes not yet identified, and with the environment. A substantial number of genes (>10) are expected to be identified to contribute to lupus or in its many subsets defined by clinical and laboratory features.

Role of B cell inhibitory receptor polymorphisms in systemic lupus erythematosus: a negative times a negative makes a positive

B lymphocytes play a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). Here, we will review our studies on the role of polymorphisms of two genes coding for B cell inhibitory receptors, FCGR2B and CD72. In FCGR2B, a single nucleotide polymorphism leading to a nonsynonymous substitution, Ile232Thr, within the transmembrane domain was identified, and a significant association of the 232Thr/Thr genotype with SLE was observed in Japanese, Thai and Chinese populations, while this allele was found to be rare in Caucasians. On the other hand, the association of FCGR2B promoter polymorphism with SLE in Caucasians has been reported by two independent groups, but this allele was not found to be present in Japanese. These observations demonstrate that the association of FCGR2B polymorphisms with SLE is common to multiple populations, but the alleles associated with SLE depend upon the genetic background of each population. Functional analyses using a human B cell line lacking endogenous FcgammaRIIb revealed that SLE-associated 232Thr allele product was partially excluded from membrane lipid rafts under resting conditions and after coligation with B cell receptor, and was significantly less potent at inhibiting B cell activation. Two haplotypes were identified in CD72, one of which was associated with increased production of an alternative splicing isoform that substantially alters the extracellular region of CD72. Interestingly, the presence of the haplotype significantly decreased the risk of SLE conferred by FCGR2B-232Thr in an epistatic manner. These observations emphasize the need to understand human immune system diversity if we are to improve our understanding of the pathogenesis of autoimmune diseases.

A novel single-nucleotide polymorphism of the Fcgamma receptor IIIa gene is associated with genetic susceptibility to systemic lupus erythematosus in Chinese populations: a family-based association study

BACKGROUND

Systemic lupus erytematosus (SLE) is characterized by the presence of various autoantibodies and the deposition of immune complexes which are cleared by Fcgamma receptors.

OBJECTIVES

Family-based association analysis was performed to investigate whether the FCGR3A-72S/R and FCGR3A-270T/R polymorphisms are risk factors for SLE in a Chinese population.

METHODS

In total, 119 patients with SLE from 95 nuclear families, aged 14-78 years, who met the American College of Rheumatology 1997 criteria were recruited, as were 316 family members of these patients. We studied two single-nucleotide polymorphisms (SNPs) encoding nonsynonymous substitution in the FCGR3A gene with respect to genetic susceptibility to SLE in a collection of 435 subjects from 95 nuclear families. We performed the genotyping using PCR restriction fragment length polymorphism.

RESULTS

Our results showed that FCGR3A-72R/S have an excess of transmission of the R allele from heterozygous parents to affected offspring (transmission disequilibrium test chi2 = 9.30, P = 0.0032). Univariate (single-marker) family-based association tests demonstrated that a variant allele at SNP rs403016 of the FCGR3A gene was significantly associated with genetic susceptibility to SLE (exon 3, Z = 2.5444, P = 0.01097) in an additive model. The R and S allele frequencies were 39.4% and 60.6%, respectively. The frequencies of FCGR3A 72R/R, R/S and SS genotypes were 9.1%, 60.6% and 30.3%, respectively. However, the FCGR3A-270T/S SNP was not found in this Chinese population.

CONCLUSION

This study suggests a linkage disequilibrium of the FCGR3A-72R/S SNP with SLE, and supports the notion that a novel polymorphism of the FCGR3A-72R/S SNP is associated with genetic susceptibility to SLE in Chinese populations.

Coordination of NF-kappaB and NFAT antagonism by the forkhead transcription factor Foxd1

Forkhead transcription factors play critical roles in the maintenance of immune homeostasis. In this study, we demonstrate that this regulation most likely involves intricate interactions between the forkhead family members and inflammatory transcription factors: the forkhead member Foxd1 coordinates the regulation of the activity of two key inflammatory transcription factors, NF-AT and NF-kappaB, with Foxd1 deficiency resulting in multiorgan, systemic inflammation, exaggerated Th cell-derived cytokine production, and T cell proliferation in autologous MLRs. Foxd1-deficient T cells possess increased activity of both NF-AT and NF-kappaB: the former correlates with the ability of Foxd1 to regulate casein kinase 1, an NF-AT inhibitory kinase; the latter with the ability of Foxd1 to regulate Foxj1, which regulates the NF-kappaB inhibitory subunit IkappaB beta. Thus, Foxd1 modulates inflammatory reactions and prevents autoimmunity by directly regulating anti-inflammatory regulators of the NF-AT pathway, and by coordinating the suppression of the NF-kappaB pathway via Foxj1. These findings indicate the presence of a general network of forkhead proteins that enforce T cell quiescence.

Association of a non-synonymous single-nucleotide polymorphism of DNASEI with SLE susceptibility

OBJECTIVES

To investigate the association of a non-synonymous single-nucleotide polymorphism (SNP) in DNASEI with susceptibility to systemic lupus erythematosus (SLE) and the production of autoantibodies to nuclear antigens.

METHODS

The Gln244Arg (rs1053874) SNP was studied in 276 SLE patients and in 368 healthy controls of Spanish ancestry. Its relationship with SLE susceptibility, serum DNase I activity, anti-ribonucleoprotein (RNP), anti-double-stranded DNA (dsDNA), anti-nucleosome and anti-single-stranded DNA (ssDNA) antibodies was determined.

RESULTS

An association of the Gln244Arg SNP with SLE susceptibility that followed a recessive genetic model (P=0.002) was found. The GG genotype was more common in SLE patients (59.8%) than in controls (47.3%). However, the Gln244Arg genotype did not correlate with DNase I activity in sera from SLE patients or from controls. In addition, the Gln244Arg SNP did not influence autoantibody titres significantly.

CONCLUSION

The association of the Gln244Arg SNP with SLE susceptibility indicates that common polymorphisms in DNASEI play a role in the genetics of SLE. However, the lack of effect of the Gln244Arg SNP on serum DNase I activity calls into question the direct involvement of this specific SNP.

Identification and characterization of an Xp22.33;Yp11.2 translocation causing a triplication of several genes of the pseudoautosomal region 1 in an XX male patient with severe systemic lupus erythematosus

The X;Y translocation break point sequence in an XX male patient with prepubertal systemic lupus erythematosus (SLE) was characterized with the intention of identifying a predisposing gene(s) for SLE. Spectral karyotyping of the patient's metaphase chromosomes showed normal autosomes and 2 X chromosomes, one of which displayed a small portion of the Y chromosome. Using a Y chromosome polymerase chain reaction (PCR) walking strategy and inverse PCR, we found that the abnormal recombination occurred between retroviral long terminal repeats located at Xp22.33 (position 0.95 Mb; inside the pseudoautosomal regions) and Yp11.2 (4.20 Mb) downstream of the sex-determining region Y (SRY) gene. The complete DNA sequence of the break point was determined, revealing a partial duplication of the pseudoautosomal region 1 (PAR1) in the derivative X chromosome and causing a partial trisomy of the 12 known genes located between the interleukin-3 receptor alpha (IL3RA; position 1.1 Mb on the X and Y chromosomes) and CD99 (position 2.2 Mb) genes inclusively. All other X chromosome genes were present as 2 copies. Real-time quantitative PCR confirmed the presence of 3 copies of each of the 12 genes in the patient's genomic DNA. We also found that RNA for 1 of the candidate genes was indeed overexpressed in the patient's blood as compared with normal subjects. Taken together, the uniqueness of the translocation, the rarity of severe prepubertal SLE in males, and the presence of SLE in some patients with Klinefelter's syndrome (who have a triplication of the 2 PAR regions) point to a possible relationship between the partial triplication of the PAR1 region and the development of SLE.