Higher Genetic Risk Loads Confer More Diverse Manifestations and Higher Risk of Lupus Nephritis in Systemic Lupus Erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is a highly heritable complex disorder with heterogeneous clinical manifestations. In this study, we aimed to identify the genetic risk load using clinical and serological manifestations in SLE patients.

METHODS

We genotyped a total of 1,655 Korean patients with SLE (n = 1,243 as a discovery set and n = 412 as a replication set) using a customized genome-wide single-nucleotide polymorphism (SNP) array, KoreanChip. A weighted genetic risk score (wGRS) for an individual was calculated from 112 well-validated non-HLA SNPs and HLA haplotypes of SLE-risk loci. We analyzed associations between individual wGRS and clinical SLE subphenotypes and autoantibodies using multivariable linear or logistic regression adjusted by onset age, sex, and disease duration.

RESULTS

Childhood-onset SLE (<16 years) conferred the highest genetic risk compared with adult-onset (16-50 years) or late-onset (>50 years) SLE (P = 6.8 × 10-6 ). High wGRS significantly increased associations with SLE manifestations, regardless of onset age, sex, and disease duration. Individual wGRS significantly correlated positively with more clinical American College of Rheumatology criteria (β = 0.143, P = 1.8 × 10-6 ). Subphenotype analysis revealed significant associations between the highest and lowest wGRS quartile with risk of renal disorder (hazard ratio [HR] 1.74, P = 2.2 × 10-8 ) and anti-Sm antibody production (HR 1.85, P = 2.8 × 10-5 ). Higher wGRS markedly modulated the pathogenesis of proliferative and membranous lupus nephritis class III or IV (HR 1.98, P = 1.6 × 10-5 ) and class V (HR 2.79, P = 1.0 × 10-3 ), but especially lupus nephritis class V in anti-Sm-positive SLE (area under the curve 0.68, P = 1.8 × 10-4 ).

CONCLUSION

Patients with SLE and high wGRS tended to have earlier age of SLE onset, higher anti-Sm antibody positivity, and more diverse clinical phenotypes. Genetic profiling may predict high risk for lupus nephritis and a diverse clinical course in SLE patients.

Biological insights into systemic lupus erythematosus through an immune cell-specific transcriptome-wide association study

OBJECTIVE

Genome-wide association studies (GWAS) have identified >100 risk loci for systemic lupus erythematosus (SLE), but the disease genes at most loci remain unclear, hampering translation of these genetic discoveries. We aimed to prioritise genes underlying the 110 SLE loci that were identified in the latest East Asian GWAS meta-analysis.

METHODS

We built gene expression predictive models in blood B cells, CD4+ and CD8+ T cells, monocytes, natural killer cells and peripheral blood cells of 105 Japanese individuals. We performed a transcriptome-wide association study (TWAS) using data from the latest genome-wide association meta-analysis of 208 370 East Asians and searched for candidate genes using TWAS and three data-driven computational approaches.

RESULTS

TWAS identified 171 genes for SLE (p<1.0×10-5); 114 (66.7%) showed significance only in a single cell type; 127 (74.3%) were in SLE GWAS loci. TWAS identified a strong association between CD83 and SLE (p<7.7×10-8). Meta-analysis of genetic associations in the existing 208 370 East Asian and additional 1498 cases and 3330 controls found a novel single-variant association at rs72836542 (OR=1.11, p=4.5×10-9) around CD83. For the 110 SLE loci, we identified 276 gene candidates, including 104 genes at recently-identified SLE novel loci. We demonstrated in vitro that putative causal variant rs61759532 exhibited an allele-specific regulatory effect on ACAP1, and that presence of the SLE risk allele decreased ACAP1 expression.

CONCLUSIONS

Cell-level TWAS in six types of immune cells complemented SLE gene discovery and guided the identification of novel genetic associations. The gene findings shed biological insights into SLE genetic associations.

Novel susceptibility loci for steroid-associated osteonecrosis of the femoral head in systemic lupus erythematosus

INTRODUCTION

Osteonecrosis of the femoral head (ONFH) involves necrosis of bone and bone marrow of the femoral head caused by ischemia with unknown etiology. Previous genetic studies on ONFH failed to produce consistent results, presumably because ONFH has various causes with different genetic backgrounds and the underlying diseases confounded the associations. Steroid-associated ONFH (S-ONFH) accounts for one-half of all ONFH, and systemic lupus erythematosus (SLE) is a representative disease underlying S-ONFH. We performed a genome-wide association study (GWAS) to identify genetic risk factors for S-ONFH in patients with SLE.

METHODS

We conducted a two-staged GWAS on 636 SLE patients with S-ONFH and 95 588 non-SLE controls. Among the novel loci identified, we determined S-ONFH specific loci by comparing allele frequencies between SLE patients without S-ONFH and non-SLE controls. We also used Korean datasets comprising 148 S-ONFH cases and 37 015 controls to assess overall significance. We evaluated the functional annotations of significant variants by in-silico analyses.

RESULTS

The Japanese GWAS identified four significant loci together with 12 known SLE susceptibility loci. The four significant variants showed comparable effect sizes on S-ONFH compared with SLE controls and non-SLE controls. Three of the four loci, MIR4293/MIR1265 (OR = 1.99, P-value = 1.1 × 10-9), TRIM49/NAALAD2 (OR = 1.65, P-value = 4.8 × 10-8) and MYO16 (OR = 3.91, P-value = 4.9 × 10-10), showed significant associations in the meta-analysis with Korean datasets. Bioinformatics analyses identified MIR4293, NAALAD2 and MYO16 as candidate causal genes. MIR4293 regulates a PPARG-related adipogenesis pathway relevant to S-ONFH.

CONCLUSIONS

We identified three novel susceptibility loci for S-ONFH in SLE.

Clinical and Genetic Risk Factors Associated With the Presence of Lupus Nephritis

Objective

To elucidate whether clinical features and the weighted genetic risk score (wGRS) were associated with the presence of lupus nephritis (LN).

Methods

We retrospectively divided patients with systemic lupus erythematosus (SLE, n=1,078) into biopsy-proven LN (n=507) and non-LN groups (non-LN, n=571) Baseline clinical features, serologic markers, and the wGRS were collected The wGRS was calculated from 112 non-human leukocyte antigen (non-HLA) loci and HLA-DRβ1 amino acid haplotypes for SLE Associations among clinical features, wGRS, and the presence of LN were identified.

Results

In the multivariate analysis, patients with LN were younger at diagnosis (odds ratio [OR]=0.97, p<0.001), had more pleuritis (OR=2.44, p<0.001) and pericarditis (OR=1.62, p=0.029), had a higher detection rate of anti-double stranded deoxyribonucleic acid (anti-dsDNA antibodies, OR=2.22, p<0.001), anti-Smith antibodies (anti-Sm antibodies, OR=1.70, p=0.002), low level of complement (OR=1.37, p=0.043) and absence of antiphospholipid antibodies (aPL antibodies, OR=1.60, p=0.002), and had higher wGRS (OR=1.16, p=0.012) Mediation analysis suggested that anti-Sm antibodies and low complement could be mediators in the relationship between high wGRS and the presence of LN.

Conclusion

Onset age, pleuritis, pericarditis, several serologic markers, and wGRS were associated with the presence of LN Anti-Sm antibodies and low complement appeared to mediate the indirect relationship between wGRS and the presence of LN.

Meta-analysis of 208370 East Asians identifies 113 susceptibility loci for systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE), an autoimmune disorder, has been associated with nearly 100 susceptibility loci. Nevertheless, these loci only partially explain SLE heritability and their putative causal variants are rarely prioritised, which make challenging to elucidate disease biology. To detect new SLE loci and causal variants, we performed the largest genome-wide meta-analysis for SLE in East Asian populations.

METHODS

We newly genotyped 10 029 SLE cases and 180 167 controls and subsequently meta-analysed them jointly with 3348 SLE cases and 14 826 controls from published studies in East Asians. We further applied a Bayesian statistical approach to localise the putative causal variants for SLE associations.

RESULTS

We identified 113 genetic regions including 46 novel loci at genome-wide significance (p<5×10^-8). Conditional analysis detected 233 association signals within these loci, which suggest widespread allelic heterogeneity. We detected genome-wide associations at six new missense variants. Bayesian statistical fine-mapping analysis prioritised the putative causal variants to a small set of variants (95% credible set size ≤10) for 28 association signals. We identified 110 putative causal variants with posterior probabilities ≥0.1 for 57 SLE loci, among which we prioritised 10 most likely putative causal variants (posterior probability ≥0.8). Linkage disequilibrium score regression detected genetic correlations for SLE with albumin/globulin ratio (r_g=-0.242) and non-albumin protein (r_g=0.238).

CONCLUSION

This study reiterates the power of large-scale genome-wide meta-analysis for novel genetic discovery. These findings shed light on genetic and biological understandings of SLE.

Genome-wide association study in a Korean population identifies six novel susceptibility loci for rheumatoid arthritis

OBJECTIVE

Genome-wide association studies (GWAS) in rheumatoid arthritis (RA) have discovered over 100 RA loci, explaining patient-relevant RA pathogenesis but showing a large fraction of missing heritability. As a continuous effort, we conducted GWAS in a large Korean RA case-control population.

METHODS

We newly generated genome-wide variant data in two independent Korean cohorts comprising 4068 RA cases and 36 487 controls, followed by a whole-genome imputation and a meta-analysis of the disease association results in the two cohorts. By integrating publicly available omics data with the GWAS results, a series of bioinformatic analyses were conducted to prioritise the RA-risk genes in RA loci and to dissect biological mechanisms underlying disease associations.

RESULTS

We identified six new RA-risk loci (SLAMF6, CXCL13, SWAP70, NFKBIA, ZFP36L1 and LINC00158) with pmeta<5×10-8 and consistent disease effect sizes in the two cohorts. A total of 122 genes were prioritised from the 6 novel and 13 replicated RA loci based on physical distance, regulatory variants and chromatin interaction. Bioinformatics analyses highlighted potentially RA-relevant tissues (including immune tissues, lung and small intestine) with tissue-specific expression of RA-associated genes and suggested the immune-related gene sets (such as CD40 pathway, IL-21-mediated pathway and citrullination) and the risk-allele sharing with other diseases.

CONCLUSION

This study identified six new RA-associated loci that contributed to better understanding of the genetic aetiology and biology in RA.

Update on the Genetics of Systemic Lupus Erythematosus: Genome-Wide Association Studies and Beyond

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of complex etiology that primarily affects women of childbearing age. The development of SLE is attributed to the breach of immunological tolerance and the interaction between SLE-susceptibility genes and various environmental factors, resulting in the production of pathogenic autoantibodies. Working in concert with the innate and adaptive arms of the immune system, lupus-related autoantibodies mediate immune-complex deposition in various tissues and organs, leading to acute and chronic inflammation and consequent end-organ damage. Over the past two decades or so, the impact of genetic susceptibility on the development of SLE has been well demonstrated in a number of large-scale genetic association studies which have uncovered a large fraction of genetic heritability of SLE by recognizing about a hundred SLE-susceptibility loci. Integration of genetic variant data with various omics data such as transcriptomic and epigenomic data potentially provides a unique opportunity to further understand the roles of SLE risk variants in regulating the molecular phenotypes by various disease-relevant cell types and in shaping the immune systems with high inter-individual variances in disease susceptibility. In this review, the catalogue of SLE susceptibility loci will be updated, and biological signatures implicated by the SLE-risk variants will be critically discussed. It is optimistically hoped that identification of SLE risk variants will enable the prognostic and therapeutic biomarker armamentarium of SLE to be strengthened, a major leap towards precision medicine in the management of the condition.

cdc37 is essential for JNK pathway activation and wound closure in Drosophila

Wound closure in the Drosophila larval epidermis mainly involves nonproliferative, endocyling epithelial cells. Consequently, it is largely mediated by cell growth and migration. We discovered that both cell growth and migration in Drosophila require the cochaperone-encoding gene cdc37. Larvae lacking cdc37 in the epidermis failed to close wounds, and the cells of the epidermis failed to change cell shape and polarize. Likewise, wound-induced cell growth was significantly reduced, and correlated with a reduction in the size of the cell nucleus. The c-Jun N-terminal kinase (JNK) pathway, which is essential for wound closure, was not typically activated in injured cdc37 knockdown larvae. In addition, JNK, Hep, Mkk4, and Tak1 protein levels were reduced, consistent with previous reports showing that Cdc37 is important for the stability of various client kinases. Protein levels of the integrin β subunit and its wound-induced protein expression were also reduced, reflecting the disruption of JNK activation, which is crucial for expression of integrin β during wound closure. These results are consistent with a role of Cdc37 in maintaining the stability of the JNK pathway kinases, thus mediating cell growth and migration during Drosophila wound healing.

Identification of the TIFAB Gene as a Susceptibility Locus for Coronary Artery Aneurysm in Patients with Kawasaki Disease

Kawasaki disease (KD) is a self-limiting systemic vasculitis of unknown etiology. KD is often complicated by coronary artery aneurysms (CAAs), which develop in about 20-25% of untreated children and 3-5% of children treated with intravenous immunoglobulin therapy. To identify the risk loci for CAA susceptibility in patients with KD, we performed a genome-wide association study (GWAS) using our previous Illumina HumanOmni1-Quad BeadChip data (296 KD patients) and a new replication study in an independent sample set (713 KD patients) by grouping KD patients without CAA (control) versus KD patients with extremely large aneurysms (diameter ≥ 5 mm) (case). Among 44 candidate single -nucleotide polymorphisms (SNPs) selected from the initial GWAS data (33 cases vs. 215 controls), a SNP (rs899162) located 7 kb upstream of the TIFAB gene on chromosome five was replicated in an independent sample (12 cases vs. 532 controls). In the combined analysis (45 cases vs. 747 controls), the SNP (rs899162) showed a highly significant association with CAA formation (diameter ≥ 5 mm) in patients with KD (odds ratio = 3.20, 95% confidence interval = 2.02-5.05, P_combined = 1.95 × 10^-7). These results indicate that the TIFAB gene may act as a CAA susceptibility locus in patients with KD.

Male-specific association of the FCGR2A His167Arg polymorphism with Kawasaki disease

Kawasaki disease (KD) is an acute systemic vasculitis that can potentially cause coronary artery aneurysms in some children. KD occurs approximately 1.5 times more frequently in males than in females. To identify sex-specific genetic variants that are involved in KD pathogenesis in children, we performed a sex-stratified genome-wide association study (GWAS), using the Illumina HumanOmni1-Quad BeadChip data (249 cases and 1,000 controls) and a replication study for the 34 sex-specific candidate SNPs in an independent sample set (671 cases and 3,553 controls). Male-specific associations were detected in three common variants: rs1801274 in FCGR2A [odds ratio (OR) = 1.40, P = 9.31 × 10-5], rs12516652 in SEMA6A (OR = 1.87, P = 3.12 × 10-4), and rs5771303 near IL17REL (OR = 1.57, P = 2.53 × 10-5). The male-specific association of FCGR2A, but not SEMA6A and IL17REL, was also replicated in a Japanese population (OR = 1.74, P = 1.04 × 10-4 in males vs. OR = 1.22, P = 0.191 in females). In a meta-analysis with 1,461 cases and 5,302 controls, a very strong association of KD with the nonsynonymous SNP rs1801274 (p.His167Arg, previously assigned as p.His131Arg) in FCGR2A was confirmed in males (OR = 1.48, P = 1.43 × 10-7), but not in the females (OR = 1.17, P = 0.055). The present study demonstrates that p.His167Arg, a KD-associated FCGR2A variant, acts as a susceptibility gene in males only. Overall, the gender differences associated with FCGR2A in KD provide a new insight into KD susceptibility.

PINK1 phosphorylates transglutaminase 2 and blocks its proteasomal degradation

Parkinson's disease (PD) is characterized by progressive dopaminergic neuronal loss and the formation of abnormal protein aggregates, referred to as Lewy bodies (LBs). PINK1 is a serine/threonine protein kinase that protects cells from stress-induced mitochondrial dysfunction. PINK1 gene mutations cause one form of autosomal recessive early-onset PD. Transglutaminase 2 (TG2) is an intracellular protein cross-linking enzyme that has an important role in LB formation during PD pathogenesis. This study identifies PINK1 as a novel TG2 binding partner and shows that PINK1 stabilizes the half-life of TG2 via inhibition of TG2 ubiquitination and subsequent proteasomal degradation. PINK1 affects TG2 stability in a kinase-dependent manner. In addition, PINK1 directly phosphorylates TG2 in carbonyl cyanide m-chlorophenyl hydrazine-induced mitochondrial damaged states, thereby enhancing TG2 accumulation and intracellular protein cross-linking products. This study further confirms the functional link between upstream PINK1 and downstream TG2 in Drosophila melanogaster. These data suggest that PINK1 positively regulates TG2 activity, which may be closely associated with aggresome formation in neuronal cells.

Curing viruses in Pleurotus ostreatus by growth on a limited nutrient medium containing cAMP and rifamycin

Oyster mushroom spherical virus (OMSV) and oyster mushroom isometric virus (OMIV) are the causative agents of a fruiting body deformation disease in the edible mushroom Pleurotus ostreatus. The curing of these mycoviruses was facilitated by a serial transfer of infected mycelia onto a limited nutrient medium containing 1mM of cAMP and 75 μg/ml of rifamycin (cAMP-rifamycin plate). The mycelia were grown on cAMP-rifamycin plates for 5 successive passages. ELISA and RT-PCR showed that the amount of mycoviruses inside the mycelia decreased significantly with increasing numbers of passages. The mycelia became free of viruses after 5 successive passages. Cultivation of the virus-cured mycelia on a mushroom compost medium produced a normal harvest, whereas the spawn infected with viruses failed to produce any fruiting bodies.

Requirement for Pak3 in Rac1-induced organization of actin and myosin during Drosophila larval wound healing

Rho-family small GTPases regulate epithelial cell sheet migration by organizing actin and myosin during wound healing. Here, we report that Pak3, but not Pak1, is a downstream target protein for Rac1 in wound closure of the Drosophila larval epidermis. Pak3-deficient larvae failed to close a wound hole and this defect was not rescued by Pak1 expression, indicating differential functions of the two proteins. Pak3 localized to the wound margin, which selectively required Rac1. Pak3-deficient larvae showed severe defects in actin-myosin organization at the wound margin and in submarginal cells, which was reminiscent of the phenotypes of Rac1-deficient larvae. These results suggest that Pak3 specifically mediates Rac1 signaling in organizing actin and myosin during Drosophila epidermal wound healing.

Impact of perception of socioeconomic burden on advocacy for patient autonomy in end-of-life decision making: a study of societal attitudes

We investigated the impact of perception of socioeconomic burden on beliefs regarding a patient's autonomy in end-of-life (EOL) decision making. We also sought to identify the characteristics of individuals who advocate patient autonomy and their attitudes toward other EOL issues. A total of 1055 individuals from the Korean general population were interviewed through a telephone survey using a structured questionnaire that was designed to investigate public attitudes toward various EOL issues. Of 1019 individuals included in the analysis, 635 (62.3%) specified the patient and 221 (21.7%) the family, when asked who is the appropriate decision maker in terms of EOL decisions in the absence of perception of socioeconomic burden. In contrast, the numbers were 458 (44.9%) and 500 (49.1%), respectively, if substantial burden was assumed. Respondents who favoured the patient's right to make decisions regardless of perception of socioeconomic burden numbered only 312 (30.6%) and were likely to be younger and have knowledge of hospice than who favoured family decision. Former group also favoured the disclosure of terminal illness to patients, withholding life-sustaining treatment, and preparation of advanced directives. Societal attitudes toward patient autonomy were significantly influenced by perception of socioeconomic burden. Open and balanced discussion about burden to family and adequate welfare support are thus suggested.