Evidence for a susceptibility gene, SLEV1, on chromosome 17p13 in families with vitiligo-related systemic lupus erythematosus

Association between systemic lupus erythematosus and myasthenia gravis: A population-based National Study

BACKGROUND

Systemic lupus erythematosus (SLE) and myasthenia gravis (MG) are autoimmune diseases. Previous case reports and case series suggest an association may exist between these diseases, as well as an increased risk of SLE after thymectomy for MG. We undertook this study to determine whether SLE and MG were associated in large cohorts.

METHODS

We searched the IBM Watson Health Explorys platform and the Department of Veterans Affairs Million Veteran Program (MVP) database for diagnoses of SLE and MG. In addition, we examined subjects enrolled in the Lupus Family Registry and Repository (LFRR) as well as controls for a diagnosis of MG.

RESULTS

Among 59,780,210 individuals captured in Explorys, there were 25,750 with MG and 65,370 with SLE. 370 subjects had both. Those with MG were >10 times more likely to have SLE than those without MG. Those with both diseases were more likely to be women, African American, and at a younger age than MG subjects without SLE. In addition, the MG patients who underwent thymectomy had an increased risk of SLE compared to MG patients who had not undergone thymectomy (OR 3.11, 95% CI: 2.12 to 4.55). Autoimmune diseases such as pernicious anemia and miscellaneous comorbidities such as chronic kidney disease were significantly more common in MG patients who developed SLE. In the MVP, SLE and MG were also significantly associated. Association of SLE and MG in a large SLE cohort with rigorous SLE classification confirmed the association of SLE with MG at a similar level.

CONCLUSION

While the number of patients with both MG and SLE is small, SLE and MG are strongly associated together in very large databases and a large SLE cohort.

A Novel Gene CDC27 Causes SLE and Is Associated With the Disease Activity

Background

As genetic genetic factors are important in SLE, so screening causative genes is of great significance for the prediction and early prevention in people who may develop SLE. At present, it is very difficult to screen causative genes through pedigrees. The analytical method described herein can be used to screen causative genes for SLE and other complex diseases through pedigrees.

Methods

For the first time, 24 lupus pedigrees were analyzed by combining whole exon sequencing and a variety of biological information tools including common-specific analysis, pVAAST (pedigree variant annotation, analysis and search tool), Exomiser (Combining phenotype and PPI associated analysis), and FARVAT (family based gene burden), and the causative genes of these families with lupus identified. Selected causative genes in peripheral-blood mononuclear cells (PBMCs) were evaluated by quantitative polymerase chain reaction (qPCR).

Results

Cell division cycle 27 (CDC27) was screened out by common-specific analysis and Exomiser causative gene screening. FARVAT analysis on these families detected only CDC27 at the extremely significant level (false discovery rate <0.05) by three family-based burden analyses (BURDEN, CALPHA, and SKATO). QPCR was performed to detect for CDC27 in the PBMCs of the SLE family patients, sporadic lupus patients, and healthy people. Compared with the healthy control group, CDC27 expression was low in lupus patients (familial and sporadic patients) (P<0.05) and correlated with lupus activity indicators: negatively with C-reactive protein (CRP) (P<0.05) and erythrocyte sedimentation rate (P<0.05) and positively with complement C3 and C4 (P<0.05). The CDC27 expression was upregulated in PBMCs from SLE patients with reduced lupus activity after immunotherapy (P<0.05). Based on Receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity of CDC27 in diagnosing SLE were 82.30% and 94.40%.

Conclusion

The CDC27 gene, as found through WES combined with multiple analytical method may be a causative gene of lupus. CDC27 may serve as a marker for the diagnosis of SLE and is closely related to the lupus activity. We hope that the analytical method in this study will be used to screen causative genes for other diseases through small pedigrees, especially among non-close relatives.

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

The Genetic Basis of Vitiligo

Vitiligo is a complex disease in which autoimmune destruction of epidermal melanocytes results in patches of depigmented white skin. Vitiligo has an estimated prevalence of about 0.2-2% in different populations and approximately 0.4% in the European-derived white (EUR) population. The fraction of disease risk attributable to genetic variation, termed heritability, is high, with estimates from family studies in EUR of 0.75-0.83 and from SNP based studies estimated at 0.78. About 70% of genetic risk comes from common genetic variants and about 30% from rare genetic variants. Through candidate gene, genomewide linkage, and genomewide association studies, over 50 vitiligo susceptibility loci have been discovered. These have been combined into a vitiligo polygenic risk score, which has allowed various aspects of vitiligo genetic architecture in the EUR population to be better understood. Vitiligo has thus proved to be a particularly tractable model for investigation of complex disease genetic architecture. Here, we summarize progress to date including dissection of heritability, discovery of vitiligo susceptibility loci through candidate gene, genomewide linkage, and genomewide association studies, relationships to other autoimmune diseases, polygenic architecture of vitiligo risk, vitiligo triggering, and disease onset, and provide suggestions for future directions.

Genetics of Vitiligo

Vitiligo reflects simultaneous contributions of multiple genetic risk factors and environmental triggers. Genomewide association studies have discovered approximately 50 genetic loci contributing to vitiligo risk. At many vitiligo susceptibility loci, the relevant genes and DNA sequence variants are identified. Many encode proteins involved in immune regulation, several play roles in cellular apoptosis, and others regulate functions of melanocytes. Although many of the specific biologic mechanisms need elucidation, it is clear that vitiligo is an autoimmune disease involving a complex relationship between immune system programming and function, aspects of the melanocyte autoimmune target, and dysregulation of the immune response.

A holistic review on the autoimmune disease vitiligo with emphasis on the causal factors

Vitiligo is an idiopathic systemic autoimmune disease affecting skin, hair and oral mucosa. This genetic yet acquired disease characterized by melanin loss is a cause of morbidity across all races. Though thyroid disturbance has been recognized as a key trigger of this pathology, an array of other factors plays critical role in its manifestation. Multiple hormones (corticotropin-releasing hormone, adrenocorticotropic hormone, α-melanocyte-stimulating hormone, melatonin, calcitriol, testosterone, estrogen), genes (Human leukocyte antigen (HLA), Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), Forkhead box D3 (FOXD3), Cluster of differentiation 117 (CD117), Estrogen receptor (ESR) 1, Cyclooxygenase-2 (COX2), Vitiligo-associated protein 1 (VIT1)), and lifestyle choices (stress, diet, cosmetic products, and medications) have been suspected as drivers of this disorder. The pathological mechanisms have been understood in recent times, with the aid of genomic studies; however a universally-effective therapy is yet to be achieved. This review discusses these under-investigated facets of vitiligo onset and progression; hence, it is expected to enrich vitiligo research.

Pharmacology and psychiatry at the origins of Greek medicine: The myth of Melampus and the madness of the Proetides

Melampus is a seer-healer of Greek myth attributed with having healed the young princesses of Argos of madness. Analysis of this legend and its sources sheds light on the early stages of the "medicalizing" shift in the history of ancient Greek medicine. Retrospective psychological diagnosis suggests that the descriptions of the youths' madness rose from actual observation of behavioral and mental disorders. Melampus is credited with having healed them by administering hellebore. Pharmacological analysis of botanical specimens proves that Helleborus niger features actual neurological properties effective in the treatment of mental disorders. The discussion aims at examining the rational aspects of the treatment of mental conditions in Greco-Roman antiquity.

Association Study of a Proliferation-inducing Ligand, Spermatogenesis Associated 8, Platelet-derived Growth Factor Receptor-alpha, and POLB Polymorphisms with Systemic Lupus Erythematosus in Chinese Han Population

Background:

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. This study was conducted to examine whether the association of a proliferation-inducing ligand (APRIL), spermatogenesis associated 8 (SPATA8), platelet-derived growth factor receptor-alpha (PDGFRA), and DNA polymerase beta (POLB) with SLE can be replicated in a Chinese Han population.

Methods:

Chinese SLE patients (n = 1247) and ethnically and geographically matched healthy controls (n = 1440) were genotyped for the APRIL, SPATA8, PDGFRA, and POLB single-nucleotide polymorphisms (SNPs), rs3803800, rs8023715, rs1364989, and rs12678588 using the Sequenom MassARRAY System.

Results:

The Chinese Han SLE patients and controls had statistically similar frequencies of alleles and genotypes of four gene polymorphisms. Moreover, no association signal was detected on different genetic models (additive, dominant, and recessive, all, P > 0.05) or in SLE subgroups stratified by various clinical manifestations (all, P > 0.05).

Conclusions:

Different genetic backgrounds from different ancestries and various populations may result in different genetic risk factors for SLE. We did not detect any significant association with SNPs of APRIL, SPATA8, PDGFRA, and POLB.

Vitiligo blood transcriptomics provides new insights into disease mechanisms and identifies potential novel therapeutic targets

BACKGROUND

Significant gaps remain regarding the pathomechanisms underlying the autoimmune response in vitiligo (VL), where the loss of self-tolerance leads to the targeted killing of melanocytes. Specifically, there is incomplete information regarding alterations in the systemic environment that are relevant to the disease state.

METHODS

We undertook a genome-wide profiling approach to examine gene expression in the peripheral blood of VL patients and healthy controls in the context of our previously published VL-skin gene expression profile. We used several in silico bioinformatics-based analyses to provide new insights into disease mechanisms and suggest novel targets for future therapy.

RESULTS

Unsupervised clustering methods of the VL-blood dataset demonstrate a "disease-state"-specific set of co-expressed genes. Ontology enrichment analysis of 99 differentially expressed genes (DEGs) uncovers a down-regulated immune/inflammatory response, B-Cell antigen receptor (BCR) pathways, apoptosis and catabolic processes in VL-blood. There is evidence for both type I and II interferon (IFN) playing a role in VL pathogenesis. We used interactome analysis to identify several key blood associated transcriptional factors (TFs) from within (STAT1, STAT6 and NF-kB), as well as "hidden" (CREB1, MYC, IRF4, IRF1, and TP53) from the dataset that potentially affect disease pathogenesis. The TFs overlap with our reported lesional-skin transcriptional circuitry, underscoring their potential importance to the disease. We also identify a shared VL-blood and -skin transcriptional "hot spot" that maps to chromosome 6, and includes three VL-blood dysregulated genes (PSMB8, PSMB9 and TAP1) described as potential VL-associated genetic susceptibility loci. Finally, we provide bioinformatics-based support for prioritizing dysregulated genes in VL-blood or skin as potential therapeutic targets.

CONCLUSIONS

We examined the VL-blood transcriptome in context with our (previously published) VL-skin transcriptional profile to address a major gap in knowledge regarding the systemic changes underlying skin-specific manifestation of vitiligo. Several transcriptional "hot spots" observed in both environments offer prioritized targets for identifying disease risk genes. Finally, within the transcriptional framework of VL, we identify five novel molecules (STAT1, PRKCD, PTPN6, MYC and FGFR2) that lend themselves to being targeted by drugs for future potential VL-therapy.

The functional p53 codon 72 polymorphism is associated with systemic lupus erythematosus

The aim of the study is to investigate whether the functional p53 codon 72 polymorphism is associated with susceptibility to SLE and its clinical features. A polymerase chain reaction of genomic DNA-restriction fragment length polymorphism was used to determine genotypes of the p53 codon 72 in 90 SLE patients and 114 healthy controls. Clinical/serological manifestations were analysed in each patient and correlated with the genotypes. The OR of the association of the Pro allele with SLE was 1.70 (95% CI, 1.15-2.53, P = 0.0079) and the OR of the Pro/Pro (a recessive model) was significantly increased (OR = 2.58, 95% CI = 1.24-5.39, P = 0.0093). The Armitage’s trend test indicated a significant dosage effect of the Pro allele for SLE (OR = 1.73, chi-square = 7.08, P = 0.0078). However, there was no significant association of the polymorphism with clinical/serological manifestations studied here. In conclusion, our finding suggests the functional p53 codon 72 polymorphism may be associated with SLE susceptibility, suggesting individuals who carry the Pro allele may have a higher risk to SLE susceptibility than those with the Arg allele. Further studies for replications are needed to confirm that the p53 polymorphism contributes to SLE.

Vitiligo--part 1

Vitiligo is a chronic stigmatizing disease, already known for millennia, which mainly affects melanocytes from epidermis basal layer, leading to the development of hypochromic and achromic patches. Its estimated prevalence is 0.5% worldwide. The involvement of genetic factors controlling susceptibility to vitiligo has been studied over the last decades, and results of previous studies present vitiligo as a complex, multifactorial and polygenic disease. In this context, a few genes, including DDR1, XBP1 and NLRP1 have been consistently and functionally associated with the disease. Notwithstanding, environmental factors that precipitate or maintain the disease are yet to be described. The pathogenesis of vitiligo has not been totally clarified until now and many theories have been proposed. Of these, the autoimmune hypothesis is now the most cited and studied among experts. Dysfunction in metabolic pathways, which could lead to production of toxic metabolites causing damage to melanocytes, has also been investigated. Melanocytes adhesion deficit in patients with vitiligo is mainly speculated by the appearance of Köebner phenomenon, recently, new genes and proteins involved in this deficit have been found.

Current aspects of vitiligo genetics

Vitiligo is a common acquired depigmentation disorder of the skin manifested by the presence of white macules. The disease occurs at a frequency of approximately 1–4% of the world population. Currently, the most popular theory of vitiligo development is a multifactorial hypothesis according to which genetic conditions predispose vitiligo macules to occur as a result of specific environmental factors. According to the genetic hypothesis, vitiligo inheritance is multigenic. Genetic studies conducted so far concern patients with non-segmental vitiligo. There are three basic techniques of genetic studies: candidate gene association studies, genomewide linkage studies and genome-wide association studies (GWAS). The GWAS are the “gold standard” for detecting susceptibility genes. Up to now, approximately 36 convincing non-segmental vitiligo susceptibility loci have been identified. Approximately 90% of them encode immunoregulatory proteins, while approximately 10% encode melanocyte proteins. The existence of various associations between vitiligo and other autoimmune diseases may provide new knowledge on the causes of many disorders. Examples include the inverse relationship between vitiligo and melanoma and association of vitiligo with other autoimmune diseases. The main goal of all researches is to find new, optimal therapeutic strategies for vitiligo and other autoimmune diseases.

Modern vitiligo genetics sheds new light on an ancient disease

Vitiligo is a complex disorder in which autoimmune destruction of melanocytes results in white patches of skin and overlying hair. Over the past several years, extensive genetic studies have outlined a biological framework of vitiligo pathobiology that underscores its relationship to other autoimmune diseases. This biological framework offers insight into both vitiligo pathogenesis and perhaps avenues towards more effective approaches to treatment and even disease prevention.

Three new single nucleotide polymorphisms identified by a genome-wide association study in Korean patients with vitiligo

Genetic susceptibility is involved in the pathogenesis of vitiligo. Association studies with a whole genome-based approach instead of a single or a few candidate genes may be useful for discovering new susceptible genes. Although the etiology of non-segmental and segmental types is different, the association between gene polymorphisms and vitiligo has been reported, without defining types or in non-segmental type. Whole genome-based single nucleotide polymorphisms (SNPs) were examined in patients with non-segmental and segmental types of vitiligo using the Affymetrix GeneChip 500K mapping array, and 10 functional classes of significant SNPs were selected. Genotyping and data analysis of selected 10 SNPs was performed using real-time PCR. Genotype and allele frequencies were significantly different between both types of vitiligo and three of the target SNPs, DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758). A stronger association was suggested between the mutation in KIAA1005 (rs3213758) and the segmental type compared to the non-segmental type of vitiligo. DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758) may be new vitiligo-related SNPs in Korean patients, either non-segmental or segmental type.

Association of ACE gene I/D polymorphism with vitiligo: a meta-analysis

Associations of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) functional single-nucleotide polymorphisms (SNPs) with vitiligo have been reported, but the results were inconsistent. To investigate the association of SNPs in the intron 16 of ACE gene with vitiligo susceptibility by the meta-analysis, case-control studies were conducted by searching from PubMed, HighWire and China National Knowledge Infrastructure as of May 2011. A total of 6 studies with 828 patients and 1,215 controls was finally identified. All control samples were in Hardy-Weinberg equilibrium. According to the clinical typing, the data were divided into pooled subgroup and generalized subgroup. Our meta-analysis showed that a significantly increased vitiligo risk was associated with the D/D genotype compared with the I/I + I/D genotype (Odds ratio (OR) 1.79, 95% confidence interval (95% CI) 1.35-2.38, P < 0.0001) and the D allele compared with the I allele (OR 1.72, 95% CI 1.45-2.04, P < 0.00001) in pooled subgroup. In summary, this meta-analysis demonstrated that ACE D/D homozygote and D allele were significantly associated with an increased risk of vitiligo in pooled population. The results indicated that the people with ACE D/D homozygote and D allele may suffer from vitiligo, but of a generalized type. ACE polymorphism might be used as biomarkers for vitiligo risk prediction for pooled vitiligo.

Genome-wide association study of skin complex diseases

Complex diseases are caused by both genetic and environmental factors. Over decades, scientists endeavored to uncover the genetic myth of complex diseases by linkage and association studies. Since 2005, the genome-wide association study (GWAS) has been proved to be the most powerful and efficient study design thus far in identifying genetic variants that are associated with complex diseases. More than 230 complex diseases and traits have been investigated by this approach. In dermatology, 10 skin complex diseases have been investigated, a wealth of common susceptibility variants conferring risk for skin complex diseases have been discovered. These findings point to genes and/or loci involved in biological systems worth further investigating by using other methodologies. Certainly, as our understanding of the genetic etiology of skin complex diseases continues to mature, important opportunities will emerge for developing more effective diagnostic and clinical management tools for these diseases.

Polimorphisms in inflammasome genes are involved in the predisposition to systemic lupus erythematosus

Recent findings provide evidence of inflammasome critical role in the predisposition to autoimmune disorders. The involvement of inflammasome in the pathogenesis of systemic lupus erythematosus (SLE) has been hypothesized even if no significant association within inflammasome genes mutations or polymorphisms and lupus has been reported yet. We analyzed 14 single nucleotide polymorphisms (SNPs) within 7 inflammasome genes (NLRP1, NLRP3, NLRC4, AIM2, CARD8, CASP1, IL1B) in 144 patients affected by systemic lupus erythematosus and in 158 healthy controls from Southern Brazilian (state of São Paulo) with the aim of disclosing the possible role of inflammasome genes in the susceptibility of SLE. Our results demonstrated that NLRP1 rs2670660 SNP and the NLRP1 rs12150220-rs2670660 A-G haplotype were associated with SLE in our study population, and in particular with the development of nephritis, rash and arthritis. These findings are concordant with previously reported association of NLRP1 with vitiligo and type-1 diabetes underlining once more the involvement of NALP1 inflammasome in the pathogenesis of autoimmune disorders.

Six decades of vitiligo genetics: genome-wide studies provide insights into autoimmune pathogenesis

Generalized vitiligo (GV) is a complex disease in which patchy depigmentation results from autoimmune loss of melanocytes from affected regions. Genetic analyses of GV span six decades, with the goal of understanding biological mechanisms and elucidating pathways that underlie the disease. The earliest studies attempted to describe the mode of inheritance and genetic epidemiology. Early genetic association studies of biological candidate genes resulted in some successes, principally HLA and PTPN22, but in hindsight many such reports now seem to be false-positives. Later, genome-wide linkage studies of multiplex GV families identified NLRP1 and XBP1, which appear to be valid GV susceptibility genes that control key aspects of immune regulation. Recently, the application of genome-wide association studies to analysis of GV has produced a rich yield of validated GV susceptibility genes that encode components of biological pathways reaching from immune cells to the melanocyte. These genes and pathways provide insights into underlying pathogenetic mechanisms and possible triggers of GV, establish relationships to other autoimmune diseases, and may provide clues to potential new approaches to GV treatment and perhaps even prevention. These results thus validate the hopes and efforts of the early investigators who first attempted to comprehend the genetic basis of vitiligo.

Genes, tolerance and systemic autoimmunity

The characterization of functional CD8(+) inhibitory or regulatory T cells and their gene regulation remains a critical challenge in the field of tolerance and autoimmunity. Investigating the genes induced in regulatory cells and the regulatory networks and pathways that underlie mechanisms of immune resistance and prevent apoptosis in the CD8(+) T cell compartment are crucial to understanding tolerance mechanisms in systemic autoimmunity. Little is currently known about the genetic control that governs the ability of CD8(+) Ti or regulatory cells to suppress anti-DNA Ab production in B cells. Silencing genes with siRNA or shRNA and overexpression of genes with lentiviral cDNA transduction are established approaches to identifying and understanding the function of candidate genes in tolerance and immunity. Elucidation of interactions between genes and proteins, and their synergistic effects in establishing cell-cell cross talk, including receptor modulation/antagonism, are essential for delineating the roles of these cells. In this review, we will examine recent reports which describe the modulation of cells from lupus prone mice or lupus patients to confer anti-inflammatory and protective gene expression and novel associated phenotypes. We will highlight recent findings on the role of selected genes induced by peptide tolerance in CD8(+) Ti.

Update on the genetics characterization of vitiligo

Vitiligo is an autoimmune skin disorder in which autoimmune-mediated destruction of melanocytes caused depigmentation of skin patches. The complex genetics of vitiligo involves multiple susceptibility loci, genetic heterogeneity and incomplete penetrance with gene-gene and gene-environment interactions. In order to clarify the genetic factors, two different principal approaches have applied for the identification of genomic regions or candidate genes that mediate susceptibility to vitiligo. First approach is the genome-wide linkage analyses, which is conducted by scanning of entire human genome for genomic regions that are linked to the development of vitiligo. The other approach is functional candidate gene association (FCGA) analyses that detect specific candidate genes, which are expected to involve in disease on the basis of their priori biological functions. Genomic-wide scans have provided a strong support for vitiligo susceptibility genes on chromosomes 4q13-q21, 1p31, 7q22, 8p12 and 17p13, while loci of interest at 6p, 6q, 14q, 9q, 13q, 19p and 22q required further follow-up. Whereas, FCGA studies have identified some candidate genes which are associated with vitiligo, such as HLA, AIRE, VIT1, CAT, FOXD3, ESR1, COMT, PTPN22, NALP1, PDGFRA, MYG1, MITF, CD117, XBP1, FAS, COX2, EDN1 and ACE, but few of them reports now appear to be false-positive. This review will provides an update on genetics of vitiligo based on the identification of novel candidate genes that represent, in my opinion as optimal utility for future therapeutic targets in the pathogenesis of vitiligo.

Recent progress in the genetics of generalized vitiligo

Vitiligo is an acquired disease characterized principally by patchy depigmentation of skin and overlying hair. Generalized vitiligo (GV), the predominant form of the disorder, results from autoimmune loss of melanocytes from affected regions. GV is a "complex trait", inherited in a non-Mendelian polygenic, multifactorial manner. GV is epidemiologically associated with other autoimmune diseases, both in GV patients and in their close relatives, suggesting that shared genes underlie susceptibility to this group of diseases. Early candidate gene association studies yielded a few successes, such as PTPN22, but most such reports now appear to be false-positives. Subsequent genomewide linkage studies identified NLRP1 and XBP1, apparent true GV susceptibility genes involved in immune regulation, and recent genome-wide association studies (GWAS) of GV in Caucasian and Chinese populations have yielded a large number of additional validated GV susceptibility genes. Together, these genes highlight biological systems and pathways that reach from the immune cells to the melanocyte, and provide insights into both disease pathogenesis and potential new targets for both treatment and even prevention of GV and other autoimmune diseases in genetically susceptible individuals.

Cystinosis and lupus erythematosus: coincidence or causation

A 14-year-old boy with known stable cystinosis, treated with cysteamine since infancy, presented with a deterioration of renal function with haematuria in conjunction with a nodular rash, arthralgia, leucopenia, hypocomplementaemia and raised antinuclear antibodies. He was diagnosed with spontaneous onset of systemic lupus erythematosus (SLE), and his renal biopsy was consistent with lupus nephritis. It is unusual for patients with one severe disease to develop another disease process completely unrelated to their original condition, but it can occur. However, other distinct variants of lupus have been described, including drug-induced lupus (DIL), which have features that over-lap with SLE. The potential differential diagnosis of the SLE as a form of DIL in association with cysteamine is discussed.

Shared genetic relationships underlying generalized vitiligo and autoimmune thyroid disease

BACKGROUND

Generalized vitiligo is an autoimmune disease of skin pigmentation that is associated with increased prevalence of other autoimmune diseases, particularly autoimmune thyroid disease (AITD; principally Hashimoto's disease and Graves' disease), both in vitiligo patients and their close relatives, suggesting a heritable predisposition involving, in part, shared susceptibility genes.

SUMMARY

This review summarizes current knowledge of vitiligo epidemiology and genetics, highlighting recent findings from genome-wide approaches to disease gene identification, emphasizing susceptibility loci shared with other autoimmune diseases, particularly AITD, as well as some important differences.

CONCLUSIONS

Inherited susceptibility to generalized vitiligo involves a number of specific genes, many of which are shared with other autoimmune diseases that are epidemiologically associated with vitiligo, including AITD, confirming a longstanding hypothesis about the genetic basis of these disorders. These genes provide potential therapeutic targets for novel approaches to treatment as well as for approaches to presymptomatic diagnosis and disease prevention in individuals with inherited susceptibility to this group of autoimmune diseases.

Genome-wide association study for vitiligo identifies susceptibility loci at 6q27 and the MHC

We conducted a genome-wide association study of generalized vitiligo in the Chinese Han population by genotyping 1,117 cases and 1,429 controls. The 34 most promising SNPs were carried forward for replication in samples from individuals of the Chinese Han (5,910 cases and 9,916 controls) and Chinese Uygur (713 cases and 824 controls) populations. We identified two independent association signals within the major histocompatibility complex (MHC) region (rs11966200, Pcombined=1.48x10(-48), OR=1.90; rs9468925, Pcombined=2.21x10(-33), OR=0.74). Further analyses suggested that the strong association at rs11966200 might reflect the reported association of the HLA-A*3001, HLA-B*1302, HLA-C*0602 and HLA-DRB1*0701 alleles and that the association at rs9468925 might represent a previously unknown HLA susceptibility allele. We also identified one previously undescribed risk locus at 6q27 (rs2236313, Pcombined=9.72x10(-17), OR=1.20), which contains three genes: RNASET2, FGFR1OP and CCR6. Our study provides new insights into the genetic basis of vitiligo.

Beta-arrestin 2 is required for complement C1q expression in macrophages and constrains factor-independent survival

The beta-arrestins (ARRB1 and ARRB2) regulate G-protein coupled receptor (GPCR) dependent- and independent-signaling pathways and are ubiquitously expressed. Here we show that ARRB2 mRNA and protein expression is enriched in macrophages, and that it regulates complement C1q expression and cell survival. Basal and Toll-like receptor (TLR) inducible expression of mRNAs encoding the complement subcomponents C1qa, C1qb and C1qc was greatly reduced in bone marrow-derived macrophages (BMM) from ARRB2-deficient, but not ARRB1-deficient mice, while factor-independent survival of ARRB2(-/-) BMM was enhanced compared to wildtype BMM. TatARRB2(23), a cell-permeable peptide that contains the MAPK JNK-binding motif from within the ARRB2 C-domain, impaired ARRB2 interaction with JNK3, down-regulated C1q expression and permitted factor-independent survival in BMM, thus suggesting that this peptide antagonises ARRB2 function in macrophages. In addition, TatARRB2(23) transiently activated the phosphorylation of JNK and ERK, but not p38 in BMM. These data imply that ARRB2 acts to limit JNK/ERK activation and survival in macrophages, but is required for basal and TLR-inducible complement C1q expression. Given that loss of C1q function is strongly associated with the development of systemic lupus erythematosus, ARRB2 may act to limit the development of autoimmune disease.

Genetic variation of promoter sequence modulates XBP1 expression and genetic risk for vitiligo

Our previous genome-wide linkage analysis identified a susceptibility locus for generalized vitiligo on 22q12. To search for susceptibility genes within the locus, we investigated a biological candidate gene, X-box binding protein 1(XBP1). First, we sequenced all the exons, exon-intron boundaries as well as some 5′ and 3′ flanking sequences of XBP1 in 319 cases and 294 controls of Chinese Hans. Of the 8 common variants identified, the significant association was observed at rs2269577 (p__trend = 0.007, OR = 1.36, 95% CI = 1.09–1.71), a putative regulatory polymorphism within the promoter region of XBP1. We then sequenced the variant in an additional 365 cases and 404 controls and found supporting evidence for the association (p__trend = 0.008, OR = 1.31, 95% CI = 1.07–1.59). To further validate the association, we genotyped the variant in another independent sample of 1,402 cases and 1,288 controls, including 94 parent-child trios, and confirmed the association by both case-control analysis (p__trend = 0.003, OR = 1.18, 95% CI = 1.06–1.32) and the family-based transmission disequilibrium test (TDT, p = 0.005, OR = 1.93, 95% CI = 1.21–3.07). The analysis of the combined 2,086 cases and 1,986 controls provided highly significant evidence for the association (p__trend = 2.94×10⁻⁶, OR = 1.23, 95% CI = 1.13–1.35). Furthermore, we also found suggestive epistatic effect between rs2269577 and HLA-DRB1*07 allele on the development of vitiligo (p = 0.033). Our subsequent functional study showed that the risk-associated C allele of rs2269577 had a stronger promoter activity than the non-risk G allele, and there was an elevated expression of XBP1 in the lesional skins of patients carrying the risk-associated C allele. Therefore, our study has demonstrated that the transcriptional modulation of XBP1 expression by a germ-line regulatory polymorphism has an impact on the development of vitiligo.

Vitiligo is a genetically complex skin disorder that afflicts 0.1%–2% of the population throughout the world. Linkage and association studies in different populations have implicated several genomic regions and candidate genes that are linked to the development of vitiligo. Our previous genome-wide linkage analysis identified a genetic susceptibility locus for vitiligo on 22q12 in a Chinese population. In this study, we conducted a genetic and molecular study of a biologically plausible candidate gene, XBP1, within the region. We first performed a progressive association analysis in three independent samples of vitiligo, which revealed significant association between a putative promoter polymorphism, rs2269577, and vitiligo. Then, our functional analysis also demonstrated that the risk-associated allele of this variant has a stronger promoter activity and was associated with a significantly elevated expression of XBP1 in lesional skins in patients carrying the risk-associated allele. Our findings have provided the first evidence for XBP1 to play an important role in the development of vitiligo.

Effect of menopause on gene expression profiles of circulating monocytes: a pilot in vivo microarray study

Menopause is one of the key physiological events in the female life and can increase the risk for a number of complex autoimmune, neurodegenerative, metabolic, and cardiovascular disorders. Circulating monocytes can differentiate into various cell types and play an important role in tissue morphogenesis and immune response. We studied gene expression profiles of peripheral blood monocytes in healthy pre- and postmenopausal women using Affymetrix Human U133A GeneChip array that contains probes for approximately 14,500 genes. Comparative analyses between the samples showed that 20 genes were up- and 20 were down-regulated. Of these genes, 28 were classified into six major GO categories relevant to such biological processes as the cell proliferation, immune response, cellular metabolism, and the others. The remaining 12 genes have yet unidentified biological functions. Our results support the hypothesis that functional state of circulating monocytes is indeed affected by menopause, and resulting changes may be determined through the genomewide gene expression profiling. Several differentially expressed genes identified in this study may be candidates for further studies of menopause-associated systemic autoimmune, neurodegenerative, and cardiovascular disorders. Our study is only the first attempt in this direction, but it lays a basis for further research.

Lack of association of the TP53 Arg72Pro SNP and the MDM2 SNP309 with systemic lupus erythematosus in Caucasian, African American, and Asian children and adults

The p53 tumour suppressor is the central regulator of apoptosis. Previously, the functional TP53 Arg72Pro polymorphism was found to be associated with systemic lupus erythematosus (SLE) in Koreans but not Spaniards. MDM2 is the major negative regulator of p53. An intronic polymorphism in MDM2, the SNP309, attenuates p53 activity and is associated with accelerated tumour development in premenopausal women. Polymorphic variation in MDM2 has never been studied in SLE. The aim of this study is to further assess the contribution of p53-pathway genetic variation to SLE by testing the association of the TP53 Arg72Pro polymorphism and the MDM2 SNP309 with SLE in a well-characterised and ethnically diverse cohort of patients with both childhood- and adult-onset SLE (n = 314). No association was found between the TP53 Arg72Pro polymorphism and SLE in patients of European descent, Asian descent or in African Americans, nor was an association found between the MDM2 SNP309 and SLE in patients of European descent or in African Americans. In addition, there was no correlation between either variant and early-onset disease or nephritis, an index of severe disease. It is concluded that neither the TP53 Arg72Pro polymorphism nor the MDM2 SNP309 contributes significantly to either susceptibility or disease severity in SLE.

Association study between keratinocyte-derived growth factor gene polymorphisms and susceptibility to vitiligo vulgaris in a Taiwanese population: potential involvement of stem cell factor

BACKGROUND

Vitiligo vulgaris is a depigmentary disorder resulting from the disappearance of functional melanocytes. Currently, the pathogenesis of this disorder remains obscure.

OBJECTIVES

Genetic analysis of patients with vitilgo may provide important clues for elucidating the complex pathomechanisms involved in the disease process. Because dysfunctional keratinocytes have recently been implicated in the pathogenesis of vitiligo vulgaris, we conducted a case-control association study to investigate this phenomenon.

PATIENTS AND METHODS

Fifty-one patients with vitiligo vulgaris and 118 healthy controls from Taiwan were recruited to investigate the association between relevant keratinocyte-related genes and the occurrence of vitiligo vulgaris. This study genotyped 11 single-nucleotide polymorphisms (SNPs) in five genes including stem cell factor (SCF, also known as KITLG), basic fibroblast growth factor (bFGF, also known as NuDT6), endothelin-1 (EDN1), hepatocyte growth factor (HGF) and stem cell growth factor (SCGF, also known as CLEC11A).

RESULTS

Our results revealed that the A allele for SNP rs11104947 in the SCF gene and the T allele for SNP rs13866 in the SCGF gene were, respectively, associated with a 1.95- and a 2.14-fold risk of developing vitiligo vulgaris. A higher risk was also detected among subjects who carried the SCF rs995029/rs11104947 C/A haplotype (odds ratio = 2.45). Furthermore, the at-risk alleles for SCF rs11104947 (A allele) and for SCGF SNP rs13866 (T allele) were found to display a 7.92-fold increased gene-gene combined risk. No significant relationship between polymorphic frequency for genes bFGF, EDN1 as well as HGF and occurrence of vitiligo vulgaris was observed.

CONCLUSIONS

These novel genetic findings provide new insights in relation to the mechanisms that might be involved in the development of vitiligo vulgaris.

The analysis of genetics and associated autoimmune diseases in Chinese vitiligo patients

Vitiligo is a common skin and hair depigmentary disorder that results from selective destruction of melanocytes. It occurs in a typical multifactorial, polygenic inheritance. Several studies have indicated that vitiligo is associated with some autoimmune diseases. In this paper we examined 6,516 vitiligo patients including clinical characteristics, familial involvement, and their association with other autoimmune diseases. Compared with sporadic vitiligo probands, familial vitiligo probands have earlier age onset and longer disease duration. The prevalences of four autoimmune diseases namely rheumatoid arthritis, chronic urticaria, alopecia areata and psoriasis, were significantly elevated in generalized vitiligo probands and their first-degree relatives. The prevalences of chronic urticaria, rheumatoid arthritis, psoriasis were much higher in familial generalized vitiligo probands. In addition, the prevalences of diabetes mellitus and asthma were also higher in familial vitiligo probands. These findings indicate that generalized vitiligo may share common genetic aetiologic links with other autoimmune diseases, and the genetic component of familial generalized vitiligo is stronger.

The Arg160Trp allele of melanocortin-1 receptor gene might protect against vitiligo

Melanocortin-1 receptor (MC1R) and agouti signaling protein (ASIP) play pivotal roles in the regulation of human pigmentation. We aimed to study whether single nucleotide polymorphisms (SNPs) of the MC1R and ASIP genes contribute to the pathogenesis of the polygenic pigment skin disorder, vitiligo. The PCR-amplified, full-length MC1R gene was studied with sequence analysis, and the 3' untranslated region (3' UTR) SNP of ASIP was detected using restriction fragment length polymorphism. The allele frequency of the ASIP SNP did not show any difference between the skin type, hair color and eye color-matched 97 vitiligo patients and the 59 healthy control individuals. As one of the MC1R polymorphisms showed significantly higher incidence among fair-skinned individuals (Fitzpatrick I+II, n=140) than among dark-skinned individuals (Fitzpatrick III+IV, n=90), both vitiligo patients and controls were divided into two groups and the frequency of the MC1R alleles was studied separately in fair-skinned and dark-skinned subgroups of diseased and healthy groups. C478T, one of the MC1R SNPs studied in 108 fair-skinned vitiligo patients and in 70 fair-skinned healthy control individuals, showed a significant difference (P=0.0262, odds ratio [95% confidence interval]=3.6 [0.0046-0.1003]) in allele frequency between the two groups: the allele frequency was higher in the control group, suggesting protection against vitiligo. Computer prediction of antigenicity has revealed that the Arg160Trp amino acid change caused by this SNP results in a decrease in antigenicity of the affected peptide epitope.

Contribution of polymorphism in codon 72 of p53 gene to systemic lupus erythematosus in Poland

The contribution of the p53 Arg72Pro polymorphism in the development of systemic lupus erythematosus (SLE) remains controversial. We investigated the frequency of the p53 Arg72Pro genotype in patients with SLE ( n = 155) and in controls ( n = 150) in Poland. We found a weak contribution of the Arg/Arg genotype to the morbidity of SLE. Odds ratio (OR) for patients with SLE and p53 Arg/Arg genotype was 1.875 [95% CI = 1.180—2.979], P = 0.0075 and OR of the Arg/Arg and Arg/Pro genotypes was 1.549 [95% CI = 0.752—3.195], P = 0.2328.

Since the p53Arg variant supports apoptosis better than the p53Pro variant, our findings can be linked to an increase in the number of apoptotic leucocytes in SLE patients. The distinction between various populations may be because of differences in racial composition and/or exposure to distinct environmental factors that have a different impact on SLE incidence along with the changed Argp53Pro genotype. Lupus (2008) 17, 148—151.

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.

Autoimmunity as an aetiological factor in vitiligo

Vitiligo is a common dermatological disorder characterized by the presence on the skin of depigmented macules resulting from the destruction of cutaneous melanocytes. Autoimmunity is an important hypothesis with regard to vitiligo aetiology and the evidence for autoimmune responses being involved in the pathogenesis of this disorder will be discussed in the present review. All immune system compartments, including innate and adaptive immunity have been implicated in vitiligo development. Particularly relevant are autoantibodies and autoreactive T cells in vitiligo patients that have cytotoxic effects upon pigment cells. Furthermore, predisposition to vitiligo appears to be associated with certain alleles of the major histocompatibility complex class II antigens as well as with other autoimmune-susceptibility genes. Moreover, the association of vitiligo with autoimmune disorders, the animal models of the disease, and the positive response to immunosuppressive therapeutic agents emphasize the role of autoimmunity in the development of this disorder.

The genetics of generalized vitiligo and associated autoimmune diseases

Vitiligo is an acquired disorder in which patches of depigmented skin and often overlying hair, and mucous membranes, are the result of progressive autoimmune loss of melanocytes from the involved areas. Considered the most common pigmentary disorder, vitiligo involves complex interaction of environmental and genetic factors that ultimately contribute to melanocyte destruction, resulting in the characteristic depigmented lesions. In the past few years, studies of the genetic epidemiology of vitiligo have led to the recognition that generalized vitiligo is part of a broader autoimmune disease diathesis. Attempts to identify genes involved in susceptibility to generalized vitiligo have involved gene expression studies, genetic association studies of candidate genes, and genome-wide linkage analyses to discover new genes. These studies have begun to yield results that shed light on the mechanisms of vitiligo pathogenesis. It is anticipated that the discovery of biological pathways of vitiligo pathogenesis will provide novel targets for future approaches to the treatment and prevention of vitiligo and its associated autoimmune diseases.

From inflammasomes to fevers, crystals and hypertension: how basic research explains inflammatory diseases

Pattern-recognition receptors, such as Toll-like receptors and NOD-like receptors (NLRs), are able through the recognition of pathogen-associated molecular patterns and danger-associated molecular patterns to sense microbe-dependent and microbe-independent danger and thereby initiate innate immune responses. In some autoinflammatory conditions, abnormalities in NLR signaling pathways are involved in pathogenesis, as exemplified by NOD2 mutations associated with Crohn's disease. Some other NLRs are components of the inflammasome, a caspase-1- and prointerleukin-1beta-activating complex. Clinical and experimental studies are beginning to reveal the central role of the inflammasome in innate immunity. Here, we focus on monogenic hereditary inflammatory diseases, such as Muckle-Wells syndrome, which are associated with mutations in proteins that modulate the activity of the inflammasome, and on some multifactorial disorders, such as Type 2 diabetes and hypertension.

Genetic variations in NALP1 are associated with generalized vitiligo in a Romanian population

Generalized vitiligo is a common, multifactorial, polygenic disease in which autoimmune loss of melanocytes results in depigmented spots of skin, overlying hair, and mucous membranes. In Caucasian families from the United States of America and United Kingdom, susceptibility to generalized vitiligo and associated autoimmune diseases is genetically associated with variants of NALP1, encoding NACHT leucine-rich repeat protein 1. Here, we describe a population-based case-control association analysis of single-nucleotide polymorphisms (SNPs) distributed through the NALP1 region in Caucasian generalized vitiligo patients and controls from Romania. This study confirms genetic association of generalized vitiligo with variation in NALP1, which contains at least two independent risk signals, one tagged by SNP rs6502867 and another tagged by SNPs rs2670660 and rs8182352. Individuals carrying high-risk alleles of both rs6502867 and rs2670660 had an odds ratio of 4.20 compared with individuals carrying a high-risk allele from only one signal. These findings support the involvement of NALP1 in predisposition to generalized vitiligo.

The association between endothelin-1 gene polymorphisms and susceptibility to vitiligo in a Korean population

BACKGROUND

Vitiligo is a skin disorder affected by genetic, environmental, local and endocrine factors. Endothelin-1, which is expressed by keratinocytes, has paracrine effects on melanocytes, influencing their homeostasis, proliferation and pigmentation. It is thought to play a role in the skin response to 311-nm, narrow-band ultraviolet irradiation.

OBJECTIVE

To investigate the association of endothelin-1 gene (EDN1) polymorphisms with vitiligo in a Korean population.

METHODS

To evaluate the expression of endothelin-1 in cultured human keratinocytes after irradiation with narrow-band ultraviolet B (NBUVB), we performed RT-PCR and ELISA. In addition, we genotyped 312 vitiligo patients and 313 matched-healthy controls, and compared the genotype, allele and haplotype frequencies of EDN1 polymorphisms (intron 4 G/A, rs2071942 and exon 5 G/T, rs5370) between the two groups, using PCR-restriction fragment length polymorphism. The effects of sex, onset age, the presence of autoimmune diseases, family history and clinical type were analysed statistically.

RESULTS

NBUVB induced the expression of endothelin-1 in cultured human keratinocytes. The genotype distributions and allele frequencies of EDN1 polymorphisms did not differ significantly between vitiligo patients and healthy controls. Moreover, the results were not related to sex, onset age, the presence of autoimmune diseases or family history. Interestingly, the haplotype frequencies of EDN1 polymorphisms differed significantly between vitiligo patients and healthy controls. When analysed according to clinical type, the haplotype frequencies in the focal and segmental clinical types differed significantly from healthy controls.

CONCLUSION

This study suggests that EDN1 is related to the development of vitiligo in the Korean population.