Association of the thyroid stimulating hormone receptor gene (TSHR) with Graves' disease

Polymorphisms of the TNFAIP3 region and Graves' disease

Autoimmune thyroid disease (AITD) is a multifactorial organ-specific autoimmune disorder, and both genetic susceptibility and environmental factors are involved in its etiology. TNFAIP3 encodes the ubiquitin-modifying enzyme (A20), a key regulator of inflammatory signaling pathways. The aim of the present study was to evaluate the association between TNFAIP3 gene polymorphisms and AITD in Chinese Han population. Three single nucleotide polymorphisms (SNPs) in TNFAIP3 gene locus (rs598493, rs610604 and rs661561) were detected in a set of 667 patients with AITD and 301 controls in Han Chinese population using the Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometer (MALDI-TOF-MS) Platform. Compared with those of the controls, the frequencies of GG genotype of rs598493, the AA genotype of rs610604, the allele G and GG genotype of rs661561 were significantly increased in Graves' disease (GD) patients. However, the frequencies of AG genotype of rs598493 and AC genotype of rs610604 were significantly decreased in GD patients. The ATC haplotype (rs598493, rs661561 and rs610604) was associated with a decreased risk of GD. No significant differences in the three SNPs were observed between HT patients and controls. Our study shows a clear association between the polymorphisms of TNFAIP3 gene and GD, not HT, suggesting that TNFAIP3 gene is likely to be a genetic susceptibility factor to GD.

Dual effect of a polymorphism in the macrophage migration inhibitory factor gene is associated with new-onset Graves disease in a Taiwanese Chinese population

Graves disease (GD) is an autoimmune disease. Macrophage migration inhibitory factor (MIF) is a potent cytokine that plays an important role in the regulation of immune responses. Two polymorphisms in the promoter region of MIF, rs5844572 and rs755622, are known to affect MIF expression. The purpose of this study was to investigate the relationship between polymorphisms in the MIF gene promoter and the severity of GD. A total of 677 individuals, including 481 GD patients and 196 ethnically matched healthy controls, were genotyped to identify differences in the distribution of the MIF polymorphisms rs5844572 and rs755622. Although there were no significant differences in the allele or genotype distributions among patients with different grades of goiter in GD and healthy controls, the distribution of the C allele, especially C/C genotype, of the rs755622 single nucleotide polymorphism (SNP) in MIF, may be as a risk factor for goiter initiation whereas a protector against development of severe goiter in patients with untreated GD (p<0.05). A goiter-developmental model incorporating genetic (MIF SNP rs755622) and environmental risk factors (gender, radioiodine treatment, thyroid gland surgery and vitiligo) significantly increased the prediction accuracy. Further studies are required to address the role of MIF polymorphisms, as well as their association with other candidate genes, in GD.

Lack of association of IRF5 gene polymorphisms with autoimmune thyroid disease: a case-control study. IRF5 gene and AITD

BACKGROUND

Several studies support a link between autoimmunity and interferon regulatory factor 5 (IRF5) gene polymorphisms. We have taken the opportunity to examine association of the autoimmune disease risk gene, the interferon regulatory factor 5 (IRF5) to survey its susceptibility to autoimmune thyroid disease. "A total of 667 patients with autoimmune thyroid diseases and 301 healthy controls were genotyped for rs10954213, rs2004640, rs3807306, rs752637 and rs7808907 of IRF5 gene polymorphisms". We further investigated the association between BANK1 gene and IRF5 gene in AITD patients.

RESULTS

For IRF5 gene, both in allele and genotype frequencies from both GD and HT patients were not significantly different from those of controls. Association between rs7808907C allele and Graves' disease showed trend towards significance (P=0.067). Haplotype results in IRF5 represented in the same block, without significant association. No significant association was found between all IRF5 SNPs and ophthalmopathy in Graves' patients. Additive interaction analysis revealed no interactions between IRF5 and BANK1 gene in AITD patients.

CONCLUSION

Our data fail to reveal IRF5 as a susceptibility gene to AITD and do not support additive effect of IRF5 to BANK1 gene.

Association of TLR7 and TSHR copy number variation with Graves' disease and Graves' ophthalmopathy in Chinese population in Taiwan

BACKGROUND

Graves' disease (GD) and Graves' ophthalmopathy (GO) are autoimmune disorders, which might be influenced by genetic factors. Copy number variation (CNV) is an important source of genomic diversity in humans, and influences disease susceptibility. This study investigated the association between CNV in the TSHR and TLR7 genes and the development of GD and GO in a Chinese population in Taiwan.

METHODS

For this case-control study, sample from 196 healthy controls and 484 GD patients, including 203 patients with GO were studied. CNV was detected by real-time polymerase chain reaction (PCR) using TaqMan™ probes and the relative copy number (CN) was estimated by using the comparative Ct method.

RESULTS

The differences in the distribution of TSHR CNV in healthy controls and GD patients were statistically significant (p value = 0.01). However, the difference in the distribution of TSHR CNV in the control group and the GO group was not statistically significant (p value = 0.06). For TLR7 CNV, the results were not significantly different when we compared the distribution in healthy controls and GD patients and in healthy controls and GO patients (p values for Fisher's exact test were 0.13 and 0.09, respectively). However, a lower than normal CNV for TLR7 (CNV < 2 for female and CNV < 1 for male) was found to have a protective effect against the development of GD (odds ratio (OR) = 0.24; 95% confidence interval (CI), 0.07-0.75) after adjusting for age and gender.

CONCLUSIONS

These results suggested that TSHR and TLR7 CNV might be associated with susceptibility to GD.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Refined association of TSH receptor susceptibility locus to Graves' disease in the Chinese Han population

BACKGROUND

Convincing evidence has demonstrated the association of TSH receptor (TSHR) with Graves' disease (GD) in the Chinese Han population.

OBJECTIVE

The aim of this study was to identify the causal variants for GD in the region encompassing TSHR by a refining association study.

DESIGN AND METHODS

GD patients (1536) and 1516 sex-matched controls were recruited in the first stage, and an additional 3832 GD patients and 3426 sex-matched controls were recruited in the replication stage. Genotyping was performed using Illumina Human660-Quad BeadChips or TaqMan single nucleotide polymorphism (SNP) Genotyping Assays and the Fluidigm EP1 platform.

RESULTS

When the results of regression analysis for 74 genotyped SNPs and 922 imputed SNPs in the first-stage cohort were combined, rs179243 and rs3783949 were the probable susceptibility SNPs associated with GD in TSHR. Eleven SNPs, including rs179243 and rs3783949, were selected to further refine the association in the replication study. Finally, rs12101261 and rs179243 were confirmed as independent GD susceptibility variants in the replication and combined populations. Further, we also found that the rate of persistent TSHR autoantibody positivity (pTRAb+) was significantly higher in the GD patients with the susceptible genotypes rs12101261 or rs179243 than in the GD patients carrying the protective genotypes, after the GD patients had been treated for more than 1 year.

CONCLUSIONS

These findings indicate that rs12101261 and rs179243 are the possible causal SNPs for GD susceptibility in the TSHR gene and could serve as genetic markers to predict the outcome of pTRAb+ in GD patients.

Genetic heterogeneity of susceptibility gene in different ethnic populations: refining association study of PTPN22 for Graves' disease in a Chinese Han population

In our previous studies, we presumed subtypes of Graves’ disease (GD) may be caused by different major susceptibility genes or different variants of a single susceptibility gene. However, more evidence is needed to support this hypothesis. Single-nucleotide polymorphism (SNP) rs2476601 in PTPN22 is the susceptibility loci of GD in the European population. However, this polymorphism has not been found in Asian populations. Here, we investigate whether PTPN22 is the susceptibility gene for GD in Chinese population and further determine the susceptibility variant of PTPN22 in GD. We conducted an imputation analysis based on the results of our genome-wide association study (GWAS) in 1,536 GD patients and 1,516 control subjects. Imputation revealed that 255 common SNPs on a linkage disequilibrium (LD) block containing PTPN22 were associated with GD (P<0.05). Nine tagSNPs that captured the 255 common variants were selected to be further genotyped in a large cohort including 4,368 GD patients and 4,350 matched controls. There was no significant difference between the nine tagSNPs (P>0.05) in either the genotype distribution or allelic frequencies between patients and controls in the replication study. Although the combined analysis exhibited a weak association signal (P_combined = 0.003263 for rs3811021), the false positive report probability (FPRP) analysis indicated it was most likely a false positive finding. Our study did not support an association of common SNPs in PTPN22 LD block with GD in Chinese Han population. This suggests that GD in different ethnic population is probably caused by distinct susceptibility genes.

rs3827440, a nonsynonymous single nucleotide polymorphism within GPR174 gene in X chromosome, is associated with Graves' disease in Polish Caucasian population

Recently Chu et al. conducted a two-stage genome wide association study in Chinese that identified a novel X-linked Graves' disease (GD) susceptibility marker at rs3827440 - a nonsynonymous (P162S) nucleotide transition (519C<T) within G protein-coupled receptor 174 (GPR174) gene. We aimed to replicate this finding in Caucasians. Using the TaqMan approach we typed rs3827440 in 560 GD patients from Warsaw and 196 patients from Gliwice as well as ethically matched controls (N = 748, N = 198, respectively). We found an association of the rs3827440 T allele with GD using both an allelic and genotype comparison [odds ratio (OR) = 1.19, 95% confidence interval (CI): 1.03-1.38, P = 0.021; OR=1.32, 95% CI: 1.03-1.69, P = 0.03, respectively]. There was no difference in distribution of rs3827440 alleles/genotypes vs gender, tobacco smoking, ophthalmopathy or age at disease onset. Also, no statistically significant differences were observed after stratifying patients for DRB1*03- or GD-associated variants in CTLA4 or TSHR genes. Our study provides the first replication in a Caucasian population of the association between GD and rs3827440 originally reported among Chinese. Our results also validate statistical methodology used by Chu et al. to detect associations with X-linked markers.

An epistatic interaction between the PAX8 and STK17B genes in papillary thyroid cancer susceptibility

Papillary Thyroid Cancer (PTC) is a heterogeneous and complex disease; susceptibility to PTC is influenced by the joint effects of multiple common, low-penetrance genes, although relatively few have been identified to date. Here we applied a rigorous combined approach to assess both the individual and epistatic contributions of genetic factors to PTC susceptibility, based on one of the largest series of thyroid cancer cases described to date. In addition to identifying the involvement of TSHR variation in classic PTC, our pioneer study of epistasis revealed a significant interaction between variants in STK17B and PAX8. The interaction was detected by MD-MBR (p = 0.00010) and confirmed by other methods, and then replicated in a second independent series of patients (MD-MBR p = 0.017). Furthermore, we demonstrated an inverse correlation between expression of PAX8 and STK17B in a set of cell lines derived from human thyroid carcinomas. Overall, our work sheds additional light on the genetic basis of thyroid cancer susceptibility, and suggests a new direction for the exploration of the inherited genetic contribution to disease using association studies.

The new perspectives on genetic studies of type 2 diabetes and thyroid diseases

Recently, genome-wide association studies (GWAS) have led to the discovery of hundreds of susceptibility loci that are associated with complex metabolic diseases, such as type 2 diabetes and hyperthyroidism. The majority of the susceptibility loci are common across different races or populations; while some of them show ethnicity-specific distribution. Though the abundant novel susceptibility loci identified by GWAS have provided insight into biology through the discovery of new genes or pathways that were previously not known, most of them are in introns and the associated variants cumulatively explain only a small fraction of total heritability. Here we reviewed the genetic studies on the metabolic disorders, mainly type 2 diabetes and hyperthyroidism, including candidate genes-based findings and more recently the GWAS discovery; we also included the clinical relevance of these novel loci and the gene-environmental interactions. Finally, we discussed the future direction about the genetic study on the exploring of the pathogenesis of the metabolic diseases.

GWAS in autoimmune thyroid disease: redefining our understanding of pathogenesis

The ability of the immune system to protect the body from attack by foreign antigens is essential for human survival. The immune system can, however, start to attack the body's own organs. An autoimmune response against components of the thyroid gland affects 2-5% of the general population. Considerable familial clustering is also observed in autoimmune thyroid disease (AITD). Teasing out the genetic contribution to AITD over the past 40 years has helped unravel how immune disruption leads to disease onset. Breakthroughs in genome-wide association studies (GWAS) in the past decade have facilitated screening of a greater proportion of the genome, leading to the identification of a before unimaginable number of AITD susceptibility loci. This Review will focus on the new susceptibility loci identified by GWAS, what insights these loci provide about the pathogenesis of AITD and how genetic susceptibility loci shared between different autoimmune diseases could help explain disease co-clustering within individuals and families. This Review also discusses where future efforts should be focused to translate this step forward in our understanding of the genetic contribution to AITD into a better understanding of disease presentation and progression, and improved therapeutic options.

A refined study of FCRL genes from a genome-wide association study for Graves' disease

To pinpoint the exact location of the etiological variant/s present at 1q21.1 harboring FCRL1-5 and CD5L genes, we carried out a refined association study in the entire FCRL region in 1,536 patients with Graves' disease (GD) and 1,516 sex-matched controls by imputation analysis, logistic regression, and cis-eQTL analysis. Among 516 SNPs with P<0.05 in the initial GWAS scan, the strongest signals associated with GD and correlated to FCRL3 expression were located at a cluster of SNPs including rs7528684 and rs3761959. And the allele-specific effects for rs3761959 and rs7528684 on FCRL3 expression level revealed that the risk alleles A of rs3761959 and C of rs7528684 were correlated with the elevated expression level of FCRL3 whether in PBMCs or its subsets, especially in CD19(+) B cells and CD8(+) T subsets. Next, the combined analysis with 5,300 GD cases and 4,916 control individuals confirmed FCRL3 was a susceptibility gene of GD in Chinese Han populations, and rs3761959 and rs7528684 met the genome-wide association significance level (P(combined) = 2.27×10(-12) and 7.11×10(-13), respectively). Moreover, the haplotypes with the risk allele A of rs3761959 and risk allele C of rs7528684 were associated with GD risk. Finally, our epigenetic analysis suggested the disease-associated C allele of rs7528684 increased affinity for NF-KB transcription factor. Above data indicated that FCRL3 gene and its proxy SNP rs7528684 may be involved in the pathogenesis of GD by excessive inhibiting B cell receptor signaling and the impairment of suppressing function of Tregs.

The immunopathogenesis of chronic autoimmune thyroiditis one century after hashimoto

Hakaru Hashimoto described 4 patients with a hitherto unknown cause for goitre, struma lymphomatosa, a century ago. He was careful to distinguish this from Riedel thyroiditis but it has become clear that fibrosis and atrophy of the thyroid are indeed components of Hashimoto thyroiditis, and in rare cases IgG4-related sclerosing disease may be an outcome. Although the cause of the lymphocytic infiltration was unknown to Hashimoto, we now know through the pioneering studies of N.R. Rose and E. Witebsky [J Immunol 1956;76:417-427] that this condition is the archetype for autoimmune destruction as a disease mechanism. In the last two decades in particular, there has been huge interest in unravelling the genetic basis for this and related autoimmune disorders. The list of polymorphisms associated with autoimmune thyroid disease grows each year, and in the case of vitiligo, which is frequently found in association with thyroid autoimmunity, we know that 27 separate susceptibility loci account for less than 20% of the heritability of this condition. Environmental and existential factors may turn out to be just as complex in number and in interactions. We can thus imagine a 'Swiss cheese' model for the causation of autoimmune thyroid disease, in which the effects of cumulative weaknesses line up - like the holes in slices of cheese - to allow the catastrophic event of autoimmune destruction to occur.

The genetic basis of graves' disease

The presented comprehensive review of current knowledge about genetic factors predisposing to Graves’ disease (GD) put emphasis on functional significance of observed associations. In particular, we discuss recent efforts aimed at refining diseases associations found within the HLA complex and implicating HLA class I as well as HLA-DPB1 loci. We summarize data regarding non-HLA genes such as PTPN22, CTLA4, CD40, TSHR and TG which have been extensively studied in respect to their role in GD. We review recent findings implicating variants of FCRL3 (gene for FC receptor-like-3 protein), SCGB3A2 (gene for secretory uteroglobin-related protein 1- UGRP1) as well as other unverified possible candidate genes for GD selected through their documented association with type 1 diabetes mellitus: Tenr–IL2–IL21, CAPSL (encoding calcyphosine-like protein), IFIH1(gene for interferon-induced helicase C domain 1), AFF3, CD226 and PTPN2. We also review reports on association of skewed X chromosome inactivation and fetal microchimerism with GD. Finally we discuss issues of genotype-phenotype correlations in GD.

Immunogenetic mechanisms leading to thyroid autoimmunity: recent advances in identifying susceptibility genes and regions

The autoimmune thyroid diseases (AITD) include Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), which are characterised by a breakdown in immune tolerance to thyroid antigens. Unravelling the genetic architecture of AITD is vital to better understanding of AITD pathogenesis, required to advance therapeutic options in both disease management and prevention. The early whole-genome linkage and candidate gene association studies provided the first evidence that the HLA region and CTLA-4 represented AITD risk loci. Recent improvements in; high throughput genotyping technologies, collection of larger disease cohorts and cataloguing of genome-scale variation have facilitated genome-wide association studies and more thorough screening of candidate gene regions. This has allowed identification of many novel AITD risk genes and more detailed association mapping. The growing number of confirmed AITD susceptibility loci, implicates a number of putative disease mechanisms most of which are tightly linked with aspects of immune system function. The unprecedented advances in genetic study will allow future studies to identify further novel disease risk genes and to identify aetiological variants within specific gene regions, which will undoubtedly lead to a better understanding of AITD patho-physiology.

Effective expression of human proteins on bacterial magnetic particles in an anchor gene deletion mutant of Magnetospirillum magneticum AMB-1

Biologically synthesized magnetic particles by magnetotactic bacteria (BacMPs) have promising potential in the area of functional protein display technology for various biotechnological and biomedical applications. Functional proteins fused with an anchor protein, Mms13, have been demonstrated to be an effective and stable method for the display of functional proteins on BacMPs. However, the expression of some human proteins is relatively low. Useful host strains of Escherichia coli have been developed for the enhanced expression of recombinant proteins using a genetic engineering approach. To improve human protein expression level on BacMPs in Magnetospirillummagneticum AMB-1, a mutant strain with a deleted native mms13 gene (Δmms13 strain) was established and evaluated for effective functional protein display technology. As a result, the Δmms13 strain synthesized BacMPs with significantly improved expression of two human proteins, thyroid-stimulating hormone receptor (TSHR) and the class II major histocompatibility complex (MHC II) molecules. The Δmms13 strain could therefore be an effective strain for the display of other important human proteins on BacMPs and may be useful for further applications.

Targeting the thyrotropin receptor in thyroid disease

INTRODUCTION

The thyrotropin receptor (TSHR) is essential for thyroid growth and for the production of thyroid hormones. It is unique among the glycoprotein hormone receptors, in that some of the TSHRs undergo cleavage and shedding of the alpha subunit.

AREAS COVERED

This review discusses the structure and function of the TSHR, followed by an evaluation of its role in thyroid disease. Possible limitations of the TSHR as a therapeutic target are also discussed.

EXPERT OPINION

The TSHR is involved in a number of hereditary and acquired disorders of the thyroid making it of potential importance as a therapeutic target in thyroid disease. Expression of the TSHR in several non-thyroidal tissues and the development of systemic manifestations of thyroid disease suggest that the TSHR is also of interest as a therapeutic target outside the thyroid.

Thyrotoxicosis

Thyrotoxicosis is a common disorder, especially in women. The most frequent cause is Graves' disease (autoimmune hyperthyroidism). Other important causes include toxic nodular hyperthyroidism, due to the presence of one or more autonomously functioning thyroid nodules, and thyroiditis caused by inflammation, which results in release of stored hormones. Antithyroid drugs are the usual initial treatment (thionamides such as carbimazole or its active metabolite methimazole are the drugs of choice). A prolonged course leads to remission of Graves' hyperthyroidism in about a third of cases. Because of the low remission rate in Graves' disease and the inability to cure toxic nodular hyperthyroidism with antithyroid drugs alone, radioiodine is increasingly used as first line therapy, and is the preferred choice for relapsed Graves' hyperthyroidism. Total thyroidectomy is an option in selected cases. Future efforts are likely to concentrate on novel and safe ways to modulate the underlying disease process rather than stopping excess thyroid hormone production.

Genetic factors of autoimmune thyroid diseases in Japanese

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are caused by immune response to self-thyroid antigens and affect approximately 2–5% of the general population. Genetic susceptibility in combination with external factors, such as smoking, viral/bacterial infection, and chemicals, is believed to initiate the autoimmune response against thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITDs. Various techniques have been employed to identify genes contributing to the etiology of AITDs, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked to AITDs, and, in some of these loci, putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to GD and HT and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. Known AITD-susceptibility genes are classified into three groups: HLA genes, non-HLA immune-regulatory genes (e.g., CTLA-4, PTPN22, and CD40), and thyroid-specific genes (e.g., TSHR and Tg). In this paper, we will summarize the latest findings on AITD susceptibility genes in Japanese.

Association between thyroid stimulating hormone receptor gene intron polymorphisms and autoimmune thyroid disease in a Chinese Han population

Autoimmune thyroid disease (AITD) is a multifactorial disease with a genetic susceptibility and environmental factors. The thyroid stimulating hormone receptor gene (TSHR) which is expressed on the surface of the thyroid epithelial cell is thought to be the main auto-antigen and a significant candidate for genetic susceptibility to AITD. This case-control study aimed at evaluating the association between single nucleotide polymorphisms (SNP) of TSHR and AITD in a Chinese Han population. We recruited 404 patients with Graves' disease (GD), 230 patients with Hashimoto's thyroiditis (HT) and 242 healthy controls. The Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometer (MALDI-TOF-MS) Platform was used to detect five SNPs (rs179247, rs12101255, rs2268475, rs1990595, and rs3783938) in TSHR gene. The frequencies of allele T and TT genotype of rs12101255 in GD patients were significantly increased compared with those of the controls (P=0.004/0.015, OR=1.408/1.446). The allele A frequency of rs3783938 was greater in HT patients than in the controls (P=0.025, OR=1.427). The AT haplotype (rs179247-rs12101255) was associated with an increased risk of GD (P=0.010, OR=1.368). The allele A of rs179247 was associated with ophthalmopathy in GD patients. These data suggest that the polymorphisms of rs12101255 and rs3783938 are associated with GD and HT, respectively.

A genome-wide association study identifies two new risk loci for Graves' disease

Graves' disease is a common autoimmune disorder characterized by thyroid stimulating hormone receptor autoantibodies (TRAb) and hyperthyroidism. To investigate the genetic architecture of Graves' disease, we conducted a genome-wide association study in 1,536 individuals with Graves' disease (cases) and 1,516 controls. We further evaluated a group of associated SNPs in a second set of 3,994 cases and 3,510 controls. We confirmed four previously reported loci (in the major histocompatibility complex, TSHR, CTLA4 and FCRL3) and identified two new susceptibility loci (the RNASET2-FGFR1OP-CCR6 region at 6q27 (P(combined) = 6.85 × 10(-10) for rs9355610) and an intergenic region at 4p14 (P(combined) = 1.08 × 10(-13) for rs6832151)). These newly associated SNPs were correlated with the expression levels of RNASET2 at 6q27, of CHRNA9 and of a previously uncharacterized gene at 4p14, respectively. Moreover, we identified strong associations of TSHR and major histocompatibility complex class II variants with persistently TRAb-positive Graves' disease.

Association of an SNP with intrathymic transcription of TSHR and Graves' disease: a role for defective thymic tolerance

Graves' disease (GD) is the paradigm of an anti-receptor autoimmune disease, with agonistic auto-antibodies against the thyrotropin receptor (TSHR-thyroid-stimulating hormone receptor) being the underlying pathogenic effector mechanism. The TSHR belongs to the category of tissue-restricted antigens, which are promiscuously expressed in the thymus and thereby induce central T cell tolerance. In order to understand the association between TSHR gene polymorphisms and GD, we tested the hypothesis that TSHR gene variants affect susceptibility to GD by influencing levels of TSHR transcription in the thymus. We show that thymic glands from non-autoimmune donors homozygous for the rs179247 SNP predisposing allele of TSHR had significantly fewer TSHR mRNA transcripts than carriers of the protective allele. In addition, in heterozygous individuals, the TSHR predisposing allele was expressed at a lower level than the protective one as demonstrated by allele-specific transcript quantification. This unbalanced allelic expression was detectable in both thymic epithelial cells and thymocytes. Since the level of self-antigen expression is known to influence the threshold of central tolerance, these results are compatible with the notion that defective central tolerance contributes to the pathogenesis of GD, a scenario already implicated in type 1 diabetes mellitus, myasthenia gravis and autoimmune myocarditis.

Diseases associated with thyroid autoimmunity: explanations for the expanding spectrum

Anyone who has been in an endocrine clinic will appreciate that associations exist between autoimmune thyroid disease (AITD) and other autoimmune disorders. However, the full extent of these associations is still not fully appreciated, and new associations are being uncovered which may shed new light on the pathogenic basis for these connections, and the underlying reasons for them are only now becoming understood. This review is based on the British Thyroid Association Pitt-Rivers Lecture 2010. The first section provides an update on studies which have detailed the strength of various autoimmune disease associations, the second section discusses the environmental and genetic factors which underlie these associations and the final section describes some recently identified, unexpected AITD associations. Unravelling these associations further will illuminate the pathogenesis of autoimmune diseases and offers the prospect of new therapeutic approaches.

The clinical presentation of autoimmune thyroid disease in men is associated with IL12B genotype

BACKGROUND

Common variants in the interleukin 12B (IL12B) gene are associated with predominantly inflammatory (Th1) or antibody-mediated (Th2) immune responses. As Hashimoto's disease and Graves' disease are thought to arise from mainly Th1 and Th2 immune responses respectively, we hypothesized that IL12B genotype may influence the clinical presentation of autoimmune thyroid disease.

OBJECTIVE

We tested for differences in IL12B genotype between Graves' disease and Hashimoto's disease.

PATIENTS

We studied a discovery cohort of 203 Australian women and 37 men with autoimmune thyroid disease, a replication cohort of 100 European men and a cohort of 146 Chinese men.

INTERVENTION

We analysed three IL12B variants: rs41292470, in the promoter; rs3212227, in the 3' untranslated region and rs6887695, located 60 kilobases upstream from the coding region.

RESULTS

In the discovery cohort, rs41292470 and rs3212227 genotypes did not differ significantly between Hashimoto's disease and Graves' disease. In Australian men (but not women), rs6887695 genotype differed between Hashimoto's disease and Graves' disease, with a minor allele frequency (MAF) of 14% and 41%, respectively (P=0·034). This result was confirmed in the European men (MAF 24% and 41%; P=0·013). On combined analysis of Australian, European and Chinese men (N=285), the difference was highly significant (MAF 23% and 45%; P=3×10(-5) ). In 233 men without thyroid disease, the MAF was 34%, significantly different from Graves' disease (P=0·005) and Hashimoto's disease (P=0·029).

CONCLUSION

In men with autoimmune thyroid disease, a common variant located upstream of the IL12B coding region may influence whether patients present with Graves' disease or Hashimoto's disease.

Association study of interleukin-12A gene polymorphisms with Graves' disease in two Chinese populations

OBJECTIVE

Graves' disease (GD) is a common autoimmune disorder and genetic and environmental factors contributing to its aetiology. The pro-inflammatory cytokine interleukin-12 (IL-12) is believed to be critically involved in the pathogenesis of GD. This study aims to elucidate the effect of IL-12A gene polymorphisms on GD.

DESIGN AND METHODS

A case-control association study of five tag single nucleotide polymorphisms (SNPs) (rs2243115, rs2243123, rs583911, rs568408 and rs2243143) within the IL-12A gene was performed in two independent Chinese cohorts. A pilot cohort conducted in Shanghai consisted of 701 patients and 686 controls and a replicate cohort in Xiamen Island included 378 patients and 312 controls. The five SNPs were genotyped by the SNPstream Genotyping Systems and Taqman PCR method.

RESULTS

Polymorphism of rs568408, located at the 3'-UTR region, was found to have a significant association with GD in both the cohorts (P(allele) = 2·96 × 10⁻⁷ and P(allele) = 0·013 for Shanghai and Xiamen Island cohorts, respectively). Haplotype analysis showed that the haplotype of the five SNPs (TTAAG) was associated with a significant risk of GD in both the cohorts (OR = 2·04 and OR = 1·70 for Shanghai and Xiamen Island cohorts, respectively).

CONCLUSION

Our results have established an association between IL-12A polymorphism and GD susceptibility in the Chinese population.

Endocrine autoimmune disease: genetics become complex

The endocrine system is a frequent target in pathogenic autoimmune responses. Type 1 diabetes and autoimmune thyroid disease are the prevailing examples. When several diseases cluster together in one individual, the phenomenon is called autoimmune polyglandular syndrome. Progress has been made in understanding the genetic factors involved in endocrine autoimmune diseases. Studies on monogenic autoimmune diseases such as autoimmune polyglandular syndrome type 1, immunodysregulation, polyendocrinopathy, enteropathy, X-linked and primary immune deficiencies helped uncover the role of key regulators in the preservation of immune tolerance. Alleles of the major histocompatibility complex have been known to contribute to the susceptibility to most forms of autoimmunity for more than 3 decades. Furthermore, sequencing studies revealed three non-major histocompatibility complex loci and some disease specific loci, which control T lymphocyte activation or signalling. Recent genome-wide association studies (GWAS) have enabled acceleration in the identification of novel (non-HLA) loci and hence other relevant immune response pathways. Interestingly, several loci are shared between autoimmune diseases, and surprisingly some work in opposite direction. This means that the same allele which predisposes to a certain autoimmune disease can be protective in another. Well powered GWAS in type 1 diabetes has led to the uncovering of a significant number of risk variants with modest effect. These studies showed that the innate immune system may also play a role in addition to the adaptive immune system. It is anticipated that next generation sequencing techniques will uncover other (rare) variants. For other autoimmune disease (such as autoimmune thyroid disease) GWAS are clearly needed.

Thyroid stimulating hormone receptor (TSHR) intron 1 variants are major risk factors for Graves' disease in three European Caucasian cohorts

BACKGROUND

The thyroid stimulating hormone receptor (TSHR) gene is an established susceptibility locus for Graves' disease (GD), with recent studies refining association to two single nucleotide polymorphisms (SNPs), rs179247 and rs12101255, within TSHR intron 1.

METHODOLOGY AND PRINCIPAL FINDINGS

We aimed to validate association of rs179247 and rs12101255 in Polish and UK Caucasian GD case-control subjects, determine the mode of inheritance and to see if association correlates with specific GD clinical manifestations. We investigated three case-control populations; 558 GD patients and 520 controls from Warsaw, Poland, 196 GD patients and 198 controls from Gliwice, Poland and 2504 GD patients from the UK National collection and 2784 controls from the 1958 British Birth cohort. Both rs179247 (P = 1.2×10(-2)-6.2×10(-15), OR = 1.38-1.45) and rs12101255 (P = 1.0×10(-4)-3.68×10(-21), OR = 1.47-1.87) exhibited strong association with GD in all three cohorts. Logistic regression suggested association of rs179247 is secondary to rs12101255 in all cohorts. Inheritance modeling suggested a co-dominant mode of inheritance in all cohorts. Genotype-phenotype correlations provided no clear evidence of association with any specific clinical characteristics.

CONCLUSIONS

We have validated association of TSHR intron 1 SNPs with GD in three independent European cohorts and have demonstrated that the aetiological variant within the TSHR is likely to be in strong linkage disequilibrium with rs12101255. Fine mapping is now required to determine the exact location of the aetiological DNA variants within the TSHR.

The genetics of the thyroid stimulating hormone receptor: history and relevance

BACKGROUND

The thyroid stimulating hormone receptor (TSHR) is the key regulator of thyrocyte function. The gene for the TSHR on chromosome 14q31 has been implicated as coding for the major autoantigen in the autoimmune hyperthyroidism of Graves' disease (GD) to which T cells and autoantibodies are directed.

SUMMARY

The TSHR is a seven-transmembrane domain receptor that undergoes complex posttranslational processing. In this brief review, we look at the genetics of this important autoantigen and its influence on a variety of tissue functions in addition to its role in the induction of GD.

CONCLUSIONS

There is convincing evidence that the TSH receptor gene confers increased susceptibility for GD, but not Hashimoto's thyroiditis. GD is associated with polymorphisms in the intron 1 gene region. How such noncoding nucleotide changes influence disease susceptibility remains uncertain, but is likely to involve TSHR splicing variants and/or microRNAs arising from this gene region. Whether such influences are confined to the thyroid gland or whether they influence cell function in the many extrathyroidal sites of TSHR expression remains unknown.

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.

Follow-up of potential novel Graves' disease susceptibility loci, identified in the UK WTCCC genome-wide nonsynonymous SNP study

A recent association scan using a genome-wide set of nonsynonymous coding single-nucleotide polymorphisms (nsSNPs) conducted in four diseases including Graves' disease (GD), identified nine novel possible regions of association with GD. We used a case-control approach in an attempt to replicate association of these nine regions in an independent collection of 1578 British GD patients and 1946 matched Caucasian controls. Although none of these loci showed evidence of association with GD in the independent data set, when combined with the original Wellcome Trust Case-Control Consortium study group, minor differences in allele frequencies (P>or=10(-3)) remained in the combined collection of 5924 subjects for four of the nsSNPs, present within HDLBP, TEKT1, JSRP1 and UTX. An additional 29 Tag SNPs were screened within these four gene regions to determine if further associations could be detected. Similarly, minor differences only (P=0.042-0.002) were detected in two HDLBP and two TEKT1 Tag SNPs in the combined UK GD collection. In conclusion, it is unlikely that the SNPs selected in this replication study have a significant effect on the risk of GD in the United Kingdom. Our study confirms the need for large data sets and stringent analysis criteria when searching for susceptibility loci in common diseases.

Confirmation of association of chromosome 5q31-33 with United Kingdom Caucasian Graves' disease

BACKGROUND

Previous genome-wide microsatellite screening in Graves' disease (GD) has suggested several regions of linkage to disease. Although replication has been inconsistent, some regions such as chromosome 5q31-33 have been associated with several Oriental GD patient cohorts. Recently, two studies have reported association of single-nucleotide polymorphism (SNP) rs31480 in interleukin 3 (IL-3) and the rs1368408 and SNP75 (-623 approximately -622 AG/-T) SNPs in secretoglobulin family 3a member 2 (SCGB3A2) with GD and suggested that this may account for linkage to the 5q31-33 region in Oriental GD datasets. We sought to confirm this association in a large Caucasian U.K. GD cohort.

METHODS

The rs31480 SNP was shown to tag all known common variations in IL-3 and the rs1368408 SNP was shown to tag all common variations in SCGB3A2. The SCGB3A2 SNP75 was found to be rare in the U.K. Caucasian population and, therefore, was not screened. We genotyped rs31480 and rs1368408 and performed a case-control association study in 2504 GD cases and 2688 controls from the U.K.

RESULTS

Association between the SCGB3A2 rs1368408 SNP and GD was detected (p = 0.007, odds ratio = 1.18, 95% confidence intervals = 1.05-1.33). No association between the IL-3 rs31804 SNP and U.K. Caucasian GD patients was observed.

CONCLUSIONS

These data suggest that chromosome 5q31-q33 contains a susceptibility locus for Caucasian GD patients as well as Oriental GD patients. Although association was detected between SCGB3A2 and U.K. Caucasian GD subjects, the size of effect was smaller than that seen in the Oriental population (odds ratio = 1.28-1.73). Fine mapping within this region will be required to determine the exact location of the etiological variants present within this region for both Caucasian and Oriental GD patients.

Association of the CTLA4 gene with Graves' disease in the Chinese Han population

To determine whether genetic heterogeneity exists in patients with Graves' disease (GD), the cytotoxic T-lymphocyte associated 4 (CTLA-4) gene, which is implicated a susceptibility gene for GD by considerable genetic and immunological evidence, was used for association analysis in a Chinese Han cohort recruited from various geographic regions. Our association study for the SNPs in the CTLA4 gene in 2640 GD patients and 2204 control subjects confirmed that CTLA4 is the susceptibility gene for GD in the Chinese Han population. Moreover, the logistic regression analysis in the combined Chinese Han cohort revealed that SNP rs231779 (allele frequencies p = 2.81x10(-9), OR = 1.35, and genotype distributions p = 2.75x10(-9), OR = 1.42) is likely the susceptibility variant for GD. Interestingly, the logistic regression analysis revealed that SNP rs35219727 may be the susceptibility variant to GD in the Shandong population; however, SNP, rs231779 in the CTLA4 gene probably independently confers GD susceptibility in the Xuzhou and southern China populations. These data suggest that the susceptibility variants of the CTLA4 gene varied between the different geographic populations with GD.

Association of polymorphism in genes encoding kappaB inhibitors (IkappaB) with susceptibility to and phenotype of Graves' disease: a case-control study

Background

Genes related to the nuclear factor-κB (NF-κB), a key transcription factor involved in regulation of immune responses, are interesting candidates for association studies in autoimmune disorders. The aim of this study was to investigate an association of polymorphisms in two genes encoding NF-κB inhibitors: IKBL (encoding inhibitor of κB-like) and NFKBIA (encoding κB inhibitor α), withsusceptibility to and phenotype of Graves' disease (GD).

Methods

A population-based, case-control association study comprising 481 patients with GD and 455 healthy controls was performed. We analyzed 3 single nucleotide polymorphisms (SNPs) in IKBL [promoter region -62T/A substitution (rs2071592), intron 1 C/T substitution (rs2071591) and exon 4 T/C substitution (rs3130062)] and 3 SNPs in NFKBIA [G/A substitution in 3' untranslated region (rs696) and two promoter region polymorphisms -297C/T (rs2233409) and -826C/T (rs2233406)] by the PCR-restriction fragment length polymorphism (RFLP) method.

Results

The two SNPs in IKBL (rs2071592 and rs2071591) were in a strong linkage disequilibrium (D' = 0.835) and the AT haplotype was associated with susceptibility to GD (p < 10^-4, OR = 1.61 [95%CI:1.21-2.14]). Moreover subgroup analysis revealed a gen-gen interaction between the investigated IKBL haplotype and HLA-DRB1*03 allele (p < 10^-4). The investigated NFKBIA SNPs were not associated with susceptibility to GD. However, when correlated with phenotype, the -297T (rs2233409) and -826T (rs2233406) alleles were associated with the development of clinically evident ophthalmophaty (p = 0.004, p_c = 0.07, OR = 1.65 [95%CI: 1.18-2.38] and p = 0.002, p_c = 0.036, OR = 1.67 [95%CI: 1.20-2.36], respectively).

Conclusion

Our results suggest that SNPs in genes encoding NF-κB inhibitors may contribute to the development and clinical phenotype of GD.

Employing a recombinant HLA-DR3 expression system to dissect major histocompatibility complex II-thyroglobulin peptide dynamism: a genetic, biochemical, and reverse immunological perspective

Previously, we have shown that statistical synergism between amino acid variants in thyroglobulin (Tg) and specific HLA-DR3 pocket sequence signatures conferred a high risk for autoimmune thyroid disease (AITD). Therefore, we hypothesized that this statistical synergism mirrors a biochemical interaction between Tg peptides and HLA-DR3, which is key to the pathoetiology of AITD. To test this hypothesis, we designed a recombinant HLA-DR3 expression system that was used to express HLA-DR molecules harboring either AITD susceptibility or resistance DR pocket sequences. Next, we biochemically generated the potential Tg peptidic repertoire available to HLA-DR3 by separately treating 20 purified human thyroglobulin samples with cathepsins B, D, or L, lysosomal proteases that are involved in antigen processing and thyroid biology. Sequences of the cathepsin-generated peptides were then determined by matrix-assisted laser desorption ionization time-of-flight-mass spectroscopy, and algorithmic means were employed to identify putative AITD-susceptible HLA-DR3 binders. From four predicted peptides, we identified two novel peptides that bound strongly and specifically to both recombinant AITD-susceptible HLA-DR3 protein and HLA-DR3 molecules expressed on stably transfected cells. Intriguingly, the HLA-DR3-binding peptides we identified had a marked preference for the AITD-susceptibility DR signatures and not to those signatures that were AITD-protective. Structural analyses demonstrated the profound influence that the pocket signatures have on the interaction of HLA-DR molecules with Tg peptides. Our study suggests that interactions between Tg and discrete HLA-DR pocket signatures contribute to the initiation of AITD.