Common and unique susceptibility loci in Graves and Hashimoto diseases: results of whole-genome screening in a data set of 102 multiplex families

Genetic and epigenetic mechanisms in thyroid autoimmunity

Autoimmune thyroid diseases (AITD), including Graves' disease and Hashimoto's thyroiditis, are among the commonest autoimmune disorders, affecting approximately 5 % of the population. Epidemiological data support strong genetic influences on the development of AITD. Since the identification of HLA-DR3 as a major AITD susceptibility gene, there have been significant advances made in our understanding of the genetic mechanisms leading to AITD. We have shown that an amino acid substitution of alanine or glutamine with arginine at position 74 in the HLA-DR peptide binding pocket is a critical factor in the development of AITD, and we are continuing to dissect these mechanisms at the molecular level. In addition to the MHC class II genes, there are now several other confirmed gene loci associated with AITD, including immune-regulatory (CD40, CTLA-4, PTPN22, FOXP3, and CD25) and thyroid-specific genes (thyroglobulin and TSHR). Mechanistically, it is postulated that susceptibility genes interact with certain environmental triggers to induce AITD through epigenetic effects. In this review, we summarize some of the recent advances made in our laboratory dissecting the genetic-epigenetic interactions underlying AITD. As shown in our recent studies, epigenetic modifications offer an attractive mechanistic possibility that can provide further insight into the etiology of AITD.

Fine mapping of loci linked to autoimmune thyroid disease identifies novel susceptibility genes

CONTEXT

Genetic factors play a major role in the etiology of autoimmune thyroid disease (AITD) including Graves' disease (GD) and Hashimoto's thyroiditis (HT). We have previously identified three loci on chromosomes 10q, 12q, and 14q that showed strong linkage with AITD, HT, and GD, respectively.

OBJECTIVES

The objective of the study was to identify the AITD susceptibility genes at the 10q, 12q, and 14q loci.

DESIGN AND PARTICIPANTS

Three hundred forty North American Caucasian AITD patients and 183 healthy controls were studied. The 10q, 12q, and 14q loci were fine mapped by genotyping densely spaced single-nucleotide polymorphisms (SNPs) using the Illumina GoldenGate genotyping platform. Case control association analyses were performed using the UNPHASED computer package. Associated SNPs were reanalyzed in a replication set consisting of 238 AITD patients and 276 controls.

RESULTS

Fine mapping of the AITD locus, 10q, showed replicated association of the AITD phenotype (both GD and HT) with SNP rs6479778. This SNP was located within the ARID5B gene recently reported to be associated with rheumatoid arthritis and GD in Japanese. Fine mapping of the GD locus, 14q, revealed replicated association of the GD phenotype with two markers, rs12147587 and rs2284720, located within the NRXN3 and TSHR genes, respectively.

CONCLUSIONS

Fine mapping of three linked loci identified novel susceptibility genes for AITD. The discoveries of new AITD susceptibility genes will engender a new understanding of AITD etiology.

Pili annulati coincident with alopecia areata, autoimmune thyroid disease, and primary IgA deficiency: case report and considerations on the literature

Pili annulati is a rare autosomal dominant hair disorder clinically characterized by a pattern of alternating bright and dark bands of the hair, the bright bands appearing dark if observed by transmitted light. This pattern is due to the periodic occurrence of air-filled cavities along the hair cortex which scatter and reflect the light while precluding its transmission. A susceptibility region, including a possibly responsible Frizzled gene, has been mapped to the telomeric region of chromosome 12q, although a specific mutation has not been identified. The condition has sometimes been observed in concurrence with alopecia areata, and in this paper we report a case in whom the concomitant severe alopecia areata was associated with autoimmune thyroid disease and primary IgA deficiency - a quadruple complex which, to our knowledge, has never been previously described. The occurrence of multiple immune disorders in the same patient affected by pili annulati could represent a key to understanding the high prevalence of alopecia areata in this condition. Specifically, in individuals predisposed to autoimmune disease, the molecular alterations that cause the anatomical changes of pili annulati could prompt the immune response against the hair root that underlies alopecia areata.

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.

CTLA-4 gene polymorphisms and their influence on predisposition to autoimmune thyroid diseases (Graves' disease and Hashimoto's thyroiditis)

INTRODUCTION

Autoimmune thyroid disease (AITD) is associated with both genetic and environmental factors which lead to the overactivity of immune system. Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) gene polymorphisms belong to the main genetic factors determining the susceptibility to AITD (Hashimoto's thyroiditis, HT and Graves' disease, GD) development. The aim of the study was to evaluate the relationship between CTLA-4 polymorphisms (A49G, 1822 C/T and CT60 A/G) and HT and/or GD in Polish patients.

MATERIAL AND METHODS

Molecular analysis involved AITD group, consisting of HT (n=28) and GD (n=14) patients, and a control group of healthy persons (n=20). Genomic DNA was isolated from peripheral blood and CTLA-4 polymorphisms were assessed by polymerase chain reaction-restriction fragment length polymorphism method, using three restriction enzymes: Fnu4HI (A49G), BsmAI (1822 C/T) and BsaAI (CT60 A/G).

RESULTS

Statistical analysis (χ(2) test) confirmed significant differences between the studied groups concerning CTLA-4 A49G genotypes. CTLA-4 A/G genotype was significantly more frequent in AITD group and OR analysis suggested that it might increase the susceptibility to HT. In GD patients, OR analysis revealed statistically significant relationship with the presence of G allele. In controls, CTLA-4 A/A genotype frequency was significantly increased suggesting a protective effect. There were no statistically significant differences regarding frequencies of other genotypes and polymorphic alleles of the CTLA-4 gene (1822 C/T and CT60 A/G) between the studied groups.

CONCLUSIONS

CTLA-4 A49G polymorphism seems to be an important genetic determinant of the risk of HT and GD in Polish patients.

PTPN22 polymorphism presumably plays a role in the genetic background of chronic spontaneous autoreactive urticaria

BACKGROUND

The association of chronic urticaria (CU) with autoimmune disorders is relatively well proved. Protein tyrosine phosphatase-22 (PTPN22) is considered to be one of the strongest genetic factors for human autoimmunity. We decided to evaluate whether additional, non 1858C>T, PTPN22 variants are independent contributors to the risk of CU occurrence in the Polish population.

METHODS

A total of 91 CU patients with a positive result of autologous serum skin test and 100 healthy volunteers were enrolled in the study. The Urticaria Activity Score was used in disease intensity assessment. In all subjects rs3811021, rs1310182 and rs2488457 polymorphisms were genotyped.

RESULTS

We found a higher prevalence of -1123 C allele among CU patients. No differences in the allele and genotype distribution were found in the other analyzed polymorphisms. Haplotype construction of the three SNPs revealed statistically significant CU association of rs2488457C, rs1310182T and rs3811021T.

CONCLUSIONS

Contrary to previous findings, the contribution of PTPN22 to disease susceptibility is suggested. We can speculate that CU is a genetically complex disease and that its occurrence needs multiple genetic and environmental risk factors.

Multiple SNPs in intron 41 of thyroglobulin gene are associated with autoimmune thyroid disease in the Japanese population

Background

The etiology of the autoimmune thyroid diseases (AITDs), Graves' disease (GD) and Hashimoto's thyroiditis (HT), is largely unknown. However, genetic susceptibility is believed to play a major role. Two whole genome scans from Japan and from the US identified a locus on chromosome 8q24 that showed evidence for linkage with AITD and HT. Recent studies have demonstrated an association between thyroglobulin (Tg) polymorphisms and AITD in Caucasians, suggesting that Tg is a susceptibility gene on 8q24.

Objectives

The objective of the study was to refine Tg association with AITD, by analyzing a panel of 25 SNPs across an extended 260 kb region of the Tg.

Methods

We studied 458 Japanese AITD patients (287 GD and 171 HT patients) and 221 matched Japanese control subjects in association studies. Case-control association studies were performed using 25 Tg single nucleotide polymorphisms (SNPs) chosen from a database of the Single Nucleotide Polymorphism Database (dbSNP). Haplotype analysis was undertaken using the computer program SNPAlyze version 7.0.

Principal Findings and Conclusions

In total, 5 SNPs revealed association with GD (P<0.05), with the strongest SNP associations at rs2256366 (P = 0.002) and rs2687836 (P = 0.0077), both located in intron 41 of the Tg gene. Because of the strong LD between these two strongest associated variants, we performed the haplotype analysis, and identified a major protective haplotype for GD (P = 0.001).These results suggested that the Tg gene is involved in susceptibility for GD and AITD in the Japanese.

Twin studies as a model for exploring the aetiology of autoimmune thyroid disease

Twins are an important resource for evaluating the relative contribution of genetic and environmental factors in determining a phenotype. During the last decades, a number of twin studies have investigated the aetiology of several phenotypes related to thyroid autoimmunity. Taken together, these studies have provided valid and unbiased information regarding the influence of genetic and environmental factors in the aetiology of autoimmune thyroid disease (AITD). The comparison of concordance rates between monozygotic (MZ) and dizygotic twins provides irrefutable evidence of a genetic component, and biometric twin modelling shows that approximately 75% of the total phenotypic variance in AITD is because of genetic effects. On the other hand, the lack of complete concordance in MZ twin pairs is proof of environmental and/or epigenetic factors also playing an important role. The impact of environmental triggers such as cigarette smoking, birth characteristics, infection with Yersinia enterocolitica, microchimerism and degree of X chromosome inactivation (XCI) has been evaluated by investigating AITD discordant twin pairs. These studies indicate that smoking, Y. enterocolitica infection and skewed XCI may be causally associated with clinically overt AITD, but not with the presence of thyroid autoantibodies in euthyroid subjects. Microchimerism, but not birth weight, might play a role in AITD. Twin studies offer several features that uniquely enhance our ability to localize genes and understand their function. Future twin studies should incorporate information on genetic, epigenetic and environmental variation thereby enhancing our ability to quantify the precise effect of specific risk factors.

New genetic insights from autoimmune thyroid disease

The autoimmune thyroid diseases (AITDs) (Graves' disease and Hashimoto's thyroiditis) are complex genetic diseases which most likely have more than 20 genes contributing to the clinical phenotypes. To date, the genes known to be contributing fall into two categories: immune regulatory genes (including HLA, CTLA4, PTPN22, CD40, CD25, and FCRL3) and thyroid-specific genes (TG and TSHR). However, none of these genes contribute more than a 4-fold increase in risk of developing one of these diseases, and none of the polymorphisms discovered is essential for disease development. Hence, it appears that a variety of different gene interactions can combine to cause the same clinical disease pattern, but the contributing genes may differ from patient to patient and from population to population. Furthermore, this possible mechanism leaves open the powerful influence of the environment and epigenetic modifications of gene expression. For the clinician, this means that genetic profiling of such patients is unlikely to be fruitful in the near future.

Cutting edge: the etiology of autoimmune thyroid diseases

Significant progress has been made in our understanding of the mechanisms leading to autoimmune thyroid diseases (AITD). For the first time, we are beginning to unravel these mechanisms at the molecular level. AITD, including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are common autoimmune diseases affecting the thyroid. They have a complex etiology that involves genetic and environmental influences. Seven genes have been shown to contribute to the etiology of AITD. The first AITD gene discovered, HLA-DR3, is associated with both GD and HT. More recently, this association was dissected at the molecular level when it was shown that substitution of the neutral amino acids Ala or Gln with arginine at position beta 74 in the HLA-DR peptide binding pocket is the specific sequence change causing AITD. Non-MHC genes that confer susceptibility to AITD can be classified into two groups: (1) immune-regulatory genes (e.g., CD40, CTLA-4, and PTPN22); (2) thyroid-specific genes-thyroglobulin and TSH receptor genes. These genes interact with environmental factors, such as infection, likely through epigenetic mechanisms to trigger disease. In this review, we summarize the latest findings on disease susceptibility and modulation by environmental factors.

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.

Hashimoto's Thyroiditis: From Genes to the Disease

Hashimoto's thyroiditis (HT) is the most prevalent autoimmune thyroid disorder. Intrathyroidal lymphocytic infiltration is followed by a gradual destruction of the thyroid gland which may lead to subclinical or overt hypothyroidism. Biochemical markers of the disease are thyroid peroxidase and/or thyroglobulin autoantibodies in the serum which are present with a higher prevalence in females than in males and increase with age. Although exact mechanisms of aetiology and pathogenesis of the disorder are not completely understood, a strong genetic susceptibility to the disease has been confirmed predominantly by family and twin studies. Several genes were shown to be associated with the disease occurrence, progression, and severity. Genes for human leukocyte antigen, cytotoxic T lymphocyte antigen-4, protein tyrosine phosphatase nonreceptor-type 22, thyroglobulin, vitamin D receptor, and cytokines are considered to be of utmost importance. Amongst endogenous factors for the disease development, the attention is focused predominantly on female sex, pregnancy with postpartum period and fetal microchimerism. Environmental factors influencing HT development are iodine intake, drugs, infections and different chemicals. Disturbed self-tolerance accompanied by the increased antigen presentation is a prerequisite for the HT occurrence, whereas proper interaction of thyroid cells, antigen presenting cells, and T cells are necessary for the initiation of thyroid autoimmunity. Secreted cytokines lead predominantly to T-helper type 1 (Th1) response as well as to Th 17 response which has only recently been implicated. Final outcome of HT is thyroid destruction which is mostly a consequence of the apoptotic processes combined with T-cell mediated cytotoxicity.

Role of cytokines in the pathogenesis and suppression of thyroid autoimmunity

Autoimmune thyroid diseases (AITD) are one of the most common organ-specific autoimmune disorders, of which Hashimoto's thyroiditis (HT) and Graves' disease (GD) are 2 of the most common clinical expressions. HT is characterized by hypothyroidism that results from the destruction of the thyroid by thyroglobulin-specific T cell-mediated autoimmune response. In contrast, GD is characterized by hyperthyroidism due to excessive production of thyroid hormone induced by thyrotropin receptor-specific stimulatory autoantibodies. Cytokines play a crucial role in modulating immune responses that affect the balance between maintenance of self-tolerance and initiation of autoimmunity. However, the role of cytokines is often confusing and is neither independent nor exclusive of other immune mediators. A regulatory cytokine may either favor induction of tolerance against thyroid autoimmune disease or favor activation and/or exacerbation of autoimmune responses. These apparently contradictory functions of a given cytokine are primarily influenced by the nature of co-signaling delivered by other cytokines. Consequently, a thorough understanding of the role of a particular cytokine in the context of a specific immune response is essential for the development of appropriate strategies to modulate cytokine responses to maintain or restore health. This review provides a summary of recent research pertaining to the role of cytokines in the pathogenesis of AITD with a particular emphasis on the therapeutic applications of cytokine modulation.

Novel variant of thyroglobulin promoter triggers thyroid autoimmunity through an epigenetic interferon alpha-modulated mechanism

Autoimmune thyroid diseases (AITD) arise from complex interactions between genetic, epigenetic, and environmental factors. Whole genome linkage scans and association studies have established thyroglobulin (TG) as a major AITD susceptibility gene. However, the causative TG variants and the pathogenic mechanisms are unknown. Here, we describe a genetic/epigenetic mechanism by which a newly identified TG promoter single-nucleotide polymorphism (SNP) variant predisposes to AITD. Sequencing analyses followed by case control and family-based association studies identified an SNP (-1623A→G) that was associated with AITD in the Caucasian population (p = 0.006). We show that the nucleotide substitution introduced by SNP (-1623A/G) modified a binding site for interferon regulatory factor-1 (IRF-1), a major interferon-induced transcription factor. Using chromatin immunoprecipitation, we demonstrated that IRF-1 binds to the 5' TG promoter motif, and the transcription factor binding correlates with active chromatin structure and is marked by enrichment of mono-methylated Lys-4 residue of histone H3, a signature of active transcriptional enhancers. Using reporter mutations and siRNA approaches, we demonstrate that the disease-associated allele (G) conferred increased TG promoter activity through IRF-1 binding. Finally, treatment of thyroid cells with interferon α, a known trigger of AITD, increased TG promoter activity only when it interacted with the disease-associated variant through IRF-1 binding. These results reveal a new mechanism of interaction between environmental (IFNα) and genetic (TG) factors to trigger AITD.

cDNA immunization of mice with human thyroglobulin generates both humoral and T cell responses: a novel model of thyroid autoimmunity

Thyroglobulin (Tg) represents one of the largest known self-antigens involved in autoimmunity. Numerous studies have implicated it in triggering and perpetuating the autoimmune response in autoimmune thyroid diseases (AITD). Indeed, traditional models of autoimmune thyroid disease, experimental autoimmune thyroiditis (EAT), are generated by immunizing mice with thyroglobulin protein in conjunction with an adjuvant, or by high repeated doses of Tg alone, without adjuvant. These extant models are limited in their experimental flexibility, i.e. the ability to make modifications to the Tg used in immunizations. In this study, we have immunized mice with a plasmid cDNA encoding the full-length human Tg (hTG) protein, in order to generate a model of Hashimoto's thyroiditis which is closer to the human disease and does not require adjuvants to breakdown tolerance. Human thyroglobulin cDNA was injected and subsequently electroporated into skeletal muscle using a square wave generator. Following hTg cDNA immunizations, the mice developed both B and T cell responses to Tg, albeit with no evidence of lymphocytic infiltration of the thyroid. This novel model will afford investigators the means to test various hypotheses which were unavailable with the previous EAT models, specifically the effects of hTg sequence variations on the induction of thyroiditis.

Analysis of immune regulatory genes' copy number variants in Graves' disease

BACKGROUND

Copy number variants (CNVs) have recently been reported to be associated with several autoimmune conditions. Moreover, loci involved in immunity are enriched in CNVs. Therefore, we hypothesized that CNVs in immune genes associated with Graves' disease (GD) may contribute to the etiology of disease.

METHODS

One hundred ninety-one North American Caucasian GD patients and 192 Caucasian controls were analyzed for CNVs in three major immune regulatory genes: CD40, PTPN22, and CTLA-4. Copy number was determined using quantitative-PCR (Q-PCR) assays specifically designed for determining copy numbers in genomic DNA. Additionally, a well-characterized CNV in the amylase gene was typed in a separate dataset of DNA samples that were derived from cell lines or blood.

RESULTS

No CNVs could be confirmed in the CD40 and CTLA-4 genes, even though a CD40 CNV is cataloged in the Database of Genomic Variants. Only the PTPN22 CNV was confirmed in our cohort, but it was rare and appeared in only two individuals. A key finding was that the source of DNA has a significant effect on CNV typing. There was a statistically significant increase in amylase locus deletions in cell line-derived DNA compared to blood-derived DNA samples.

CONCLUSIONS

We conclude that CNV analysis should be performed only using blood-derived DNA Samples. Additionally, the CTLA-4, CD40, and PTPN22 loci do not harbor CNVs that play a role in the etiology of GD.

Autoimmune thyroid diseases in children

The two major autoimmune thyroid diseases (ATDs) include Graves' disease (GD) and autoimmune thyroiditis (AT); both of which are characterized by infiltration of the thyroid by T and B cells reactive to thyroid antigens, by the production of thyroid autoantibodies and by abnormal thyroid function (hyperthyroidism in GD and hypothyroidism in AT). While the exact etiology of thyroid autoimmunity is not known, it is believed to develop when a combination of genetic susceptibility and environmental encounters leads to breakdown of tolerance. It is important to recognize thyroid dysfunction at an early stage by maintaining an appropriate index of suspicion.

Association of the TGrI29 microsatellite in thyroglobulin gene with autoimmune thyroiditis in a Argentinian population: a case-control study

Autoimmune thyroid disease (AITD) is a multifactorial disorder that involves a putative association with thyroid autoantigen-specific and immune regulatory genes, as well as environmental factors. The thyroglobulin gene is the main identified thyroid autoantigen-specific gene associated to autoimmune thyroiditis. The aim of this work was to test for evidence of allelic association between autoimmune thyroiditis (AT) and thyroglobulin polymorphism markers in Argentinian patients. We studied six polymorphisms distributed throughout all the thyroglobulin gene: four microsatellites (Tgms1, Tgms2, TGrI29, and TGrI30), one insertion/deletion polymorphism (IndelTG-IVS18), and one exonic single nucleotide polymorphism (c.7589G>A) in 100 AT patients and 100 healthy control subjects. No differences in allele and genotype frequencies distribution were observed between autoimmune thyroiditis cases and controls for Tgms1, Tgms2, TGrI30, IndelTG-IVS18, and c.7589G>A. However, when we analyzed autoimmune thyroiditis patients with the TGrI29 microsatellite we found a significant association between the 197-bp allele and autoimmune thyroiditis (33.50% vs. 19.00% in control group) (P = 0.001). In addition, a significant major prevalence of the 197/201-bp genotype has been also seen in autoimmune thyroiditis subjects (59% vs. 24% in control group, P < 0.0001). In conclusion, our work showed the association between the thyroglobulin gene and autoimmune thyroiditis in Argentinian population and supports the described evidence of thyroglobulin as a thyroid-specific gene linked to AITD.

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.

Association analysis of polymorphisms in IL-3, IL-4, IL-5, IL-9, and IL-13 with Graves' disease

BACKGROUND

Graves' disease (GD) is a common autoimmune disorder with genetic predisposition. There is strong evidence that the Chr.5q31-33 region, which contains the immune response cytokine genes [interleukin (IL)-3, IL-4, IL-5, IL-9, and IL-13], is linked to autoimmune thyroid disorders in Chinese and Japanese populations. The aim of the present study is to elucidate whether the single nucleotide polymorphisms (SNP) and the interaction of variants in the 5 genes are associated with the development of GD and Graves' ophthalmopathy (GO).

MATERIALS AND METHODS

GD patients (no.=751), with 190 of GO patients and healthy control subjects (no.=748) were included in this study. Six SNP [rs40401 (IL-3), rs2070874 (IL-4), rs2069812 (IL-5), rs1859430 (IL-9), rs2069868 (IL-9), and rs20541 (IL-13)] were genotyped by SNPstream Genotyping System.

RESULTS

There was a significant increase of C allele of rs40401 in GD [odds ratio (OR)=1.18 [95% confidence interval (CI): 1.02-1.36], pallele=0.028] and GO [OR=1.30 (95%CI: 1.04-1.63), pallele=0.022] patients compared with those in the controls. The C allele of the rs2069812 was also significantly associated with GD [OR=1.22 (95%CI: 1.04-1.44), pallele=0.015] and GO [OR=1.45 (95%CI: 1.13-1.86), pallele=0.003] patients. Haplotype analysis showed a predominant increase of the 2 SNP (rs40401-rs2069812, CC) and all the 6 SNP (CCCCCC) haplotype in GD (OR=1.70, OR=3.70, respectively) and even stronger in GO (OR=2.18, OR=7.01, respectively) patients.

CONCLUSIONS

The results suggested that the polymorphism of IL-3 (rs40401) and IL-5 (rs2069812) were associated with GD and GO susceptibility in Chinese population. The interaction of 6-locus from the 5 genes might confer higher risk for GD and GO than single risk allele.

Genetic susceptibility to autoimmune thyroid disease: past, present, and future

BACKGROUND

Autoimmune thyroid diseases (AITD), including Graves' disease and Hashimoto's thyroiditis, arise due to complex interactions between environmental and genetic factors. There are sound data coming from epidemiological, family, and twin studies demonstrating a strong genetic influence on the development of AITD. In this review we summarize the new findings on the genetic susceptibility to AITD focusing on emerging mechanisms of susceptibility.

SUMMARY

Candidate gene analysis, whole-genome linkage screening, genome-wide association studies, and whole-genome sequencing are the major technologies that have advanced this field, leading to the identification of at least seven genes whose variants have been associated with AITD. One of the major ones is the HLA-DR gene locus. Recently, it was shown that substitution of the neutral amino acids Ala or Gln with arginine at position beta 74 in the HLA-DR peptide-binding pocket is key to the etiology of both Graves' disease and Hashimoto's thyroiditis. Several other genes have also been shown to confer susceptibility to AITD. These can be classified into two groups: (i) immune regulatory genes (cytotoxic T lymphocyte-associated protein 4, CD40, protein tyrosine phosphatase-22, and CD25) and (ii) thyroid-specific genes (thyroglobulin and thyrotropin receptor genes). The influence of individual genes on the development of AITD when assessed in a population appears to be weaker than would be expected from the data showing strong genetic susceptibility to AITD. Two possible mechanisms explaining this discrepancy are gene-gene interactions and subset effects.

CONCLUSIONS

Significant progress has been made in our understanding of the immunogenetic mechanisms leading to thyroid autoimmunity. For the first time we are beginning to unravel these mechanisms at the molecular level. It is hoped that these new data will be translated into novel therapies and prevention strategies in AITD, such as costimulatory blockade.

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.

Hashimoto's thyroiditis: TGAb, TPOAb, TRAb and recovery from hypothyroidism

Hashimoto described four patients with goiter. The histology of the goiter was characterized by diffuse lymphocytic infiltration, fibrosis and epithelial cell destruction. Thyroglobulin antibody (TGAb) and thyroid peroxidase antibody (TPOAb) have been used to diagnose Hashimoto's thyroiditis. Patients with positive TGAb and/or TPOAb have been assumed to have Hashimoto's thyroiditis. Approximately 10% of those with positive TGAb and/or TPOAb have hypothyroidism. There are two types of autoimmune thyroiditis: goitrous Hashimoto's thyroiditis and atrophic thyroiditis. The latter patients have blocking antibody (thyroid-stimulating hormone [TSH]-stimulation blocking antibody [TSBAb]). TSBAb is a TSH-receptor antibody (TRAb). TSBAb causes thyroid atrophy and hypothyroidism. TGAb and/or TPOAb do not necessarily cause hypothyroidism. Hypothyroid patients with Hashimoto's thyroiditis usually receive life-long l-thyroxine therapy. However, spontaneous recovery from hypothyroidism has been reported. Patients who had Hashimoto's hypothyroidism and then Graves' hyperthyroidism (and vice versa), have also been reported. Hashimoto's hypothyroidism and Graves' hyperthyroidism could be the opposite spectrums of one disease.

Determinants of thyroid autoantibody production in Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is the most prevalent thyroid autoimmune disorder, characterized by the presence of specific thyroid autoantibodies (TAb). The development of autoimmunity, including TAb production and clinical presentation of HT, is determined by a complex interplay of genetic susceptibility and several endogenous and environmental factors, which are discussed in this article. During the progression of the disease, TAb production precedes clinical manifestations, although the correlation between TAb concentrations and thyroid function is weak. We do not treat euthyroid HT patients despite elevated TAb; while in hypothyroidism, replacement therapy with l-thyroxine is required. Until now, an effective approach to prevent TAb production and the development of clinical disease has not yet been established. However, further identification of risk factors and their interaction may help in the prevention of thyroid autoimmunity.

Analysis of thyroglobulin gene polymorphisms in patients with autoimmune thyroiditis

The autoimmune thyroid disease is a complex disorder caused by a combination of genetic susceptibility and environmental factors, which are believed to initiate the autoimmune response to thyroid antigens. Identification of the susceptibility genes has found that unique and diverse genetic factors are in association with Graves' disease and autoimmune thyroiditis. The thyroglobulin gene is an identified thyroid-specific gene associated to autoimmune thyroid disease and, principally, with autoimmune thyroiditis. The aim of this work was to test for evidence of allelic association between autoimmune thyroiditis and thyroglobulin polymorphism markers. We studied six polymorphisms distributed throughout all the thyroglobulin gene: four microsatellites (Tgms1, Tgms2, TGrI29 and TGrI30), one insertion/deletion (Indel) polymorphism (IndelTG-IVS18) and one exonic single nucleotide polymorphism (SNP) (c.7589G>A) in 122 patients with autoimmune thyroiditis compared with 100 non-related normal subjects. No differences in allele and genotype distribution were observed between autoimmune thyroiditis cases and controls for Tgms1, Tgms2, TGrI30, IndelTG-IVS18 and c.7589G>A. However, when we analyzed the patients with the TGrI29 microsatellite we found a significant association between the 199-bp allele and AT (33.7% vs. 24.5% in control group) (P = 0.0372). In addition, a higher prevalence of the 201-bp allele has been observed in control subjects (47.5% vs. 38.1% in patients group), although not statistically significant (P = 0.0536). Our work shows the association between the thyroglobulin gene and autoimmune thyroiditis and reinforce that thyroglobulin is a thyroid-specific susceptibility gene for this disease.

Clinical features of spontaneous hypothyroidism in one physician's practice in Jamaica

OBJECTIVE

To describe the clinical characteristics of patients with spontaneous hypothyroidism, the frequency of chronic autoimmune thyroiditis, and the thyroid autoantibody most often associated with this condition in a referral population in Jamaica.

METHODS

A retrospective study of all cases referred to the author's endocrinology practice from 1995 to 2005 with a diagnosis of spontaneous hypothyroidism was undertaken. The clinical history, examination findings, biochemical test results, thyroid autoimmune antibodies, and imaging data were reviewed.

RESULTS

Spontaneous primary hypothyroidism was correctly diagnosed in 53 subjects. Fifty of the patients were females and three were males. Mean age was 43.3 years (range 12-82 years); 24.4% of the patients had a family member with thyroid disease; 27.1% presented because of a goiter; and 54.2% because of symptoms suggestive of hypothyroidism. The thyroid was palpable in 56.3% and thyroid ultrasound was consistent with Hashimoto's thyroiditis on 64% of occasions. Only 8% of the patients had the atrophic variant of hypothyroidism. Antithyroid peroxidase and antithyroglobulin antibody were positive in 75.8% and 37.5% of patients, respectively. Chronic autoimmune thyroiditis was confirmed in 78.8% of cases.

CONCLUSION

In these cases in Jamaica, spontaneous hypothyroidism was predominantly a female disorder. Chronic autoimmune thyroiditis was the commonest cause, and antithyroid peroxidase antibody was the thyroid antibody most likely to be positive in this population.

Review Article: The Familial Counterparts of Follicular Cell—Derived Thyroid Tumors

The follicular cell—derived thyroid cancers (termed nonmedullary thyroid cancers—NMTCs) occur mostly sporadically, but intriguingly, NMTC has the highest familial risk among all cancer sites. This epidemiological observation is strengthened by the clinical occurrence of NMTC in familial aggregation (FNMTC) and by the detection of chromosomal loci in linkage with the disease phenotype. FNMTC loci have been proposed at 14q, 1q21, 19p13.2, 2q21, 8p23, 8q24, 1q21, and 6q22, but to date, no causative mutations have been linked to FNMTCs. In this review, the authors focus on the clinical, morphological, and molecular aspects that characterize familial tumors. Some morphological patterns may alert for a familial disease. FNMTCs share several of the somatic molecular changes associated with sporadic tumors. New genes affected by somatic changes have been disclosed within regions harboring FNMTC loci.

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.

Immunoglobulin heavy chain variable region genes contribute to the induction of thyroid-stimulating antibodies in recombinant inbred mice

Graves' hyperthyroidism is an autoimmune disease occurring spontaneously in humans and caused by autoantibodies that stimulate the thyrotropin receptor. In mice, inducing Graves'-like hyperthyroidism requires in vivo expression of the thyrotropin receptor using plasmid or adenovirus vectors. However, mice with different genetic backgrounds vary markedly in their susceptibility to induced hyperthyroidism. Further, in some strains major disparities exist between the induction of hyperthyroidism and detection of thyroid-stimulating antibodies. To break tolerance, virtually all Graves' mouse models involve immunization with human thyrotropin-receptor DNA and the standard thyroid-stimulating antibody bioassay uses cells expressing the human thyrotropin receptor. We hypothesized, and now report, that disparities between hyperthyroidism and thyroid-stimulating antibody bioactivity are explained, at least in part, by differential antibody recognition of the human vs the mouse thyrotropin receptor. The genetic basis for these species differences was explored using genotyped, recombinant-inbred mouse strains. We report that loci in the immunoglobulin heavy chain variable region as well as in the major histocompatibility complex region contribute in a strain-specific manner to the development of antibodies specific for the human or the mouse thyrotropin receptor. The novel finding of a role for immunoglobulin heavy chain variable region gene involvement in thyroid-stimulating antibody epitopic specificity provides potential insight into genetic susceptibility in human Graves' disease.

Tg.2098 is a major human thyroglobulin T-cell epitope

An HLA-DR variant containing Arginine at position 74 of the DRbeta1 chain confers a strong genetic susceptibility to autoimmune thyroid diseases (AITD), Graves' disease (GD) and Hashimoto's thyroiditis (HT), while Glutamine at position DRbeta1-74 is protective. We hypothesized that the DRbeta1-Arg74 variant is able to present pathogenic thyroglobulin (Tg) peptides to T-cells more efficiently, thereby triggering thyroid autoimmunity. Indeed, we have previously identified 4 human Tg (hTg) peptides that bind specifically to DRbeta1-Arg74 with much weaker binding to the protective variant DRbeta1-Gln74. The aim of our study was to examine in vivo whether an hTg peptide that binds strongly and specifically to DRbeta1-Arg74 is capable of stimulating T-cells during the induction of thyroiditis in a "humanized" mouse expressing human DR3, and in patients positive for Tg antibodies. Sequencing of exon 2 of the DR transgene in the DR3 mice, null for endogenous MHC II molecules, confirmed that they expressed the disease-associated DRbeta1-Arg74 variant, thus making them an ideal in vivo model to test the presentation of hTg peptides by DRbeta1-Arg74 HLA-DR. Induction of EAT in the DR3 mice lead to T-cell stimulation and proliferation to Tg.2098, a strong and specific DRbeta1-Arg74 binder, while a non-binding control peptide, Tg.2766 did not induce this response. Moreover, Tg.2098 stimulated T-cells from 4 individuals who were positive for thyroglobulin antibodies, demonstrating that Tg.2098 is an immunogenic peptide capable of being presented in vivo and activating T-cells in EAT and AITD. Energetic analysis of the complex formed by Tg.2098 and DRbeta-Arg74 has shown that the origin of the affinity was determined by residues 1, 7 and 9 in the peptide, while the selectivity of the peptide for the MHC was determined by the Asp in position 4. The disease-protective substitution R74Q, leads to reduction in affinity due to changes in local interaction with D4 as well as non-local interaction with other residues. The electrostatic potential on the surface of the DRbeta-Arg74-Tg.2098 complex has a unique signature which may be recognized by T-cell receptors leading to autoimmune thyroiditis. Taken together these findings suggest that Tg.2098, a strong and specific binder to the disease-associated HLA-DRbeta-Arg74, is a major human T-cell epitope and participant in the pathoetiology of AITD.

The etiology of autoimmune thyroid disease: a story of genes and environment

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT) are prevalent autoimmune diseases, affecting up to 5% of the general population. Autoimmune thyroid diseases arise due to complex interactions between environmental and genetic factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. However, the interactions between genes and environment are yet to be defined. Among the major AITD susceptibility genes that have been identified and characterized is the HLA-DR gene locus, as well as non-MHC genes including the CTLA-4, CD40, PTPN22, thyroglobulin, and TSH receptor genes. The major environmental triggers of AITD include iodine, medications, infection, smoking, and possibly stress. Recent data on the genetic predisposition to AITD lead to novel putative mechanisms by which the genetic-environmental interactions may lead to the development of thyroid autoimmunity.

Fast and accurate calculation of a computationally intensive statistic for mapping disease genes

Many statistical methods in biology utilize numerical integration in order to deal with moderately high-dimensional parameter spaces without closed form integrals. One such method is the PPL, a class of models for mapping and modeling genes for complex human disorders. While the most common approach to numerical integration in statistics is MCMC, this is not a good option for the PPL for a variety of reasons, leading us to develop an alternative integration method for this application. We utilize an established sub-region adaptive integration method, but adapt it to specific features of our application. These include division of the multi-dimensional integrals into three separate layers, implementing internal constraints on the parameter space, and calibrating the approximation to ensure adequate precision of results for our application. The proposed approach is compared with an empirically driven fixed grid scheme as well as other numerical integration methods. The new method is shown to require far fewer function evaluations compared to the alternatives while matching or exceeding the best of them in terms of accuracy. The savings in evaluations is sufficiently large that previously intractable problems are now feasible in real time.

Association studies of the SAS-ZFAT, IL-23R, IFIH1 and FOXP3 genes in autoimmune thyroid disease

Autoimmune thyroid diseases (AITDs) are complex diseases caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors, such as dietary iodine, is believed to initiate the autoimmune response against thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence in 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 Graves' disease (GD) and Hashimoto's thyroiditis (HT), and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune-modifying genes (e.g., HLA, CTLA-4 and PTPN22) and thyroid-specific genes (e.g., TSHR and Tg). In this special report, we focus on the newest genes identified and not on those previously identified, such as HLA and CTLA-4, for which there are many reviews.

Autoimmune thyroid diseases: genetic susceptibility of thyroid-specific genes and thyroid autoantigens contributions

Autoimmune thyroid diseases are common polygenic multifactorial disorders with the environment contributing importantly to the emergence of the disease phenotype. Some of the disease manifestations, such as severe thyroid-associated ophthalmopathy, pretibial myxedema and thyroid antigen/antibody immune complex nephritis are unusual to rare. The spectrum of autoimmune thyroid diseases includes: Graves' disease (GD), Hashimoto's thyroiditis (HT), atrophic autoimmune thyroiditis, postpartum thyroiditis, painless thyroiditis unrelated to pregnancy and thyroid-associated ophthalmopathy. This spectrum present contrasts in terms of thyroid function, disease duration and spread to other anatomic location. The genetic basis of autoimmune thyroid disease (AITD) is complex and likely to be due to genes of both large and small effects. In GD the autoimmune process results in the production of thyroid-stimulating antibodies and lead to hyperthyroidism, whereas in HT the end result is destruction of thyroid cells and hypothyroidism. Recent studies in the field of autoimmune thyroid diseases have largely focused on (i) the genes involved in immune response and/or thyroid physiology with could influence susceptibility to disease, (ii) the delineation of B-cell autoepitopes recognized by the main autoantigens, thyroglobulin, thyroperoxidase and TSH receptor, to improve our understanding of how these molecules are seen by the immune system and (iii) the regulatory network controlling the synthesis of thyroid hormones and its dysfunction in AITD. The aim of the present review is to summarize the current knowledge regarding the relation existing between some susceptibility genes, autoantigens and dysfunction of thyroid function during AITD.

Major histocompatibility complex class II (DRB1*, DQA1*, and DQB1*) and DRB1*04 subtypes' associations of Hashimoto's thyroiditis in a Greek population

Hashimoto's thyroiditis (HT) is an autoimmune disease resulting from complex interactions between genetic and environmental factors. The disease is associated with certain human leukocyte antigen (HLA) class II alleles in various populations. We aimed to determine in this study, for the first time in a Greek population, the association of HLA-DRB1*, -DQA1*, and -DQB1* alleles with HT. HLA-DRB1*, -DQA1*, and -DQB1* alleles' and -DRB1*04 subtypes' distribution was evaluated in 125 patients with HT and in 500 healthy control individuals by using a DNA-based sequence-specific primer method. Chi(_)squared tests and Bonferroni correction method were applied in the statistical analysis of the data. Significantly higher frequency of DRB1*04 (24.8% vs 7.7%, P < 0.0001) was observed in HT patients, while HLA-DRB1*07 was significantly decreased (2.8% vs 7.9%, P < 0.05). HLA-DRB1*04 subtyping showed a significant increase of DRB1*0405 (21% vs 7.8%, P < 0.0001) in HT patients. Also significant high frequencies of DQB1*0201 (14.8% vs 8.2%, P < 0.001), DQB1*0302 (18.8% vs 7.0%, P < 0.0001), and DQA1*0301 (25.6% vs 7.8%, P < 0.0001) were recorded in the patient group. Conducting the first research of this kind in a Greek population, our study tries to provide an evaluation of the prevalence of HT relating to HLA-DRB1*0405, and we report a relative risk of 2.7 for HT in a Greek population.

Autoimmune thyroiditis and diabetes: dissecting the joint genetic susceptibility in a large cohort of multiplex families

CONTEXT

Epidemiological data support a shared genetic susceptibility to autoimmune thyroid disease (AITD) and type 1 diabetes (T1D). Both diseases frequently occur within the same family and in the same individual. Patients developing both T1D and AITD are considered to have an autoimmune polyglandular syndrome type 3 variant (APS3v).

OBJECTIVE

The goals of this study were to identify the joint susceptibility loci/genes for T1D and AITD.

SETTINGS

The study was conducted at an academic medical center.

PARTICIPANTS AND MAIN OUTCOME MEASURES

We used whole genome and candidate gene approaches in a data set of 88 families multiplex for T1D and AITD (448 individuals).

RESULTS

We identified three loci, on chromosomes 2p, 6p, and Xp, showing linkage when individuals with either T1D or AITD were classified as affected. The 6p locus contained the human leukocyte antigen class II genes, and the Xp locus contained the FOXP3 gene. Three loci, on 2q, 6p (human leukocyte antigen class II), and Xp, showed evidence for linkage when only APS3v individuals (T1D+AITD) were classified as affected. Analysis of positional candidate genes strongly supported CTLA-4 as the gene on 2q associated with APS3v and FOXP3 as the gene on Xp associated with T1D or AITD and APS3v. In addition, the PTPN22 and insulin variable number tandem repeat genes showed significant associations with T1D or AITD in our families.

CONCLUSIONS

Our results demonstrate a strong shared genetic susceptibility to T1D and AITD, with most shared genes involved in immune regulation, suggesting that immune dysregulation plays an important role in the joint susceptibility to T1D and AITD.

Polymorphisms in the ADRB2 gene and Graves disease: a case-control study and a meta-analysis of available evidence

Background

The beta-2-Adrenergic receptor (ADRB2) gene on chromosome 5q33.1 is an important immunoregulatory factor. We and others have previously implicated chromosomal region 5q31-33 for contribution to the genetic susceptibility to Graves disease (GD) in East-Asian populations. Two recent studies showed associations between the single nucleotide polymorphism (SNP) rs1042714 in the ADRB2 gene and GD. In this study, we aimed to fully investigate whether the ADRB2 gene conferred susceptibility to GD in Chinese population, and to perform a meta-analysis of association between ADRB2 and GD.

Methods

Approximately 1 kb upstream the transcription start site and the entire coding regions of the ADRB2 gene were resequenced in 48 Han Chinese individuals to determine the linkage disequilibrium (LD) patterns. Tag SNPs were selected and genotyped in a case-control collection of 1,118 South Han Chinese subjects, which included 428 GD patients and 690 control subjects. A meta-analysis was performed with the data obtained in the present samples and those available from prior studies.

Results

Fifteen SNPs in the ADRB2 gene were identified by resequencing and one SNP was novel. Ten tag SNPs were investigated further to assess association of ADRB2 in the case-control collection. Neither individual tag SNP nor haplotypes showed association with GD in Han Chinese population (P > 0.05). Our meta-analysis of the ADRB2 SNP rs1042714 measured heterogeneity between the ethnic groups (I² = 53.1%) and no association to GD was observed in the overall three studies with a random effects model (OR = 1.13, 95% CI, 0.95 to 1.36; P = 0.18). However, significant association was found from the combined data of Caucasian population with a fixed effects model (OR = 1.18, 95% CI, 1.06 to 1.32; P = 0.002; I² = 5.9%).

Conclusion

Our study indicated that the ADRB2 gene did not exert a substantial influence on GD susceptibility in Han Chinese population, but contributed to a detectable GD risk in Caucasian population. This inconsistency resulted largely from between-ethnicity heterogeneity.

Polymorphisms in the interleukin 3 gene show strong association with susceptibility to Graves' disease in Chinese population

Graves' disease (GD) is a common organ-specific autoimmune disorder, which is multifactorial and develops in genetically susceptible individuals. We had earlier mapped a susceptibility locus for GD to chromosome 5q31-33 in a linkage study. Here we used tag single-nucleotide polymorphisms (SNPs) to search for genetic variants associated with GD, and examined 19 functional candidate genes in this chromosomal region. We identified 192 polymorphisms by re-sequencing the candidate genes, and selected 51 tagSNPs to genotype in a case-control collection of 1118 south Han Chinese subjects (428 cases and 690 controls). Initial analysis suggested that a non-synonymous SNP rs40401 (P27S) of interleukin 3 (IL3) was associated with GD, and further fine-mapping showed that rs40401, or its perfect proxy SNP rs31480 in the 5' flanking region of IL3, fully accounted for the association signal at this locus. We replicated significant association of rs40401 with GD in an independent sample collection of 839 north Han Chinese subjects. A combined analysis revealed strong validation of this association (odds ratio (OR(common))=1.63, combined P (P(comb))=4 x 10(-6) in the Recessive disease model). This study provides convincing evidence that the IL3 gene is a susceptibility locus for GD in the Chinese population.

Patogênese das doenças tiroidianas autoimunes

A doença tiroidiana autoimune (DAIT), que afeta de 2% a 5% da população ocidental, é o transtorno autoimune órgão-específico mais comum. Sua apresentação clínica varia do hipertiroidismo da doença de Graves (DG) ao hipotiroidismo associado à tiroidite de Hashimoto (TH). A exata etiologia da DAIT permanece desconhecida, mas a interação entre suscetibilidade genética e fatores ambientais desencadeadores parece ser de fundamental importância no seu desenvolvimento. Postula-se que fatores genéticos responderiam por 79% da suscetibilidade à DAIT e os ambientais por 21%. Genes imunomoduladores, como o complexo maior de histocompatibilidade (MHC), antígeno-4 associado ao linfócito T citotóxico (CTLA-4), a molécula CD40 e a proteína tirosina fosfatase-22 (PTPN22) e os genes específicos da glândula tiróide, como receptor do TSH (TSHR) e tiroglobulina (TG) têm sido identificados. A natureza exata do envolvimento do meio ambiente no desenvolvimento da DAIT não é bem conhecida, mas vários fatores ambientais têm sido envolvidos, como o conteúdo de iodo na dieta, estresse, drogas e infecções. Entretanto, não há evidência clara de causalidade e os mecanismos pelos quais fatores ambientais desencadeariam a autoimunidade tiroidiana, em indivíduos geneticamente predispostos, ainda permanecem não completamente entendidos. O conhecimento dos mecanismos precisos de interação entre fatores ambientais e genes na indução da autoimunidade tiroidiana poderia resultar desenvolvimento de novas estratégias de prevenção e tratamento.

The protein tyrosine phosphatase non-receptor type 22 C1858T polymorphism is a joint susceptibility locus for immunthyroiditis and autoimmune diabetes

BACKGROUND

The lymphoid tyrosine phosphatase (LYP) encoded by the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene is a strong inhibitor of T cells. The single nucleotide polymorphism (SNP) C1858T within the PTPN22 gene was recently associated with autoimmune thyroid disease (AITD) and type I diabetes (T1D). The purpose of this study was to examine the joint association of this polymorphism with the co-occurrence of AITD and T1D.

METHODS

In this association study, 310 white subjects were genotyped for the C1858T polymorphism. The study population included 70 patients with both AITD and T1D (AITD+T1D), 70 patients with AITD only, 70 patients with T1D only, and 100 healthy controls. Patients with both AITD and T1D, and controls were also typed for HLA-DRB1. PTPN22 C1858T genotyping was performed by minisequencing. For HLA-DRB1 typing, polymerase chain reaction (PCR) sequence-specific oligonucleotide probes were used.

RESULTS

The PTPN22 1858 minor T-allele frequency was strongly increased in patients with AITD+T1D (23.6%) compared with controls (8.0%, pc<0.001), with patients with AITD only (8.6%, pc=0.006), or with T1D only (10.7%, pc=0.028). T-allele carriers were also more frequently present in the group with AITD+T1D versus controls (41.4% vs. 14.0%, OR=4.35, 95% CI=2.08-9.09), AITD (17.1%, OR=3.42, 95% CI=1.56-7.48), and T1D (21.4%, OR=2.59, 95% CI=1.23-5.45). Especially in subjects with Hashimoto's thyroiditis (HT)+T1D, T-allele carriers were mostly frequent (50% vs. 14%, OR=6.14, 95% CI=2.62-14.38, pc<0.001). Considering all included patients with AITD, T-allele carriers were 29.3% vs. 14.0% in controls (p=0.008, OR=2.54, 95% CI=1.30-4.98). Patients carrying the PTPN22 1858 T allele had a twofold increased frequency of the HLA-DRB1*03 allele (64.7% vs. 37.3%, pc=0.034).

CONCLUSION

The PTPN22 gene is a joint susceptibility locus for AITD (especially HT) and T1D.

Mannose binding lectin gene polymorphisms and associated auto-immune diseases in type 1 diabetes Brazilian patients

In our study we investigated the possible role of MBL2 functional single nucleotide polymorphisms (SNPs) in the augmented susceptibility to develop other autoimmune diseases in presence of type 1 diabetes (T1D) in a group of Brazilian patients. Patients were stratified for the presence of autoimmune diseases known to be associated with T1D, such as autoimmune thyroid disease (AITD) and celiac disease (CD), and compared with healthy controls (HC). Our findings suggest that MBL2 functional SNPs are more closely related to AITD than to T1D, being MBL2 SNPs frequencies in T1D patients not affected by AITD comparable to the HC ones, while significantly different between AITD patients and patients not affected by the disease. Thus, the association between MBL2 polymorphisms and T1D that we previously reported, seems to result from the stronger association of MBL2 SNPs with another autoimmune disease, the AITD, frequently associated with T1D.