Screening for an AIRE-1 mutation in patients with Addison's disease, type 1 diabetes, Graves' disease and Hashimoto's thyroiditis as well as in APECED syndrome

The role behind the scenes of Tregs and Th17s in Hashimoto's thyroiditis: Toward a pivotal role of FOXP3 and BACH2

In Hashimoto's thyroiditis (HT), the genetic bases play a central role in determining development of the disease. In particular, the most frequent genes involved in the onset of HT are the Human Leukocyte Antigen (HLA). However, there are other genes and transcription factors in the autoimmune background of HT, both isolated and as part of autoimmune polyendocrine syndromes (APS). Recently more interest is being fueled toward BACH2 (BTB Domain and CNC Homolog 2), that promotes Tregs (T regulators lymphocytes) differentiation and enhances Treg-mediated immunity. The synergistic interaction between environmental agents and the aforementioned genes leads to the onset of autoimmunity and ultimately to damage of the thyroid gland. In this scenario, the role of Th17 (T helper-17 lymphocytes) and Treg cells is still less defined as compared to action of Th1 cells (T helper-1 lymphocytes) and cytotoxic lymphocytes (CD8 ⁺ T lymphocytes). Evidences show that an imbalance of Th17/Treg ratio represents a prognostic factor with respect to the gland damage. Moreover, the deficient ability of Treg to inhibit the proliferation of T cells against the self can break the immune balance. In light of these considerations, the use of genetic panels and the progress of immunotherapy could allow for better targeting treatment and preventive interventions in subjects with potential or early stage of HT.

Molecular and clinical characterization of autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome (APECED) in Iranian non-Jewish patients: report of two novel AIRE gene pathogenic variants

Objective

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome (APECED) is a rare autosomal recessive systemic autoimmune disease caused by mutations in the autoimmune regulator (AIRE) gene. Incidence of this genetic disorder is estimated at 1/90,000–200,000 worldwide and 1/6500–9000 in genetically isolated populations such as Iran. Here, we investigated AIRE gene mutations in eight independent Iranian non-Jewish families.

Methods

We sequenced the coding regions of the AIRE gene and documented mutations which were further confirmed in respective parents.

Results

In total, 11 cases from 8 independent families were recruited. Mucosal candidiasis, Addison’s disease and hypoparathyroidism were the most common clinical manifestations in these patients. One novel homozygous splice acceptor mutation (c.308-1G>C), and one novel heterozygous stop-gain mutation (c.1496delC) combined with a known heterozygous c.232T>C missense mutation were found. Moreover, we observed previously described splice donor (c.1095+2T>A), frameshift (c.967-979del), stop-gain (c.415C>T), and missense (c.62C>T) mutations among the patients. All results were co-segregated in parents.

Conclusion

Here, we reported two novel mutations in the AIRE gene leading to APECED. Our data could provide insight into the phenotypic and genotypic spectrum of APECED in the non-Jewish Iranian population. These findings, in addition to future functional assays, can elucidate disease-causing mechanisms related to the AIRE gene and assist in genetic counseling and diagnosis.

Twenty Years of AIRE

About two decades ago, cloning of the autoimmune regulator (AIRE) gene materialized one of the most important actors on the scene of self-tolerance. Thymic transcription of genes encoding tissue-specific antigens (ts-ags) is activated by AIRE protein and embodies the essence of thymic self-representation. Pathogenic AIRE variants cause the autoimmune polyglandular syndrome type 1, which is a rare and complex disease that is gaining attention in research on autoimmunity. The animal models of disease, although not identically reproducing the human picture, supply fundamental information on mechanisms and extent of AIRE action: thanks to its multidomain structure, AIRE localizes to chromatin enclosing the target genes, binds to histones, and offers an anchorage to multimolecular complexes involved in initiation and post-initiation events of gene transcription. In addition, AIRE enhances mRNA diversity by favoring alternative mRNA splicing. Once synthesized, ts-ags are presented to, and cause deletion of the self-reactive thymocyte clones. However, AIRE function is not restricted to the activation of gene transcription. AIRE would control presentation and transfer of self-antigens for thymic cellular interplay: such mechanism is aimed at increasing the likelihood of engagement of the thymocytes that carry the corresponding T-cell receptors. Another fundamental role of AIRE in promoting self-tolerance is related to the development of thymocyte anergy, as thymic self-representation shapes at the same time the repertoire of regulatory T cells. Finally, AIRE seems to replicate its action in the secondary lymphoid organs, albeit the cell lineage detaining such property has not been fully characterized. Delineation of AIRE functions adds interesting data to the knowledge of the mechanisms of self-tolerance and introduces exciting perspectives of therapeutic interventions against the related diseases.

AIRE genetic variants and predisposition to polygenic autoimmune disease: The case of Graves' disease and a systematic literature review

Autoimmune Regulator (AIRE) is a transcriptional regulator that is crucial for establishing central tolerance as illustrated by the Mendelian Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED) syndrome associated with AIRE-inactivating recessive or dominant mutations. Polymorphisms in AIRE have been proposed to be implicated in genetic susceptibility to non-Mendelian organ specific autoimmune diseases. Because there is evidence that in predisposition to Graves' disease (GD) central tolerance is crucial, we investigated whether AIRE polymorphisms could modulate risk of GD. A case-control association study using 29 variants and conducted in 150 GD patients and 200 controls did not detect any significant association. This result is not exceptional: a systematic review of the literature, including GWAS, on the association of AIRE variants with organ specific autoimmune diseases did not show clear associations; similarly heterozygous recessive mutations are not associated to non-Mendelian autoimmunity. Dominant negative mutations of AIRE are associated to autoimmunity but as mild forms of APECED rather than to non-Mendelian organ specific autoimmunity. The lack of association of common AIRE polymorphisms with polygenic autoimmune diseases is counterintuitive as many other genes less relevant for immunological tolerance have been found to be associated. These findings give rise to the intriguing possibility that evolution has excluded functionally modifying polymorphisms in AIRE.

Novel Findings into AIRE Genetics and Functioning: Clinical Implications

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), formerly known as autoimmune polyendocrine syndrome type 1, is a paradigm of a monogenic autoimmune disease caused by mutations of a gene, named autoimmune regulator (AIRE). AIRE acts as a transcription regulator that promotes immunological central tolerance by inducing the ectopic thymic expression of many tissue-specific antigens. Although the syndrome is a monogenic disease, it is characterized by a wide variability of the clinical expression with no significant correlation between genotype and phenotype. Indeed, many aspects regarding the exact role of AIRE and APECED pathogenesis still remain unraveled. In the last decades, several studies in APECED and in its mouse experimental counterpart have revealed new insights on how immune system learns self-tolerance. Moreover, novel interesting findings have extended our understanding of AIRE's function and regulation thus improving our knowledge on the pathogenesis of APECED. In this review, we will summarize recent novelties on molecular mechanisms underlying the development of APECED and their clinical implications.

Mechanisms in endocrinology: autoimmune thyroid disease: old and new players

The last 10 years have seen some progress in understanding the etiology of autoimmune thyroid disease (AITD). The female preponderance can now be explained - at least in part - by fetal microchimerism and X-chromosome inactivation. The number of identified susceptibility genes for AITD is increasing (among others now including TSHR, TG, HLA, CTLA4, PTPN22, CD40, FCRL3, IL2RA, and FOXP3), but these genes together probably do not explain more than about 10% of the heritability of AITD. As twin studies indicate that genes contribute for 70% of AITD, it follows that there must be many more loci, each of them contributing a little. While the genetic studies have clarified why various autoimmune diseases so often cluster in the same patient, the molecular mechanism of action of these genetic polymorphisms (frequently located in introns) has hardly been explained. Polymorphisms in AITD susceptibility genes may become helpful in clinical practice, e.g. in assessing risk of recurrent Graves' hyperthyroidism (GH) after a course of antithyroid drugs. Moderate alcohol intake decreases the risk on overt GH and overt Hashimoto's hypothyroidism. Current smokers - as well known - are at increased risk for Graves' disease, but - surprisingly - at diminished risk for Hashimoto's thyroiditis. Low selenium and low vitamin D levels might increase the risk of developing AITD, but data are still inconclusive. Current options for preventive interventions in subjects at risk to develop AITD are very limited.

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.

Human APECED; a Sick Thymus Syndrome?

Loss-of-function mutations in the Autoimmune Regulator (AIRE) gene cause a rare inherited form of autoimmune disease, autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, also known as autoimmune polyglandular syndrome type 1. The patients suffer from multiple endocrine deficiencies, the most common manifestations being hypoparathyroidism, Addison’s disease, hypogonadism, and secondary amenorrhea, usually accompanied by typical autoantibodies against the target tissues. Chronic mucocutaneous candidiasis is also a prominent part of the disease. The highest expression of AIRE is found in medullary thymic epithelial cells (mTECs). Murine studies suggest that it promotes ectopic transcription of self antigens in mTECs and is thus important for negative selection. However, failed negative selection alone is not enough to explain key findings in human patients, necessitating the search for alternative or additional pathogenetic mechanisms. A striking feature of the human AIRE-deficient phenotype is that all patients develop high titers of neutralizing autoantibodies against type I interferons, which have been shown to downregulate the expression of interferon-controlled genes. These autoantibodies often precede clinical symptoms and other autoantibodies, suggesting that they are a reflection of the pathogenetic process. Other cytokines are targeted as well, notably those produced by Th17 cells; these autoantibodies have been linked to the defect in anti-candida defenses. A defect in regulatory T cells has also been reported in several studies and seems to affect already the recent thymic emigrant population. Taken together, these findings in human patients point to a widespread disruption of T cell development and regulation, which is likely to have its origins in an abnormal thymic milieu. The absence of functional AIRE in peripheral lymphoid tissues may also contribute to the pathogenesis of the disease.

[Polyglandular autoimmune syndromes]

Polyglandular autoimmune syndromes (PGA) are a heterogeneous group of diseases in which a genetically caused dysfunction of the immune system leads to a destruction of endocrine glands with subsequent loss of function. In addition non-endocrine autoimmune diseases are also frequently present. Due to different patterns of inheritance and occurrence of disease a differentiation is made between juvenile PGA (also called APECED, autoimmune polyendocrinopathy candidiasis ectodermal dystrophy) with a monogenetic alteration of the AIRE (autoimmune regulator) gene, different ethnic distribution and a typical triad of diseases and the adult form, mainly conditioned by mutations of the HLA (human leukocyte antigens) alleles on chromosome 6. The article will briefly deal with the very rare IPEX (immune dysfunction, polyendocrinopathy, enteropathy, x-linked) syndrome, where the FOXP3 gene on chromosome X is altered. Important for the diagnosis are the clinical appearance and functional tests of the endocrine glands and the testing for antibodies. Additionally for PGA I and IPEX genetic testing is advisable. Currently patient-adjusted hormone replacement therapy is very important and screening of family members is recommended.

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.

Autoimmune polyglandular syndromes

The autoimmune polyglandular syndromes-a group of syndromes comprising a combination of endocrine and nonendocrine autoimmune diseases-differ in their component diseases and in the immunologic features of their pathogenesis. One of the three main syndromes, type 1 autoimmune polyglandular syndrome (APS-1), has a unique pathogenic mechanism owing to mutations in the autoimmune regulator (AIRE) gene, which results in the loss of central tolerance-a process by which developing T cells with potential reactivity for self-antigens are eliminated during early differentiation in the thymus. Patients with IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked) syndrome harbor mutations in the forkhead box P3 (FOXP3) gene in regulatory T cells, which leads to severe autoimmunity and immune deficiency. Although both of these disorders are rare, their well-defined mechanisms of disease provide a basis for the understanding of the more common condition, APS-2. In this syndrome, alleles of human leukocyte antigens (HLAs) determine the targeting of specific tissues by autoreactive T cells, which leads to organ-specific autoimmunity as a result of this loss of tolerance. Non-HLA genes also contribute to autoimmunity in APS-2 and, depending on the polymorphism, potentially predispose to a loss of tolerance or influence which organ is specifically targeted. This Review discusses the genetic basis of APS-1, APS-2 and IPEX syndrome, with an emphasis on the mechanisms of autoimmunity and presents currently available therapies to treat their underlying autoimmune disorders.

Immunologic endocrine disorders

Autoimmunity affects multiple glands in the endocrine system. Animal models and human studies highlight the importance of alleles in HLA-like molecules determining tissue-specific targeting that, with the loss of tolerance, leads to organ-specific autoimmunity. Disorders such as type 1A diabetes, Graves disease, Hashimoto thyroiditis, Addison disease, and many others result from autoimmune-mediated tissue destruction. Each of these disorders can be divided into stages beginning with genetic susceptibility, environmental triggers, active autoimmunity, and finally metabolic derangements with overt symptoms of disease. With an increased understanding of the immunogenetics and immunopathogenesis of endocrine autoimmune disorders, immunotherapies are becoming prevalent, especially in patients with type 1A diabetes. Immunotherapies are being used more in multiple subspecialty fields to halt disease progression. Although therapies for autoimmune disorders stop the progress of an immune response, immunomodulatory therapies for cancer and chronic infections can also provoke an unwanted immune response. As a result, there are now iatrogenic autoimmune disorders arising from the treatment of chronic viral infections and malignancies.

Recent advances in adrenal autoimmunity

Autoimmune Addison's disease (AAD) results from the immune-mediated destruction of adrenocortical cells. AAD is a major component of the autoimmune polyendocrine syndromes type 1 (APS 1) and type 2. The adrenal autoimmune process is made evident by the apperance of circulating autoantibodies against the steroidogenic enzyme 21-hydroxylase. Detection of 21-hydroxylase in patients with endocrine autoimmune diseases enables the identification of subjects with preclinical AAD. An impaired response to a corticotrophin stimulation test marks the irreversible stage of preclinical AAD and predicts progression towards clinical AAD in over 80% of cases. APS 1 is caused by mutations of the autoimmune regulator (AIRE) gene, which encodes an activator of transcription, Aire, that induces the expression of autoantigens in thymic medullary epithelial cells and promotes immunological tolerance. Isolated and APS 2-related AAD is an autoimmune disease with evidence for complex genetic susceptibility caused by T-cell-mediated destruction of adrenocortical cells, with a major contribution of HLA genes. The target cells in the adrenal cortex participate in the immune reaction by releasing chemokines, such as CXCL-10, that attract Th1 cells.

Studies in mice deficient for the autoimmune regulator (Aire) and transgenic for the thyrotropin receptor reveal a role for Aire in tolerance for thyroid autoantigens

The autoimmune regulator (Aire) mediates central tolerance for many autoantigens, and autoimmunity occurs spontaneously in Aire-deficient humans and mice. Using a mouse model of Graves' disease, we investigated the role of Aire in tolerance to the TSH receptor (TSHR) in Aire-deficient and wild-type mice (hyperthyroid-susceptible BALB/c background). Mice were immunized three times with TSHR A-subunit expressing adenovirus. The lack of Aire did not influence T-cell responses to TSHR protein or TSHR peptides. However, antibody levels were higher in Aire-deficient than wild-type mice after the second (but not the third) immunization. After the third immunization, hyperthyroidism persisted in a higher proportion of Aire-deficient than wild-type mice. Aire-deficient mice were crossed with transgenic strains expressing high or low-intrathyroidal levels of human TSHR A subunits. In the low-expressor transgenics, Aire deficiency had the same effect on the pattern of the TSHR antibody response to immunization as in nontransgenics, although the amplitude of the response was lower in the transgenics. High-expressor A-subunit transgenics were unresponsive to immunization. We examined intrathymic expression of murine TSHR, thyroglobulin, and thyroid peroxidase (TPO), the latter two being the dominant autoantigens in Hashimoto's thyroiditis (particularly TPO). Expression of the TSHR and thyroglobulin were reduced in the absence of Aire. Dramatically, thymic expression of TPO was nearly abolished. In contrast, the human A-subunit transgene, lacking a potential Aire-binding motif, was unaffected. Our findings provide insight into how varying intrathymic autoantigen expression may modulate thyroid autoimmunity and suggest that Aire deficiency may contribute more to developing Hashimoto's thyroiditis than Graves' disease.

Autoimmune polyendocrine syndrome type 1 (APS-1) as a model for understanding autoimmune polyendocrine syndrome type 2 (APS-2)

Autoimmune polyendocrine syndromes type 1 and 2 (APS-1 and APS-2) are diverse in regards to their component diseases and immunologic features of pathogenesis. Animal models and human studies highlight the importance of alleles of HLA (human leukocyte antigen)-like molecules determining tissue specific targeting that with the loss of tolerance leads to organ specific autoimmunity. Knowledge of the syndromes and component diseases allows clinicians to recognize and prevent illness prior to morbidity. With the current understanding of the syndromes, a paradigm for diagnosis, screening and treatment can be established. Once genetically susceptible individuals are identified screening for autoantibodies can be performed. Amongst autoantibody positive individuals, monitoring for physiologic decompensation, with a goal of treating prior to morbidity and in some cases mortality, follows. With continued basic and clinical research, therapies aimed at treating the underlying autoimmunity and disease prevention should become possible.

Monogenic autoimmune diseases: insights into self-tolerance

Autoimmune diseases affect a significant segment of the population and are typically thought to be multifactorial in etiology. Autoimmune diseases due to single gene defects are rare, but offer an invaluable window into understanding how defects in the immune system can lead to autoimmunity. In this review, we will focus on autoimmune polyendocrinopathy syndrome type 1 and recent advances in our understanding of this disease. We will also discuss two other monogenic autoimmune diseases: immunodysregulation, polyendocrinopathy, and enteropathy, X-linked and Autoimmune lymphoproliferative syndrome. Importantly, the knowledge and principles gained from studying these diseases have been applicable to more common autoimmune diseases and have opened the door to better diagnostic and therapeutic modalities.

The proinflammatory cytokine TNF-alpha -308 AA genotype is associated with polyglandular autoimmunity

Data regarding polymorphisms of immunoregulatory genes in polyglandular autoimmunity (PGA) are lacking. We have analyzed whether the polymorphism of the proinflammatory cytokine gene TNF-alpha; -308 and mutations of the autoimmune regulator (AIRE) gene were associated with PGA in adults. Sixty-seven patients with PGA and 209 healthy controls were genotyped by multiplex minisequencing with capillary electrophoresis on an ABI PRISM-310 genetic analyzer. HLA DRB1 typing was performed using polymerase-chain-reaction-amplified DNA hybridized with sequence-specific-oligonucleotide probes (PCR-SSO). The TNF-alpha; -308*A allele occurred more frequently in patients (0.269) than in controls (0.163, P = 0.008, P(c) = 0.016). Also, TNF-alpha; -308*A carriers were more frequent in patients than controls (47.8% vs. 31.1%, OR = 1.89, 95%CI = 1.19-3.00). The frequency of the AA genotype was increased in PGA (P = 0.014, P(c) = 0.042). PGA patients with autoimmune thyroid disease and the TNF-alpha; -308 AA genotype showed the highest prevalence of thyroid autoantibodies (TPO, P = 0.04; Tg, P = 0.003). HLA-DRB1*03 and TNF-alpha; -308*A alleles were strongly associated in patients with PGA (87.5%, P(c) < 0.00001). The AIRE R257X and 13bpdel mutations were not observed in patients with PGA. The association of TNF-alpha; -308*A with PGA might be directly or indirectly due to the association with HLA-DRB1*03.

Aire

Mutations in the transcriptional regulator, Aire, cause APECED, a polyglandular autoimmune disease with monogenic transmission. Animal models of APECED have revealed that Aire plays an important role in T cell tolerance induction in the thymus, mainly by promoting ectopic expression of a large repertoire of transcripts encoding proteins normally restricted to differentiated organs residing in the periphery. The absence of Aire results in impaired clonal deletion of self-reactive thymocytes, which escape into the periphery and attack a variety of organs. In addition, Aire is a proapoptotic factor, expressed at the final maturation stage of thymic medullary epithelial cells, a function that may promote cross-presentation of the antigens encoded by Aire-induced transcripts in these cells. Transcriptional regulation by Aire is unusual in being very broad, context-dependent, probabilistic, and noisy. Structure/function analyses and identification of its interaction partners suggest that Aire may impact transcription at several levels, including nucleosome displacement during elongation and transcript splicing or other aspects of maturation.

Menin regulates endocrine diseases by controlling histone modification and gene transcription

Multiple endocrine neoplasia type 1 (MEN1), a human familial tumor syndrome, results from mutations in the Men1 gene. Although much progress has been made in demonstrating the definitive role for menin in suppressing tumorigenesis in endocrine organs, the molecular pathways responsible for menin action in normal tissues and tumors remain poorly defined. Here, we review the recent progress on the molecular functions of menin in controlling cell proliferation, apoptosis, and DNA repair. The majority of these functions are largely executed by menin-mediated influencing of histone modifications and chromatin structure. These findings lead to a new model of understanding menin's tumor-suppressing function, providing insights into understanding of how menin regulates cell proliferation and the development of endocrine tumors. The new knowledge could also be translated into new strategies to improve therapeutic interventions against MEN1 and other endocrine diseases including diabetes.

Mechanisms of an autoimmunity syndrome in mice caused by a dominant mutation in Aire

Homozygous loss-of-function mutations in AIRE cause autoimmune polyglandular syndrome type 1 (APS 1), which manifests in a classic triad of hypoparathyroidism, adrenal insufficiency, and candidiasis. Interestingly, a kindred with a specific G228W AIRE variant presented with an autosomal dominant autoimmune phenotype distinct from APS 1. We utilized a novel G228W-knockin mouse model to show that this variant acted in a dominant-negative manner to cause a unique autoimmunity syndrome. In addition, the expression of a large number of Aire-regulated thymic antigens was partially inhibited in these animals, demonstrating the importance of quantitative changes in thymic antigen expression in determining organ-specific autoimmunity. Furthermore, the dominant-negative effect of the G228W variant was exerted through recruitment of WT Aire away from active sites of transcription in the nucleus of medullary thymic epithelial cells in vivo. Together, these results may demonstrate a mechanism by which autoimmune predisposition to phenotypes distinct from APS 1 can be mediated in a dominant-negative fashion by Aire.

AIRE variations in Addison's disease and autoimmune polyendocrine syndromes (APS): partial gene deletions contribute to APS I

Autoimmune Addison's disease (AAD) is often associated with other components in autoimmune polyendocrine syndromes (APS). Whereas APS I is caused by mutations in the AIRE gene, the susceptibility genes for AAD and APS II are unclear. In the present study, we investigated whether polymorphisms or copy number variations in the AIRE gene were associated with AAD and APS II. First, nine SNPs in the AIRE gene were analyzed in 311 patients with AAD and APS II and 521 healthy controls, identifying no associated risk. Second, in a subgroup of 25 of these patients, AIRE sequencing revealed three novel polymorphisms. Finally, the AIRE copy number was determined by duplex quantitative PCR in 14 patients with APS I, 161 patients with AAD and APS II and in 39 healthy subjects. In two Scandinavian APS I patients previously reported to be homozygous for common AIRE mutations, we identified large deletions of the AIRE gene covering at least exon 2 to exon 8. We conclude that polymorphisms in the AIRE gene are not associated with AAD and APS II. We further suggest that DNA analysis of the parents of patients found to be homozygous for mutations in AIRE, always should be performed.

Association analysis of the AIRE and insulin genes in Finnish type 1 diabetic patients

Mutations in the autoimmune regulator (AIRE) gene cause a recessive Mendelian disorder autoimmune polyendocrinopathy syndrome type 1 (APS-1 or autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy). APS-1 patients develop multiorgan autoimmune diseases including type 1 diabetes (prevalence 12%). The AIRE protein controls the central tolerance induction in the thymus by regulating the expression levels of tissue-specific peripheral antigens, such as insulin. We hypothesized that the insulin gene (INS) polymorphisms together with the AIRE variations may predispose individuals to diabetes. The role of the AIRE gene was tested both independently and on the condition of the INS risk genotype in the Finnish type 1 diabetes sample. A total of 733 type 1 diabetic cases and 735 age- and sex-matched healthy controls were used in the analysis. Five common single nucleotide polymorphisms (SNPs) in the AIRE gene were selected from the public database (dbSNP). The -23HphI polymorphism was used as a surrogate marker for the INS gene promoter repeat. The five genotyped SNPs in the AIRE gene showed no evidence of association with type 1 diabetes. As expected, the INS gene polymorphism -23HphI was significantly associated with susceptibility to type 1 diabetes (P=6.8 x 10(-12), chi(2) test). When the subclass of patients carrying the homozygote genotype of the INS gene was used in the analysis, the AIRE polymorphisms showed no association with the disease. In conclusion, the AIRE gene does not seem to contribute to disease susceptibility in Finnish type 1 diabetic patients, whereas the insulin gene represents a notable risk factor for disease in this population.

Fine mapping of a region on chromosome 21q21.11-q22.3 showing linkage to type 1 diabetes

BACKGROUND

Results of a Scandinavian genome scan in type 1 diabetes mellitus (T1D) have recently been reported. Among the novel, not previously reported chromosomal regions showing linkage to T1D was a region on chromosome 21.

OBJECTIVE

To fine map this region on chromosome 21.

METHODS AND RESULTS

The linked region was initially narrowed by linkage analysis typing microsatellite markers. Linkage was significantly increased, with a peak NPL score of 3.61 (p = 0.0002), suggesting the presence of one or several T1D linked genes in the region. The support interval for linkage of 6.3 Mb was then studied by linkage disequilibrium (LD) mapping with gene based single nucleotide polymorphisms (SNPs). Thirty two candidate genes were identified in this narrowed region, and LD mapping was carried out with SNPs in coding regions (cSNPs) of all these genes. However, none of the SNPs showed association to T1D in the complete material, whereas some evidence for association to T1D of variants of the TTC3, OLIG2, KCNE1, and CBR1 genes was observed in conditioned analyses. The disease related LD was further assessed by a haplotype based association study, in which several haplotypes showed distorted transmission to diabetic offspring, substantiating a possible T1D association of the region.

CONCLUSIONS

Although a single gene variant responsible for the observed linkage could not be identified, there was evidence for several combinations of markers, and for association of markers in conditioned analyses, supporting the existence of T1D susceptibility genes in the region.

Atypical presentation of shock from acute adrenal insufficiency in an adolescent male

OBJECTIVE

To report an atypical presentation of shock and acute adrenal insufficiency in an adolescent male.

CASE SUMMARY

A 14-year-old boy with a history of nocturnal enuresis presented with a clinical picture suggestive of septic shock refractory to aggressive fluid and vasopressor management. History and physical examination were suggestive of shock secondary to an infectious etiology, associated with skin findings of hyperpigmentation. The laboratory studies were remarkable for normal sodium, potassium, glucose, as well as normal renin levels. Hydrocortisone therapy led to improvement of his blood pressure and allowed weaning of vasopressor medications. Further laboratory studies, including adrenocorticotropic hormone stimulation test and adrenal antibodies, confirmed the diagnosis of primary adrenal insufficiency.

CONCLUSION

Acute adrenal insufficiency is an uncommon cause of shock in the adolescent population. We report a clinical presentation suggestive of shock secondary to acute adrenal insufficiency remarkable for an atypical clinical and laboratory presentation. We further provide information on the management of acute adrenal crisis.

Immunoregulatory and susceptibility genes in thyroid and polyglandular autoimmunity

The etiology of autoimmune thyroid diseases (AITD) is based on genetic and nongenetic factors. Genome-wide screening and linkage analyses have identified several chromosomal regions that are linked to AITD. These are HT-1 (on chromosome 13q33) and HT-2 (chromosome 12q22) for Hashimoto's thyroiditis (HT), and GD-1 (chromosome 14q31), GD-2 (chromosome 20q11.2), and GD-3 (chromosome Xq21) for Graves' disease (GD). Several genes have been proposed as susceptibility or immunoregulatory genes. Most promising genes are those of the major histocompatibility complex (MHC) complex (chromosome 6), the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene (chromosome 2), the CD40 (chromosome 20), the thyroglobulin gene (chromosome 8), and the autoimmune regulator gene (chromosome 21). This review summarizes evidence for pathogenetic involvement of several of these genes in various forms of autoimmune thyropathies. Most genetic data refer to GD, whereas less data are available for HT and thyroid-associated ophthalmopathy. Scarce data refer to AITD within the autoimmune polyglandular syndromes I and II. The realization of family studies in large samples from different populations might provide further insight in the genetic contribution to AITD. Data are also needed on the interaction among susceptibility genes. Finally, additional functional studies are warranted to clarify the possible role of allelic variants in the underlying pathogenic mechanisms of AITD.

Absence of Heterozygous K83E and R257X Mutations of the AIRE-1 Gene in 46 Children with Type 1 Diabetes and 44 Children with Graves' Disease

Type 1 diabetes mellitus (DM) and Graves’ disease are autoimmune diseases, and a number of genetic factors, including HLA and CTLA-4 genes, have been reported to contribute to their etiology. The gene responsible for autoimmune polyendocrinopathy- candidiasis-ectodermal dystrophy (APECED) has been cloned and named the autoimmune regulator-1 (AIRE-1) gene. AIRE-1 protein is thought to be a transcription regulatory protein and to have a role in the maintenance of immunological tolerance. The aim of this study was to determine whether heterozygous AIRE-1 gene mutations are associated with childhood-onset type 1 diabetes and Graves’ disease in the Japanese population. We investigated 46 children with type 1 DM (29 females and 17 males; age at the time of diagnosis, 0.5–16 yr) and 44 children with Graves’ disease (34 females and 10 males; age at the time of diagnosis, 3–16 yr) for the presence of the K83E mutation in exon 2 and the R257X mutation in exon 6 of the AIRE-1 gene. The alleles were identified by polymerase chain reaction of genomic DNA and restriction fragment-length polymorphism analysis (PCR-RFLP) with endonuclease TaqI. Since no patients with type 1 DM or Graves’ disease were found to carry the K83E or the R257X heterozygous mutation, we concluded that neither the K83E nor the R257X heterozygous mutation in the AIRE-1 gene seem to be the cause of the more common isolated endocrinopathies, i.e., type 1 diabetes mellitus and Graves’ disease, in Japanese children.

Autoimmune polyglandular syndrome Type 2: the tip of an iceberg?

Autoimmune polyglandular syndromes (APS) are conditions characterized by the association of two or more organ-specific disorders. Type 2 APS is defined by the occurrence of Addison's disease with thyroid autoimmune disease and/or Type 1 diabetes mellitus. Clinically overt disorders are considered only the tip of the autoimmune iceberg, since latent forms are much more frequent. Historical, clinical, genetic, and immunological aspects of Type 2 APS are reviewed. Furthermore, data on 146 personal cases of Type 2 APS are also reported.

Autoimmune regulator: from loss of function to autoimmunity

The autoimmune regulator (AIRE) is a gene where mutations cause the recessively inherited disorder called autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) or autoimmune polyendocrinopathy syndrome type 1 (APS1). Variable combinations of autoimmune endocrine diseases such as Addison's disease, hypoparathyroidism, and type 1 diabetes characterize APECED. The AIRE protein has several domains indicative of a transcriptional regulator. AIRE contains two PHD (plant homeodomain) type zinc fingers, four nuclear receptor binding LXXLL motifs, a putative DNA-binding domain named SAND and, in addition, a highly conserved N-terminal domain similar to the homogenously staining region domain of the Sp100 protein. At the subcellular level, AIRE is expressed in nuclear dots resembling promyelocytic leukemia nuclear bodies, which are associated with several transcriptionally active proteins. AIRE is primarily expressed in thymic medullary epithelial cells and monocyte-dendritic cells in the thymus but also in a rare subset of cells in the lymph nodes, spleen and fetal liver. The disease, caused by mutations in AIRE, its function as a protein involved in transcription, and its restricted expression in cells important in negative selection, all together suggest that AIRE is a central protein in the maintenance of immune tolerance. In this review of the recent literature we discuss the results of these studies with particular attention on the AIRE expression pattern and its function as a transcriptional regulator, as well as the effects of patient mutations on the molecular characteristics of the protein.

Autoimmune endocrine disease

The immune system can attack almost any given organ in a very specific and directed fashion. The endocrine system appears to be particularly vulnerable to this kind of insult. Which endocrine organs are most susceptible and why? Genetic studies and animal models have revealed some commonalities for these diseases. The MHC locus appears to help control not only susceptibility to disease but also which endocrine organs are attacked. Autoimmune thymectomy models have revealed suppressor cell populations, which are being intensely sought after as a protective mechanism against endocrine autoimmunity. Finally, the recent cloning of the causative gene for autoimmune polyglandular syndrome type I, called AIRE, has brought central tolerance back into focus as an important mechanism in these endocrine diseases.

A novel missense mutation of AIRE gene in a patient with autoimmune polyendocrinopathy, candidiasis and ectodermal dystrophy (APECED), accompanied with progressive muscular atrophy: case report and review of the literature in Japan

Autoimmune polyendocrinopathy, candidiasis, and ectodermal dystrophy (APECED) also known as autoimmune polyglandular syndrome type I, is a rare autosomal recessive disorder that results in several autoimmune diseases due to mutations in the AIRE (autoimmune regulator) gene. A 39-year-old female patient developed chronic mucocutaneous candidiasis at 3 yrs, idiopathic hypoparathyroidism at 11 yrs, chronic hepatitis at 23 yrs, Addison's disease and diabetes mellitus type I at 27 yrs. In addition, the patient developed progressive muscular atrophy of unknown etiology at the beginning of the third decade, and is bedridden at the present time. Her grandparents, parents, brother and daughter did not develop any features of APECED, but her father died of hepatoma. Direct sequencing of the AIRE gene revealed a novel missense mutation at exon 1 (R15C), which was identified to be of maternal origin. The other mutation was not found despite repeated sequencing of the whole coding regions. The R15C mutation was not detected in patients with idiopathic hypoparathyroidism (N= 10), idiopathic Addison's disease (N = 3), and normal subjects (N = 55). Although we could not analyze the father's gene, these results suggest that the patient is probably a compound heterozygote of the AIRE gene, in which the other abnormal allele could not be identified by the present analytical method. These data are compatible with the recent review that only one defective allele was detectable in some patients with clinically evident APECED. We found only six Japanese patients compatible with diagnosis of APECED, indicating that this autoimmune disease is extremely rare in our country.

Autoimmune regulator (AIRE) gene on chromosome 21: implications for autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) any more common manifestations of endocrine autoimmunity

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare, but well-defined monogenic disorder that is caused by mutations in the autoimmune regulator (AIRE) gene on chromosome 21q22.3. Patients most often suffer from loss of endocrine function in the parathyroid and adrenal glands but may also develop Type 1 diabetes, thyroid disease or hypogonadism. The disease may therefore serve as a model for sporadic endocrine autoimmunity and help to develop new screening and prevention methods. To date at least 46 mutations of AIRE have been identified in affected individuals. Little is known about heterozygosity states but patients with the more prevalent isolated autoimmune endocrinopathies such as Type 1 diabetes, Hashimoto's thyroiditis, Graves' or Addison's disease do not have any of the common mutations. This does not rule out AIRE to be affected either by so far unknown or regulatory variants. The recent characterization of AIRE knockout mice with similar immune pathological findings compared to the human setting will help to elucidate endocrine autoimmunity.

Thyroid autoimmunity in children and adolescents with type 1 diabetes: a multicenter survey

OBJECTIVE

To investigate thyroid autoimmunity in a very large nationwide cohort of children and adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Data were analyzed from 17,749 patients with type 1 diabetes aged 0.1-20 years who were treated in 118 pediatric diabetes centers in Germany and Austria. Antibodies to thyroglobulin (anti-TG) and thyroperoxidase (anti-TPO) were measured and documented at least once in 7,097 patients. A total of 49.5% of these patients were boys, the mean age was 12.4 years (range 0.3-20.0 years), and the mean duration of diabetes was 4.5 years (range 0.0-19.5 years). A titer exceeding 100 units/ml or 1:100 was considered significantly elevated.

RESULTS

In 1,530 patients, thyroid antibody levels were elevated on at least one occasion, whereas 5,567 were antibody-negative during the observation period. Patients with thyroid antibodies were significantly older (P < 0.001), had a longer duration of diabetes (P < 0.001), and developed diabetes later in life (P < 0.001) than those without antibodies. A total of 63% of patients with positive antibodies were girls, compared with 45% of patients without antibodies (P < 0.001). The prevalence of significant thyroid antibody titers increased with increasing age; the highest prevalence was in the 15- to 20-year age group (anti-TPO: 16.9%, P < 0.001; anti-TG: 12.8%, P < 0.001). Thyroid-stimulating hormone (TSH) levels were higher in patients with thyroid autoimmunity (3.34 microU/ml, range 0.0-615.0 microU/ml) than in control subjects (1.84 microU/ml, range 0.0-149.0 microU/ml) (P < 0.001). Even higher TSH levels were observed in patients with both anti-TPO and anti-TG (4.55 microU/ml, range 0.0-197.0 microU/ml).

CONCLUSIONS

Thyroid autoimmunity seems to be particularly common in girls with diabetes during the second decade of life and may be associated with elevated TSH levels, indicating subclinical hypothyroidism.

Population genetics and functions of the autoimmune regulator (AIRE)

The autoimmune polyglandular syndrome type 1 (APS1), also known as autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APS1), is a monogenic autosomal disease with recessive inheritance. It is characterized by chronic mucocutaneous candidiasis, multiple autoimmune endocrinopathies, and ectodermal dystrophies. The defective gene responsible for this disease has been identified and named "autoimmune regulator" (AIRE). The AIRE gene is located on chromosome 21q22.3. At least 45 different disease-causing mutations in AIRE have been discovered. This review summarizes the global distribution of AIRE mutations and the relevance of major mutations to the clinical disorders associated with APS1. We also will review studies on the structure and DNA-binding ability of the AIRE protein and the possible malfunctions of the AIRE protein as a result of major disease-causing mutations.

New perspectives on the immunology of chronic mucocutaneous candidiasis

Chronic mucocutaneous candidiasis is a primary immune deficiency presenting as an inability to clear fungal infections and consequently as persisting and recurring infections of the skin and mucous membranes with yeasts, mostly Candida albicans. Chronic mucocutaneous candidiasis is a heterogeneous clinical syndrome which usually presents in childhood and can have an autosomal recessive, dominant or sporadic mode of inheritance. Most chronic mucocutaneous candidiasis patients also develop accompanying endocrine and inflammatory disorders that suggest an underlying deregulation of the immune system. It has long been recognized that protection from mucocutaneous candidiasis relies on cell-mediated immunity and studies on animal models have highlighted the essential role of type 1 cytokines in protection against Candida spp. Recent data in patients with chronic mucocutaneous candidiasis have documented altered patterns of cytokine production in response to Candida spp. with decreased production of some but not all type 1 cytokines and increased levels of interleukin-10. The defect underlying altered cytokine production remains unknown but studies are in progress addressing the putative role of dendritic cells and pattern recognition receptors in directing cytokine responses. These novel insights into immune mechanisms responsible for protection against Candida spp. are opening new possibilities of immunomodulation and vaccination that could prove beneficial in the management of chronic mucocutaneous candidiasis.