HLA-DRB1*03 is a susceptibility gene in patients with Graves' disease with and without ophthalmopathy

Pooled genome wide association detects association upstream of FCRL3 with Graves' disease

Background

Graves’ disease is an autoimmune thyroid disease of complex inheritance. Multiple genetic susceptibility loci are thought to be involved in Graves’ disease and it is therefore likely that these can be identified by genome wide association studies. This study aimed to determine if a genome wide association study, using a pooling methodology, could detect genomic loci associated with Graves’ disease.

Results

Nineteen of the top ranking single nucleotide polymorphisms including HLA-DQA1 and C6orf10, were clustered within the Major Histo-compatibility Complex region on chromosome 6p21, with rs1613056 reaching genome wide significance (p = 5 × 10⁻⁸). Technical validation of top ranking non-Major Histo-compatablity complex single nucleotide polymorphisms with individual genotyping in the discovery cohort revealed four single nucleotide polymorphisms with p ≤ 10⁻⁴. Rs17676303 on chromosome 1q23.1, located upstream of FCRL3, showed evidence of association with Graves’ disease across the discovery, replication and combined cohorts. A second single nucleotide polymorphism rs9644119 downstream of DPYSL2 showed some evidence of association supported by finding in the replication cohort that warrants further study.

Conclusions

Pooled genome wide association study identified a genetic variant upstream of FCRL3 as a susceptibility locus for Graves’ disease in addition to those identified in the Major Histo-compatibility Complex. A second locus downstream of DPYSL2 is potentially a novel genetic variant in Graves’ disease that requires further confirmation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3276-z) contains supplementary material, which is available to authorized users.

The clinical value of human leukocyte antigen HLA-DRB1 subtypes associated to Graves' disease in Romanian population

The aim of this study was to identify the primary susceptibility HLA-DRB1 alleles associated with GD in Romanian population and to seek whether specific HLA-DRB1 haplotypes are associated with differences in the clinical presentation of GD at diagnosis. Molecular typing of HLA-DRB1 alleles was performed in 77 Romanian Caucasian GD patients and 445 racially matched controls. In GD patients, age, presence of eye disease, goiter grade, autoantibody status and titer, TSH, FT4, FT3, TT3 levels were recorded at diagnosis. The allelic frequencies of HLA-DRB1*03 (41.55% vs. 17.75%, p < 0.0001, χ(2) = 20.81) and DRB1*11 (42.85% vs. 30.56%, p = 0.045, χ(2) = 3.98)were higher, whereas those of HLA-DRB1*01(3.89% vs. 16.40%, p = 0.007, χ(2) = 7.281) and DRB1*15 (10.38% vs. 21.34%, p = 0.038, χ(2) = 4.309)were lower in GD patients than in controls. FT4/TT3 ratio (p = 0.015) and anti-thyroglobulin antibodies (p = 0.024) were higher in *03/11 patients compared to *X/X, *11/Z, *03/Y patients (where X is any other allele than *03 and *11, Y is any other allele than *11, Z is any other allele than *03). In conclusion, HLA-DRB1*03 and DRB1*11 may be the primary susceptibility HLA-DRB1 alleles associated with GD in Romanian population, whereas HLA-DRB1*01 and DRB1*15 seem to be protective. At diagnosis, HLA-DRB1*03/11 GD patients had higher FT4/TT3 ratio and anti-thyroglobulin antibody levels.

[The role of hereditary and environmental factors in autoimmune thyroid diseases]

Autoimmune thyroid diseases are the most common organ-specific autoimmune disorders affecting 5% to 10% of the population in Western countries. The clinical presentation varies from hyperthyroidism in Graves' disease to hypothyroidism in Hashimoto's thyroiditis. While the exact etiology of thyroid autoimmunity is not known, the interaction between genetic susceptibility and environmental factors appears to be of fundamental importance to initiate the process of thyroid autoimmunity. The identified autoimmune thyroid disease susceptibility genes include immune-modulating genes, such as the major histocompatibility complex, and thyroid-specific genes, including TSH receptor, thyroglobulin and thyroid peroxidase. The majority of the anti-TSH-receptor antibodies have a stimulating capacity and are responsible for hyperthyroidism. The anti-thyroglobulin- and anti-thyroid peroxidase antibodies belonging to the catalytic type of antibodies destroy the thyrocytes resulting in hypothyroidism. The appearance of anti-thyroid peroxidase antibodies precedes the induction of thyroiditis and the manifestation of hypothyroidism. The molecular analysis of thyroglobulin gene polymorphism is important in the mechanism of autoimmune thyroiditis. The autoantigen presentation by major histocompatibility complex molecules is a key point of the autoimmune mechanism. It has been shown that a HLA-DR variant containing arginine at position 74 of the DRβ1 chain confers a strong genetic susceptibility to autoimmune thyroid diseases, Graves' disease and Hashimoto's thyroiditis, while glutamine at position DRβ1-74 is protective. Human thyroglobulin 2098 peptide represents a strong and specific DRβ1-Arg74 binder, while a non-binding control peptide, thyroglobulin 2766 fails to induce this response. Moreover, thyroglobulin 2098 stimulated T-cells from individuals who were positive for thyroglobulin antibodies, demonstrating that thyroglobulin 2098 is an immunogenic peptide capable of being presented in vivo and activating T-cells in autoimmune thyroid diseases. Taken together these findings suggest that thyroglobulin 2098, a strong and specific binder to the disease-associated HLA-DRβ1-Arg74, is a major human T-cell epitope and it participates in the pathomechanism of the autoimmune thyroid disease. The exact nature of the role of environmental factors in the autoimmune thyroid disease is still not well known, but the importance of several factors such as iodine, drugs and infections has been reported. Further knowledge of the precise mechanisms of interaction between environmental factors and genes in inducing thyroid autoimmunity could result in the development of new strategies for diagnosis, prevention and treatment.

[Associations of autoimmune disorders in endocrine diseases]

Increasing data are known for dialogue between neuroendocrine and immune systems recently. Results of molecular genetic studies provided evidences for common languages of these systems by various signals including neurotransmitters, hormones, cytokines. It is proved the immune system is able to produce neurotransmitters and hormones and endocrine organs can even result in cytokines. This new integrative approach allows to investigate the physiologic events and diseases as interactions between the psycho-neuro-endocrine-immune systems. The autoimmune polyendocrine syndromes constitute a heterogeneous group of disorders characterized by loss of immune tolerance to self-antigens. In spite of distinct clinical pictures, molecular genetic studies revealed a common molecular mechanism in the associations of organ-specific diseases. Autoimmune polyendocrine syndrome-1 is characterized by associations at least two out of three cardinal signs: Addison's disease, autoimmune hypoparathyroidism and mucocutaneous candidiasis. This is a rare autosomal recessive syndrome induced by mutations in autoimmune regulator gene. Autoimmune polyendocrine syndrome-2 occurs more frequently and defined as the coexistence of Addison's disease, autoimmune thyroid disease and/or type-1 diabetes mellitus. Autoimmune polyendocrine syndrome-3 is characterized by association of autoimmune thyroid disease and type-1 diabetes mellitus. The HLA and other genes proved to be important in associations of the syndrome-2 and 3 in contrast to autoimmune polyendocrine syndrome-1. Identification of predisposing genetic helps to understand the common mechanisms and provide possibility for early therapy and prevention as well.

Early onset of polyglandular failure is associated with HLA-DRB1*03

OBJECTIVES

Polyglandular failure or autoimmunity (PGA) involves at least two endocrine diseases. Several genes may play a role in its etiology. This study analyzed 1) whether HLA-DRB1, HLA-DQB1, and MHC class I chain-related gene A (MICA) polymorphisms are associated in PGA and 2) whether PGA patients display stronger associations with these immune genes than patients with monoglandular autoimmunity (MGA).

DESIGN

Association study.

METHODS

HLA-DRB1, HLA-DQB1, and MICA alleles were analyzed in 73 patients with PGA, 283 with MGA, and 206 healthy controls. The HLA-DRB1 and HLA-DQB1 polymorphisms were determined with PCR-amplified DNA being hybridized with PCR-sequence-specific oligonucleotide probes. MICA microsatellites were typed by PCR amplification and fragment size analysis on a DNA sequencer.

RESULTS

HLA-DRB1*03 was strongly increased in patients with PGA (50.7%) versus both controls (21.8%, P(c)<0.0001; RR=2.32, 95% CI=1.62-3.33) and MGA (11.4%, P(c)<0.0001). HLA-DRB1*03 was highly prevalent in PGA patients with early versus late disease onset (P<0.05, logistic regression analysis). HLA-DRB1*04 allele carriers were more present in PGA versus controls (53.4% vs 22.4%, P(c)<0.0001, RR=2.38, 95% CI=1.68-3.38). Further, HLA-DQB1*02 was increased in PGA versus controls (P(c)<0.01), whereas HLA-DQB1*06 was decreased (P(c)<0.001). Patients with PGA showed more MIC A5.1 and less MIC A6 allele carriers than controls (NS). Presence of the MIC A5.1 allele was not associated with the HLA-DRB1*03 or HLA-DQB1 alleles.

CONCLUSIONS

HLA-DRB1*03 is a stronger genetic marker in PGA than in MGA, foremost in those with early disease onset.