Thyroglobulin Gene Research Articles

Never too late to discover some extra thyroid tissue

thyroid embryogenesis, in it’s normal migration process from the floor of the primitive foregut to the pretracheal location. It’s prevalence is 1 per 100000 - 300000 in general population and 1 per 4000-8000 in patients with thyroid disease. This condition is more common in females, Asians and may occur at any age, although it’s most common at younger ages. The mean age of presentation is 40,5 years. The exact mechanisms responsible are still unclear but many transcription factors appear to play a key role such as TITF1/NKX2-1, PAX 8, HHEX and FOXE 1. Thyroid ectopy may also have familial/hereditary background: heterozygous mutations in PAX 8 and expression of the Thyroid-Per-Oxidase and Thyroglobulin Genes. The most frequent (about 90%) location of ectopic thyroid tissue is at the base of the tongue and in those, 70 – 75% of cases it’s the only thyroid tissue present. The most common symptoms are related to the growth of lingual thyroid (dysphagia, dysphonia, sleep apnea or even respiratory obstruction and hemorrhage) and hypothyroidism, specially in the absence of orthotopic thyroid.

Thyroid Follicle Formation and Thyroglobulin Expression in Multipotent Endodermal Stem Cells

The aim of this study was to assess the impact of transcriptional induction on thyroid follicular cell (TFC) differentiation from endodermally matured embryonic stem (ES) cells. The thyroid transcription factors-NKx2 homeobox 1 (NKx2-1, formerly called TTF-1) and Paired box gene 8 (Pax8)-are known to associate biochemically and synergistically in the activation of thyroid functional genes including the sodium/iodide symporter (NIS), thyrotropin (TSH) receptor (TSHR), thyroglobulin (Tg), and thyroid peroxidase (TPO) genes. In this study, we investigated the ability of ectopically expressed Pax8 and NKx2-1 to further the induction and differentiation of murine ES cells into potential TFCs. ES cells were stably transfected with either the Pax8 gene, the NKx2-1 gene, or both genes to study the induction of NIS, TSHR, Tg, and TPO genes as assessed using both quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and protein expression. The derived cells were cultured with or without the presence of activin A to allow their differentiation into multipotent endodermal cells. The four thyroid-specific genes NIS, TSHR, Tg, and TPO were all significantly activated by expressing both transcription factors within the same ES cell. In contrast, significant but much lower transcriptional activity of the TSHR, Tg, and TPO genes was detected in cells expressing just NKx2-1, and only the NIS and TSHR genes responded to Pax8 alone. No Tg protein expression could be detected prior to their development into endodermal derivatives. However, after further differentiation of postembryoid body ES cells with activin A and TSH into endodermal cell lines, those cells with dual transfection of Pax8 and NKx2-1 demonstrated greatly enhanced expression of the NIS, TSHR, Tg, and TPO genes to such a degree that it was similar to that found in control thyroid cells. Furthermore, these same cells formed three-dimensional neofollicles in vitro and expressed Tg protein, but these phenomena were absent from lines expressing only Pax8 or NKx2-1. These findings provide further evidence that co-expression of Pax8 and NKx2-1 in murine ES cells may induce the differentiation of thyroid-specific gene expression within endodermally differentiated ES cells and commit them to form three-dimensional neofollicular structures.

Congenital hypothyroidism caused by a novel homozygous mutation in the thyroglobulin gene

Congenital hypothyroidism (CH) due to thyroglobulin (TG) deficit is an autosomal recessive disease (OMIM #274700) characterized by hypothyroidism, goiter, low serum TG, and a negative perchlorate discharge test. The aim of this study was to perform the genetic analysis of the TG gene in two sisters born from consanguineus parents and affected by CH and low serum TG levels. The index patient and her sister were identified at neonatal screening for CH and treated with L-thyroxine (L-T4). After discontinuation of L-T4 therapy, hypothyroidism was confirmed, serum TG was undetectable, and no organification defect after (123)I scintigraphy and perchlorate test was shown; thyroid ultrasound showed a eutopic gland of normal size. DNA was extracted from peripheral white blood cells of the two sisters and the father. All 48 exons of TG gene were amplified by polymerase chain reaction and subjected to direct sequencing. A novel homozygous point mutation in exon 10 of TG gene was identified in the patient and her sister. The mutation determined a stop codon at position 768 (R768X) resulting in an early truncated protein or in the complete absence of the protein. The father (euthyroid) was heterozygous carrier of the mutation. Genetic analysis of TG gene was performed in two sisters affected by CH. A novel point mutation of the TG gene determining a stop codon at position 768 of the protein was identified. The early truncated nonfunctioning protein or the absence of the protein due to the premature degradation of abnormal mRNA may be responsible of the observed phenotype.

Effect of TG and DGAT1 polymorphisms on beef carcass traits and fatty acid profile

The objectives of this study were to determine allele frequency and genotype count of thyroglobulin (TG) and diacylglycerol-0- acyltransferase-1 (DGAT1), genes encoding the TG and DGAT1 enzymes, and to determine the effect of the TG and DGAT1 polymorphisms on fatty acid profile in beef carcass. All genotypes were determined by PC-RFLP assay. The polymorphism of TG and DGAT1 had no significant influence on the total lipid content, backfat thickness, EUROP and carcass conformation score. The TT genotype of TG gene resulted in a lower total lipid content and backfat thickness, while KK genotype of DGAT1 gene showed a greater total lipid content and backfat thickness. The content of the majority fatty acids in MLD and subcutaneous fat tissue was not significantly affected by the TG and DGAT1 polymorphisms. The results confirm the lack of an association found by other studies. Further research should be carried out to validate the initial observation.

New insights into thyroglobulin gene: Molecular analysis of seven novel mutations associated with goiter and hypothyroidism

The thyroglobulin (TG) gene is organized in 48 exons, spanning over 270kb on human chromosome 8q24. Up to now, 62 inactivating mutations in the TG gene have been identified in patients with congenital goiter and endemic or non-endemic simple goiter.The purpose of the present study was to identify and characterize new mutations in the TG gene. We report 13 patients from seven unrelated families with goiter, hypothyroidism and low levels of serum TG. All patients underwent clinical, biochemical and imaging evaluation. Single-strand conformation polymorphism (SSCP) analysis, endonuclease restriction analysis, sequencing of DNA, genotyping, population screening, and bioinformatics studies were performed.Molecular analyses revealed seven novel inactivating TG mutations: c.378C>A [p.Y107X], c.2359C>T [p.R768X], c.2736delG [p.R893fsX946], c.3842G>A [p.C1262Y], c.5466delA [p.K1803fsX1833], c.6000C>G [p.C1981W] and c.6605C>G [p.P2183R] and three previously reported mutations: c.886C>T [p.R277X], c.6701C>A [p.A2215D] and c.7006C>T [p.R2317X]. Six patients from two families were homozygous for p.R277X mutation, four were compound heterozygous mutations (p.Y107X/p.C1262Y, p.R893fsX946/p.A2215D, p.K1803fsX1832/p.R2317X), one carried three identified mutations (p.R277X/p.C1981W-p.P2183R) together with a hypothetical micro deletion and the remaining two siblings from another family with typical phenotype had a single p.R768X mutated allele.In conclusion, our results confirm the genetic heterogeneity of TG defects and the pathophysiological importance of altered TG folding as a consequency of truncated TG proteins and missense mutations located in ACHE-like domain or that replace cysteine.

Selection for genetic markers in beef cattle reveals complex associations of thyroglobulin and casein1-s1 with carcass and meat traits1,2

Genetic markers in casein (CSN1S1) and thyroglobulin (TG) genes have previously been associated with fat distribution in cattle. Determining the nature of these genetic associations (additive, recessive, or dominant) has been difficult, because both markers have small minor allele frequencies in most beef cattle populations. This results in few animals homozygous for the minor alleles. selection to increase the frequencies of the minor alleles for 2 SNP markers in these genes was undertaken in a composite population. The objective was to obtain better estimates of genetic effects associated with these markers and determine if there were epistatic interactions. Selection increased the frequencies of minor alleles for both SNP from <0.30 to 0.45. Bulls (n = 24) heterozygous for both SNP were used in 3 yr to produce 204 steer progeny harvested at an average age of 474 d. The combined effect of the 9 CSN1S1 × TG genotypes was associated with carcass-adjusted fat thickness (P < 0.06) and meat tenderness predicted at the abattoir by visible and near-infrared reflectance spectroscopy (P < 0.04). Genotype did not affect BW from birth through harvest, ribeye area, marbling score, slice shear force, or image-based yield grade (P > 0.10). Additive, dominance, and epistatic SNP association effects were estimated from genotypic effects for adjusted fat thickness and predicted meat tenderness. Adjusted fat thickness showed a dominance association with TG SNP (P < 0.06) and an epistatic additive CSN1S1 × additive TG association (P < 0.03). For predicted meat tenderness, heterozygous TG meat was more tender than meat from either homozygote (P < 0.002). Dominance and epistatic associations can result in different SNP allele substitution effects in populations where SNP have the same linkage disequilibrium with causal mutations but have different frequencies. Although the complex associations estimated in this study would contribute little to within-population selection response, they could be important for marker-assisted management or reciprocal selection schemes.

A clinically euthyroid child with a large goiter due to a thyroglobulin gene defect: clinical features and genetic studies

A 10-year old child born to consanguineous parents presented with an extremely large goiter, a low free T4 level and free T4 index, and normal TSH concentration. The findings of undetectable thyroglobulin (TG) and low free T4, and an elevated free T3/free T4 ratio suggested the possibility of a defect in TG synthesis. Noteworthy aspects of this case were the extremely elevated thyroidal radioiodide uptake despite a normal TSH concentration and the fact that the reduction in the size of her goiter only occurred when her TSH was suppressed below the normal range. Gene sequencing revealed that the patient was homozygous for a donor splice site mutation in intron 30 (IVS30+1G>C). Isolation of RNA obtained from the thyroid gland by fine needle aspiration and sequencing of the TG cDNA confirmed the prediction that exon 30 was skipped, resulting in an in-frame loss of 46 amino acids.

Antitumor Effects of Proteasome Inhibition in Anaplastic Thyroid Carcinoma

The ubiquitin-proteasome pathway has been identified as a potential molecular target for cancer therapy. In this study, we investigated the effect of the proteasome inhibitor bortezomib on anaplastic thyroid carcinoma (ATC) characterized by complete refractoriness to multimodal therapeutic approaches. The ATC cell lines C643 and SW1736 were treated with bortezomib (1 nM to 1 μM) for 12-72 h. Thereafter, growth inhibition was analyzed by thymidine uptake experiments and determination of the viable cell number. Apoptosis was measured and a cell cycle analysis was done. Using gene chip analysis and the real-time quantitative PCR system, we measured transcriptional changes. The activity of the nuclear factor (NF)-κB and p53 signal transduction pathways was monitored using the reporter constructs pNF-κB-TA-Luc and pp53-TA-Luc in the luciferase activity assay. Uptake measurements using (3)H-FDG, (14)C-aminoisobutyric acid, and Na(125)iodide were performed to investigate metabolic changes and iodide symporter activity in vitro. Moreover, the (18)F-FDG uptake was evaluated in ATC tumor-bearing nude mice 1 or 2 d after treatment with bortezomib. Bortezomib induced growth inhibition, apoptosis, and G(2)-M cell cycle arrest associated with upregulation of p21(CIP1/WAF1) expression in SW1736 and C643 cells. Moreover, the glucose metabolism and aminoisobutyric acid uptake significantly decreased in vitro in both of the ATC cell lines in vivo only in SW1736 tumors at 2 d after the bortezomib treatment. The transcriptional profile in bortezomib-treated SW1736 and C643 cells revealed increased expression of genes involved in stress response, apoptosis, regulation of the cell cycle, and differentiation. Using real-time quantitative PCR for the quantification of gene expression, we additionally noticed upregulation of the tumor necrosis factor-related apoptosis-inducing ligand and the thyroid-specific transcription factors Pax8 and TTF-1, leading to expression of the thyroid-specific target genes thyroglobulin, sodium iodide symporter, thyroperoxidase, and thyroid-stimulating hormone receptor and to a moderate accumulation of iodide in ATC cells. On the basis of our data, bortezomib represents a promising antineoplastic agent for the treatment of ATC. To improve the clinical outcome, further investigation into the potential of bortezomib therapy of thyroid cancer is clearly warranted.

Association of polymorphisms in the leptin and thyroglobulin genes with meat quality and carcass traits in beef cattle

The objective of the present study was to estimate the allelic and genotypic frequencies of the polymorphisms E2FB (AY138588.1: c.305C> T), located in the leptin gene (LEP), and TG5 (X05380.1:g.-422C>T), located in the thyroglobulin gene (TG), and evaluate the association of these polymorphisms in crossbred cattle of seven distinct genetic groups with the following traits: slaughter weight (SW), hot carcass weight (HCW), hot carcass yield (HCY), carcass fat thickness (CFT), ribeye area (REA), marbling (MARM) and shear force (SF). The animals were genotyped using the PCR-RFLP (Polymorphism Chain Reaction-Restriction Fragment Length Polymorphism) technique, using 201 products obtained from F1 Caracu × Nellore, Angus × Nellore and Valdostana × Nellore cows, mated to Canchim, Caracu and Red Angus bulls (only Caracu × Nellore cows were used with Red Angus bulls). The allelic and genotypic frequencies were compared using the Chi-squared test. Associations between the genotype of each polymorphism and the traits were analyzed using the General Linear Model (GLM) of statistical software SAS. The least squares means of genotypes of the polymorphisms were compared using Student's t test. The E2FB polymorphism in the LEP gene was associated with CFT, showing the potential for use in national programs for genetic improvement of beef cattle, through the inclusion of SNP in genotyping commercial tests. The TG5 polymorphism in the TG gene was not associated with any of the evaluated traits and was considered ineffective for selection of beef cattle in Brazilian herds.

한우에서 TG와 EDG1 유전자의 단일염기다형 확인 및 도체형질과의 연관성 분석

Thyroglobulin (TG) gene was known to be regulated fat cell growth and differentiation and the endothelial differentiation sphingolipid G-protein-coupled receptor 1 (EDG1) gene involves blood vessel formation and known to be affecting carcass traits in beef cattle. The aim of this study was to identify the single nucleotide polymorphisms (SNPs) in both TG and EDG1 genes and to analyze the association with carcass traits in Korean cattle (Hanwoo). The T354C SNP in TG gene located at the 3' flanking region and c.-312A>G SNP located at 3'-UTR of EDG1 gene were used for genotyping the animals using PCR-RFLP method. Three genotypes were identified in T354C SNP in TG gene and only two AA and AG genotypes were observed for the c.-312A>G SNP in EDG1 gene. The results indicated that T354C SNP in TG gene was not significantly associated with carcass traits. However, the c.-312A>G SNP in EDG1 gene had significant effects on backfat thickness (BF) and yield index (YI). These results may provide valuable information for further candidate gene studies affecting carcass traits in Korean cattle and may use as marker assisted selection for improving the quality of meat in Hanwoo.

The Potassium Channel Interacting Protein 3 (DREAM/KChIP3) Heterodimerizes with and Regulates Calmodulin Function

Downstream regulatory element antagonistic modulator (DREAM/KChIP3), a neuronal EF-hand protein, modulates pain, potassium channel activity, and binds presenilin 1. Using affinity capture of neuronal proteins by immobilized DREAM/KChIP3 in the presence and absence of calcium (Ca(2+)) followed by mass spectroscopic identification of interacting proteins, we demonstrate that in the presence of Ca(2+), DREAM/KChIP3 interacts with the EF-hand protein, calmodulin (CaM). The interaction of DREAM/KChIP3 with CaM does not occur in the absence of Ca(2+). In the absence of Ca(2+), DREAM/KChIP3 binds the EF-hand protein, calcineurin subunit-B. Ca(2+)-bound DREAM/KChIP3 binds CaM with a dissociation constant of ∼3 μM as assessed by changes in DREAM/KChIP3 intrinsic protein fluorescence in the presence of CaM. Two-dimensional (1)H,(15)N heteronuclear single quantum coherence spectra reveal changes in chemical shifts and line broadening upon the addition of CaM to (15)N DREAM/KChIP3. The amino-terminal portion of DREAM/KChIP3 is required for its binding to CaM because a construct of DREAM/KChIP3 lacking the first 94 amino-terminal residues fails to bind CaM as assessed by fluorescence spectroscopy. The addition of Ca(2+)-bound DREAM/KChIP3 increases the activation of calcineurin (CN) by calcium CaM. A DREAM/KChIP3 mutant incapable of binding Ca(2+) also stimulates calmodulin-dependent CN activity. The shortened form of DREAM/KChIP3 lacking the NH(2)-terminal amino acids fails to activate CN in the presence of calcium CaM. Our data demonstrate the interaction of DREAM/KChIP3 with the important EF-hand protein, CaM, and show that the interaction alters CN activity.

82nd Annual Meeting of the American Thyroid AssociationMEETING ABSTRACTS &amp; PROGRAM

82nd Annual Meeting of the American Thyroid AssociationMEETING ABSTRACTS &amp; PROGRAM

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.

Multiple SNPs in Intron 41 of Thyroglobulin Gene Are Associated with Autoimmune Thyroid Disease in the Japanese Population

BackgroundThe 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.ObjectivesThe 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.MethodsWe 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 ConclusionsIn 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.

Clinical and Genetic Analysis of a Compound Heterozygous Mutation in the Thyroglobulin Gene in a Chinese Twin Family With Congenital Goiter and Hypothyroidism

Mutations in the thyroglobulin (TG) gene, which has an estimated incidence of approximately 1 in 100,000 new-borns, cause autosomal recessive congenital hypothyroidism. The mutational spectrum of the TG gene and the phenotype-genotype correlations have not yet fully been established. We report a compound heterozygous mutation in the TG gene in a Chinese twin family with congenital goiter and hypothyroidism. We also describe the gene mutation associated with the genotype-phenotype of these children with congenital goiter and hypothyroidism. The whole coding sequence of the TG gene was analyzed by direct sequence, and the identified changes in the sequence were tested for benign polymorphism by denaturing high-performance liquid chromatography screening of the mutation and sequencing 200 chromosomes from normal controls. Analysis of the TG gene of the affected twin revealed a compound heterozygous mutation, including a novel missense mutation G2687A, which is predicted to result in a glutamine to arginine substitution at codon 877, and a known nonsense mutation C7006T, predicted to result in an arginine to stop codon at codon 2317. Analysis of 200 normal chromosomes did not identify the same change in healthy subjects. This is the first report of a TG gene mutation in the Chinese Han population. Our study provides further evidence that mutations in the TG gene cause congenital goiter and hypothyroidism, demonstrates genetic heterogeneity of the mutation, and increases our understanding of phenotype-genotype correlations in congenital hypothyroidism.

Association of CSSM066 and ILSTS011 microsatellite markers and thyroglobulin gene SNP with backfat in Canchim cattle

Canchim, a synthetic breed of cattle derived from the Charolais and Zebu group has been used in the beef-cattle industry in Brazil as an alternative for intensifying production. One of the main concerns with this breed is its poor fat deposition and consequently, there is an effort to increase the performance for this trait. The thyroglobulin gene is located in a QTL region for fat deposition, and reports describe the influence of a polymorphism in the 5´ leader sequence of that gene on marbling and subcutaneous fat thickness. This study analyzed the association of this polymorphism in the thyroglobulin gene, as well as of two flanking microsatellite markers, CSSM066 and ILSTS011, with backfat thickness in 987 Canchim beef cattle. The CSSM066 and ILSTS011 microsatellite markers have a effect on fat thickness in the studied populations. However, this trait did not have association with the polymorphism of the thyroglobulin gene, which suggests that other genes of bovine chromosome 14 may be responsible for the variation in this trait.

Distribución de polimorfismos asociados al grado de infiltración de grasa intramuscular en siete razas bovinas de carne utilizadas en la Región de La Araucanía, Chile

SUMMARY Selection of breeding stock is a crucial step in any breeding program, therefore the methodology for animal evaluation has evolved rapidly and in recent decades has incorporated the use of molecular markers. Several multinational companies have made available to producers commercial tests based on these technologies, which allow assessing the predisposition of animals to express a specific phenotype. However, some doubts have begun to arise about negative effects of improper use of molecular markers, these are problems associated with inbreeding depression and long-term loss of response to selection. Therefore, the objective of this study was to assess allele and genotype frequencies of 4 polymorphisms associated with marbling in 7 beef cattle breeds being present in La Araucania Region of Chile. We evaluated leptin, thyroglobulin, DGAT1 and FABP4 genes, which showed different frequency distributions among breeds with higher allele frequency for marbling in Aberdeen Angus breed and a low frequency in Belgian Blue and Hereford breeds. We conclude that it is feasible to use these tools in genetic programs, but it is also necessary to have reliable genealogical records and advice of professional or technical institutions that can integrate genotypic information from molecular markers in prediction models used for selection of breeding stock.

Autoimmune Thyroid Disease Genes Identified in Non-Caucasians

Autoimmune thyroid diseases (AITDs), including Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), are among the commonest autoimmune disorders, affecting approximately 2% - 5% of the population. Epidemiological data support strong genetic influences on the development of AITD. The identification of genes placing individuals at an increased risk for the development of AITD has been a slow process. However, over the last 20 years or so real progress has been made with the mapping of novel loci, via a number of different approaches. The first AITD gene discovered, Human Leucocyte Antigen (HLA)/Major Histocompatibility Complex (MHC), is associated with both GD and HT. 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 will summarize the latest findings on AITD susceptibility genes in non-Caucasians.

Thyroglobulin Gene Mutation with Cold Nodule on Thyroid Scintigraphy

Thyroglobulin gene mutation is a rare cause of congenital hypothyroidism, but thyroglobulin gene mutations are thought to be associated with thyroid cancer development. A 21-year-old Japanese man treated with levothyroxine for congenital hypothyroidism had an enlarged thyroid gland with undetectable serum thyroglobulin despite elevated serum TSH level. The patient was diagnosed with thyroglobulin gene mutation, with compound heterozygosity for Gly304Cys missense mutation and Arg432X nonsense mutation. Ultrasonography showed a hypovascular large tumor in the left lobe that appeared as a cold nodule on thyroid scintigraphy. He underwent total thyroidectomy, but pathological study did not reveal findings of thyroid carcinoma, but rather a hyperplastic nodule with hemorrhage. Strong cytoplasmic thyroglobulin immunostaining was observed, but sodium iodide symporter immunostaining was hardly detected in the hyperplastic nodule. The clinical characteristics of patients with thyroglobulin gene mutations are diverse, and some patients are diagnosed by chance on examination of goiter in adults. The presence of thyroid tumors that appear as cold nodules on thyroid scintigraphy should consider the potential for thyroid carcinoma, if the patient has relatively low serum thyroglobulin concentration in relation to the degree of TSH without thyroglobulin autoantibody.

Molecular Basis of Thyroid Dyshormonogenesis: Genetic Screening in Population-Based Japanese Patients

Inborn errors of thyroid hormone biosynthesis are collectively referred to as thyroid dyshormonogenesis (DH). Seven genes have been implicated in DH, including the dual oxidase 2 gene (DUOX2), the thyroglobulin gene (TG), and the thyroid peroxidase gene (TPO). We aimed to define the prevalence and phenotypic spectrum of DH with single gene mutations. A population-based cohort of 102 patients with permanent congenital hypothyroidism was enrolled. Fourteen were diagnosed as DH and were analyzed for the seven causative genes including DUOX2, TG, and TPO. Several common mutations were screened in the remaining 88 patients. Pathogenicity of single amino acid mutations was verified in vitro. We identified four, five, and two patients with seemingly biallelic mutations in DUOX2, TG, and TPO, respectively. We also found two patients having one heterozygous DUOX2 mutation and one uncommon single-nucleotide polymorphism (SNP) p.H678R (rs57659670, allele frequency 0.035) and another two patients with homozygous p.H678R. Expression experiments and RT-PCR revealed that p.H678R is a functional SNP with theoretical 40% loss of function, supporting a role of p.H678R in the onset of DH. As for clinical phenotypes, patients with inactive DUOX2 alleles (mutations and/or p.H678R) showed characteristic time-dependent improvement of thyroid function and morphology. All three evaluated patients had a negative result in the perchlorate test. Mutations (or a functional SNP) in DUOX2, TG, or TPO were observed in 93% (95% confidence interval = 70-99%) of DH patients. Inactive DUOX2 alleles cause a broader phenotypic spectrum than currently accepted.