Evidence for a new Graves disease susceptibility locus at chromosome 18q21

Two Cases of Thyrotoxicosis and Euglycemic Diabetic Ketoacidosis Under Sodium-glucose Transport Protein 2 Inhibitor Treatment

Thyrotoxicosis and sodium-glucose transport protein 2 inhibitors (SGLT2is) are associated with the induction of euglycemic diabetic ketoacidosis (euDKA). We herein report two cases of euDKA in patients with diabetes mellitus wherein both thyrotoxicosis and SGLT2i treatment were the underlying causes. One patient developed thyrotoxicosis during the course of type 2 diabetes mellitus, whereas the other patient was suspected of developing slowly progressive insulin-dependent diabetes mellitus during the course of Graves' disease. Although such cases are rare, there is some concern that similar cases may occur because of the increased frequency of SGLT2i use in recent years.

Correlation of ABH blood group antigens secretion with Helicobacter pylori infection in Pakistani patients

OBJECTIVES

A and B blood group antigens are fucosylated carbohydrate present on human erythrocytes and body secretions. Their presence in body secretions depends on the expression of a dominant allele of secretor gene FUT2 and is correlated with susceptibility to various infectious and non-infectious diseases. We investigated the correlation of blood group and ABH antigen secretion with Helicobacter pylori infection and gastroduodenal symptoms and analysed the distribution of babA gene among ABH secretors and non-secretors.

METHODS

Two hundred and ninety patients who underwent gastroduodenal endoscopy during 2011 to 2012 participated. Gastric biopsy, saliva and blood samples were obtained from every patient. Gastric biopsies were subjected to rapid urease test and PCR for the detection of H. pylori and babA gene. Blood grouping and ABH antigens secretions were determined by Lewis blood group phenotyping and haemagglutination inhibition test.

RESULTS

50.34% of patients were ABH antigen secretors and 45.51% non-secretors. Distribution analysis of blood group revealed that 40 blood group B, 67 blood group A 20 blood group O and 19 blood group AB patients secreted ABH antigens in saliva. Fifty-six blood group O, 19 blood group B, 32 blood group A and 17 blood group AB patients were non-secretors. Gastroduodenal complaints were common among non-secretors. Sixty-two percent of patients with a combination of duodenal ulcer and gastro-oesophageal reflux and 54% of patients with gastritis were non-secretors. Of 290 samples, 31.02% were positive for H. pylori. Thirty percent of these tested positive for babA gene; the majority belonged to non-secretor blood group O.

CONCLUSIONS

Our results suggest that the infection of H. pylori is correlated with ABO blood groups and blood group antigens secretion in body fluids.

GWAS in autoimmune thyroid disease: redefining our understanding of pathogenesis

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

Autoimmune polyendocrinopathy associated with ring chromosome 18

Phenotypic and clinical features of individuals with ring chromosome 18 [r(18)] vary with the extent of deletion of the short (18p-) or long arm (18q-). Most patients with r(18), therefore, demonstrate a clinical spectrum of both 18p- and 18q- deletions. Short stature, microcephaly, mental and motor retardation, craniofacial dysmorphism and extremity abnormalities are the most commonly reported features in patients with r(18). Abnormalities of chromosome 18, especially 18p- syndrome, are often reported with autoimmune thyroid disease and growth hormone deficiency, but reports of endocrine abnormalities associated with r(18) are rare. Here, we report a case of an African-American female with hyperthyroidism, type 1 diabetes mellitus, vitiligo and IgA deficiency associated with a r(18) chromosome complement. This patient additionally had mild intellectual disability and dysmorphic features. Karyotype analysis showed a de novo ring chromosome 18 (deletion 18q23-18qter and deletion 18p11.3-18pter). Although this unique association of autoimmune polyglandular endocrinopathy with ring chromosome 18 could be coincidental, we speculate that a gene or genes on chromosome 18 might play a role in the autoimmune process.

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

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

Molecular diagnosis in head and neck: what a surgical pathologist must know

Molecular alterations in tumors have become interesting targets both for diagnostic and for therapeutic and prognostic applications in tumor pathology. In the head and neck, there are a variety of different alterations, encompassing all the different types of genetic events associated with carcinogenesis. This paper reviews three different types of tumors that display a spectrum of genetic alterations: the translocation in Mucoepidermoid carcinoma, Epstein Barr virus association in nasopharyngeal carcinoma, and the HRPT2 tumor suppressor gene in parathyroid carcinoma. Basic histology is reviewed and the genetic alterations are discussed, along with a brief discussion of potential diagnostic implications.

A genome-wide association for kidney function and endocrine-related traits in the NHLBI's Framingham Heart Study

BACKGROUND

Glomerular filtration rate (GFR) and urinary albumin excretion (UAE) are markers of kidney function that are known to be heritable. Many endocrine conditions have strong familial components. We tested for association between the Affymetrix GeneChip Human Mapping 100K single nucleotide polymorphism (SNP) set and measures of kidney function and endocrine traits.

METHODS

Genotype information on the Affymetrix GeneChip Human Mapping 100K SNP set was available on 1345 participants. Serum creatinine and cystatin-C (cysC; n = 981) were measured at the seventh examination cycle (1998-2001); GFR (n = 1010) was estimated via the Modification of Diet in Renal Disease (MDRD) equation; UAE was measured on spot urine samples during the sixth examination cycle (1995-1998) and was indexed to urinary creatinine (n = 822). Thyroid stimulating hormone (TSH) was measured at the third and fourth examination cycles (1981-1984; 1984-1987) and mean value of the measurements were used (n = 810). Age-sex-adjusted and multivariable-adjusted residuals for these measurements were used in association with genotype data using generalized estimating equations (GEE) and family-based association tests (FBAT) models. We presented the results for association tests using additive allele model. We evaluated associations with 70,987 SNPs on autosomes with minor allele frequencies of at least 0.10, Hardy-Weinberg Equilibrium p-value > or = 0.001, and call rates of at least 80%.

RESULTS

The top SNPs associated with these traits using the GEE method were rs2839235 with GFR (p-value 1.6*10(-05)), rs1158167 with cysC (p-value 8.5*10(-09)), rs1712790 with UAE (p-value 1.9*10(-06)), and rs6977660 with TSH (p-value 3.7*10(-06)), respectively. The top SNPs associated with these traits using the FBAT method were rs6434804 with GFR(p-value 2.4*10(-5)), rs563754 with cysC (p-value 4.7*10(-5)), rs1243400 with UAE (p-value 4.8*10(-6)), and rs4128956 with TSH (p-value 3.6*10(-5)), respectively. Detailed association test results can be found at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite. Four SNPs in or near the CST3 gene were highly associated with cysC levels (p-value 8.5*10(-09) to 0.007).

CONCLUSION

Kidney function traits and TSH are associated with SNPs on the Affymetrix GeneChip Human Mapping 100K SNP set. These data will serve as a valuable resource for replication as more SNPs associated with kidney function and endocrine traits are identified.

Genome-wide meta-analysis for rheumatoid arthritis

Meta-analysis is being increasingly used as a tool for integrating data from different studies of complex phenotypes, because the power of any one study to identify causal loci is limited. We applied a novel meta-analytical approach (Loesgen et al. in Genet Epidemiol 21(Suppl 1):S142-S147, 2001) in compiling results from four studies of rheumatoid arthritis in Caucasians including two studies from NARAC (Jawaheer et al. in Am J Hum Genet 68:927-936, 2001; Jawaheer et al. in Arthritis Rheum 48:906-916, 2003), one study from the UK (MacKay et al. in Arthritis Rheum 46:632-639, 2001) and one from France (Cornelis et al. in Proc Natl Acad Sci USA 95:10746-10750, 1998). For each study, we obtained NPL scores by performing interval mapping (2 cM intervals) using GeneHunter2 (Kruglyak et al. in Am J Hum Genet 58:1347-1363, 1996; Markianos et al. in Am J Hum Genet 68:963-977, 2001). The marker maps differed among the three consortium groups, therefore, the marker maps were aligned after the interval mapping was completed and the NPL scores that were within 1 cM of each other were combined using the method of Loesgen et al. (Genet Epidemiol 21(Suppl 1):S142-S147, 2001) by calculating the weighted average of the NPL score. This approach avoids some problems in analysis encountered by using GeneHunter2 when some markers in the sample are not genotyped. This procedure provided marginal evidence (P<0.05) of linkage on chromosome 1, 2, 5 and 18, strong evidence (P<0.01) on chromosomes 8 and 16, and overwhelming evidence in the HLA region of chromosome 6.

Evidence for linkage and association between autoimmune thyroid diseases and the 18q12-q21 region in a large Tunisian family

Many studies have shown linkage between IDDM6 locus on 18q12-q21 chromosome and several autoimmune diseases, suggesting that it might harbour susceptibility genes common to autoimmunity. Using 12 families deriving from a large Tunisian multiplex family (the Akr family) from which 38 people were affected with autoimmune thyroid diseases (AITD), and 193 unrelated AITD patients, tested against 100 healthy subjects, we tried to replicate the positive results previously reported for the IDDM6. Akr members were genotyped with eight microsatellite markers harbouring the IDDM6 region. Multipoint non-parametric linkage analysis have shown a clear peak values of NPL score around D18S41 marker (Z = 3.72, P = 0.0001). Family-based association test (FBAT) and transmission disequilibrium test (TDT) have confirmed linkage results. In particular, a significant association with allele 3 of D18S41 and allele 2 of D18S57 markers was found. Case-control studies, using one intragenic microsatellite (locus CTG18.1) marker in the immunoglobulin transcription factor (ITF2) gene, a 5' flanking AC repeat of the anti-apoptotic BCL-2 gene as well as two SNPs at positions +52 and +1955 from transcription start site of BCL-2, showed no significant association between neither genes and AITD. Our study is the first replication of the 18q12-q21 chromosome region as a potential candidate to AITD genetic susceptibility. The Akr family has shown evidence for linkage between IDDM6 locus and AITD. Moreover, case-control study does not support the involvement of ITF2 and BCL2 genes in AITD pathogenesis.

Genetics of rheumatoid arthritis

Rheumatoid arthritis (RA) is a heterogeneous autoimmune disorder of unknown cause with variable clinical expression. About 70% of patients are women. Genetic factors play an important role and likely account for about 60% of disease susceptibility and expression. The association with the HLA-DRB1 gene is the best understood, although several non-HLA loci have been linked to RA, including the 18q21 region of the TNFRSR11A gene, which encodes the receptor activator of nuclear factor kappaB, important in bone resorption in RA. Genetic factors are also important in the treatment of RA because the activity of enzymes relevant in the metabolism of drugs such as methotrexate and azathioprine, including methylenetetrahydrofolate reductase and thiopurine methyltransferase, are in part genetically determined.

The spectrum of thyroid abnormalities in individuals with 18q deletions

Chromosome 18q deletions (18q-) are survivable autosomal deletions, having an estimated incidence of one in 40,000 live births. Our long-term goals were to 1) comprehensively define the endocrine phenotype, 2) determine the natural history, and 3) identify key genes leading to particular phenotypes. This report specifically emphasizes the thyroid phenotype. Medical record review and comprehensive clinical assessment(s) were performed on 120 individuals with 18q- at the Chromosome 18 Clinical Research Center, the largest group of individuals with 18q- ever assembled. Affected subjects ranged in age from 6 wk to 32 yr at initial assessment. Due to case reports of thyroid dysfunction in 18q deletions and the well-established association between hypothyroidism and aneusomies, we undertook thyroid testing in all individuals and completed TRH studies on 50 of them. Our studies demonstrated that 12% had hypothyroidism, and the results were consistent with primary thyroidal dysfunction. Furthermore, two individuals progressed from normal to abnormal over the course of 2 yr. Based on these studies, it appears that, as is the case in other aneusomies, annual thyroid testing, using TSH as a primary screening tool, is indicated. The mechanism of the hypothyroidism is not yet known, and the genetic basis has not been delineated.

Cost-effective analysis of candidate genes using htSNPs: a staged approach

We have previously shown that the selection of haplotype tag single nucleotide polymorphisms (htSNPs) and their statistical analysis in a multi-locus transmission/disequilibrium test (TDT) results in a more cost-effective genotyping strategy in disease association studies of genes by minimising redundancy due to linkage disequilibrium between SNPs. Further savings can be achieved by the use of a two-stage genotyping strategy. This approach is illustrated here in conjunction with the multi-locus TDT in determining whether common alleles of the immune regulatory genes RANK and its ligand TRANCE (RANKL) are associated with type 1 diabetes (T1D). A saving of approximately 75% of potential genotyping reactions could be made with minimal loss of power. There was little evidence from our analysis for association between the TRANCE and RANK genes and T1D in the populations tested.

Identification of two novel female-specific non-major histocompatibility complex loci regulating collagen-induced arthritis severity and chronicity, and evidence of epistasis

OBJECTIVE

To identify additional sex-specific and epistatic quantitative trait loci (QTL) regulating collagen-induced arthritis (CIA) severity overall, as well as within different stages during the disease course, in an intercross between major histocompatibility complex-identical inbred rat strains DA/Bkl (susceptible) and ACI/Hsd (resistant).

METHODS

Arthritic male (DA x ACI)F2 intercross offspring (n = 143) were analyzed separately from the females (n = 184). Phenotypic extremes (maximum arthritis scores [MAS]) were genotyped and used for QTL analysis. All 327 rats were genotyped with the simple sequence-length polymorphism (SSLP) markers closest to the peak of Cia7 and Cia10, the major loci previously identified in this intercross, and with SSLPs covering chromosomes 12 and 18. Phenotypes studied were disease onset, arthritis severity scores on days 14-39, MAS, mean and cumulative arthritis scores, delayed-type hypersensitivity, and antibody responses to rat type II collagen.

RESULTS

A new female-specific arthritis-severity recessive locus was identified on rat chromosome 12 (Cia25), with a maximum effect observed on day 28 (logarithm of odds [LOD] 4.7). The homozygous DA genotype at Cia25 was associated with a 45% higher median arthritis score in females. Sequencing analyses of the Cia25 candidate gene Ncf1 revealed polymorphisms between DA and ACI. The previously identified locus, Cia10, was found to be male-specific. A 2-locus interaction model analysis identified a novel recessive chromosome 18 QTL, Cia26, which was dependent on Cia7, with its maximum effect observed at later stages during the disease course (peak LOD score of 3.6 for arthritis scores on day 39).

CONCLUSION

This study identified 2 novel female-specific loci, and 1 male-specific locus. Cia25 regulates MAS and disease severity during the mid-to-late stages of the disease course and may be accounted for by Ncf1 polymorphisms. Cia26 is in epistasis with Cia7 and regulates later stages of disease, suggesting an involvement in disease perpetuation and/or chronicity.

A single nucleotide polymorphism in the CD40 gene on chromosome 20q (GD-2) provides no evidence for susceptibility to Graves' disease in UK Caucasians

OBJECTIVE

A genome-wide screen in Graves' disease (GD) has shown linkage to chromosome 20q, designated GD-2. The gene encoding CD40, which stimulates lymphocyte proliferation and differentiation, maps to this region, and a single nucleotide polymorphism (SNP) at position -1 of the Kozak sequence within the gene has been reported to be associated with GD. The aim of this study was to determine whether this SNP of the CD40 gene confers susceptibility to GD in UK Caucasians.

DESIGN

A large case-control cohort consisting of 800 patients with GD, and 785 control subjects with no history of autoimmune disease, was used to genotype this SNP by polymerase chain reaction restriction fragment length polymorphism.

RESULTS

Despite adequate power (> 99%) to detect an effect, if present (odds ratio of 1.5), no significant difference in allele or genotype frequency of the CD40 SNP was observed between patients with GD and control subjects (P = 0.087 and P = 0.145, respectively).

CONCLUSIONS

These data suggest that this polymorphism of the CD40 gene is not associated with GD in the UK and is therefore not contributing to disease susceptibility in the chromosomal region designated GD-2.

Role of the CD40 locus in Graves' disease

The genetic basis for Graves' disease remains largely unknown, but significant linkage to microsatellite markers on 20q11 suggests that this region harbors a susceptibility gene. One obvious candidate gene at this 20q11 locus is CD40, which encodes a B-cell-surface receptor that is involved in T-cell to B-cell signaling and is implicated in control of T-cell autoreactivity. In addition, an allele of a single nucleotide polymorphism (SNP) in the Kozak consensus sequence of the 5' untranslated region of CD40 exon 1 has been reported to show modest evidence for association with Graves' disease. We have investigated the role of this 5' untranslated region (5' UTR) in Graves' disease susceptibility in our cohort of 451 unrelated white subjects with Graves' disease and 446 healthy controls. The CD40 5'UTR SNP (C --> T, position -1) was polymerase chain reaction (PCR)amplified and genotyped using the restriction enzyme NcoI. The frequency of the C allele was 74.8% in Graves' probands compared to 75.1% in controls (not significant [NS]). We find no evidence to support allelic association with Graves' disease at this CD40 SNP, despite the adequate power of the study. We are unable to confirm a role for CD40 in Graves' disease pathogenesis in our U.K. population, however, further studies involving larger patient cohorts and a saturated SNP marker map are required to resolve this issue.

The genetics of autoimmune thyroid disease

Autoimmune thyroid diseases (AITDs), such as Graves' hyperthyroidism, are common disorders involving multiple genes and the environment. Some pathogenetic genes are probably shared between these diseases and non-endocrine autoimmune diseases, whereas others are disease specific. Population studies show that major histocompatibility complex alleles and CTLA4 confer risk for AITDs. Genetic studies have identified over 20 potential loci; only one, mapping to 5q31, has been convincingly replicated. Despite its recent emergence as an autoimmunity gatekeeper gene, linkage of CLTA4 to AITDs was described in only one Caucasian population subset. Like in the case of many complex genetic disorders, identifying AITD pathogenetic genes is limited by the ability of data analysis methods to discern the influence of genes of minor effect in a relatively small database.

The deleted in colorectal carcinoma (DCC) gene 201 R → G polymorphism: no evidence for genetic association with autoimmune disease

The product of the deleted in colorectal carcinoma (DCC) gene has a role in apoptosis and is a positional candidate for IDDM6, the putative chromosome 18q12-q23 autoimmune disease locus. We hypothesised that a nonconservative substitution (DCC 201 R --> G; nucleotide (nt) 601 C --> G), located in an extracellular immunoglobulin-like domain of DCC, is an aetiological determinant of autoimmunity. We tested this hypothesis by genetically testing the nt 601 C --> G polymorphism for association with three autoimmune phenotypes in a large population-based case-control study. There was no evidence for association of DCC nt 601 C --> G with autoimmune disease in cohorts comprising 2253 subjects with rheumatoid arthritis, type I diabetes and Graves' disease, and 2225 control subjects, from New Zealand and the United Kingdom. Furthermore, using the transmission disequilibrium test, there was no significant evidence for biased transmission of the nt 601 C --> G polymorphism to probands within a 382 family type I diabetes affected sibpair cohort from the United Kingdom. Thus, the DCC 201 R --> G polymorphism does not appreciably influence risk of developing the autoimmune diseases tested.

A Murine Locus on Chromosome 18 Controls NKT Cell Homeostasis and Th Cell Differentiation

Th cell differentiation is a critical event in the adaptive immune response. C57BL strains develop predominant Th1 responses while BALB/c develops a predominant Th2 response. To identify quantitative trait loci controlling this variation, we performed Th1/Th2 differentiation assays of F(1) x BALB/c progeny. A single strong quantitative trait locus was identified on chromosome 18, with weaker effects detectable on chromosomes 5, 12, and 14. By preparing a congenic BALB.B10.D2c18 strain, we were able to demonstrate that this single locus was sufficient to "repolarize" spleen cell cultures. This difference was not due to intrinsic differences in CD4(+) T cells. Rather, introgression of the chromosome 18 locus into BALB/c disrupted Va14Ja18 NKT cell homeostasis resulting in the almost complete absence of this T cell subset. Taken together, these data indicate that genes within chromosome 18 control strain-dependent development of Va14Ja18 NKT cells.

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

The autoimmune thyroid diseases (AITDs), comprising Graves disease (GD) and Hashimoto thyroiditis (HT), develop as a result of a complex interaction between predisposing genes and environmental triggers. Previously, we identified six loci that showed evidence for linkage with AITD in a data set of 56 multiplex families. The goals of the present study were to replicate/reject the previously identified loci before fine mapping and sequencing the candidate genes in these regions. We performed a whole-genome linkage study in an expanded data set of 102 multiplex families with AITD (540 individuals), through use of 400 microsatellite markers. Seven loci showed evidence for linkage to AITD. Three loci, on chromosomes 6p, 8q, and 10q, showed evidence for linkage with both GD and HT (maximum multipoint heterogeneity LOD scores [HLOD] 2.0, 3.5, and 4.1, respectively). Three loci showed evidence for linkage with GD: on 7q (HLOD 2.3), 14q (HLOD 2.1), and 20q (LOD 3.3, in a subset of the families). One locus on 12q showed evidence of linkage with HT, giving an HLOD of 3.4. Comparison with the results obtained in the original data set showed that the 20q (GD-2) and 12q (HT-2) loci continued to show evidence for linkage in the expanded data set; the 6p and 14q loci were located within the same region as the previously identified 6p and 14q loci (AITD-1 and GD-1, respectively), but the Xq (GD-3) and 13q (HT-1) loci were not replicated in the expanded data set. These results demonstrated that multiple genes may predispose to GD and HT and that some may be common to both diseases and some are unique. The loci that continue to show evidence for linkage in the expanded data set represent serious candidate regions for gene identification.

Searching for the autoimmune thyroid disease susceptibility genes: from gene mapping to gene function

The autoimmune thyroid diseases (AITD) are complex diseases that are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility, in combination with external factors (e.g., dietary iodine), is believed to initiate the autoimmune response to thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Various techniques have been used to identify the genes contributing to the etiology of AITD, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked with AITD, and in some of these loci putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD) and Hashimoto's thyroiditis (HT), and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune modifying genes (e.g., human leukocyte antigen, cytotoxic T lymphocyte antigen-4) and thyroid-specific genes (e.g., TSH receptor, thyroglobulin). Most likely these loci interact, and their interactions may influence disease phenotype and severity. It is hoped that in the near future additional AITD susceptibility genes will be identified and the mechanisms by which they induce AITD will be unraveled.

Association study of autoimmune thyroid disease at 5q23-q33 in Japanese patients

As part of a genome scan to locate familial Graves' disease (GD) and Hashimoto's thyroiditis (HT) genes, an autoimmune thyroid disease (AITD) susceptibility locus has recently been identified at 5q31-q33 in a Japanese population. We performed an association study using six microsatellite markers located at this locus in a set of 440 unrelated Japanese AITD patients and 218 Japanese controls. We found significant allelic association between AITD and three markers located in 5q23-q33. GD demonstrated significant associations with two of these markers, while HT did not show significant associations with any markers. Further, when patients with GD were stratified according to clinical manifestations, the association was significantly different from the other subgroup of each category. These findings suggest the presence of susceptible genes of AITD, especially distinct subgroups of GD, in or near 5q23-q33.

The genetics of autoimmune endocrine disease

The common autoimmune endocrinopathies result from an interaction between environmental factors and genetic predisposition. Several chromosomal gene regions have been shown to contribute to more than one disease, supporting the clinical observation that the autoimmune endocrine diseases cluster within individuals and families. Genetic studies have implicated the major histocompatability complex (MHC)-human leucocyte antigen (HLA) genes on chromosome 6p21, although this chromosomal region does not explain all of the genetic contribution to the various disorders. Non-MHC-HLA genes, including disease-specific loci, are beginning to be identified and the publication of the draft sequence of the human genome will undoubtedly expediate future discoveries. Combined with the establishment of large cohorts of subjects with disease and the development of technology capable of performing high-throughput genotyping, genetic studies are likely to impact on the future treatment and prevention of the common autoimmune endocrine diseases.

Trapping and sequence analysis of 1138 putative exons from human chromosome 18

In a search for novel genes on chromosome 18 (HC18), on which several regions have been linked to bipolar disorder, we applied exon trapping to HC18-specific cosmids. Among the 1138 exons trapped, 1052 of them have been mapped to HC18, and the remaining 86 have not been localized. No exons were localized to genomic regions other than HC18. BLAST database search revealed that 190 exons were identical to 98 Unigenes on HC18; 98 identical to additional 82 clusters of ESTs not present in the HC18 Unigene set; 39 homologous to genes from human and other species (e<10(-3)); and the remaining 811 exons had no significant homology to transcripts in public databases. The mapped exons were compared to the 867 annotated genes on HC18 in the Celera databases; 216 exons were identical to 104 Celera 'genes' and the remaining 836 exons were not found in the Celera databases. On average, there were two exons for a matched transcript (known genes and ESTs). Therefore, the 850 novel exons may represent hundreds of novel genes on chromosome 18.

PDS is a new susceptibility gene to autoimmune thyroid diseases: association and linkage study

Autoimmune thyroid disease (AITD), including Graves' disease (GD), Hashimoto thyroiditis (HT), and primary idiopathic myxedema, is caused by multiple genetic and environmental factors. Genes involved in immune response and/or thyroid physiology appear to influence susceptibility to disease. The PDS gene (7q31), responsible for Pendred syndrome (congenital sensorineural hearing loss and goiter), encodes a transmembrane protein known as pendrin. Pendrin is an apical porter of iodide in the thyroid. To evaluate the contribution of PDS gene in the genetic susceptibility of AITD, we examined four microsatellite markers in the gene region. Two hundred thirty-three unrelated patients (GD,141; HT, 54; primary idiopathic myxedema, 38), 15 multiplex AITD families (104 individuals/46 patients) and 154 normal controls were genotyped. Analysis of case-control data showed a significant association of D7S496 and D7S2459 with GD (P = 10(-3)) and HT (P = 1.07 10(-24)), respectively. The family-based association test showed significant association and linkage between AITDs and alleles 121 bp of D7S496 and 173 bp of D7S501. Results obtained by transmission disequilibrium test are in good agreement with those obtained by the family-based association test. Indeed, evidence for linkage and association of allele 121 bp of D7S496 with AITD was confirmed (P = 0.0114). Multipoint nonparametric linkage analysis using MERLIN showed intriguing evidence for linkage with marker D7S496 in families with only GD patients [Z = 2.12, LOD = 0.81, P = 0.026]. Single-point and multipoint parametric LOD score linkage analysis was also performed. Again, the highest multipoint parametric LOD score was found for marker D7S496 (LOD = 1.23; P = 0.0086) in families segregating for GD under a dominant model. This work suggests that the PDS gene should be considered a new susceptibility gene to AITDs with varying contributions in each pathology.

Genetics of type 1 diabetes mellitus

At least 20 different chromosomal regions have been linked to type 1 diabetes (T1D) susceptibility in humans, using genome screening, candidate gene testing, and studies of human homologues of mouse susceptibility genes. The largest contribution from a single locus (IDDM1) comes from several genes located in the MHC complex on chromosome 6p21.3, accounting for at least 40% of the familial aggregation of this disease. Approximately 30% of T1D patients are heterozygous for HLA-DQA1*0501-DQB1*0201/DQA1*0301-DQB1*0302 alleles (formerly referred to as HLA-DR3/4 and for simplification usually shortened to HLA-DQ2/DQ8), and a particular HLA-DQ6 molecule (HLA-DQA1*0102-DQB1*0602) is associated with dominant protection from the disease. There is evidence that certain residues important for structure and function of both HLA-DQ and DR peptide-binding pockets determine disease susceptibility and resistance. Independent confirmation of the IDDM2 locus on chromosome 11p15.5 has been achieved in both case-control and family-based studies, whereas associations with the other potential IDDM loci have not always been replicated. Several possibilities to explain these variable results from different studies are discussed, and a key factor affecting both linkage and association studies is that the genetic basis of T1D susceptibility may differ between ethnic groups. Some future strategies to address these problems are proposed. These include increasing the sample size in homogenous ethnic groups, high throughput genotyping and genomewide linkage disequilibrium (LD) mapping to establish disease associated ancestral haplotypes. Elucidation of the function of particular genes ('functional genomics') in the pathogenesis of T1D will be a most important element in future studies in this field, in addition to more sophisticated methods of statistical analyses.

The influence of human leucocyte antigen (HLA) genes on autoimmune thyroid disease (AITD): results of studies in HLA-DR3 positive AITD families

OBJECTIVE

Population-based, case-control studies have consistently shown association of Graves' disease (GD) with human leucocyte antigen (HLA)-DR3 in Caucasian populations. HLA association studies in Hashimoto's thyroiditis (HT) have also suggested an association with DR3, as well as with other HLA alleles. In contrast, HLA linkage studies in autoimmune thyroid disease (AITD) have been largely negative. The aim of the present study was to investigate the role of HLA in AITD and to explain the observed associations, but lack of linkage, by examining only AITD families with the associated allele, DR3.

PATIENTS

We studied 99 probands (60 with GD and 39 with HT) from 99 multiplex, multigenerational Caucasian AITD families, and 135 age- and sex-matched Caucasian controls in association studies. In addition, a dataset of 34 Caucasian AITD families (out of the 99 families) with HLA-DR3 positive probands were analysed in linkage studies.

DESIGN

HLA typing was performed using the technique of group-specific polymerase chain reaction-amplification with restriction enzyme digestion. Whole genome screening was performed using the ABI microsatellite panels. For fine mapping of the HLA region, we used the following markers: D6S276, D6S464, D6S439, D6S273, tumour necrosis factor alpha and D6S1610. LOD scores were calculated using the LIPED and GeneHunter programs.

RESULTS

Case-control association analyses using the probands from our 99 Caucasian families showed an association of GD with DRB1*03 [P = 0.00032, relative risk (RR) = 3.4]. Linkage analysis for the HLA region in the 34 DR3 positive AITD families showed negative LOD scores throughout the region. The two-point LOD score at marker D6S273 (the closest to HLA-DRB1) was -3.0, and the multipoint LOD score was -7.6, demonstrating strong evidence against linkage to the HLA region in the subset of DR3 positive families. Whole genome screening in the subset of 34 DR3 positive families revealed one locus showing evidence for linkage to AITD: D3S1580 on chromosome 3q27 with a maximum two-point LOD score of 2.1.

CONCLUSIONS

The HLA locus did not cosegregate with disease in DR3 positive families, suggesting that HLA genes are not major genes for AITD expression even within DR3 positive families; Hence, although HLA-DR3 was associated with GD in the probands, it was most likely a modulating gene and not causative; and, as the DR3 positive families showed evidence for linkage with D3S1580, it may imply that the DR3 gene modulated the effect of a susceptibility gene within the D3S1580 locus.

Pancreatic lymph node-derived CD4(+)CD25(+) Treg cells: highly potent regulators of diabetes that require TRANCE-RANK signals

Inflammation can activate self-reactive CD8(+) T cells and induce autoimmunity. Here we show in a CD8(+) T cell-mediated model of type 1 diabetes that CD4(+)CD25(+) Treg cells prevent beta cell destruction following localized inflammation in the islets of Langerhans. These Treg cells accumulate preferentially in the pancreatic lymph nodes and islets but not other lymph nodes or spleen. PLN-derived Treg cells are extremely potent; only 2 x 10(3) cells are needed to prevent diabetes development, and their capacity to regulate is dependent on TNF-related activation induced cytokine-receptor activator of NFkappaB signals. Indeed, blockade of this pathway results in decreased frequency of CD4(+)CD25(+) Treg cells in the PLN, resulting in intra-islet differentiation of CD8(+) T cells into CTLs and rapid progression to diabetes.

Autoimmune thyroid disease susceptibility loci in a large Chinese family

OBJECTIVES

The autoimmune thyroid diseases (AITDs) comprising Graves' disease (GD) and Hashimoto's thyroiditis (HT) are complex genetic diseases, which result from an interaction between predisposing genes and environmental triggers. The aim of our study was to dissect the genetic predisposition to GD and HT in one large Chinese family with multiple members affected with AITD.

PATIENTS

We completed a whole genome screen of a large multiplex Chinese-American family. We enrolled 27 family members from three generations. Eight members were affected with AITD, six had GD and two had HT.

DESIGN

We determined the information limits of the family. Power calculations indicated that the maximum attainable LOD scores were 5.1 assuming dominant inheritance, and 3.4 assuming recessive inheritance. These estimates both assumed 100% penetrance and one gene. Whole genome screening was performed using 400 highly polymorphic and densely spaced microsatellite markers spanning the entire human genome (intermarker distance < 10 cM). Linkage analysis was performed using two-point and multipoint parametric and nonparametric methods.

RESULTS

Initial whole genome screening performed with 400 microsatellite markers identified two markers that showed evidence for linkage to AITD in this family, D11S4191 and D9S175, with two-point LOD scores of 2.31 and 2.05, respectively. Multipoint linkage analysis focusing on the regions containing these markers revealed a maximum multipoint LOD score (MLS) of 2.13 and a nonparametric linkage score (NPL) of 6.1 for D11S4191 and an MLS of 2.01 and NPL of 7.5 for D9S175.

CONCLUSIONS

These results showed that this Chinese family harboured susceptibility loci for AITD which were distinct from those previously found in the Caucasian population. This suggests that different susceptibility loci exist between different ethnic groups. Furthermore, even within a single family from a genetically homogenous population, more than one gene was involved in the genetic susceptibility to AITD, supporting the notion that AITDs are caused by multiple genes of varying influences.

NEDD4L on human chromosome 18q21 has multiple forms of transcripts and is a homologue of the mouse Nedd4-2 gene

The validation of full-length cDNA represents a crucial step in gene identification and subsequent functional analysis. In searching for candidate genes for bipolar disorder on chromosome 18q21, a novel gene homologous to NEDD4 (Neural precursor cells expressed developmentally down-regulated) was identified using exon trapping and cDNA cloning. This novel gene is termed NEDD4L (Human Gene Nomenclature Committee symbol). Typical NEDD4 orthologues that contain a C2 (Ca(2+)/lipid-binding) and a HECT (Homologous to the E6-AP Carboxyl Terminus) ubiquitin-protein ligase domain, and multiple WW domains have been shown to regulate the epithelial sodium channel (ENaC). In mice, Nedd4 has two distinct isoforms termed Nedd4-1 that belongs to the typical NEDD4 class, and Nedd4-2 that is homologous to Nedd4-1 but lacks the C2 domain. NEDD4L contains the WW and HECT domains seen in the NEDD4 gene family, but lacks the C2 domain in the N-terminus. BLAST database search showed that the deduced polypeptide of NEDD4L has 97 and 62% sequence identity to mouse Nedd4-2 and human NEDD4, respectively. Multiple forms of transcripts of NEDD4L have been isolated, which differ in transcription start and termination sites together with the presence or absence of an alternative spliced exon. Northern blot analysis showed a 3.4 kb mRNA species was specifically expressed in heart and skeletal muscle, while a 3.2 kb band and/or an additional 3.6 kb band is seen in other tissues tested. Striking homology of NEDD4L to mouse Nedd4-2 suggests it is the human homologue of mouse Nedd4-2. Its position in a region of linkage for autosomal dominant orthostatic hypotensive disorder and its potential role in regulating ENaC make NEDD4L a candidate gene for this disorder.

CTLA-4 gene polymorphisms in Tunisian patients with Graves' disease

Graves' disease (GD) is an organ-specific autoimmune disorder of multifactorial etiology with a polygenic mode of inheritance. A recent report has demonstrated that there is a linkage and an association between the genetic markers of the CTLA-4 gene on chromosome 2q33 and GD. In order to confirm this association in a Tunisian population, three polymorphisms of the CTLA-4 gene were analyzed: the first is at the -318 position from the ATG start codon consisting of a C/T change; the second is in position 49 of exon 1, which lies in the A/G transition; and the third is in the 3' untranslated region with variant lengths of the dinucleotide (AT)n repeat. The genomic DNA from 144 patients with GD and 205 healthy individuals was genotyped after specific polymerase chain reaction amplification. Comparative analysis using a chi(2) test showed a weak yet significant difference in allele frequencies of the A/G dimorphic marker between patients and controls (P < 0.05), and a significant increase of A/A homozygous individuals among patients (21.53 vs 12.7%, P = 0.02, odds ratio (OR) = 1.89) was found. Analyses of CTLA-4 A/G polymorphism with respect to sex showed a significant difference in A/A genotypes between female patients and controls (OR = 2.14; 95%, 1.13 < OR < 4.04, P < 0.05). The distribution of CTLA-4 (AT)n allele frequencies differed between patients and controls (chi(2) = 38.18, 20 degrees of freedom, P = 0.0084) and the highest OR was found with the CTLA-4 (AT)-224-bp allele (OR = 6.43, 1.7 < OR < 28.64; P = 0.001). In conclusion, these results show that the CTLA-4 gene, or one closely associated with it, confers susceptibility to GD in a Tunisian population.

Histocompatibility leucocyte antigens and closely linked immunomodulatory genes in autoimmune thyroid disease

OBJECTIVES

Associations between autoimmune thyroid disease and antigens of the major histocompatibility complex (MHC) have long been recognized. Graves' disease (GD) is associated with the histocompatibility leucocyte antigen (HLA) haplotype A*01-B*0801-DRB1*0301-DQA1*0501-DQB1*0201 (or B8/DR3) whereas autoimmune hypothyroidism (AIH) has been weakly associated with HLA DRB1*03, *04 and *11/*12 alleles (or DR3, DR4 and DR5). However, the presence of important immunoregulatory genes within the HLA Class II and III regions raises the possibility that these genes harbour the primary susceptibility locus. This study examines genetic variation across the MHC in UK Caucasoid subjects with autoimmune thyroid disease.

PATIENTS AND METHODS

DNA extracted from venous blood samples from 215 patients with autoimmune thyroid disease (GD 135, AIH 77) and 267 control subjects was analysed. Genotyping was performed using polymerase chain reaction and sequence specific primers for HLA Class I and II alleles and polymorphisms within the TAP1, TAP2, tumour necrosis factor (TNF), lymphotoxin alpha (LTalpha), heat shock protein (HSP)70-1, HSP70-2 and HSP70-Hom genes.

RESULTS

For GD, the strongest association was with DRB1*03 [56% patients positive vs. 24% controls, P = 2 x 10(-10), odds ratio (OR) 4.0]. Positive associations were also seen for DRB1*03 linked alleles, B*0801, DRB3*01/02, DQA1*05, DQB1*02 and DPB1*0101 (OR 2.3-3.4). Specific TNF and LTalpha alleles were strongly associated with GD (Pc = 3 x 10(-5) and 0.001) and weak associations were seen for HSP70-1 + 190C and HSP70-2 + 1267G polymorphisms (Pc = 0.05 and 0.01). These associations were not significant when DRB1*03 status was considered. Patients with AIH showed only a weak association with DQB1*03 (P = 0.02).

CONCLUSIONS

These results show that, of the polymorphisms tested within the MHC, GD is most strongly associated with DRB1*03, and associations with other immunoregulatory genes previously described in Caucasian subjects most likely reflect linkage disequilibrium. AIH differs from GD, being less influenced by the MHC region.

An immune defect causing dominant chronic mucocutaneous candidiasis and thyroid disease maps to chromosome 2p in a single family

We describe a large family in which a combination of chronic mucocutaneous candidiasis (fungal infections of the skin, nails, and mucous membranes) and thyroid disease segregate as an autosomal dominant trait with reduced penetrance. The family includes (a) four members with both candidiasis and thyroid disease, (b) five members, including one pair of phenotype-concordant MZ twins, with candidiasis only, and (c) three members with thyroid disease only. A whole-genome scan using DNA samples from 20 members of the family identified a candidate linkage region on chromosome 2p. By sampling additional individuals and genotyping supplementary markers, we established linkage to a region of approximately 15 cM bounded by D2S367 and D2S2240 and including seven adjacent markers consistent with linkage. With a penetrance estimate of.8, which was based on pedigree and affected status, the peak two-point LOD score was 3.70 with marker D2S2328, and the peak three-point LOD score was 3.82. This is the first linkage assignment of a dominant locus for mucocutaneous candidiasis.

Two HLA DRB 1 alleles confer independent genetic susceptibility to Graves disease: relevance of cross-population studies

Recent studies of Graves disease (GD) employing genome scanning techniques excluded the major histocompatibility complex as a contributor to disease liability. These findings contradict earlier population association studies. Our own earlier studies have also emphasized that genetic variation in human populations may give novel clues to disease liability and manifestations. To this end, we studied HLA class II alleles in 47 Latvian GD patients and 111 matched healthy controls. As expected, we found that DRB1*03 and DQA1*0501 (OR = 3.6, P = 0.029 and OR 2.35, P = 0.0373, respectively) were associated with GD. Unforeseen, DRB1*04 was found to be significantly increased in the patients compared to controls (OR 3.267, corrected P = 0.0319). The two DRB1 alleles conferred two non-overlapping and independent susceptibilities to GD, in that only three patients were positive for both alleles, and the removal of each allele in turn resulted in only the other DRB1 allele showing significant association with the disease. There was no heterogeneity between the two patient groups (DRB1*03 positive and DRB1*04 positive) in clinical characteristics or disease manifestations. The phenotype DRB1*03 and/or DRB1*04 was found in 34/47 patients compared to 27/111 controls yielding an OR of 7.395 (P corrected = 0.000019). We examined the structural basis of DRB1 susceptibility to GD in light of this and previous studies, showing that DRB1*03, 04, and 08 were positively associated with the disease, whereas DRB1*07 was negatively associated. Differences in protein sequences were noted at residues 54, 57, 59, and 66; positions 54, 57, and 66 are on the same face of the alpha helix. The canonical arginine 54 is replaced by glutamine in DRB1*07. At position 66, asparagine in DRB1*03 and tyrosine in DRB1*04 are replaced by phenylalanine in DRB1*07. Residue 59, likely involved in pocket formation in the antigen binding groove, is modified by replacement of tyrosine in DRB1*03, 08, and 04 and by leucine in DRB1*07. The predicted differences in the shape and charges of the proximal reaches of the antigen binding groove between DRB1*07, and 03, 04, and 08, could determine whether or not a peptide from an auto-antigen would be bound or not. Genetic variation among human populations may yield important clues to specific disease liability.

Suggestive evidence for association of human chromosome 18q12-q21 and its orthologue on rat and mouse chromosome 18 with several autoimmune diseases

Some immune system disorders, such as type 1 diabetes, multiple sclerosis (MS), and rheumatoid arthritis (RA), share common features: the presence of autoantibodies and self-reactive T-cells, and a genetic association with the major histocompatibility complex. We have previously published evidence, from 1,708 families, for linkage and association of a haplotype of three markers in the D18S487 region of chromosome 18q21 with type 1 diabetes. Here, the three markers were typed in an independent set of 627 families and, although there was evidence for linkage (maximum logarithm of odds score [MLS] = 1.2; P = 0.02), no association was detected. Further linkage analysis revealed suggestive evidence for linkage of chromosome 18q21 to type 1 diabetes in 882 multiplex families (MLS = 2.2; lambdas = 1.2; P = 0.001), and by meta-analysis the orthologous region (also on chromosome 18) is linked to diabetes in rodents (P = 9 x 10(-4)). By meta-analysis, both human chromosome 18q12-q21 and the rodent orthologous region show positive evidence for linkage to an autoimmune phenotype (P = 0.004 and 2 x 10(-8), respectively, empirical P = 0.01 and 2 x 10(-4), respectively). In the diabetes-linked region of chromosome 18q12-q21, a candidate gene, deleted in colorectal carcinoma (DCC), was tested for association with human autoimmunity in 3,380 families with type 1 diabetes, MS, and RA. A haplotype ("2-10") of two newly characterized microsatellite markers within DCC showed evidence for association with autoimmunity (P = 5 x 10(-6)). Collectively, these data suggest that a locus (or loci) exists on human chromosome 18q12-q21 that influences multiple autoimmune diseases and that this association might be conserved between species.

Genetic dissection of a rat model for rheumatoid arthritis: significant gender influences on autosomal modifier loci

Rheumatoid arthritis (RA) is a common, chronic, autoimmune, inflammatory disease that is influenced by genetic factors including gender. Many studies suggest that the genetic risk for RA is determined by the MHC, in particular class II alleles with a 'shared epitope' (SE), and multiple non-MHC loci. Other studies indicate that RA and other autoimmune diseases, in particular insulin-dependent diabetes mellitus (IDDM) and autoimmune thyroid disease (ATD), share genetic risk factors. Rat collagen-induced arthritis (CIA) is an experimental model with many features that resemble RA. The spontaneous diabetes-resistant bio-breeding rat, BB(DR), is of interest because it is susceptible to experimentally induced CIA, IDDM and ATD, and it has an SE in its MHC class II allele. To explore the genetics of CIA, including potential gender influences and the genetic relationships between CIA and other autoimmune diseases, we conducted a genome-wide scan for CIA regulatory loci in the F(2) progeny of BB(DR) and CIA-resistant BN rats. We identified 10 quantitative trait loci (QTLs), including 5 new ones (Cia15, Cia16*, Cia17, Cia18* and Cia19 on chromosomes 9, 10, 18 and two on the X chromosome, respectively), that regulated CIA severity. We also identified four QTLs, including two new ones (Ciaa4* and Ciaa5* on chromosomes 4 and 5, respectively), that regulated autoantibody titer to rat type II collagen. Many of these loci appeared to be gender influenced, and most co-localized with several other autoimmune trait loci. Our data support the view that multiple autoimmune diseases may share genetic risk factors, and suggest that many of these loci are gender influenced.