Preliminary evidence of genetic anticipation in Graves' disease

Inclusion of ALKBH5 as a candidate gene for the susceptibility of autoimmune thyroid disease

PURPOSE

RNA demethylase AlkB homolog 5 (ALKBH5) gene is pivotal in N6-methyladenosine (m6A) modification. Therefore, this study aimed to explore the potential relationship between polymorphisms of ALKBH5 gene and the development of autoimmune thyroid disease (AITD).

MATERIAL AND METHODS

A case-control study of 979 AITD patients, including 620 Graves' disease (GD) and 359 Hashimoto's thyroiditis (HT), and 732 normal controls of the Chinese Han population was performed using high-throughput sequencing (HiSeq) genotyping method for detecting 5 variants in ALKBH5 gene (rs12936694, rs2124370, rs4925144, rs8068517, and rs9913266). In addition, the associations between ALKBH5 single nucleotide polymorphisms (SNPs) and clinical phenotypes of AITD were investigated.

RESULTS

Compared to normal controls, rs9913266 displayed significant differences in allele and genotype distributions in AITD and GD. rs12936694 also showed significantly different frequencies of alleles in AITD and GD. The link of these 2 loci polymorprhisms to AITD and GD also existed after adjusting for age and gender. When stratified by sex, the minor allele of rs9913266 was associated with the risk of female AITD and HT development before and after adjusting for age and gender. There was a significant association between rs8068517 locus and GD in females after adjusting for the confounders. Finally, we observed significant correlations of haplotypes CGACA and CAGCG to the susceptibility of AITD and GD.

CONCLUSIONS

Our results provided evidence of association of polymorphisms in ALKBH5 gene with AITD, GD, and HT patients, and hence ALKBH5 might be the candidate gene for susceptibility to AITD.

Genetic Variants in TMEM39A Gene Are Associated with Autoimmune Thyroid Diseases

Transmembrane protein 39A (TMEM39A) gene polymorphisms have been related to various autoimmune diseases, but the relationship between TMEM39A polymorphisms and autoimmune thyroid disease (AITD) remains unknown. This study was aimed at investigating whether the polymorphisms of the TMEM39A were associated with AITD in the Chinese Han population. A case-control study was performed in a total of 906 AITD patients and 744 healthy controls. Four single nucleotide polymorphisms, including rs1132200, rs12492609, rs2282175, and rs7629750, in TMEM39A were examined by polymerase chain reaction-ligase detection reaction. We found that the allele T of rs12492609 in TMEM39A was associated with AITD and Hashimoto's thyroiditis (HT) (p = 0.023; p = 0.028 respectively). Compared with controls, the frequency of haplotype CCA in AITD patients was higher than that in controls (p = 0.036), but the frequency of haplotype CTA in AITD and HT patients was lower than that in controls (p = 0.046; p = 0.047 respectively). In addition, the frequency of allele A at rs7629750 in AITD patients with onset age ≤18 years old was higher than that in AITD patients with onset age ≥19 (p = 0.046). Further, there was an obvious difference in the genotype distributions of rs12492609 and rs7629750 between HT patients with hypothyroidism and those without hypothyroidism (p = 0.034 and p = 0.023, respectively). Our study first reveals that the polymorphisms of the TMEM39A gene are associated with the susceptibility to AITD, especially for early-onset AITD and HT with hypothyroidism.

TNFSF4 Gene Variations Are Related to Early-Onset Autoimmune Thyroid Diseases and Hypothyroidism of Hashimoto's Thyroiditis

The aim of the current study was to examine whether the polymorphism loci of the tumor necrosis factor superfamily member 4 (TNFSF4) gene increase the risk of susceptibility to autoimmune thyroid diseases (AITDs) in the Han Chinese population, and a case-control study was performed in a set of 1,048 AITDs patients and 909 normal healthy controls in the study. A total of four tagging single nucleotide polymorphisms (SNPs) in the TNFSF4 region, including rs7514229, rs1234313, rs16845607 and rs3850641, were genotyped using the method of ligase detection reaction. An association between GG genotype of rs3850641 in TNFSF4 gene and AITDs was found (p = 0.046). Additionally, the clinical sub-phenotype analysis revealed a significant association between GG genotype in rs7514229 and AITDs patients who were ≤18 years of age. Furthermore, rs3850641 variant allele G was in strong association with hypothyroidism in Hashimoto’s thyroiditis (HT) (p = 0.018). The polymorphisms of the TNFSF4 gene may contribute to the susceptibility to AITDs pathogenesis.

Genetic anticipation in BRCA1/BRCA2 families after controlling for ascertainment bias and cohort effect

BACKGROUND

Genetic anticipation, the earlier onset of disease in successive generations, has been reported in hereditary breast and ovarian cancer syndrome (HBOC), but little is known about its underlying mechanisms. Ascertainment bias has been suggested as a reason in previous studies. Likewise, cohort effect, which may be caused by environmental factors, can be misinterpreted as genetic anticipation.

METHODS

The authors reviewed the pedigrees of 176 kindreds, segregating those with deleterious mutations in breast cancer genes 1 and 2 (BRCA1/BRCA2) who had at least 2 consecutive generations of the same cancer (breast or ovarian). By using mutation probabilities as analytical weights in weighted random-effect models, generational differences in the age at onset of breast/ovarian cancer were calculated. The analyses were further controlled for ascertainment bias by excluding probands and adjusting for birth-cohort effect in the anticipation models.

RESULTS

The mean age at the onset of breast cancer for the probands' generation was 41.9 years, which was 6.8 years and 9.8 years earlier than the parents' and grandparents' generations, respectively. The anticipation effect for breast cancer remained significant after excluding the probands. There was a birth-cohort effect: patients who were born in 1930s and 1940s had breast cancer 5.0 years and 7.6 years earlier than patients who were born before 1920. The difference in breast cancer age of onset across generations was no longer significant after adjusting for birth-cohort effect.

CONCLUSIONS

The observed anticipation effect was driven mainly by a decrease in age of onset across birth cohorts, underscoring the need for risk-reducing interventions that target changing environmental/lifestyle factors in BRCA1/BRCA2 carriers. Cancer 2016;122:1913-20. © 2016 American Cancer Society.

Dissecting the Genetic Susceptibility to Graves' Disease in a Cohort of Patients of Italian Origin

Graves' disease (GD) is an autoimmune oligogenic disorder with a strong hereditary component. Several GD susceptibility genes have been identified and confirmed during the last two decades. However, there are very few studies that evaluated susceptibility genes for GD in specific geographic subsets. Previously, we mapped a new locus on chromosome 3q that was unique to GD families of Italian origin. In the present study, we used association analysis of single-nucleotide polymorphism (SNPs) at the 3q locus in a cohort of GD patients of Italian origin in order to prioritize the best candidates among the known genes in this locus to choose the one(s) best supported by the association. DNA samples were genotyped using the Illumina GoldenGate genotyping assay analyzing 690 SNP in the linked 3q locus covering all 124 linkage disequilibrium blocks in this locus. Candidate non-HLA (human-leukocyte-antigen) genes previously reported to be associated with GD and/or other autoimmune disorders were analyzed separately. Three SNPs in the 3q locus showed a nominal association (p < 0.05): rs13097181, rs763313, and rs6792646. Albeit these could not be further validated by multiple comparison correction, we were prioritizing candidate genes at a locus already known to harbor a GD-related gene, not hypothesis testing. Moreover, we found significant associations with the thyroid-stimulating hormone receptor (TSHR) gene, the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene, and the thyroglobulin (TG) gene. In conclusion, we identified three SNPs on chromosome 3q that may map a new GD susceptibility gene in this region which is unique to the Italian population. Furthermore, we confirmed that the TSHR, the CTLA-4, and the TG genes are associated with GD in Italians. Our findings highlight the influence of ethnicity and geographic variations on the genetic susceptibility to GD.

Association between age at diagnosis of Graves' disease and variants in genes involved in immune response

Background

Graves' disease (GD) is a complex disease in which genetic predisposition is modified by environmental factors. The aim of the study was to examine the association between genetic variants in genes encoding proteins involved in immune response and the age at diagnosis of GD.

Methods

735 GD patients and 1216 healthy controls from Poland were included into the study. Eight genetic variants in the HLA-DRB1, TNF, CTLA4, CD40, NFKb, PTPN22, IL4 and IL10 genes were genotyped. Patients were stratified by the age at diagnosis of GD and the association with genotype was analysed.

Results

Polymorphism in the HLA-DRB1, TNF and CTLA4 genes were associated with GD. The carriers of the HLA DRB1*03 allele were more frequent in patients with age at GD diagnosis ≤30 years than in patients with older age at GD diagnosis.

Conclusions

HLADRB1*03 allele is associated with young age at diagnosis of Graves' disease in polish population.

Development of thyroid dysfunction and autoantibodies in Graves' multiplex families: an eight-year follow-up study in Chinese Han pedigrees

BACKGROUND

This 8-year follow-up study is aimed at determining the relapse and development of Graves' disease (GD) and the potential risk factors that could be associated with the development of thyroid dysfunction and autoantibodies in Chinese pedigrees.

METHODS

Fifty-four Chinese Han GD pedigrees (322 members) were recruited in 2000. Forty-five pedigrees (263 members) were followed up. Their clinical and laboratory characteristics and fasting urinary iodine were measured with the same method at the two time points.

RESULTS

We found that the mean age for onset of GD in offspring was much younger than that of their parents (p=0.013). At baseline, the prevalence of hyperthyroidism, hypothyroidism, and subclinical hypothyroidism in first-degree relatives were 5.5%, 1.6%, and 1.1%, respectively. Individuals with thyroid dysfunction were positive for thyroid autoantibodies. The prevalence of positive thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), or TSH receptor antibody (TRAb) in the first-degree relatives with euthyroidism in these pedigrees was 18.6%, 17.4%, or 56.9%, respectively. At follow-up, individuals with positive TPOAb were at risk of developing thyroid dysfunction, whereas patients with positive TRAb had increased risk for relapse even after drug treatment. The percentage of nonsmokers with positive TPOAb and TgAb was significantly higher than that of smokers (p<0.05), but the levels of serum TRAb were significantly higher in smokers at follow-up than baseline (p<0.01).

CONCLUSIONS

Genetic factors are crucial for the development of autoimmune thyroid disease (AITD), thyroid dysfunction, and the outcomes of Graves' patients following treatment with medicines. Although smoking was negatively associated with the presence of thyroid antibodies (TPOAb/TgAb), smoking may induce or aggravate GD.

Immunopathogenesis of thyroid eye disease: emerging paradigms

Graves disease represents a systemic autoimmune process targeting the thyroid, orbit, and pretibial skin. The thyroid dysfunction is treatable, but no consistently effective medical therapy has yet been described for the orbital manifestations of Graves disease, also known as thyroid-associated ophthalmopathy or thyroid eye disease. Several autoantigens are potentially relevant to the pathogenesis of thyroid eye disease. Activating antibodies generated against the thyrotropin receptor can be detected in a majority of patients, and these drive hyperthyroidism. However, stimulating antibodies against the insulin-like growth factor-1 receptor (IGF-1R) may also play a role in the extra-thyroid manifestations of Graves disease. IGF-1R is overexpressed by orbital fibroblasts derived from patients with thyroid eye disease, whereas IGF-1R(+) T and IGF-1R(+) B cells are considerably more frequent in Graves disease. Actions of several cytokines and the molecular interplay peculiar to the orbit appear to provoke the inflammation, fat expansion, and deposition of excessive extracellular matrix molecules in thyroid eye disease. Based upon these new insights, several therapeutic strategies can now be proposed that, for the first time, might specifically interrupt its pathogenesis.

Preliminary evidence of a noncausal association between the X-chromosome inactivation pattern and thyroid autoimmunity: a twin study

An increased frequency of skewed X-chromosome inactivation (XCI) is found in clinically overt autoimmune thyroid disease (AITD) compared with controls. Whether skewed XCI is involved in the pathogenesis of autoantibodies to thyroid peroxidase (TPOAb) in euthyroid subjects is unknown. To examine the impact of XCI on the serum concentration of TPOAb, we studied whether within-cohort and within-twin-pair differences in XCI are associated with differences in serum concentrations of TPOAb. A total of 318 euthyroid female twin individuals distributed in 159 pairs were investigated. XCI was determined by PCR analysis of a polymorphic CAG repeat in the first exon of the androgen receptor gene. TPOAb concentrations were measured using a solid-phase time-resolved fluoroimmunometric assay. Overall (within cohort), there was a significant association between XCI and serum concentrations of TPOAb; regression coefficient (beta)=1.45 (95% confidence interval, 0.52-2.38), P=0.003. The association remained significant in the within-pair analysis; beta=1.74 (0.79-2.69), P<0.001. The relationship was nonsignificant within the 82 monozygotic pairs (beta=0.57 (-0.78-1.92), P=0.405), whereas the association was significant in the 77 dizygotic pairs (beta=2.17 (0.81-3.53), P=0.002). This preliminary finding of a significant association between TPOAb concentrations and XCI within cohort and within dizygotic but not within monozygotic twin pairs may indicate that XCI per se does not have a major role in the pathogenesis of TPOAb. More likely, XCI and TPOAb are influenced by shared genetic determinants.

Association of tumour necrosis factor alpha (TNF-alpha) polymorphisms with Graves' disease: A meta-analysis

OBJECTIVE

To quantitatively summarize the association between tumour necrosis factor alpha (TNF-alpha) gene polymorphisms and Graves' disease.

DESIGN AND METHODS

Relevant studies were identified from the following electronic databases: Cochrane Library, MEDLINE, EMBASE and Chinese Bio-medicine Database. A meta-analysis of relevant studies was performed.

RESULTS

This meta-analysis included 10 case-control studies, which included 2271 Graves' disease cases and 2633 controls. The combined results based on all studies showed that there was significant difference in genotype distribution (-308A/G; -308G/G; -863C/C; -863C/A; -1031C/T) between Graves' disease and controls. When stratifying for race, statistically significant results were observed in three genotype distribution (-863C/C; -863C/A; -1031C/T) between Graves' disease and controls among Asians. Statistically significant results were observed in only two genotype distribution (-308A/G; -308G/G) between Graves' disease and controls among Caucasians.

CONCLUSIONS

This meta-analysis suggests that TNF-alpha gene polymorphisms at positions -308 (G-308A), -863 (C-863A), and -1031 (T-1031C) were associated with Graves' disease.

Anticipation in families with Hodgkin's and non-Hodgkin's lymphoma in their pedigree

Anticipation is an earlier onset and/or increasing severity in successive generations. This study was conducted to determine whether anticipation occurs in families that exhibit both Hodgkin's (HD) and non-Hodgkin's (NHL) lymphoma in their pedigrees. Nine published reports of multi-generational lymphoma and 33 previously unreported families with both lymphomas were analysed for evidence of anticipation. The difference between age at onset for each affected related pair was tested against the null hypothesis that there is no difference in age at onset. Differences between disease-free survival in affected generations were determined. These analyses were also conducted separately using only parent - child pairs with an age of onset above 25 years in an effort to avoid ascertainment bias. Age at onset in studied cases was also compared with the HD and NHL series from the Surveillance Epidemiology and End Results (SEER) Program of the US National Cancer Institute. The mean age at onset in the child and parent generations of all case families (60.2 and 35.7 years, respectively) and in the selected pairs (61.5 and 45.6, years) were significantly different (mean difference -24.5 years; P < 0.00001, and -15.9 years, P < 0.00001, respectively). Mean anticipation for parents with HD and children with NHL was -6.8 years (P = 0.01) for the unpublished and -14.4 years (P = 0.002) for the published families (overall anticipation -10.1 years). Mean anticipation for parents with NHL and children with HD was -34.4 years (P < 0.0001) for the unpublished and -32.7 years (P < 0.0001) for the published families (overall anticipation -34.2 years, P < 0.0001). The signed rank test rejected the null hypothesis which stated that there was no difference in age at onset between parents and children for overall, as well as selected pairs (P < 0.00001). The null hypothesis was also rejected for both the parents with HD/children with NHL group and the parents with NHL/children with HD group pairs (P < 0.0001). Age at onset distributions were significantly different for all generations with HD or NHL when compared to the SEER population (P < 0.00001), except for the parents with NHL, which showed no difference. In addition, this study reports four previously unpublished families with three generations of lymphoma in their pedigrees. These data suggest that anticipation occurs in families that exhibit both HL and NHL and that both neoplasms may have a common genetic basis.

Influences of age, gender, smoking, and family history on autoimmune thyroid disease phenotype

CONTEXT

Both genetic and environmental factors contribute to susceptibility to Graves' disease (GD) and Hashimoto's thyroiditis (HT), as well as disease manifestations.

OBJECTIVE

The objective of the study was to define how endogenous/environmental factors contribute to variation in phenotype.

DESIGN/SETTING

This was a multicenter cohort study. PATIENTS/OUTCOME MEASURES: We prospectively collected clinical/biochemical data as part of the protocol for a United Kingdom DNA collection for GD and HT. We investigated, in 2805 Caucasian subjects, whether age at diagnosis, gender, family history (FH), smoking history, and presence of goiter influenced disease manifestations.

RESULTS

For 2405 subjects with GD, the presence of goiter was independently associated with disease severity (serum free T4 at diagnosis) (P < 0.001). Free T4 (P < 0.05) and current smoking (P < 0.001) were both independent predictors of the presence of ophthalmopathy. Approximately half of those with GD (47.4% of females, 40.0% of males) and HT (n = 400) (56.4% of females, 51.7% of males) reported a FH of thyroid dysfunction. In GD, a FH of hyperthyroidism in any relative was more frequent than hypothyroidism (30.1 vs. 24.4% in affected females, P < 0.001). In HT, a FH of hypothyroidism was more common than hyperthyroidism (42.1 vs. 22.8% in affected females, P < 0.001). For GD (P < 0.001) and HT (P < 0.05), a FH was more common in maternal than paternal relatives. The reporting of a parent with thyroid dysfunction (hyper or hypo) was associated with lower median age at diagnosis of both GD (mother with hyperthyroidism, P < 0.001) and HT (father with hypothyroidism, P < 0.05). In GD and HT, there was an inverse relationship between the number of relatives with thyroid dysfunction and age at diagnosis (P < 0.01).

CONCLUSIONS

Marked associations among age at diagnosis, disease severity, goiter, ophthalmopathy, smoking, and FH provide evidence for interactions between genetic and environmental/endogenous factors; understanding these may allow preventive measures or better tailoring of therapies.