RESUMO
The Pendred syndrome (PS) gene, SLC26A4, was involved in the genetic susceptibility of autoimmune thyroid disease (AITD) in Tunisian population. Recently, functional assays have shown a differential expression of SLC26A4 gene between Graves' disease (GD) and Hashimoto's thyroiditis (HT). Here, by the mean of DHPLC and HRM, we explored the 21 exons and their flanking intronic sequences of 128 patients affected with GD (n = 64) or HT (n = 64). The pathogenic effect of identified variations on splice was investigated using the web server HSF. Eighteen allelic variations were identified and ranged on missense, sens and splice variations. Nine identified variations (c.-66C>G, c.898A>C, c.1002-9A>C, c.1061T>C, c.1544 + 9G>T, c.1545-5T>G, c.1790T>C, c.1826T>G, c.2139T>G) were previously reported in hearing impairment studies. Forty-seven per cent (30/64) of GD patients and 37,5% (24/64) of HT patients present at least one variant in the explored sequences. Moreover, the analysis of the variant distribution between HT (9 (5'UTR), 12 exonic and 13 intronic) and GD (18 (5'UTR), 13 exonic and 5 intronic) patients showed a significant difference (χ² = 6.54, 2df, P = 0.03). Interestingly, missense changes (I300L, p.M283I, F354S and p.L597S) affected conserved residues of pendrin. On the other hand, the HSF analyses ascertain that some variants identified in HT disease are predicted to have a pathogenic effect on splice. In conclusion, our analysis of SLC26A4 sequence variations suggested a distinct genetics basis between HT and GD patients, which should be confirmed on a large cohort.
Assuntos
Doença de Graves/genética , Doença de Hashimoto/genética , Proteínas de Membrana Transportadoras/genética , Adulto , Alelos , Estudos de Coortes , Feminino , Expressão Gênica/genética , Predisposição Genética para Doença , Testes Genéticos , Variação Genética , Bócio Nodular/genética , Perda Auditiva Neurossensorial/genética , Humanos , Masculino , Mutação de Sentido Incorreto , Isoformas de Proteínas/genética , Transportadores de Sulfato , TunísiaRESUMO
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.
