ECE2011 Poster Presentations Thyroid (non cancer) (78 abstracts)
ESE Young Investigator Award
Stefania Moia 1 , Flavia Prodam 1 , Alice Monzani 1 , Simonetta Bellone 1 , Stefania Riccomagno 1 , Gillian Walker 1 , Letizia Trovato 1 , Marta Roccio 1 , Patrizia Agretti 2 & Gianni Bona 1
1University of Piemonte Orientale, Novara, Italy; 2University of Pisa, Pisa, Italy.
TSH receptor (TSHR) is a G-protein-coupled seven-transmembrane domain receptor located in the basolateral membrane of thyroid follicular cells. The activated receptor couples to two major signal transductions pathways: the Gs/adenylate cyclase and the Gq/11/phospholipase C signalling. Many loss of function mutations have been identified in this gene leading to a wide spectrum of thyroid abnormalities, ranging from hyperthyrotropinemia and TSH resistance to severe hypothyroidism. We identified in one child a non-sense mutations in exon 10 for the substitution of tryptophan at position 520 with a stop codon (W520X). Because the mutated receptor loses its C-terminal portion necessary for the cellular signalling, the functional significance of this variation was assessed in vitro.
Methods: Molecular analysis of TSHR gene was performed in 112 pediatric patients (M/F: 56/56; age range: 1–18 years) showing elevated serum TSH levels and normal thyroid hormones and in 112 healthy subjects. W520X mutation was introduced into the pSVL vector by mutagenesis. Wild-type and mutated vectors were expressed in CHO cells and cAMP assay, inositol phosphate (PI) assay and immunofluorescence analysis were performed.
Results: We identified in exon 9 the new synonymous variation D232D and the intronic substitution A/G at position IVS9+3 bp. Both were found in heterozygous state and were not present in our group of controls. We observed that CHO cells expressing the W520X mutated receptor showed a lower cAMP and PI production with respect to wild-type receptor. Moreover, a reduced expression of mutated receptor on the cell surface was observed.
Conclusion: Our data demonstrate that the premature stop codon introduced by the W520X mutation causes a reduction of TSHR expression at the cell surface. This reduces TSHR signalling pathway, thus being responsible of the hormonal pattern of subclinical hypothyroidism observed in our child.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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