The W520X mutation in the TSHR gene brings on subclinical hypothyroidism through an haploinsufficiency mechanism

摘要: Background: TSHR is a G-protein-coupled seven transmembrane domain receptor that activates the two major signal transduction pathways: Gαs/adenylate cyclase and Gαq/11/phospholipase C pathways. Inactivating mutations in gene have been demonstrated to be responsible for subclinical hypothyroidism, disorder characterized by elevated serum TSH concentrations despite normal thyroid hormones levels. Aim: We identified child nonsense mutation (W520X) third of causes lack C-terminus portion receptor. The functional significance this variation was assessed vitro. Material/subject methods: W520X introduced into pSVL vector containing wild-type sequence gene. Wild-type mutated vectors were expressed Chinese Hamster Ovary (CHO) cells, cAMP, inositol phosphate (IP), immunofluorescence FACS analyses performed. Results: Transfection with pSVL-TSHR induced basal cAMP IP production absence stimulation, indicating constitutive activity TSHR. An impairment function observation cells expressing mutant exhibited lower second messenger respect wild-type, expression at cell surface. Conclusions: mechanism through which exerts its effect more likely haploinsufficiency rather than dominant-negative effect. This could explain phenotype our patient, who has hormonal pattern range mild without an overt disease phenotype.