Functional studies of new TSH receptor (TSHr) mutations identified in patients affected by hypothyroidism or isolated hyperthyrotrophinaemia.
OBJECTIVE
To establish the role of new TSH receptor (TSHr) variants (P27T, E34 K, R46P, D403N, W488R and M527T) recently identified in children with congenital hypothyroidism (CH) or subclinical hypothyroidism (SH) with a thyroid gland of normal size.


METHODS
TSHr variants were obtained by mutagenesis. Wild-type (wt) and TSHr mutants were expressed in COS cells and cAMP assay, (125)I-TSH binding and microchip flow cytometry analyses were performed.


RESULTS
D403N and M527T mutants showed a lower cAMP response to bovine TSH (bTSH) with respect to the wtTSHr. R46P and W488R mutants did not show any response to bTSH stimulation in terms of cAMP production. The E34 K mutant showed a significantly lower cAMP response to stimulation with bTSH, while P27T had a lower cAMP response only to the highest dose of bTSH used. P27T, E34 K, D403N and M527T mutants showed a lower TSH binding capacity with respect to the wtTSHr. R46P and W488R mutants did not show any TSH binding.


CONCLUSIONS
E34 K, D403N, M527T, R46P and W488R TSHr variants seem to cause a functional abnormality of the receptor which is responsible for the observed phenotype. The P27T TSHr variant does not seem to play a functional role in the pathogenesis of CH and should be considered as a polymorphism.
De Marco
Giuseppina
G
Dipartimento di Endocrinologia e Metabolismo, Centro Eccellenza AmbiSEN, Università di Pisa, Pisa, Italy.
Agretti
Patrizia
P
Camilot
Marta
M
Teofoli
Francesca
F
Tatò
Luciano
L
Vitti
Paolo
P
Pinchera
Aldo
A
Tonacchera
Massimo
M
D000818:Animals; D019556:COS Cells; D002648:Child; D002675:Child, Preschool; D002522:Chlorocebus aethiops; D003409:Congenital Hypothyroidism / Q000235:genetics*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000235:genetics*; D007231:Infant, Newborn; D008297:Male; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D011989:Receptors, Thyrotropin / Q000235:genetics*; D013972:Thyrotropin / Q000097:blood*
D011989:Receptors, Thyrotropin; D013972:Thyrotropin