INVESTIGADORES
NICOLA Juan Pablo
artículos
Título:
Iodide transport defect: functional characterization of a novel mutation in the Na+/I- symporter 5'-untranslated region in a patient with congenital hypothyroidism
Autor/es:
NICOLA, JP; NAZAR, M; SERRANO-NASCIMENTO, C; GOULART-SILVA, F; SOBRERO, G; TESTA, G; NUNEZ, MT; MUÑOZ, L; MIRAS, M; MASINI-REPISO, AM
Revista:
JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM
Editorial:
ENDOCRINE SOC
Referencias:
Año: 2011 vol. 96 p. 1100 - 1107
ISSN:
0021-972X
Resumen:
Context:
Iodide transport defect (ITD) is an autosomal recessive disorder caused by
impaired Na+/I- symporter (NIS)-mediated
active iodide accumulation into thyroid follicular cells. Clinical
manifestations comprise a variable degree of congenital hypothyroidism and
goiter, and low to absent radioiodide uptake, as determined by thyroid
scintigraphy. Hereditary molecular defects in NIS have been shown to cause ITD.
Objective:
To perform molecular studies on NIS
in a patient with congenital hypothyroidism presenting a clinical phenotype of
ITD.
Design: The
genomic DNA encoding NIS was sequenced, and in
vitro functional study of a newly identified NIS mutation was performed.
Results:
The analysis revealed the presence of an undescribed homozygous C to T
transition at nucleotide -54 (-54C>T) located in the 5-untranslated region
in the NIS
sequence. Functional studies in vitro demonstrated that the mutation was
associated with a substantial decrease in iodide uptake when transfected into
Cos-7 cells. The mutation severely impaired NIS
protein expression, although NIS mRNA levels
remained similar to those in cells transfected with wild-type NIS, suggesting a translational deficiency
elicited by the mutation. Polysome profile analysis demonstrated reduced levels
of polyribosomes-associated mutant NIS
mRNA, consistent with reduced translation efficiency.
Conclusions:
We described a novel mutation in the 5-unstranslated region of the NIS gene in a newborn
with congenital hypothyroidism bearing a clinical ITD phenotype. Functional
evaluation of the molecular mechanism responsible for impaired NIS-mediated
iodide concentration in thyroid cells indicated that the identified mutation
reduces NIS
translation efficiency with a subsequent decrease in protein expression and
function.