Screening for mutations in transcription factors in a Czech cohort of 170 patients with congenital and early-onset hypothyroidism: identification of a novel PAX8 mutation in dominantly inherited early-onset non-autoimmune hypothyroidism.
OBJECTIVE
Mutations in NKX2.1, NKX2.5, FOXE1 and PAX8 genes, encoding for transcription factors involved in the development of the thyroid gland, have been identified in a minority of patients with syndromic and non-syndromic congenital hypothyroidism (CH).


METHODS
In a phenotype-selected cohort of 170 Czech paediatric and adolescent patients with non-goitre CH, including thyroid dysgenesis, or non-goitre early-onset hypothyroidism, PAX8, NKX2.1, NKX2.5, FOXE1 and HHEX genes were analysed for mutations.


METHODS
NKX2.1, NKX2.5, FOXE1 and HHEX genes were directly sequenced in patients with syndromic CH. PAX8 mutational screening was performed in all 170 patients by single-stranded conformation polymorphism, followed by direct sequencing of samples with abnormal findings. The R52P PAX8 mutation was functionally characterized by DNA binding studies.


RESULTS
We identified a novel PAX8 mutation R52P, dominantly inherited in a three-generation pedigree and leading to non-congenital, early-onset, non-goitre, non-autoimmune hypothyroidism with gradual postnatal regression of the thyroid size and function. The R52P PAX8 mutation results in the substitution of a highly conserved residue of the DNA-binding domain with a loss-of-function effect.


CONCLUSIONS
The very low frequency of genetic defects in a population-based cohort of children affected by non-goitre congenital and early-onset hypothyroidism, even in a phenotype-focussed screening study, suggests the pathogenetic role of either non-classic genetic mechanisms or the involvement of genes unknown so far. Identification of a novel PAX8 mutation in a particular variant of non-congenital early-onset hypothyroidism indicates a key function of PAX8 in the postnatal growth and functional maintenance of the thyroid gland.
Al Taji
Eva
E
Department of Paediatrics, 3rd Faculty of Medicine, Charles University, Prague, Czech Republic. evataji@seznam.cz
Biebermann
Heike
H
Límanová
Zdenka
Z
Hníková
Olga
O
Zikmund
Jaroslav
J
Dame
Christof
C
Grüters
Annette
A
Lebl
Jan
J
Krude
Heiko
H
D000293:Adolescent; D000595:Amino Acid Sequence; D002648:Child; D003001:Cloning, Molecular; D015331:Cohort Studies; D003409:Congenital Hypothyroidism / Q000000981:diagnostic imaging / Q000235:genetics*; D003604:Czechoslovakia; D004247:DNA / Q000737:chemistry / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D050033:Thyroid Dysgenesis / Q000000981:diagnostic imaging / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014463:Ultrasonography
D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; D004247:DNA