Transcription factor mutations and congenital hypothyroidism: systematic genetic screening of a population-based cohort of Japanese patients.
BACKGROUND
Gene mutations of transcription factors that are predominantly expressed in the thyroid gland cause congenital hypothyroidism (CH). The prevalence of CH due to transcription factor mutations remains undetermined.


OBJECTIVE
This study was designed to define the prevalence of CH due to mutations of PAX8, NKX2-1 [encoding thyroid transcription factor (TTF)-1], FOXE1 (encoding TTF-2), and NKX2-5 among patients with permanent primary CH and in the general population in Japan.


METHODS
We enrolled 102 CH patients that represent 353,000 newborns born in Kanagawa prefecture from October 1979 to June 2006. We sequenced PAX8, NKX2-1, FOXE1, and NKX2-5 using PCR-based methods. Additionally, deletion/duplication of PAX8, NKX2-1, and FOXE1 was screened by multiplex ligation-dependent probe amplification. Molecular functions of putative mutations were verified in vitro.


RESULTS
We identified a novel small duplication of PAX8 (p.K80_A84dup) in two half-sibling patients with thyroid hypoplasia. We also found a novel NKX2-1 variation (p.H60W) in a sporadic nonsyndromic CH patient. In vitro experiments showed that K80_A84dup PAX8 had impaired transactivation of the thyroglobulin promoter. H60W TTF-1 exhibited a comparable transactivating capacity with wild-type TTF-1, suggesting a benign variation. We estimate the prevalence of PAX8 mutations to be 2.0% (two in 102) among Japanese CH patients and one in 176,000 (two in 353,000) in the general Japanese population.


CONCLUSIONS
Using a population-based sample, we confirmed that a minor subset of CH patients has transcription factor mutations, but they are rare. In our cohort, PAX8 mutations were the leading cause of such a rare condition.
Narumi
Satoshi
S
Department of Pediatrics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Muroya
Koji
K
Asakura
Yumi
Y
Adachi
Masanori
M
Hasegawa
Tomonobu
T
D015331:Cohort Studies; D003409:Congenital Hypothyroidism / Q000235:genetics* / Q000503:physiopathology; D004247:DNA / Q000235:genetics; D017353:Gene Deletion; D020440:Gene Duplication; D005820:Genetic Testing; D006367:HeLa Cells; D006801:Humans; D007564:Japan; D021141:Nucleic Acid Amplification Techniques; D010641:Phenotype; D011153:Population; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*
D014157:Transcription Factors; D004247:DNA