CONTEXT: Screening of the known candidate genes involved in thyroid organogenesis has revealed mutations in a small subset of patients with congenital hypothyroidism due to thyroid dysgenesis (TD). OBJECTIVE: We studied a girl with TD who had mutations in two transcription factors involved in thyroid development. RESULTS: Sequencing analysis of candidate genes involved in thyroid gland development revealed a new paternally inherited heterozygous mutation in the NKX2.5 gene (S265R) and a new maternally inherited heterozygous mutation in the PAX8 promoter region (-456C>T). Both parents and a brother, who was also heterozygous for both mutations, were phenotypically normal. Immunofluorescence microscopy showed a correct nuclear localization of both wild-type (WT) and mutant NKX2.5 proteins. EMSA demonstrated that the mutant NKX2.5 binds to the NKE_2, DIO2, TG, and TPO promoter elements equally well as the WT protein. However, the mutant NKX2.5 protein showed a 30-40% reduced transactivation of the thyroglobulin and the thyroid peroxidase promoters and a dominant-negative effect of the mutant NKX2.5. EMSA studies of the WT and mutant PAX8 promoter sequences incubated with nuclear extracts from PCCL3 cells exhibited a loss of protein binding capacity of the mutant promoter. In addition, the mutant PAX8 promoter showed a significantly reduced transcriptional activation of a luciferase reporter gene in vitro. Thus, this promoter mutation is expected to lead to reduced PAX8 expression. CONCLUSIONS: We identified new heterozygous mutations in both NKX2.5 and PAX8 genes of a girl with TD. Both defects might contribute to the phenotype.
CONTEXT: Screening of the known candidate genes involved in thyroid organogenesis has revealed mutations in a small subset of patients with congenital hypothyroidism due to thyroid dysgenesis (TD). OBJECTIVE: We studied a girl with TD who had mutations in two transcription factors involved in thyroid development. RESULTS: Sequencing analysis of candidate genes involved in thyroid gland development revealed a new paternally inherited heterozygous mutation in the NKX2.5 gene (S265R) and a new maternally inherited heterozygous mutation in the PAX8 promoter region (-456C>T). Both parents and a brother, who was also heterozygous for both mutations, were phenotypically normal. Immunofluorescence microscopy showed a correct nuclear localization of both wild-type (WT) and mutant NKX2.5 proteins. EMSA demonstrated that the mutant NKX2.5 binds to the NKE_2, DIO2, TG, and TPO promoter elements equally well as the WT protein. However, the mutant NKX2.5 protein showed a 30-40% reduced transactivation of the thyroglobulin and the thyroid peroxidase promoters and a dominant-negative effect of the mutant NKX2.5. EMSA studies of the WT and mutant PAX8 promoter sequences incubated with nuclear extracts from PCCL3 cells exhibited a loss of protein binding capacity of the mutant promoter. In addition, the mutant PAX8 promoter showed a significantly reduced transcriptional activation of a luciferase reporter gene in vitro. Thus, this promoter mutation is expected to lead to reduced PAX8 expression. CONCLUSIONS: We identified new heterozygous mutations in both NKX2.5 and PAX8 genes of a girl with TD. Both defects might contribute to the phenotype.
Authors: Joachim Pohlenz; Alexandra Dumitrescu; Dorothee Zundel; Ursula Martiné; Winfried Schönberger; Eugene Koo; Roy E Weiss; Ronald N Cohen; Shioko Kimura; Samuel Refetoff Journal: J Clin Invest Date: 2002-02 Impact factor: 14.808
Authors: J J Schott; D W Benson; C T Basson; W Pease; G M Silberbach; J P Moak; B J Maron; C E Seidman; J G Seidman Journal: Science Date: 1998-07-03 Impact factor: 47.728
Authors: Klaartje van Engelen; Mathilda T M Mommersteeg; Marieke J H Baars; Jan Lam; Aho Ilgun; A S Paul van Trotsenburg; Anne M J B Smets; Vincent M Christoffels; Barbara J M Mulder; Alex V Postma Journal: PLoS One Date: 2012-12-28 Impact factor: 3.240