A Novel Missense Mutation in Human TTF-2 (FKHL15) Gene Associated with Congenital Hypothyroidism But Not Athyreosis

Abstract

Thyroid dysgenesis is the most frequent cause of congenital hypothyroidism (CH), and its genetic basis is largely unknown. Hitherto, two mutations in the human thyroid transcription factor 2 (TTF-2) gene have been described in unrelated cases of CH with cleft palate, spiky hair, variable choanal atresia, and complete thyroid agenesis. Here, we describe a novel TTF-2 mutation in a female child resulting in syndromic CH in the absence of thyroid agenesis. The index case is homozygous for an arginine to cysteine mutation (R102C) of a highly conserved residue within the forkhead, DNA binding domain of TTF-2. Her consanguineous, heterozygous parents are unaffected, and the mutation was not detected in 100 control chromosomes. Consonant with its location, the R102C mutant TTF-2 protein showed loss of DNA binding and was transcriptionally inactive. CH in the proposita was associated with cleft palate, spiky hair, and bilateral choanal atresia. However, radiological studies showed the presence of thyroid tissue in a eutopic location. Our findings indicate that human thyroid development can occur despite loss of TTF-2 function and suggest that TTF-2 gene defects should also be considered in cases of syndromic CH without total athyreosis.