Sequence Analysis of Thyroid Transcription Factor-2 (TTF-2) Gene in Ten Patients with Congenital Hypothyroidism due to Thyroid Dysgenesis

Abstract

The etiology of thyroid dysgenesis is still unknown. One of the thyroid specific transcription factors, thyroid transcription factor-2 (TTF-2), performs a crucial role in the development of thyroid gland as shown by TTF-2 knock out mice. In the present study, we analyzed the TTF-2 gene in patients with congenital hypothyroidism due to thyroid malformation: three patients with thyroid agenesis, two with hypoplasia, and five with ectopy. Genomic DNA was isolated from peripheral leukocytes, and the TTF-2 gene, consisting of a single exon with extremely high GC content, was amplified by polymerase chain reaction (PCR) with 2 pairs of primers. The PCR products were directly sequenced. One of the patients with ectopic thyroid showed the deletion of 9 bases (GCCGCCGCC), which corresponded to 3 alanine repeats, at the region of 1, 226-1, 234 bp in one chromosome. Also in the patient’s mother the same 9 bases deletion was noted at the same position. However, the mother had normal thyroid function and ^99mTc thyroid scintigraphy revealed no abnormalities of thyroid morphology. Whether this heterozygous deletion of 9 bases corresponding 3 alanine repeats from TTF-2 gene observed in the patient with ectopy was involved in the development of thyroid abnormalities is unclear in the present study and further studies are required.