title: Polymorphism of the polyalanine tract of thyroid transcription factor-2 gene in patients with thyroid dysgenesis.
abstract: OBJECTIVE
  One of the thyroid-specific transcription factors, thyroid transcription factor-2 (TTF-2), performs a crucial role in the development of the thyroid gland. We performed genetic analysis of the TITF2 gene (encoding TTF-2) in patients with thyroid dysgenesis.
  
  
  METHODS
  By direct sequencing of the PCR products of TITF2, we screened the genomic DNA from 46 patients with thyroid dysgenesis (five had agenesis, six had hypoplasia, 15 had ectopy, and 20 were undetermined). We also studied the transcriptional activities of TITF2 by co-expressing the luciferase gene directed by the human thyroglobulin gene promoter.
  
  
  RESULTS
  Human TITF2 consists of a forkhead domain, a polyalanine tract, and unique C-terminal residues. In one of the patients with an ectopic sublingual thyroid, we found a polyalanine tract of 11 alanine residues on one chromosome instead of the 14 alanine residues found in normal controls. In one patient with hypoplasia, the polyalanine tract consisted of 12 heterozygous alanine residues. The reduced polyalanine tracts were not detected in 101 normal individuals. However, the expression study showed that the transcriptional activities of TITF2 with reduced polyalanine-tract lengths were equal to that of TITF2 with an unreduced polyalanine tract.
  
  
  CONCLUSIONS
  These results suggest that the polymorphism of the polyalanine tract of TITF2 is not a frequent cause of developmental defects of the human thyroid gland.
authors.affiliation: Department of Clinical Laboratory Medicine, Dokkyo University School of Medicine, Mibu, Tochigi 321-0293, Japan. a-hishi@dokkyomed.ac.jp
authors.forename: A
authors.initials: A
authors.lastname: Hishinuma
authors.forename: Y
authors.initials: Y
authors.lastname: Ohyama
authors.forename: T
authors.initials: T
authors.lastname: Kuribayashi
authors.forename: N
authors.initials: N
authors.lastname: Nagakubo
authors.forename: T
authors.initials: T
authors.lastname: Namatame
authors.forename: K
authors.initials: K
authors.lastname: Shibayama
authors.forename: O
authors.initials: O
authors.lastname: Arisaka
authors.forename: N
authors.initials: N
authors.lastname: Matsuura
authors.forename: T
authors.initials: T
authors.lastname: Ieiri
mesh_terms: D001483:Base Sequence / Q000235:genetics; D002460:Cell Line; D002828:Choristoma / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D051858:Forkhead Transcription Factors; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics*; D011110:Polymorphism, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D013961:Thyroid Gland / Q000002:abnormalities*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; C106894:FOXE1 protein, human; D051858:Forkhead Transcription Factors; D010455:Peptides; D012097:Repressor Proteins; C019529:polyalanine