FOXE1 polyalanine tract (FOXE1-polyA) length polymorphism in patients with thyroid hemiagenesis and subjects with normal thyroid
Ewelina Szczepanek1, Marek Ruchala1, Lidia Kilinska1, Malgorzata Jaroniec2, Witold Szaflarski2, Maciej Zabel2 & Jerzy Sowinski1
Introduction: Thyroid hemiagenesis (TH) is a rare inborn anomaly presenting as developmental failure of one thyroid lobe. Recent research on the molecular background underlying thyroid dysgenesis have mainly focused on patients with congenital hypothyroidism. In contrast, subjects presenting TH were only sporadically involved. In addition, whether the same factors are responsible for development of TH and other forms of thyroid dysgenesis is still to be elucidated. Recent studies have pointed to the correlation between FOXE1-polyA length polymorphism and genetic susceptibility to thyroid ectopy and agenesis. However, the evaluation of its length in a large group of patients with TH has never been performed. The objective to the study to assess FOXE1-polyA length in patients with TH and normal thyroid gland.
Materials and methods: The studied group consisted of 40 patients with TH, including 6 familial cases. The condition was diagnosed during medically indicated or performed as screening examination, thyroid ultrasound. Unilateral absence of functional thyroid tissue was confirmed by thyroid scintiscan. The control group consisted of 89 subjects with fully developed bilobed thyroid gland. The fragment of FOXE1 coding sequence, comprising polyA tract was amplified using standard PCR conditions; one of the primers was marked with fluorescent dye. The length of reaction products was subsequently assessed by the means of capillary electrophoresis, performed in Genetic Analyzer 3130 (Applied Biosystems) in the presence of marker LIZ 600.
Results: Short variant of FOXE1-polyA, containing 12 codones, was present in 5 control subjects (5.6%), but never in TH. However, there difference in the FOXE1-polyA length between patients with TH and control group did not reach statistical significance.
Conclusions: Short variant of FOXE1-polyA length was detected only in control subjects. However, the length of FOXE1-polyA does not seem to be the key factor determining risk of TH development.