FOXE1 polyalanine tract length polymorphism in patients with thyroid hemiagenesis and subjects with normal thyroid.

BACKGROUND/AIMS: Recent studies have pointed to the correlation between FOXE1 polyalanine tract (FOXE1-polyAla) length polymorphism and genetic susceptibility to thyroid dysgenesis causing congenital hypothyroidism. The objective of this study was a first assessment of the role of FOXE1-polyAla expansion in the genetic background of thyroid hemiagenesis (TH).

METHODS

The group studied consisted of 40 patients with TH, including 6 familial cases and a control group of 89 subjects with a normal thyroid. The polyAla tract and flanking sequence of FOXE1 was amplified using conventional PCR. Subsequently, capillary electrophoresis was performed to estimate the length of products.

RESULTS

A short variant of FOXE1-polyAla, containing 12 alanines, was present in 5 control subjects (5.6%), but was not found in TH. The incidence of longer variants (≥16 codons) of FOXE1-polyAla was significantly higher in patients with the familial form of TH in comparison to those with sporadic TH (p = 0.003) and controls (p = 0.005).

CONCLUSIONS

There is high polymorphic variability of FOXE1-polyAla in both groups. Shorter variants of FOXE1-polyAla are underrepresented in subjects with familial TH. Therefore, FOXE1-polyAla tract expansion may contribute to the molecular background of familial but not sporadic forms of TH. Further studies are still required to confirm such findings.