FOXE1 and thanatophoric dysplasia: Among TD-related genes, FOXE1 gene plays an important role in the migration of precursor cells from thyroid follicles, in addition to being a factor that regulates the transcription of target genes such as thyroglobulin and thyroperoxidase [14]. FOXE1 gene (also called TTF-2 or FKHL15) is located on chromosome 9q22.33 and contains a single exon distributed along 3,461 bp.