Thyroid hormone receptors (TR) are a nuclear receptors that are activitated by binding of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). The majority of TH bound to TR being T3 due to its 10-fold higher affinity. Bound receptors, homodimerized or heterodimerized with retinoic acid, bind to thyroid response elements and regulate gene expression by either increasing or decreasing tragent gene transcription activity. Important to note is ligand free TR can form complexes with corepressors to inhibit gene expression. There are two major thyroid hormone receptor subtypes, thyroid receptor alpha(TRα) and thyroid receptor beta (TRβ). There are two subtypes for each, TRb1, TRb2, TRa1, and TRa2. Notably, the carboxy-terminal structure of TRalpha2 prevents hormone binding and transscription (Sinha and Yen, 2018). There are a large number of genes regualated by TH. These include genes involved in
Both TRa and TRb are known to be expressed during neurodevelopment (ref).
The predominate TR form during brain develop is TRa1expression of the
Sinha R, Yen PM. Cellular Action of Thyroid Hormone. [Updated 2018 Jun 20]. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK285568/