Thyroid hormone receptor β-dependent expression of a potassium conductance in inner hair cells at the onset of hearing

摘要

To elucidate the role of thyroid hormone receptors (TRs) α1 and β in the development of hearing, cochlear functions have been investigated in mice lacking TRα1 or TRβ. TRs are ligand-dependent transcription factors expressed in the developing organ of Corti, and loss of TRβ is known to impair hearing in mice and in humans. Here, TRα1-deficient (TRα1~-/-) mice are shown to display a normal auditory-evoked brainstem response, indicating that only TRβ, and not TRα1, is essential for hearing. Because cochlear morphology was normal in TRβ~-/- mice, we postulated that TRβ regulates functional rather than morphological develop- ment of the cochlea. At the onset of hearing, inner hair cells (IHCs) in wild-type mice express a fast-activating potassium conductance, I_K,f, that transforms the immature IHC from a regenerative, spiking pacemaker to a high-frequency signal transmitter.