Effects of retinoid and thyroid receptors during development of the inner ear

The sensory epithelia of the vertebrate inner ear are comprised of a complex pattern of hair cells and supporting cells. Several different families of signaling molecules have been shown to play a role in the development and maintenance of this structure. In particular, the steroid/thyroid receptor superfamily, and specifically retinoid and thyroid receptors appear to influence the determination, differentiation, maintenance, and possibly regeneration, of the sensory epithelia of the vertebrate inner ear. Clinical and experimental evidence demonstrates that changes in the relative availability of retinoic acid and thyroid hormone, the ligands for retinoid and thyroid receptors, result in perturbations in the development of hair cell sensory epithelia. Retinoic acid and retinoid receptors appear to play a role in early developmental events including cellular proliferation and determination whereas thyroid hormone and thyroid receptors appear to play a role in later events including differentiation and maintenance.