title: Developmental and cell-specific expression of thyroid hormone transporters in the mouse cochlea.
abstract: Thyroid hormone is essential for the development of the cochlea and auditory function. Cochlear response tissues, which express thyroid hormone receptor β (encoded by Thrb), include the greater epithelial ridge and sensory epithelium residing inside the bony labyrinth. However, these response tissues lack direct blood flow, implying that mechanisms exist to shuttle hormone from the circulation to target tissues. Therefore, we investigated expression of candidate thyroid hormone transporters L-type amino acid transporter 1 (Lat1), monocarboxylate transporter (Mct)8, Mct10, and organic anion transporting polypeptide 1c1 (Oatp1c1) in mouse cochlear development by in situ hybridization and immunofluorescence analysis. L-type amino acid transporter 1 localized to cochlear blood vessels and transiently to sensory hair cells. Mct8 localized to the greater epithelial ridge, tympanic border cells underlying the sensory epithelium, spiral ligament fibrocytes, and spiral ganglion neurons, partly overlapping with the Thrb expression pattern. Mct10 was detected in a highly restricted pattern in the outer sulcus epithelium and weakly in tympanic border cells and hair cells. Organic anion transporting polypeptide 1c1 localized primarily to fibrocytes in vascularized tissues of the spiral limbus and spiral ligament and to tympanic border cells. Investigation of hypothyroid Tshr(-/-) mice showed that transporter expression was delayed consistent with retardation of cochlear tissue maturation but not with compensatory responses to hypothyroidism. The results demonstrate specific expression of thyroid hormone transporters in the cochlea and suggest that a network of thyroid hormone transport underlies cochlear development.
authors: National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Clinical Endocrinology Branch, Bethesda, Maryland 20892-1772, USA.
authors: David S
authors: DS
authors: Sharlin
authors: Theo J
authors: TJ
authors: Visser
authors: Douglas
authors: D
authors: Forrest
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D003051:Cochlea / Q000254:growth & development* / Q000378:metabolism* / Q000502:physiology; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D027501:Monocarboxylic Acid Transporters; D009928:Organ Specificity; D027362:Organic Anion Transport Protein 1 / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000378:metabolism; D027981:Symporters; D013963:Thyroid Hormones / Q000378:metabolism*
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; C464433:Oatp2 protein, mouse; D027362:Organic Anion Transport Protein 1; D027701:Organic Cation Transport Proteins; C509612:Slc16a10 protein, mouse; C484257:Slc16a2 protein, mouse; C105033:Slc22a6 protein, mouse; D027981:Symporters; D013963:Thyroid Hormones