1
|
Abstract
The senses are our window to the world, our interface with the habitat in which we live in and the basis for our communication with each other. Although sensory systems are not generally viewed as major targets of endocrine regulation, sensory development is profoundly influenced by thyroid hormone (T(3)) signalling. In this article, we discuss this developmental role of T(3) and highlight the auditory system as the best-studied example of the interplay between systemic and local tissue mechanisms by which T(3) stimulates the onset of sensory function. Several genes that mediate the action of T(3) are known to promote sensory development in mice, including genes that encode T(3) receptors and deiodinase enzymes that amplify or deplete levels of T(3). We also discuss the current knowledge of sensory defects in human genetic disorders in which T(3) signalling is impaired. As sensory input provides the only means of acquiring information from the environment, the stimulation of sensory development is one of the most fundamental functions of T(3) signalling.
Collapse
Affiliation(s)
- Lily Ng
- National Institute of Diabetes and Digestive and Kidney Disease, Laboratory of Endocrinology and Receptor Biology, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA
| | | | | |
Collapse
|
2
|
Stria vascularis and vestibular dark cells: characterisation of main structures responsible for inner-ear homeostasis, and their pathophysiological relations. The Journal of Laryngology & Otology 2008; 123:151-62. [DOI: 10.1017/s0022215108002624] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractThe regulation of inner-ear fluid homeostasis, with its parameters volume, concentration, osmolarity and pressure, is the basis for adequate response to stimulation. Many structures are involved in the complex process of inner-ear homeostasis. The stria vascularis and vestibular dark cells are the two main structures responsible for endolymph secretion, and possess many similarities. The characteristics of these structures are the basis for regulation of inner-ear homeostasis, while impaired function is related to various diseases. Their distinct morphology and function are described, and related to current knowledge of associated inner-ear diseases. Further research on the distinct function and regulation of these structures is necessary in order to develop future clinical interventions.
Collapse
|
3
|
Oshima A, Suzuki S, Takumi Y, Hashizume K, Abe S, Usami S. CRYM mutations cause deafness through thyroid hormone binding properties in the fibrocytes of the cochlea. J Med Genet 2006; 43:e25. [PMID: 16740909 PMCID: PMC2564543 DOI: 10.1136/jmg.2005.034397] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 06/11/2005] [Accepted: 06/22/2005] [Indexed: 11/03/2022]
Abstract
BACKGROUND In a search for mutations of mu-crystallin (CRYM), a taxion specific crystalline which is also known as an NADP regulated thyroid hormone binding protein, two mutations were found at the C-terminus in patients with non-syndromic deafness. OBJECTIVE To investigate the mechanism of hearing loss caused by CRYM mutations METHODS T3 binding activity of mutant mu-crystallin was compared with that of wild-type mu-crystallin, because mu-crystallin is known to be identical to T3 binding protein. To explore the sites within the cochlea where mu-crystallin is functioning, its localisation in the mouse cochlea was investigated immunocytochemically using a specific antibody. RESULTS One mutant was shown to have no binding capacity for T3, indicating that CRYM mutations cause auditory dysfunction through thyroid hormone binding properties. Immunocytochemical results indicated that mu-crystallin was distributed within type II fibrocytes of the lateral wall, which are known to contain Na,K-ATPase. CONCLUSIONS CRYM mutations may cause auditory dysfunction through thyroid hormone binding effects on the fibrocytes of the cochlea. mu-Crystallin may be involved in the potassium ion recycling system together with Na,K-ATPase. Future animal experiments will be necessary to confirm a causal relation between Na,K-ATPase, T3, and deafness.
Collapse
|
4
|
Abe S, Katagiri T, Saito-Hisaminato A, Usami SI, Inoue Y, Tsunoda T, Nakamura Y. Identification of CRYM as a candidate responsible for nonsyndromic deafness, through cDNA microarray analysis of human cochlear and vestibular tissues. Am J Hum Genet 2003; 72:73-82. [PMID: 12471561 PMCID: PMC420014 DOI: 10.1086/345398] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2002] [Accepted: 10/01/2002] [Indexed: 12/31/2022] Open
Abstract
Through cDNA microarray analysis of gene expression in human cochlea and vestibule, we detected strong expression of mu-crystallin (CRYM; also known as "NADP-regulated thyroid hormone-binding protein") only in these inner-ear tissues. In a subsequent search for mutations of CRYM, among 192 patients with nonsyndromic deafness, we identified two mutations at the C-terminus; one was a de novo change (X315Y) in a patient with unaffected parents, and the other was a missense mutation (K314T) that segregated dominantly in the proband's family. When the mutated proteins were expressed in COS-7 cells, their subcellular localizations were different from that of the normal protein: the X315Y mutant showed vacuolated distribution in the cytoplasm, and the K314T mutant localized in perinuclear areas, whereas normal protein was distributed homogeneously in the cytoplasm. Aberrant intracellular localization of the mutated proteins might cause dysfunction of the CRYM product and result in hearing impairment. In situ hybridization analysis using mouse tissues indicated its expression in the lateral region of the spiral ligament and the fibrocytes of the spiral limbus, implying its possible involvement in the potassium-ion recycling system. Our results strongly implicate CRYM in normal auditory function and identify it as one of the genes that can be responsible for nonsyndromic deafness.
Collapse
Affiliation(s)
- Satoko Abe
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Toyomasa Katagiri
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Akihiko Saito-Hisaminato
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Shin-ichi Usami
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Yasuhiro Inoue
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Tatsuhiko Tsunoda
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Yusuke Nakamura
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Department of Otorhinolaryngology, Keio University School of Medicine, and Laboratory for Medical Informatics, SNP Research Center, Riken (Institute of Physical and Chemical Research), Tokyo; and Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| |
Collapse
|
5
|
Retardation of cochlear maturation and impaired hair cell function caused by deletion of all known thyroid hormone receptors. J Neurosci 2002. [PMID: 11739587 DOI: 10.1523/jneurosci.21-24-09792.2001] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The deafness caused by early onset hypothyroidism indicates that thyroid hormone is essential for the development of hearing. We investigated the underlying roles of the TRalpha1 and TRbeta thyroid hormone receptors in the auditory system using receptor-deficient mice. TRalpha1 and TRbeta, which act as hormone-activated transcription factors, are encoded by the Thra and Thrb genes, respectively, and both are expressed in the developing cochlea. TRbeta is required for hearing because TRbeta-deficient (Thrb(tm1/tm1)) mice have a defective auditory-evoked brainstem response and retarded expression of a potassium current (I(K,f)) in the cochlear inner hair cells. Here, we show that although TRalpha1 is individually dispensable, TRalpha1 and TRbeta synergistically control an extended array of functions in postnatal cochlear development. Compared with Thrb(tm1/tm1) mice, the deletion of all TRs in Thra(tm1/tm1)Thrb(tm1/tm1) mice produces exacerbated and novel phenotypes, including delayed differentiation of the sensory epithelium, malformation of the tectorial membrane, impairment of electromechanical transduction in outer hair cells, and a low endocochlear potential. The induction of I(K,f) in inner hair cells was not markedly more retarded than in Thrb(tm1/tm1) mice, suggesting that this feature of hair cell maturation is primarily TRbeta-dependent. These results indicate that distinct pathways mediated by TRbeta alone or by TRbeta and TRalpha1 together facilitate control over an extended range of functions during the maturation of the cochlea.
Collapse
|
6
|
Rüsch A, Erway LC, Oliver D, Vennström B, Forrest D. Thyroid hormone receptor beta-dependent expression of a potassium conductance in inner hair cells at the onset of hearing. Proc Natl Acad Sci U S A 1998; 95:15758-62. [PMID: 9861043 PMCID: PMC28117 DOI: 10.1073/pnas.95.26.15758] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To elucidate the role of thyroid hormone receptors (TRs) alpha1 and beta in the development of hearing, cochlear functions have been investigated in mice lacking TRalpha1 or TRbeta. TRs are ligand-dependent transcription factors expressed in the developing organ of Corti, and loss of TRbeta is known to impair hearing in mice and in humans. Here, TRalpha1-deficient (TRalpha1(-/-)) mice are shown to display a normal auditory-evoked brainstem response, indicating that only TRbeta, and not TRalpha1, is essential for hearing. Because cochlear morphology was normal in TRbeta-/- mice, we postulated that TRbeta regulates functional rather than morphological development of the cochlea. At the onset of hearing, inner hair cells (IHCs) in wild-type mice express a fast-activating potassium conductance, IK,f, that transforms the immature IHC from a regenerative, spiking pacemaker to a high-frequency signal transmitter. Expression of IK,f was significantly retarded in TRbeta-/- mice, whereas the development of the endocochlear potential and other cochlear functions, including mechanoelectrical transduction in hair cells, progressed normally. TRalpha1(-/-) mice expressed IK,f normally, in accord with their normal auditory-evoked brainstem response. These results establish that the physiological differentiation of IHCs depends on a TRbeta-mediated pathway. When defective, this may contribute to deafness in congenital thyroid diseases.
Collapse
Affiliation(s)
- A Rüsch
- Physiologisches Institut, Gmelinstrasse 5, and Sektion Sensorische Biophysik, Hals-Nasen-Ohren Klinik, Röntgenweg 11, Universität T ubingen, D-72076 Tübingen, Germany.
| | | | | | | | | |
Collapse
|