scholarly journals Attempted rescue of circling mice by hair cell-specific expression (Myo7a promoter) of tmie transgene

2017 ◽  
Vol 73 (7) ◽  
pp. 399-403
Author(s):  
Seojin Park ◽  
Soyoung Jang ◽  
Jeong-Han Lee ◽  
Sung-Hyun Kim ◽  
Zae Young Ryoo
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Fluorescent Protein ◽  
Outer Hair Cells ◽  
Abnormal Behavior ◽  
Spontaneous Mutant ◽  
Wild Type ◽  
Specific Expression ◽  
Brainstem Response ◽  
Ganglion Neurons

The spontaneous mutant circling mouse (cir/cir) is deaf and displays abnormal behavior, particularly circling and head tossing. To rescue the circling mouse phenotype, we produced transgenic mice with hair cell-specific expression of the transmembrane inner ear (tmie) gene, using the Myo7a promoter, and generated cir/cir homozygous mice carrying the transgene (cir/cir-tg<sup>Myo7a</sup>) by breeding with circling mice. The cir/cir-tg<sup>Myo7a</sup> mice still exhibited circling behavior and were unable to swim in water unlike cir/cir-tg<sup>CMV</sup> mice and wild-type mice. An auditory brainstem response (ABR) test demonstrated that the cir/cir-tgMyo7a mice could not respond to sound. Immunohistochemical analysis showed enhanced green fluorescent protein, a marker of tmie expression, in the inner and outer hair cells of the cir/cir-tg<sup>Myo7a</sup> mice. Hair cells and spiral ganglion neurons in the cir/cir-tg<sup>Myo7a</sup> mice were recovered, but not completely. This study demonstrates that tmie transgene expression in hair cells alone could not restore wild-type hearing and behavior in circling mice.

scholarly journals The effects of Tmc1 Beethoven mutation on mechanotransducer channel function in cochlear hair cells

2015 ◽  
Vol 146 (3) ◽  
pp. 233-243 ◽  
Author(s):  
Maryline Beurg ◽  
Adam C. Goldring ◽  
Robert Fettiplace
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Wild Type ◽  
Cochlear Hair Cells ◽  
Transmembrane Channel ◽  
Adaptive Shift ◽  
Electrical Transducer ◽  
Protein Isoform ◽  
The Relationship

Sound stimuli are converted into electrical signals via gating of mechano-electrical transducer (MT) channels in the hair cell stereociliary bundle. The molecular composition of the MT channel is still not fully established, although transmembrane channel–like protein isoform 1 (TMC1) may be one component. We found that in outer hair cells of Beethoven mice containing a M412K point mutation in TMC1, MT channels had a similar unitary conductance to that of wild-type channels but a reduced selectivity for Ca2+. The Ca2+-dependent adaptation that adjusts the operating range of the channel was also impaired in Beethoven mutants, with reduced shifts in the relationship between MT current and hair bundle displacement for adapting steps or after lowering extracellular Ca2+; these effects may be attributed to the channel’s reduced Ca2+ permeability. Moreover, the density of stereociliary CaATPase pumps for Ca2+ extrusion was decreased in the mutant. The results suggest that a major component of channel adaptation is regulated by changes in intracellular Ca2+. Consistent with this idea, the adaptive shift in the current–displacement relationship when hair bundles were bathed in endolymph-like Ca2+ saline was usually abolished by raising the intracellular Ca2+ concentration.

scholarly journals Developmental changes in the cochlear hair cell mechanotransducer channel and their regulation by transmembrane channel–like proteins

2012 ◽  
Vol 141 (1) ◽  
pp. 141-148 ◽  
Author(s):  
Kyunghee X. Kim ◽  
Robert Fettiplace
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Current Amplitude ◽  
Wild Type ◽  
Cochlear Hair Cells ◽  
Cochlear Hair Cell ◽  
Channel Current ◽  
Transmembrane Channel ◽  
Sound Detection

Vibration of the stereociliary bundles activates calcium-permeable mechanotransducer (MT) channels to initiate sound detection in cochlear hair cells. Different regions of the cochlea respond preferentially to different acoustic frequencies, with variation in the unitary conductance of the MT channels contributing to this tonotopic organization. Although the molecular identity of the MT channel remains uncertain, two members of the transmembrane channel–like family, Tmc1 and Tmc2, are crucial to hair cell mechanotransduction. We measured MT channel current amplitude and Ca2+ permeability along the cochlea’s longitudinal (tonotopic) axis during postnatal development of wild-type mice and mice lacking Tmc1 (Tmc1−/−) or Tmc2 (Tmc2−/−). In wild-type mice older than postnatal day (P) 4, MT current amplitude increased ∼1.5-fold from cochlear apex to base in outer hair cells (OHCs) but showed little change in inner hair cells (IHCs), a pattern apparent in mutant mice during the first postnatal week. After P7, the OHC MT current in Tmc1−/− (dn) mice declined to zero, consistent with their deafness phenotype. In wild-type mice before P6, the relative Ca2+ permeability, PCa, of the OHC MT channel decreased from cochlear apex to base. This gradient in PCa was not apparent in IHCs and disappeared after P7 in OHCs. In Tmc1−/− mice, PCa in basal OHCs was larger than that in wild-type mice (to equal that of apical OHCs), whereas in Tmc2−/−, PCa in apical and basal OHCs and IHCs was decreased compared with that in wild-type mice. We postulate that differences in Ca2+ permeability reflect different subunit compositions of the MT channel determined by expression of Tmc1 and Tmc2, with the latter conferring higher PCa in IHCs and immature apical OHCs. Changes in PCa with maturation are consistent with a developmental decrease in abundance of Tmc2 in OHCs but not in IHCs.

scholarly journals Assessment of cochlear toxicity in response to chronic 3,3′-iminodipropionitrile in mice reveals early and reversible functional loss that precedes overt histopathology

2021 ◽  
Vol 95 (3) ◽  
pp. 1003-1021
Author(s):  
Erin A. Greguske ◽  
Jordi Llorens ◽  
Sonja J. Pyott
Keyword(s):  
Hearing Loss ◽  
Hair Cell ◽  
Auditory System ◽  
Hair Cells ◽  
Time Course ◽  
Cell Loss ◽  
Outer Hair Cells ◽  
Hair Cell Loss ◽  
Brainstem Response ◽  
Peripheral Auditory System

AbstractThe peripheral auditory and vestibular systems rely on sensorineural structures that are vulnerable to ototoxic agents that cause hearing loss and/or equilibrium deficits. Although attention has focused on hair cell loss as the primary pathology underlying ototoxicity, evidence from the peripheral vestibular system indicates that hair cell loss during chronic exposure is preceded by synaptic uncoupling from the neurons and is potentially reversible. To determine if synaptic pathology also occurs in the peripheral auditory system, we examined the extent, time course, and reversibility of functional and morphological alterations in cochleae from mice exposed to 3,3′-iminodipropionitrile (IDPN) in drinking water for 2, 4 or 6 weeks. Functionally, IDPN exposure caused progressive high- to low-frequency hearing loss assessed by measurement of auditory brainstem response wave I absolute thresholds and amplitudes. The extent of hearing loss scaled with the magnitude of vestibular dysfunction assessed behaviorally. Morphologically, IDPN exposure caused progressive loss of outer hair cells (OHCs) and synapses between the inner hair cells (IHCs) and primary auditory neurons. In contrast, IHCs were spared from ototoxic damage. Importantly, hearing loss consistent with cochlear synaptopathy preceded loss of OHCs and synapses and, moreover, recovered if IDPN exposure was stopped before morphological pathology occurred. Our observations suggest that synaptic uncoupling, perhaps as an early phase of cochlear synaptopathy, also occurs in the peripheral auditory system in response to IDPN exposure. These findings identify novel mechanisms that contribute to the earliest stages of hearing loss in response to ototoxic agents and possibly other forms of acquired hearing loss.

scholarly journals Neuroplastin expression is essential for hearing and hair cell PMCA expression

2021 ◽  
Author(s):  
Xiao Lin ◽  
Michael G. K. Brunk ◽  
Pingan Yuanxiang ◽  
Andrew W. Curran ◽  
Enqi Zhang ◽  
...  
Keyword(s):  
Hair Cell ◽  
White Noise ◽  
Hair Cells ◽  
Normal Development ◽  
Single Photon ◽  
Photon Emission ◽  
Auditory Brainstem ◽  
Outer Hair Cells ◽  
Emission Computed Tomography ◽  
Cell Degeneration

AbstractHearing deficits impact on the communication with the external world and severely compromise perception of the surrounding. Deafness can be caused by particular mutations in the neuroplastin (Nptn) gene, which encodes a transmembrane recognition molecule of the immunoglobulin (Ig) superfamily and plasma membrane Calcium ATPase (PMCA) accessory subunit. This study investigates whether the complete absence of neuroplastin or the loss of neuroplastin in the adult after normal development lead to hearing impairment in mice analyzed by behavioral, electrophysiological, and in vivo imaging measurements. Auditory brainstem recordings from adult neuroplastin-deficient mice (Nptn−/−) show that these mice are deaf. With age, hair cells and spiral ganglion cells degenerate in Nptn−/− mice. Adult Nptn−/− mice fail to behaviorally respond to white noise and show reduced baseline blood flow in the auditory cortex (AC) as revealed by single-photon emission computed tomography (SPECT). In adult Nptn−/− mice, tone-evoked cortical activity was not detectable within the primary auditory field (A1) of the AC, although we observed non-persistent tone-like evoked activities in electrophysiological recordings of some young Nptn−/− mice. Conditional ablation of neuroplastin in Nptnlox/loxEmx1Cre mice reveals that behavioral responses to simple tones or white noise do not require neuroplastin expression by central glutamatergic neurons. Loss of neuroplastin from hair cells in adult NptnΔlox/loxPrCreERT mice after normal development is correlated with increased hearing thresholds and only high prepulse intensities result in effective prepulse inhibition (PPI) of the startle response. Furthermore, we show that neuroplastin is required for the expression of PMCA 2 in outer hair cells. This suggests that altered Ca2+ homeostasis underlies the observed hearing impairments and leads to hair cell degeneration. Our results underline the importance of neuroplastin for the development and the maintenance of the auditory system.

Hes1 is a negative regulator of inner ear hair cell differentiation

Development ◽  
2000 ◽  
Vol 127 (21) ◽  
pp. 4551-4560 ◽  
Author(s):  
J.L. Zheng ◽  
J. Shou ◽  
F. Guillemot ◽  
R. Kageyama ◽  
W.Q. Gao
Keyword(s):  
Cell Differentiation ◽  
Hair Cell ◽  
Inner Ear ◽  
Cell Fate ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Negative Regulator ◽  
Pcr Analysis ◽  
Loss Of Function ◽  
Hair Cell Differentiation

Hair cell fate determination in the inner ear has been shown to be controlled by specific genes. Recent loss-of-function and gain-of-function experiments have demonstrated that Math1, a mouse homolog of the Drosophila gene atonal, is essential for the production of hair cells. To identify genes that may interact with Math1 and inhibit hair cell differentiation, we have focused on Hes1, a mammalian hairy and enhancer of split homolog, which is a negative regulator of neurogenesis. We report here that targeted deletion of Hes1 leads to formation of supernumerary hair cells in the cochlea and utricle of the inner ear. RT-PCR analysis shows that Hes1 is expressed in inner ear during hair cell differentiation and its expression is maintained in adulthood. In situ hybridization with late embryonic inner ear tissue reveals that Hes1 is expressed in supporting cells, but not hair cells, of the vestibular sensory epithelium. In the cochlea, Hes1 is selectively expressed in the greater epithelial ridge and lesser epithelial ridge regions which are adjacent to inner and outer hair cells. Co-transfection experiments in postnatal rat explant cultures show that overexpression of Hes1 prevents hair cell differentiation induced by Math1. Therefore Hes1 can negatively regulate hair cell differentiation by antagonizing Math1. These results suggest that a balance between Math1 and negative regulators such as Hes1 is crucial for the production of an appropriate number of inner ear hair cells.

High-Voltage Electron Microscopic Study of the Inner Ear: Technique and Preliminary Results

1983 ◽  
Vol 92 (1_suppl) ◽  
pp. 3-12 ◽  
Author(s):  
Tomonori Takasaka ◽  
Hideich Shinkawa ◽  
Kozo Watanuki ◽  
Sho Hashimoto ◽  
Kazutomo Kawamoto
Keyword(s):  
Electron Microscopy ◽  
Hair Cell ◽  
Inner Ear ◽  
High Voltage ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Preliminary Results ◽  
Voltage Electron ◽  
Cuticular Plate

The technique and some preliminary results of the application of high-voltage electron microscopy (HVEM) to the study of inner ear morphology in the guinea pig are reported in this paper. The main advantage of HVEM is that sharp images of thicker specimens can be obtained because of the greater penetrating power of high energy electrons. The optimum thickness of the sections examined with an accelerating voltage of 1,000 kV was found to be between 500 to 800 nm. The sections below 500 nm in thickness often had insufficient contrast, while those above 800 nm were rather difficult to interpret due to overlap of images of the organelles. The whole structure of the sensory hairs from the tip to the rootlet was more frequently observed in the 800-nm thick sections. Thus the fine details of the hair attachment to the tectorial membrane as well as the hair rootlet extension into the cuticular plate could be thoroughly studied in the HVEM. In specimens fixed in aldehyde containing 2% tannic acid, the attachment of the tips of the outer hair cell stereocilia to the tectorial membrane was observed. For the inner hair cells, however, the tips of the hairs were separated from the undersurface of the tectorial membrane. The majority of the rootlets of the outer hair cells terminated at the midportion of the cuticular plate, while most of the inner hair cell rootlets traversed the entire width of the cuticular plate and extended into the apical cytoplasm. These differences in ultrastructural appearance may indicate that the two kinds of hair cells play different roles in the acoustic transduction process. The three-dimensional arrangement of the nerve endings on the hair cells was also studied by the serial thick-sectioning technique in the HVEM. In general, an entire arrangement of the nerve endings was almost completely cut in less than ten 800-nm thick sections instead of the 50- to 100-ultrathin (ie, less than 100 nm) conventional sections for transmission electron microscopy. The present study confirms an earlier report that the first row outer hair cells in the third cochlear turn are innervated by nearly equal numbers of efferent and afferent endings, the average number being nine.

Lower skeletal muscle mass in male transgenic mice with muscle-specific overexpression of myostatin

2003 ◽  
Vol 285 (4) ◽  
pp. E876-E888 ◽  
Author(s):  
Suzanne Reisz-Porszasz ◽  
Shalender Bhasin ◽  
Jorge N. Artaza ◽  
Ruoqing Shen ◽  
Indrani Sinha-Hikim ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transgenic Mice ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Fluorescent Protein ◽  
Male Mice ◽  
Wild Type ◽  
Specific Expression ◽  
Muscle Weight ◽  
Myostatin Gene

Mutations in the myostatin gene are associated with hypermuscularity, suggesting that myostatin inhibits skeletal muscle growth. We postulated that increased tissue-specific expression of myostatin protein in skeletal muscle would induce muscle loss. To investigate this hypothesis, we generated transgenic mice that overexpress myostatin protein selectively in the skeletal muscle, with or without ancillary expression in the heart, utilizing cDNA constructs in which a wild-type (MCK/Mst) or mutated muscle creatine kinase (MCK-3E/Mst) promoter was placed upstream of mouse myostatin cDNA. Transgenic mice harboring these MCK promoters linked to enhanced green fluorescent protein (EGFP) expressed the reporter protein only in skeletal and cardiac muscles (MCK) or in skeletal muscle alone (MCK-3E). Seven-week-old animals were genotyped by PCR of tail DNA or by Southern blot analysis of liver DNA. Myostatin mRNA and protein, measured by RT-PCR and Western blot, respectively, were significantly higher in gastrocnemius, quadriceps, and tibialis anterior of MCK/Mst-transgenic mice compared with wild-type mice. Male MCK/Mst-transgenic mice had 18–24% lower hind- and forelimb muscle weight and 18% reduction in quadriceps and gastrocnemius fiber cross-sectional area and myonuclear number (immunohistochemistry) than wild-type male mice. Male transgenic mice with mutated MCK-3E promoter showed similar effects on muscle mass. However, female transgenic mice with either type of MCK promoter did not differ from wild-type controls in either body weight or skeletal muscle mass. In conclusion, increased expression of myostatin in skeletal muscle is associated with lower muscle mass and decreased fiber size and myonuclear number, decreased cardiac muscle mass, and increased fat mass in male mice, consistent with its role as an inhibitor of skeletal muscle mass. The mechanism of gender specificity remains to be clarified.

scholarly journals A counter gradient of Activin A and follistatin instructs the timing of hair cell differentiation in the murine cochlea

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Meenakshi Prajapati-DiNubila ◽  
Ana Benito-Gonzalez ◽  
Erin Jennifer Golden ◽  
Shuran Zhang ◽  
Angelika Doetzlhofer
Keyword(s):  
Cell Differentiation ◽  
Hair Cell ◽  
Hair Cells ◽  
Activin A ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Longitudinal Gradient ◽  
Hair Cell Differentiation ◽  
Local Gradient ◽  
Molecular Signals

The mammalian auditory sensory epithelium has one of the most stereotyped cellular patterns known in vertebrates. Mechano-sensory hair cells are arranged in precise rows, with one row of inner and three rows of outer hair cells spanning the length of the spiral-shaped sensory epithelium. Aiding such precise cellular patterning, differentiation of the auditory sensory epithelium is precisely timed and follows a steep longitudinal gradient. The molecular signals that promote auditory sensory differentiation and instruct its graded pattern are largely unknown. Here, we identify Activin A and its antagonist follistatin as key regulators of hair cell differentiation and show, using mouse genetic approaches, that a local gradient of Activin A signaling within the auditory sensory epithelium times the longitudinal gradient of hair cell differentiation. Furthermore, we provide evidence that Activin-type signaling regulates a radial gradient of terminal mitosis within the auditory sensory epithelium, which constitutes a novel mechanism for limiting the number of inner hair cells being produced.

scholarly journals A Tmc1 mutation reduces calcium permeability and expression of mechanoelectrical transduction channels in cochlear hair cells

2019 ◽  
Vol 116 (41) ◽  
pp. 20743-20749 ◽  
Author(s):  
Maryline Beurg ◽  
Amanda Barlow ◽  
David N. Furness ◽  
Robert Fettiplace
Keyword(s):  
Hair Cells ◽  
Single Channel ◽  
Maximum Amplitude ◽  
Outer Hair Cells ◽  
Single Amino Acid ◽  
Wild Type ◽  
Cochlear Hair Cells ◽  
Proximate Cause ◽  
Mechanoelectrical Transduction ◽  
Calcium Permeability

Mechanoelectrical transducer (MET) currents were recorded from cochlear hair cells in mice with mutations of transmembrane channel-like protein TMC1 to study the effects on MET channel properties. We characterized a Tmc1 mouse with a single-amino-acid mutation (D569N), homologous to a dominant human deafness mutation. Measurements were made in both Tmc2 wild-type and Tmc2 knockout mice. By 30 d, Tmc1 pD569N heterozygote mice were profoundly deaf, and there was substantial loss of outer hair cells (OHCs). MET current in OHCs of Tmc1 pD569N mutants developed over the first neonatal week to attain a maximum amplitude one-third the size of that in Tmc1 wild-type mice, similar at apex and base, and lacking the tonotopic size gradient seen in wild type. The MET-channel Ca2+ permeability was reduced 3-fold in Tmc1 pD569N homozygotes, intermediate deficits being seen in heterozygotes. Reduced Ca2+ permeability resembled that of the Tmc1 pM412K Beethoven mutant, a previously studied semidominant mouse mutation. The MET channel unitary conductance, assayed by single-channel recordings and by measurements of current noise, was unaffected in mutant apical OHCs. We show that, in contrast to the Tmc1 M412K mutant, there was reduced expression of the TMC1 D569N channel at the transduction site assessed by immunolabeling, despite the persistence of tip links. The reduction in MET channel Ca2+ permeability seen in both mutants may be the proximate cause of hair-cell apoptosis, but changes in bundle shape and protein expression in Tmc1 D569N suggest another role for TMC1 apart from forming the channel.

Ultrastructural Changes in the Cochlea of the Guinea Pig after Fast Neutron Irradiation

1994 ◽  
Vol 110 (4) ◽  
pp. 419-427 ◽  
Author(s):  
Ilsa Schwartz ◽  
Chong-Sun Kim ◽  
See-Ok Shin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hair Cell ◽  
Neutron Irradiation ◽  
Hair Cells ◽  
Cell Damage ◽  
Outer Hair Cells ◽  
Transmission Electron ◽  
Fast Neutron Irradiation ◽  
Hair Cell Damage

Guinea pigs were irradiated with fast neutrons. After a single dose of 2, 6, 10, or 15 Gy was applied, scanning and transmission electron microscopy of the temporal bone was performed to assess the effect of fast neutron irradiation on the cochlea. Outer hair cell damage appeared with neutron irradiation of more than 10 Gy, and Inner hair cell damage with neutron Irradiation of more than 15 Gy. Outer hair cells were more severely damaged than Inner hair cells. No statistically significant differences were found in damage of basal, middle, and apical turns. The second and third rows of outer hair cells were more severely damaged than the first row of outer hair cells. The most significant findings in transmission electron microscopy were clumping of chromatin and extension of the heterochromatin in the nuclei of hair cells. The cytoplasmic changes were sequestration of cytoplasm, various changes of mitochondria, formation of vacuoles, and irregularly arranged stereocilia. The morphologic change in stria vascularis was intercellular and perivascular fluid accumulation. It appeared to be a reversible process.

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