The temporal characteristics of Ca2+ entry through L-type and T-type Ca2+ channels shape exocytosis efficiency in chick auditory hair cells during development

Snezana Levic; Didier Dulon

doi:10.1152/jn.00555.2012

The temporal characteristics of Ca2+ entry through L-type and T-type Ca2+ channels shape exocytosis efficiency in chick auditory hair cells during development

Journal of Neurophysiology ◽

10.1152/jn.00555.2012 ◽

2012 ◽

Vol 108 (11) ◽

pp. 3116-3123 ◽

Cited By ~ 4

Author(s):

Snezana Levic ◽

Didier Dulon

Keyword(s):

Hair Cells ◽

Low Voltage ◽

Domestic Chick ◽

Cochlear Hair Cells ◽

Auditory Hair Cells ◽

Temporal Characteristics ◽

Cochlear Development ◽

Synaptic Exocytosis ◽

Fast Release ◽

Ca2 Channels

During development, synaptic exocytosis by cochlear hair cells is first initiated by patterned spontaneous Ca2+ spikes and, at the onset of hearing, by sound-driven graded depolarizing potentials. The molecular reorganization occurring in the hair cell synaptic machinery during this developmental transition still remains elusive. We characterized the changes in biophysical properties of voltage-gated Ca2+ currents and exocytosis in developing auditory hair cells of a precocial animal, the domestic chick. We found that immature chick hair cells (embryonic days 10–12) use two types of Ca2+ currents to control exocytosis: low-voltage-activating, rapidly inactivating (mibefradil sensitive) T-type Ca2+ currents and high-voltage-activating, noninactivating (nifedipine sensitive) L-type currents. Exocytosis evoked by T-type Ca2+ current displayed a fast release component (RRP) but lacked the slow sustained release component (SRP), suggesting an inefficient recruitment of distant synaptic vesicles by this transient Ca2+ current. With maturation, the participation of L-type Ca2+ currents to exocytosis largely increased, inducing a highly Ca2+ efficient recruitment of an RRP and an SRP component. Notably, L-type-driven exocytosis in immature hair cells displayed higher Ca2+ efficiency when triggered by prerecorded native action potentials than by voltage steps, whereas similar efficiency for both protocols was found in mature hair cells. This difference likely reflects a tighter coupling between release sites and Ca2+ channels in mature hair cells. Overall, our results suggest that the temporal characteristics of Ca2+ entry through T-type and L-type Ca2+ channels greatly influence synaptic release by hair cells during cochlear development.

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Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation

International Journal of Molecular Sciences ◽

10.3390/ijms21228649 ◽

2020 ◽

Vol 21 (22) ◽

pp. 8649

Author(s):

Xin Deng ◽

Zhengqing Hu

Keyword(s):

Transgenic Mice ◽

Inner Ear ◽

Hair Cells ◽

Dna Methyltransferase ◽

Dna Demethylation ◽

Egfp Expression ◽

Supporting Cells ◽

Cochlear Hair Cells ◽

Auditory Hair Cells ◽

Adult Mice

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5–7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.

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TMC1 is an essential component of a leak channel that modulates tonotopy and excitability of auditory hair cells in mice

eLife ◽

10.7554/elife.47441 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 4

Author(s):

Shuang Liu ◽

Shufeng Wang ◽

Linzhi Zou ◽

Jie Li ◽

Chenmeng Song ◽

...

Keyword(s):

Hair Cells ◽

Dependent Manner ◽

Biological Processes ◽

Action Potential Firing ◽

Cochlear Hair Cells ◽

Auditory Hair Cells ◽

Leak Channel ◽

Transmembrane Channel ◽

Electrical Transducer ◽

Potential Firing

Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate biological processes other than MET in invertebrates, ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized four amino acids that are required for the leak conductance. The leak conductance is graded in a frequency-dependent manner along the length of the cochlea and is indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and -intensity.

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TMC1 Confers a Leak Conductance to Modulate Excitability of Auditory Hair Cells in Mammals

10.1101/617472 ◽

2019 ◽

Author(s):

Shuang Liu ◽

Shufeng Wang ◽

Linzhi Zou ◽

Jie Li ◽

Chenmeng Song ◽

...

Keyword(s):

Hair Cells ◽

Biological Processes ◽

Membrane Excitability ◽

Action Potential Firing ◽

Cochlear Hair Cells ◽

Auditory Hair Cells ◽

Transmembrane Channel ◽

Electrical Transducer ◽

Potential Firing ◽

Open Question

ABSTRACTHearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which Transmembrane channel-like 1 (TMC1) and TMC2 have been proposed to be the pore-forming subunits. Meanwhile it has been reported that TMCs regulate other biological processes in a variety of lower organisms ranging from sensations to motor functions. However, it is still an open question whether TMCs play roles other than their function in MET in mammals. In this study, we report that in mouse hair cells TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitution, 4 amino acids of TMC1 are characterized critical for the leak conductance. The leak conductance is essential for action potential firing and tonotopic along the cochlear coil. Taken together, our results suggest that TMC1 confers a background leak conductance that modulates membrane excitability in cochlear hair cells.

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Fluorocitrate Neural Dystrophy of the Guinea Pig Cochlea

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100115468 ◽

1975 ◽

Vol 33 ◽

pp. 368-369

Author(s):

G.J. Spector ◽

C.D. Carr ◽

I. Kaufman Arenberg ◽

R.H. Maisel

Keyword(s):

Hearing Loss ◽

Hair Cells ◽

Sodium Phosphate ◽

Sensory Cells ◽

Barium Salt ◽

Perfusion Medium ◽

Cochlear Hair Cells ◽

Neural Degeneration ◽

Sodium Phosphate Buffer ◽

Cochlear Neurons

All studies on primary neural degeneration in the cochlea have evaluated the end stages of degeneration or the indiscriminate destruction of both sensory cells and cochlear neurons. We have developed a model which selectively simulates the dystrophic changes denoting cochlear neural degeneration while sparing the cochlear hair cells. Such a model can be used to define more precisely the mechanism of presbycusis or the hearing loss in aging man.Twenty-two pigmented guinea pigs (200-250 gm) were perfused by the perilymphatic route as live preparations using fluorocitrate in various concentrations (15-250 ug/cc) and at different incubation times (5-150 minutes). The barium salt of DL fluorocitrate, (C6H4O7F)2Ba3, was reacted with 1.0N sulfuric acid to precipitate the barium as a sulfate. The perfusion medium was prepared, just prior to use, as follows: sodium phosphate buffer 0.2M, pH 7.4 = 9cc; fluorocitrate = 15-200 mg/cc; and sucrose = 0.2M.

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Pengaruh sisplatin dosis tinggi terhadap penurunan fungsi sel rambut luar koklea

Oto Rhino Laryngologica Indonesiana ◽

10.32637/orli.v40i2.1 ◽

2013 ◽

Vol 40 (2) ◽

Author(s):

Asti Kristianti ◽

Teti Madiadipoera ◽

Bogi Soeseno

Keyword(s):

Hair Cells ◽

Malignant Neoplasm ◽

Otoacoustic Emission ◽

Outer Hair Cells ◽

High Dose ◽

Distortion Product Otoacoustic Emission ◽

Inclusion Criteria ◽

Cochlear Hair Cells ◽

Distortion Product ◽

Bilateral Sensorineural Hearing Loss

Background: Chemotherapy is worldwide used nowadays, and its toxicity still remain a problemespecially toxicity to the ear (ototoxicity). Cisplatin (cis-diamminedichloroplatinum) is one of themost commonly used chemotherapy and highly potent in treating epithelial malignancies. Ototoxicitycaused by cisplatin is irreversible, progressive, bilateral, sensorineural hearing loss especially on highfrequency (4-8 KHz) accompanied by tinnitus. Purpose: To observe the cochlear outer hair cells damagein malignancies patients treated with cisplatin. Methods: This study is an observational analytic studywith prospective design to determine the influence of high dose cisplatin on cochlear outer hair cellsfunction. The research was carried out at the ENT-HNS Department, Hasan Sadikin General HospitalBandung, from November 2007 until June 2008. Audiometry, tympanometry, and distortion productotoacoustic emission (DPOAE) examinations were conducted before chemotherapy and DPOAE, andtimpanometry was again measured three days after first and second cycles of cisplatin administration. McNemar test was performed to calculate the effects of high-dose cisplatin to the cochlear outer haircells function. To compare pre and post-cisplatin on alteration of cochlear hair cells function, Wilcoxontest was used. Results: In this study 60 ears from 30 subjects that meet the inclusion criteria, consistedof 25 man (83.3%) and 5 women (16.7%). The prevalence of damaged cochlear outer hair cells were63% at first cycle and 70% at second cycle of cisplatin administration. The decline of cochlear outerhair cells function was significant (p<0.001). Conclusion: High-dose cisplatin decreases cochlear outerhair cells function in patients with malignant neoplasm. Abstrak : Latar belakang: Kemoterapi sekarang rutin digunakan secara klinis di seluruh dunia. Sejalan denganhal tersebut toksisitas kemoterapi, khususnya terhadap telinga saat ini menjadi perhatian. Sisplatin(cis-diamminedichloroplatinum) adalah salah satu obat kemoterapi yang paling banyak digunakandan paling manjur untuk terapi keganasan epitelial. Efek ototoksik sisplatin yaitu terjadi gangguandengar sensorineural yang irreversible, progresif, bilateral pada frekuensi tinggi (4-8 kHz), dan disertaidengan tinitus. Tujuan: Untuk menilai penurunan fungsi sel rambut luar koklea pada penderita tumorganas sesudah pemberian sisplatin dosis tinggi dengan menggunakan DPOAE. Metode: Studi analitikobservasional dengan rancangan prospektif di Bagian IK. THT-KL RS. Hasan Sadikin Bandung mulaibulan November 2007 sampai dengan Juni 2008. Pada penelitian ini dilakukan pemeriksaan audiometrinada murni, timpanometri, dan distortion product otoacoustic emission (DPOAE) prakemoterapi, kemudianDPOAE dan timpanometri diulang tiga hari sesudah siklus pertama dan kedua kemoterapi sisplatin. Datayang diperoleh diuji dengan uji McNemar dan uji Wilcoxon. Hasil: Dari penelitian didapat 60 telingadari 30 subjek penelitian yang memenuhi kriteria inklusi yang terdiri dari 25 laki-laki (83,3%) dan 5perempuan (16,7%). Insidens penurunan fungsi sel rambut luar koklea sebesar 63% (38 kasus) sesudahsiklus pertama dan 70% (42 kasus) sesudah siklus kedua. Hubungan penurunan fungsi sel rambut luarkoklea memberikan nilai yang sangat bermakna sejak pemberian siklus pertama (p<0,001). Kesimpulan:Pemberian sisplatin dosis tinggi pada penderita tumor ganas menyebabkan penurunan fungsi sel rambutluar koklea.Kata kunci: kemoterapi, sisplatin dosis tinggi, sel rambut luar koklea.

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