scholarly journals Calcium-induced calcium release supports recruitment of synaptic vesicles in auditory hair cells

2016 ◽  
Vol 115 (1) ◽  
pp. 226-239 ◽  
Author(s):  
Manuel Castellano-Muñoz ◽  
Michael E. Schnee ◽  
Anthony J. Ricci
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Synaptic Vesicles ◽  
Calcium Release ◽  
Resting Potential ◽  
Calcium Stores ◽  
Potential Contribution ◽  
Auditory Hair Cells ◽  
Ribbon Synapses ◽  
Calcium Induced Calcium Release

Hair cells from auditory and vestibular systems transmit continuous sound and balance information to the central nervous system through the release of synaptic vesicles at ribbon synapses. The high activity experienced by hair cells requires a unique mechanism to sustain recruitment and replenishment of synaptic vesicles for continuous release. Using pre- and postsynaptic electrophysiological recordings, we explored the potential contribution of calcium-induced calcium release (CICR) in modulating the recruitment of vesicles to auditory hair cell ribbon synapses. Pharmacological manipulation of CICR with agents targeting endoplasmic reticulum calcium stores reduced both spontaneous postsynaptic multiunit activity and the frequency of excitatory postsynaptic currents (EPSCs). Pharmacological treatments had no effect on hair cell resting potential or activation curves for calcium and potassium channels. However, these drugs exerted a reduction in vesicle release measured by dual-sine capacitance methods. In addition, calcium substitution by barium reduced release efficacy by delaying release onset and diminishing vesicle recruitment. Together these results demonstrate a role for calcium stores in hair cell ribbon synaptic transmission and suggest a novel contribution of CICR in hair cell vesicle recruitment. We hypothesize that calcium entry via calcium channels is tightly regulated to control timing of vesicle fusion at the synapse, whereas CICR is used to maintain a tonic calcium signal to modulate vesicle trafficking.

scholarly journals A Critical E-box in Barhl1 3′ Enhancer Is Essential for Auditory Hair Cell Differentiation

Cells ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 458 ◽  
Author(s):  
Kun Hou ◽  
Hui Jiang ◽  
Md. Rezaul Karim ◽  
Chao Zhong ◽  
Zhouwen Xu ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Hair Cell ◽  
Hair Cells ◽  
Embryonic Stem ◽  
Cell Development ◽  
Homologous Gene ◽  
Auditory Hair Cells ◽  
E Box ◽  
Hair Cell Differentiation

Barhl1, a mouse homologous gene of Drosophila BarH class homeobox genes, is highly expressed within the inner ear and crucial for the long-term maintenance of auditory hair cells that mediate hearing and balance, yet little is known about the molecular events underlying Barhl1 regulation and function in hair cells. In this study, through data mining and in vitro report assay, we firstly identified Barhl1 as a direct target gene of Atoh1 and one E-box (E3) in Barhl1 3’ enhancer is crucial for Atoh1-mediated Barhl1 activation. Then we generated a mouse embryonic stem cell (mESC) line carrying disruptions on this E3 site E-box (CAGCTG) using CRISPR/Cas9 technology and this E3 mutated mESC line is further subjected to an efficient stepwise hair cell differentiation strategy in vitro. Disruptions on this E3 site caused dramatic loss of Barhl1 expression and significantly reduced the number of induced hair cell-like cells, while no affections on the differentiation toward early primitive ectoderm-like cells and otic progenitors. Finally, through RNA-seq profiling and gene ontology (GO) enrichment analysis, we found that this E3 box was indispensable for Barhl1 expression to maintain hair cell development and normal functions. We also compared the transcriptional profiles of induced cells from CDS mutated and E3 mutated mESCs, respectively, and got very consistent results except the Barhl1 transcript itself. These observations indicated that Atoh1-mediated Barhl1 expression could have important roles during auditory hair cell development. In brief, our findings delineate the detail molecular mechanism of Barhl1 expression regulation in auditory hair cell differentiation.

scholarly journals The challenge of hair cell regeneration

2010 ◽  
Vol 235 (4) ◽  
pp. 434-446 ◽  
Author(s):  
Andrew K Groves
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Electrical Energy ◽  
Cell Regeneration ◽  
Hair Cell Regeneration ◽  
Therapeutic Approaches ◽  
Auditory Hair Cells ◽  
Sensory Hair Cells ◽  
Ototoxic Drugs ◽  
Effects Of Aging

Sensory hair cells of the inner ear are responsible for translating auditory or vestibular stimuli into electrical energy that can be perceived by the nervous system. Although hair cells are exquisitely mechanically sensitive, they can be easily damaged by excessive stimulation by ototoxic drugs and by the effects of aging. In mammals, auditory hair cells are never replaced, such that cumulative damage to the ear causes progressive and permanent deafness. In contrast, non-mammalian vertebrates are capable of replacing lost hair cells, which has led to efforts to understand the molecular and cellular basis of regenerative responses in different vertebrate species. In this review, we describe recent progress in understanding the limits to hair cell regeneration in mammals and discuss the obstacles that currently exist for therapeutic approaches to hair cell replacement.

scholarly journals Synaptic mitochondria regulate hair-cell synapse size and function

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Hiu-tung C Wong ◽  
Qiuxiang Zhang ◽  
Alisha J Beirl ◽  
Ronald S Petralia ◽  
Ya-Xian Wang ◽  
...  
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Direct Application ◽  
Structural Protein ◽  
Ribbon Synapses ◽  
Presynaptic Function ◽  
Sensory Hair Cells ◽  
Synaptic Mitochondria ◽  
And Function ◽  
Cell Synapse

Sensory hair cells in the ear utilize specialized ribbon synapses. These synapses are defined by electron-dense presynaptic structures called ribbons, composed primarily of the structural protein Ribeye. Previous work has shown that voltage-gated influx of Ca2+ through CaV1.3 channels is critical for hair-cell synapse function and can impede ribbon formation. We show that in mature zebrafish hair cells, evoked presynaptic-Ca2+ influx through CaV1.3 channels initiates mitochondrial-Ca2+ (mito-Ca2+) uptake adjacent to ribbons. Block of mito-Ca2+ uptake in mature cells depresses presynaptic-Ca2+ influx and impacts synapse integrity. In developing zebrafish hair cells, mito-Ca2+ uptake coincides with spontaneous rises in presynaptic-Ca2+ influx. Spontaneous mito-Ca2+ loading lowers cellular NAD+/NADH redox and downregulates ribbon size. Direct application of NAD+ or NADH increases or decreases ribbon size respectively, possibly acting through the NAD(H)-binding domain on Ribeye. Our results present a mechanism where presynaptic- and mito-Ca2+ couple to confer proper presynaptic function and formation.

scholarly journals Temporal Vestibular Deficits in synaptojanin 1 (synj1) Mutants

2021 ◽  
Vol 13 ◽  
Author(s):  
Yan Gao ◽  
Teresa Nicolson
Keyword(s):  
Postural Control ◽  
Hair Cells ◽  
Synaptic Vesicles ◽  
Phase Locking ◽  
Vestibular Function ◽  
Loss Of Function ◽  
Vesicle Recycling ◽  
Ribbon Synapses ◽  
Synaptojanin 1 ◽  
Time Required

The lipid phosphatase synaptojanin 1 (synj1) is required for the disassembly of clathrin coats on endocytic compartments. In neurons such activity is necessary for the recycling of endocytosed membrane into synaptic vesicles. Mutations in zebrafish synj1 have been shown to disrupt the activity of ribbon synapses in sensory hair cells. After prolonged mechanical stimulation of hair cells, both phase locking of afferent nerve activity and the recovery of spontaneous release of synaptic vesicles are diminished in synj1 mutants. Presumably as a behavioral consequence of these synaptic deficits, synj1 mutants are unable to maintain an upright posture. To probe vestibular function with respect to postural control in synj1 mutants, we developed a method for assessing the vestibulospinal reflex (VSR) in larvae. We elicited the VSR by rotating the head and recorded tail movements. As expected, the VSR is completely absent in pcdh15a and lhfpl5a mutants that lack inner ear function. Conversely, lhfpl5b mutants, which have a selective loss of function of the lateral line organ, have normal VSRs, suggesting that the hair cells of this organ do not contribute to this reflex. In contrast to mechanotransduction mutants, the synj1 mutant produces normal tail movements during the initial cycles of rotation of the head. Both the amplitude and temporal aspects of the response are unchanged. However, after several rotations, the VSR in synj1 mutants was strongly diminished or absent. Mutant synj1 larvae are able to recover, but the time required for the reappearance of the VSR after prolonged stimulation is dramatically increased in synj1 mutants. Collectively, the data demonstrate a behavioral correlate of the synaptic defects caused by the loss of synj1 function. Our results suggest that defects in synaptic vesicle recycling give rise to fatigue of ribbons synapses and possibly other synapses of the VS circuit, leading to the loss of postural control.

scholarly journals Efferent Control of Hair Cell and Afferent Responses in the Semicircular Canals

2009 ◽  
Vol 102 (3) ◽  
pp. 1513-1525 ◽  
Author(s):  
Richard Boyle ◽  
Richard D. Rabbitt ◽  
Stephen M. Highstein
Keyword(s):  
Hair Cell ◽  
Brain Stem ◽  
Hair Cells ◽  
Intracellular Signaling ◽  
Dynamic Range ◽  
Reversal Potential ◽  
Semicircular Canals ◽  
Resting Potential ◽  
Efferent Neurons ◽  
The Brain

The sensations of sound and motion generated by the inner ear are controlled by the brain through extensive centripetal innervation originating within the brain stem. In the semicircular canals, brain stem efferent neurons make synaptic contacts with mechanosensory hair cells and with the dendrites of afferent neurons. Here, we examine the relative contributions of efferent action on hair cells and afferents. Experiments were performed in vivo in the oyster toadfish, Opsanus tau. The efferent system was activated via electrical pulses to the brain stem and sensory responses to motion stimuli were quantified by simultaneous voltage recording from afferents and intracellular current- and/or voltage-clamp recordings from hair cells. Results showed synaptic inputs to both afferents and hair cells leading to relatively long-latency intracellular signaling responses: excitatory in afferents and inhibitory in hair cells. Generally, the net effect of efferent action was an increase in afferent background discharge and a simultaneous decrease in gain to angular motion stimuli. Inhibition of hair cells was likely the result of a ligand-gated opening of a major basolateral conductance. The reversal potential of the efferent-evoked current was just below the hair cell resting potential, thus resulting in a small hyperpolarization. The onset latency averaged about 90 ms and latency to peak response was 150–400 ms. Hair cell inhibition often outlasted afferent excitation and, in some cases, latched hair cells in the “off” condition for >1 s following cessation of stimulus. These features endow the animal with a powerful means to adjust the sensitivity and dynamic range of motion sensation.

scholarly journals Insights into Electroreceptor Development and Evolution from Molecular Comparisons with Hair Cells

2018 ◽  
Vol 58 (2) ◽  
pp. 329-340 ◽  
Author(s):  
Clare V H Baker ◽  
Melinda S Modrell
Keyword(s):  
Gene Expression ◽  
Hair Cell ◽  
Electric Fields ◽  
Lateral Line ◽  
Hair Cells ◽  
Water Movement ◽  
Low Frequency ◽  
Lateral Line System ◽  
Line System ◽  
Ribbon Synapses

Abstract The vertebrate lateral line system comprises a mechanosensory division, with neuromasts containing hair cells that detect local water movement (“distant touch”); and an electrosensory division, with electrosensory organs that detect the weak, low-frequency electric fields surrounding other animals in water (primarily used for hunting). The entire lateral line system was lost in the amniote lineage with the transition to fully terrestrial life; the electrosensory division was lost independently in several lineages, including the ancestors of frogs and of teleost fishes. (Electroreception with different characteristics subsequently evolved independently within two teleost lineages.) Recent gene expression studies in a non-teleost actinopterygian fish suggest that electroreceptor ribbon synapses employ the same transmission mechanisms as hair cell ribbon synapses, and show that developing electrosensory organs express transcription factors essential for hair cell development, including Atoh1 and Pou4f3. Previous hypotheses for electroreceptor evolution suggest either that electroreceptors and hair cells evolved independently in the vertebrate ancestor from a common ciliated secondary cell, or that electroreceptors evolved from hair cells. The close developmental and putative physiological similarities implied by the gene expression data support the latter hypothesis, i.e., that electroreceptors evolved in the vertebrate ancestor as a “sister cell-type” to lateral line hair cells.

Intracellular calcium stores are involved in growth hormone-releasing hormone signal transduction in rat somatotrophs

1999 ◽  
Vol 77 (7) ◽  
pp. 520-528 ◽  
Author(s):  
Audrey Petit ◽  
Catherine Bleicher ◽  
Benoît T Lussier
Keyword(s):  
Growth Hormone ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Calcium Stores ◽  
Growth Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Intracellular Ca ◽  
Calcium Induced Calcium Release

In rat pituitary somatotrophs, the stimulation of growth hormone secretion by growth hormone-releasing hormone (GHRH) is a Ca2+-dependent event involving Ca2+ influx. The presence of calcium-induced calcium release (CICR) Ca2+ stores has been suggested in these cells. The aim of our study was to demonstrate the presence of CICR stores in rat somatotrophs and to determine their function in GHRH Ca2+ signalling. To this end we measured cytosolic free Ca2+ concentration ([Ca2+]i), using indo-1 in purified rat somatotrophs in primary culture, while altering intracellular Ca2+ stores. Ionomycin (10 µM) or 4-bromo-A23187 (10 µM), used to mobilise organelle-bound Ca2+, raised [Ca2+]i in the absence of extracellular Ca2+. Caffeine (5 to 50 mM), used to mobilise Ca2+ from CICR stores, transiently raised [Ca2+]i in 65% of cells tested. The response to 40 mM caffeine was abolished when Ca2+ stores were depleted, with 1 µM thapsigargin or with 10 µM ryanodine. All cells that responded to 40 mM caffeine responded to 10 nM GHRH. The [Ca2+]i response to 10 nM GHRH was reversible and repeatable. However, the second response was 38% smaller than the first. Ryanodine treatment abolished the reduction in the second [Ca2+]i response, while thapsigargin increased the reduction by 67%. We conclude that rat somatotrophs possess CICR Ca2+ stores and that they account for 30-35% of the GHRH-induced increase in [Ca2+]i, and that their partial depletion is involved in somatotroph desensitization.Key words: somatotrophs, growth hormone-releasing hormone, intracellular calcium, calcium stores, calcium-induced calcium release.

scholarly journals Calcium signaling via two-pore channels: local or global, that is the question

2010 ◽  
Vol 298 (3) ◽  
pp. C430-C441 ◽  
Author(s):  
Michael X. Zhu ◽  
Jianjie Ma ◽  
John Parrington ◽  
Peter J. Calcraft ◽  
Antony Galione ◽  
...  
Keyword(s):  
Calcium Signaling ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Calcium Stores ◽  
Calcium Signals ◽  
Calcium Release Channels ◽  
Intracellular Calcium Signaling ◽  
Global Signal ◽  
Rna Knockdown ◽  
Calcium Induced Calcium Release

Recently, we identified, for the first time, two-pore channels (TPCs, TPCN for gene name) as a novel family of nicotinic acid adenine dinucleotide phosphate (NAADP)-gated, endolysosome-targeted calcium release channels. Significantly, three subtypes of TPCs have been characterized, TPC1-3, with each being targeted to discrete acidic calcium stores, namely lysosomes (TPC2) and endosomes (TPC1 and TPC3). That TPCs act as NAADP-gated calcium release channels is clear, given that NAADP binds to high- and low-affinity sites associated with TPC2 and thereby induces calcium release and homologous desensitization, as observed in the case of endogenous NAADP receptors. Moreover, NAADP-evoked calcium signals via TPC2 are ablated by short hairpin RNA knockdown of TPC2 and by depletion of acidic calcium stores with bafilomycin. Importantly, however, NAADP-evoked calcium signals were biphasic in nature, with an initial phase of calcium release from lysosomes via TPC2, being subsequently amplified by calcium-induced calcium release (CICR) from the endoplasmic reticulum (ER). In marked contrast, calcium release via endosome-targeted TPC1 induced only spatially restricted calcium signals that were not amplified by CICR from the ER. These findings provide new insights into the mechanisms that cells may utilize to “filter” calcium signals via junctional complexes to determine whether a given signal remains local or is converted into a propagating global signal. Essentially, endosomes and lysosomes represent vesicular calcium stores, quite unlike the ER network, and TPCs do not themselves support CICR or, therefore, propagating regenerative calcium waves. Thus “quantal” vesicular calcium release via TPCs must subsequently recruit inositol 1,4,5-trisphoshpate receptors and/or ryanodine receptors on the ER by CICR to evoke a propagating calcium wave. This may call for a revision of current views on the mechanisms of intracellular calcium signaling. The purpose of this review is, therefore, to provide an appropriate framework for future studies in this area.

scholarly journals Research Progress on the Mechanism of Cochlear Hair Cell Regeneration

2021 ◽  
Vol 15 ◽  
Author(s):  
Shan Xu ◽  
Ning Yang
Keyword(s):  
Hearing Loss ◽  
Hair Cell ◽  
Sensorineural Hearing Loss ◽  
Hair Cells ◽  
Molecular Mechanisms ◽  
Sensorineural Hearing ◽  
Research Progress ◽  
Cell Regeneration ◽  
Hair Cell Regeneration ◽  
Auditory Hair Cells

Mammalian inner ear hair cells do not have the ability to spontaneously regenerate, so their irreversible damage is the main cause of sensorineural hearing loss. The damage and loss of hair cells are mainly caused by factors such as aging, infection, genetic factors, hypoxia, autoimmune diseases, ototoxic drugs, or noise exposure. In recent years, research on the regeneration and functional recovery of mammalian auditory hair cells has attracted more and more attention in the field of auditory research. How to regenerate and protect hair cells or auditory neurons through biological methods and rebuild auditory circuits and functions are key scientific issues that need to be resolved in this field. This review mainly summarizes and discusses the recent research progress in gene therapy and molecular mechanisms related to hair cell regeneration in the field of sensorineural hearing loss.

scholarly journals The Hair Cell Analysis Toolbox: A machine learning-based whole cochlea analysis pipeline

2021 ◽  
Author(s):  
Christopher J Buswinka ◽  
David B Rosenberg ◽  
Artur A Indzhykulian
Keyword(s):  
Machine Learning ◽  
Image Analysis ◽  
Hair Cell ◽  
Hair Cells ◽  
Cell Analysis ◽  
Cochlear Function ◽  
Analysis Pipeline ◽  
Auditory Hair Cells ◽  
Automated Tools ◽  
Microscopy Techniques

Auditory hair cells, the whole length of the cochlea, are routinely visualized using light microscopy techniques. It is common, therefore, for one to collect more data than is practical to analyze manually. There are currently no widely accepted tools for unsupervised, unbiased, and comprehensive analysis of cells in an entire cochlea. This represents a stark gap between image-based data and other tests of cochlear function. To close this gap, we present a machine learning-based hair cell analysis toolbox, for the analysis of whole cochleae, imaged with confocal microscopy. The software presented here allows the automation of common image analysis tasks such as counting hair cells, determining their best frequency, as well as quantifying single cell immunofluorescence intensities along the entire cochlear coil. We hope these automated tools will remove a considerable barrier in cochlear image analysis, allowing for more informative and less selective data analysis practices.

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