scholarly journals Actin Crosslinking Family Protein 7 Deficiency Does Not Impair Hearing in Young Mice

2021 ◽  
Vol 9 ◽  
Author(s):  
Benjamin L. Gilbert ◽  
Shaoyuan Zhu ◽  
Ahlam Salameh ◽  
Shenyu Sun ◽  
Kumar N. Alagramam ◽  
...  
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Conditional Knockout ◽  
Cell Protein ◽  
Apical Region ◽  
Filamentous Actin ◽  
Cuticular Plate ◽  
Family Protein ◽  
Young Mice

To enable hearing, the sensory hair cell contains specialized subcellular structures at its apical region, including the actin-rich cuticular plate and circumferential band. ACF7 (actin crosslinking family protein 7), encoded by the gene Macf1 (microtubule and actin crosslinking factor 1), is a large cytoskeletal crosslinking protein that interacts with microtubules and filamentous actin to shape cells. ACF7 localizes to the cuticular plate and the circumferential band in the hair cells of vertebrates. The compelling expression pattern of ACF7 in hair cells, combined with conserved roles of this protein in the cytoskeleton of various cell types in invertebrates and vertebrates, led to the hypothesis that ACF7 performs a key function in the subcellular architecture of hair cells. To test the hypothesis, we conditionally target Macf1 in the inner ears of mice. Surprisingly, our data show that in young, but mature, conditional knockout mice cochlear hair cell survival, planar cell polarity, organization of the hair cells within the organ of Corti, and capacity to hear are not significantly impacted. Overall, these results fail to support the hypothesis that ACF7 is an essential hair cell protein in young mice, and the purpose of ACF7 expression in the hair cell remains to be understood.

scholarly journals LMO7 deficiency reveals the significance of the cuticular plate for hearing function

2018 ◽  
Author(s):  
Ting-Ting Du ◽  
James B. Dewey ◽  
Elizabeth L. Wagner ◽  
Shimon P. Francis ◽  
Edward Perez-Reyes ◽  
...  
Keyword(s):  
Hair Cell ◽  
Late Onset ◽  
Hair Bundle ◽  
Cell Protein ◽  
Inner Hair Cell ◽  
Filamentous Actin ◽  
Cuticular Plate ◽  
Hearing Function ◽  
Cochlear Tuning ◽  
And Function

AbstractSensory hair cells, the mechanoreceptors of the auditory and vestibular system, harbor two specialized organelles, the hair bundle and the cuticular plate. Both subcellular structures have adapted to facilitate the remarkable sensitivity and speed of hair cell mechanotransduction. While the mechanosensory hair bundle is extensively studied, the molecules and mechanisms mediating the development and function of the cuticular plate are poorly understood. The cuticular plate is believed to provide a rigid foundation for stereociliar pivot movements, but specifics about its function, especially the significance of its integrity for long-term maintenance of hair cell mechanotransduction, are not known. In this study, we describe the discovery of a hair cell protein called LIM only protein 7 (LMO7). In the hair cell, LMO7 is specifically localized in the cuticular plate. Lmo7 KO mice suffer multiple deficiencies in the cuticular plate, including reduced filamentous actin density and abnormal length and distribution of stereociliar rootlets. In addition to the cuticular plate defects, older Lmo7 KO mice develop abnormalities in inner hair cell stereocilia. Together, these defects affect cochlear tuning and sensitivity and give rise to late-onset progressive hearing loss.

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.

scholarly journals Connectomics of the zebrafish's lateral-line neuromast reveals wiring and miswiring in a simple microcircuit

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Eliot Dow ◽  
Adrian Jacobo ◽  
Sajjad Hossain ◽  
Kimberly Siletti ◽  
A J Hudspeth
Keyword(s):  
Hair Cell ◽  
Lateral Line ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Developmental Stages ◽  
Notch Signaling Pathway ◽  
Nerve Fibers ◽  
Directional Sensitivity ◽  
Efferent Nerve ◽  
Polarity Gene

The lateral-line neuromast of the zebrafish displays a restricted, consistent pattern of innervation that facilitates the comparison of microcircuits across individuals, developmental stages, and genotypes. We used serial blockface scanning electron microscopy to determine from multiple specimens the neuromast connectome, a comprehensive set of connections between hair cells and afferent and efferent nerve fibers. This analysis delineated a complex but consistent wiring pattern with three striking characteristics: each nerve terminal is highly specific in receiving innervation from hair cells of a single directional sensitivity; the innervation is redundant; and the terminals manifest a hierarchy of dominance. Mutation of the canonical planar-cell-polarity gene vangl2, which decouples the asymmetric phenotypes of sibling hair-cell pairs, results in randomly positioned, randomly oriented sibling cells that nonetheless retain specific wiring. Because larvae that overexpress Notch exhibit uniformly oriented, uniformly innervating hair-cell siblings, wiring specificity is mediated by the Notch signaling pathway.

scholarly journals Fgf8 genetic labeling reveals the early specification of vestibular hair cell type in mouse utricle

Development ◽  
2020 ◽  
Vol 147 (22) ◽  
pp. dev192849
Author(s):  
Evan M. Ratzan ◽  
Anne M. Moon ◽  
Michael R. Deans
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Conditional Knockout ◽  
Developmental Model ◽  
Type I ◽  
Ear Development ◽  
Inner Ear Development ◽  
Morphological Criteria ◽  
Genetic Labeling

ABSTRACTFGF8 signaling plays diverse roles in inner ear development, acting at multiple stages from otic placode induction to cellular differentiation in the organ of Corti. As a secreted morphogen with diverse functions, Fgf8 expression is likely to be spatially restricted and temporally dynamic throughout inner ear development. We evaluated these characteristics using genetic labeling mediated by Fgf8mcm gene-targeted mice and determined that Fgf8 expression is a specific and early marker of Type-I vestibular hair cell identity. Fgf8mcm expression initiates at E11.5 in the future striolar region of the utricle, labeling hair cells following EdU birthdating, and demonstrates that sub-type identity is determined shortly after terminal mitosis. This early fate specification is not apparent using markers or morphological criteria that are not present before birth in the mouse. Although analyses of Fgf8 conditional knockout mice did not reveal developmental phenotypes, the restricted pattern of Fgf8 expression suggests that functionally redundant FGF ligands may contribute to vestibular hair cell differentiation and supports a developmental model in which Type-I and Type-II hair cells develop in parallel rather than from an intermediate precursor.

scholarly journals Par3 is essential for the establishment of planar cell polarity of inner ear hair cells

2019 ◽  
Vol 116 (11) ◽  
pp. 4999-5008 ◽  
Author(s):  
Andre Landin Malt ◽  
Zachary Dailey ◽  
Julia Holbrook-Rasmussen ◽  
Yuqiong Zheng ◽  
Arielle Hogan ◽  
...  
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Cell Polarity ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Tissue Level ◽  
Hair Bundle ◽  
Nucleotide Exchange ◽  
Genetic Mosaic ◽  
Pcp Signaling

In the inner ear sensory epithelia, stereociliary hair bundles atop sensory hair cells are mechanosensory apparatus with planar polarized structure and orientation. This is established during development by the concerted action of tissue-level, intercellular planar cell polarity (PCP) signaling and a hair cell-intrinsic, microtubule-mediated machinery. However, how various polarity signals are integrated during hair bundle morphogenesis is poorly understood. Here, we show that the conserved cell polarity protein Par3 is essential for planar polarization of hair cells. Par3 deletion in the inner ear disrupted cochlear outgrowth, hair bundle orientation, kinocilium positioning, and basal body planar polarity, accompanied by defects in the organization and cortical attachment of hair cell microtubules. Genetic mosaic analysis revealed that Par3 functions both cell-autonomously and cell-nonautonomously to regulate kinocilium positioning and hair bundle orientation. At the tissue level, intercellular PCP signaling regulates the asymmetric localization of Par3, which in turn maintains the asymmetric localization of the core PCP protein Vangl2. Mechanistically, Par3 interacts with and regulates the localization of Tiam1 and Trio, which are guanine nucleotide exchange factors (GEFs) for Rac, thereby stimulating Rac-Pak signaling. Finally, constitutively active Rac1 rescued the PCP defects in Par3-deficient cochleae. Thus, a Par3–GEF–Rac axis mediates both tissue-level and hair cell-intrinsic PCP signaling.

scholarly journals The Rho GTPase Cell Division Cycle 42 Regulates Stereocilia Development in Cochlear Hair Cells

2021 ◽  
Vol 9 ◽  
Author(s):  
Haibo Du ◽  
Hao Zhou ◽  
Yixiao Sun ◽  
Xiaoyan Zhai ◽  
Zhengjun Chen ◽  
...  
Keyword(s):  
Cell Division ◽  
Hair Cell ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Rho Gtpase ◽  
Cell Division Cycle ◽  
Pivotal Role ◽  
Apical Surface ◽  
Cochlear Hair Cells

Stereocilia are actin-based cell protrusions on the apical surface of inner ear hair cells, playing a pivotal role in hearing and balancing sensation. The development and maintenance of stereocilia is tightly regulated and deficits in this process usually lead to hearing or balancing disorders. The Rho GTPase cell division cycle 42 (CDC42) is a key regulator of the actin cytoskeleton. It has been reported to localize in the hair cell stereocilia and play important roles in stereocilia maintenance. In the present work, we utilized hair cell-specific Cdc42 knockout mice and CDC42 inhibitor ML141 to explore the role of CDC42 in stereocilia development. Our data show that stereocilia height and width as well as stereocilia resorption are affected in Cdc42-deficient cochlear hair cells when examined at postnatal day 8 (P8). Moreover, ML141 treatment leads to planar cell polarity (PCP) deficits in neonatal hair cells. We also show that overexpression of a constitutively active mutant CDC42 in cochlear hair cells leads to enhanced stereocilia developmental deficits. In conclusion, the present data suggest that CDC42 plays a pivotal role in regulating hair cell stereocilia development.

scholarly journals Essential Role of Sptan1 in Cochlear Hair Cell Morphology and Function Via Focal Adhesion Signaling

2021 ◽  
Author(s):  
Qingxiu Yao ◽  
Hui Wang ◽  
Hengchao Chen ◽  
Zhuangzhuang Li ◽  
Yumeng Jiang ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Hair Cell ◽  
Focal Adhesion ◽  
Hair Cells ◽  
Focal Adhesions ◽  
Organ Of Corti ◽  
Cochlear Hair Cell ◽  
Cuticular Plate ◽  
And Function

AbstractHearing loss is the most common human sensory deficit. Hearing relies on stereocilia, inserted into the cuticular plate of hair cells (HCs), where they play an important role in the perception of sound and its transmission. Although numerous genes have been associated with hearing loss, the function of many hair cell genes has yet to be elucidated. Herein, we focused on nonerythroid spectrin αII (SPTAN1), abundant in the cuticular plate, surrounding the rootlets of stereocilia and along the plasma membrane. Interestingly, mice with HC-specific Sptan1 knockout exhibited rapid deafness, abnormal formation of stereocilia and cuticular plates, and loss of HCs from middle and apical turns of the cochlea during early postnatal stages. Additionally, Sptan1 deficiency led to the decreased spreading of House Ear Institute-Organ of Corti 1 cells, and induced abnormal formation of focal adhesions and integrin signaling in mouse HCs. Altogether, our findings highlight SPTAN1 as a critical molecule for HC stereocilia morphology and auditory function via regulation of focal adhesion signaling.

scholarly journals Connectomics of the zebrafish’s lateral-line neuromast reveals wiring and miswiring in a simple microcircuit

2018 ◽  
Author(s):  
Eliot Dow ◽  
Adrian Jacobo ◽  
Sajjad Hossain ◽  
Kimberly Siletti ◽  
A. J. Hudspeth
Keyword(s):  
Hair Cell ◽  
Lateral Line ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Developmental Stages ◽  
Notch Signaling Pathway ◽  
Nerve Fibers ◽  
Directional Sensitivity ◽  
Efferent Nerve ◽  
Polarity Gene

AbstractThe lateral-line neuromast of the zebrafish displays a restricted, consistent pattern of innervation that facilitates the comparison of microcircuits across individuals, developmental stages, and genotypes. We used serial blockface scanning electron microscopy to determine from multiple specimens the neuromast connectome, or comprehensive set of connections between hair cells and afferent and efferent nerve fibers. This analysis delineated a complex but consistent wiring pattern with three striking characteristics: each nerve terminal is highly specific in receiving innervation from hair cells of a single directional sensitivity; the innervation is redundant; and the terminals manifest a hierarchy of dominance. Mutation of the canonical planar-cell-polarity gene vangl2, which decouples the asymmetric phenotypes of sibling hair-cell pairs, results in randomly positioned, randomly oriented sibling cells that nonetheless retain specific wiring. Because larvae that overexpress Notch exhibit uniformly oriented, uniformly innervating hair-cell siblings, wiring specificity is mediated by the Notch signaling pathway.

scholarly journals Implication of Vestibular Hair Cell Loss of Planar Polarity for the Canal and Otolith-Dependent Vestibulo-Ocular Reflexes in Celsr1–/– Mice

2021 ◽  
Vol 15 ◽  
Author(s):  
François Simon ◽  
Fadel Tissir ◽  
Vincent Michel ◽  
Ghizlene Lahlou ◽  
Michael Deans ◽  
...  
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Vestibular Function ◽  
Critical Factor ◽  
Significant Loss ◽  
Spontaneous Nystagmus ◽  
Cell Orientation ◽  
Information Encoding ◽  
Vestibular Organs

Introduction: Vestibular sensory hair cells are precisely orientated according to planar cell polarity (PCP) and are key to enable mechanic-electrical transduction and normal vestibular function. PCP is found on different scales in the vestibular organs, ranging from correct hair bundle orientation, coordination of hair cell orientation with neighboring hair cells, and orientation around the striola in otolithic organs. Celsr1 is a PCP protein and a Celsr1 KO mouse model showed hair cell disorganization in all vestibular organs, especially in the canalar ampullae. The objective of this work was to assess to what extent the different vestibulo-ocular reflexes were impaired in Celsr1 KO mice.Methods: Vestibular function was analyzed using non-invasive video-oculography. Semicircular canal function was assessed during sinusoidal rotation and during angular velocity steps. Otolithic function (mainly utricular) was assessed during off-vertical axis rotation (OVAR) and during static and dynamic head tilts.Results: The vestibulo-ocular reflex of 10 Celsr1 KO and 10 control littermates was analyzed. All KO mice presented with spontaneous nystagmus or gaze instability in dark. Canalar function was reduced almost by half in KO mice. Compared to control mice, KO mice had reduced angular VOR gain in all tested frequencies (0.2–1.5 Hz), and abnormal phase at 0.2 and 0.5 Hz. Concerning horizontal steps, KO mice had reduced responses. Otolithic function was reduced by about a third in KO mice. Static ocular-counter roll gain and OVAR bias were both significantly reduced. These results demonstrate that canal- and otolith-dependent vestibulo-ocular reflexes are impaired in KO mice.Conclusion: The major ampullar disorganization led to an important reduction but not to a complete loss of angular coding capacities. Mildly disorganized otolithic hair cells were associated with a significant loss of otolith-dependent function. These results suggest that the highly organized polarization of otolithic hair cells is a critical factor for the accurate encoding of the head movement and that the loss of a small fraction of the otolithic hair cells in pathological conditions is likely to have major functional consequences. Altogether, these results shed light on how partial loss of vestibular information encoding, as often encountered in pathological situations, translates into functional deficits.

scholarly journals C1ql1 is expressed in adult outer hair cells of the cochlea in a tonotopic gradient

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251412
Author(s):  
Joyshree Biswas ◽  
Robert S. Pijewski ◽  
Rohit Makol ◽  
Tania G. Miramontes ◽  
Brianna L. Thompson ◽  
...  
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Noise Exposure ◽  
Outer Hair Cell ◽  
Outer Hair Cells ◽  
Conditional Knockout ◽  
Afferent Neurons ◽  
Inner Hair Cells ◽  
Afferent Synapse ◽  
The Brain

Hearing depends on the transduction of sounds into neural signals by the inner hair cells of the cochlea. Cochleae also have outer hair cells with unique electromotile properties that increase auditory sensitivity, but they are particularly susceptible to damage by intense noise exposure, ototoxic drugs, and aging. Although the outer hair cells have synapses on afferent neurons that project to the brain, the function of this neuronal circuit is unclear. Here, we created a novel mouse allele that inserts a fluorescent reporter at the C1ql1 locus which revealed gene expression in the outer hair cells and allowed creation of outer hair cell-specific C1ql1 knockout mice. We found that C1ql1 expression in outer hair cells corresponds to areas with the most sensitive frequencies of the mouse audiogram, and that it has an unexpected adolescence-onset developmental timing. No expression was observed in the inner hair cells. Since C1QL1 in the brain is made by neurons, transported anterogradely in axons, and functions in the synaptic cleft, C1QL1 may serve a similar function at the outer hair cell afferent synapse. Histological analyses revealed that C1ql1 conditional knockout cochleae may have reduced outer hair cell afferent synapse maintenance. However, auditory behavioral and physiological assays did not reveal a compelling phenotype. Nonetheless, this study identifies a potentially useful gene expressed in the cochlea and opens the door for future studies aimed at elucidating the function of C1QL1 and the function of the outer hair cell and its afferent neurons.

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