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 Par3 regulates Rac1 signaling and microtubule organization during planar polarization of auditory hair cells

2018 ◽  
Author(s):  
Andre Landin Malt ◽  
Zachary Dailey ◽  
Julia Holbrook-rasmussen ◽  
Yuqiong Zheng ◽  
Quansheng Du ◽  
...  
Keyword(s):  
Inner Ear ◽  
Cell Polarity ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Tissue Level ◽  
Hair Bundle ◽  
Microtubule Organization ◽  
Reciprocal Regulation ◽  
Auditory Hair Cells ◽  
Pcp Signaling

AbstractIn the inner ear sensory epithelia, hair bundles atop sensory hair cells are mechanosensory apparati with planar polarized structure and orientation. This is established during development by the concerted action of tissue-level 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 plays a key role in planar polarization of hair cells. Par3 deletion in the inner ear resulted in defects in cochlear length, hair bundle orientation and kinocilium positioning. During PCP establishment, Par3 promotes localized Rac-Pak signaling through an interaction with Tiam1. Par3 regulates microtubule dynamics and organization, which is crucial for basal body positioning. Moreover, there is reciprocal regulation of Par3 and the core PCP molecule Vangl2. Thus, we conclude that Par3 is an effector and integrator of cell-intrinsic and tissue-level PCP signaling.One sentence summaryPar3 regulates planar polarity of auditory hair cells

scholarly journals Wnts regulate planar cell polarity via heterotrimeric G protein and PI3K signaling

2020 ◽  
Vol 219 (10) ◽  
Author(s):  
Andre Landin Malt ◽  
Arielle K. Hogan ◽  
Connor D. Smith ◽  
Maxwell S. Madani ◽  
Xiaowei Lu
Keyword(s):  
Hair Cell ◽  
G Protein ◽  
Cell Polarity ◽  
Planar Cell Polarity ◽  
Pi3k Pathway ◽  
Sensory Epithelium ◽  
Nucleotide Exchange ◽  
Cell Orientation ◽  
Complex Signals ◽  
Heterotrimeric G Protein

In the mammalian cochlea, the planar cell polarity (PCP) pathway aligns hair cell orientation along the plane of the sensory epithelium. Concurrently, multiple cell intrinsic planar polarity (referred to as iPCP) modules mediate planar polarization of the hair cell apical cytoskeleton, including the kinocilium and the V-shaped hair bundle essential for mechanotransduction. How PCP and iPCP are coordinated during development and the roles of Wnt ligands in this process remain unresolved. Here we show that genetic blockade of Wnt secretion in the cochlear epithelium resulted in a shortened cochlear duct and misoriented and misshapen hair bundles. Mechanistically, Wnts stimulate Gi activity by regulating the localization of Daple, a guanine nucleotide exchange factor (GEF) for Gαi. In turn, the Gβγ complex signals through phosphoinositide 3-kinase (PI3K) to regulate kinocilium positioning and asymmetric localizations of a subset of core PCP proteins, thereby coordinating PCP and iPCP. Thus, our results identify a putative Wnt/heterotrimeric G protein/PI3K pathway for PCP regulation.

scholarly journals The development of cooperative channels explains the maturation of hair cell’s mechanotransduction

2019 ◽  
Author(s):  
Francesco Gianoli ◽  
Thomas Risler ◽  
Andrei S. Kozlov
Keyword(s):  
Ion Channels ◽  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Hair Bundle ◽  
Mechanical Stimuli ◽  
Biophysical Properties ◽  
Tip Link ◽  
Fast Adaptation ◽  
Kinetics Of

ABSTRACTHearing relies on the conversion of mechanical stimuli into electrical signals. In vertebrates, this process of mechano-electrical transduction (MET) is performed by specialized receptors of the inner ear, the hair cells. Each hair cell is crowned by a hair bundle, a cluster of microvilli that pivot in response to sound vibrations, causing the opening and closing of mechanosensitive ion channels. Mechanical forces are projected onto the channels by molecular springs called tip links. Each tip link is thought to connect to a small number of MET channels that gate cooperatively and operate as a single transduction unit. Pushing the hair bundle in the excitatory direction opens the channels, after which they rapidly reclose in a process called fast adaptation. It has been experimentally observed that the hair cell’s biophysical properties mature gradually during postnatal development: the maximal transduction current increases, sensitivity sharpens, transduction occurs at smaller hair-bundle displacements, and adaptation becomes faster. Similar observations have been reported during tip-link regeneration after acoustic damage. Moreover, when measured at intermediate developmental stages, the kinetics of fast adaptation varies in a given cell depending on the magnitude of the imposed displacement. The mechanisms underlying these seemingly disparate observations have so far remained elusive. Here, we show that these phenomena can all be explained by the progressive addition of MET channels of constant properties, which populate the hair bundle first as isolated entities, then progressively as clusters of more sensitive, cooperative MET channels. As the proposed mechanism relies on the difference in biophysical properties between isolated and clustered channels, this work highlights the importance of cooperative interactions between mechanosensitive ion channels for hearing.SIGNIFICANCEHair cells are the sensory receptors of the inner ear that convert mechanical stimuli into electrical signals transmitted to the brain. Sensitivity to mechanical stimuli and the kinetics of mechanotransduction currents change during hair-cell development. The same trend, albeit on a shorter timescale, is also observed during hair-cell recovery from acoustic trauma. Furthermore, the current kinetics in a given hair cell depends on the stimulus magnitude, and the degree of that dependence varies with development. These phenomena have so far remained unexplained. Here, we show that they can all be reproduced using a single unifying mechanism: the progressive formation of channel pairs, in which individual channels interact through the lipid bilayer and gate cooperatively.

scholarly journals Ick Ciliary Kinase Is Essential for Planar Cell Polarity Formation in Inner Ear Hair Cells and Hearing Function

2017 ◽  
Vol 37 (8) ◽  
pp. 2073-2085 ◽  
Author(s):  
Shio Okamoto ◽  
Taro Chaya ◽  
Yoshihiro Omori ◽  
Ryusuke Kuwahara ◽  
Shun Kubo ◽  
...  
Keyword(s):  
Inner Ear ◽  
Cell Polarity ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Hearing Function

scholarly journals Parallel control of mechanosensory hair cell orientation by the PCP and Wnt pathways

2019 ◽  
Author(s):  
Joaquin Navajas Acedo ◽  
Matthew G. Voas ◽  
Richard Alexander ◽  
Thomas Woolley ◽  
Jay R. Unruh ◽  
...  
Keyword(s):  
Hair Cell ◽  
Cell Polarity ◽  
Lateral Line ◽  
Hair Cells ◽  
Wnt Pathway ◽  
Neural Tube Closure ◽  
Cell Phenotype ◽  
Cell Orientation ◽  
Pcp Signaling ◽  
Wnt Pathways

ABSTRACTCell polarity plays a crucial role during development of vertebrates and invertebrates. Planar Cell Polarity (PCP) is defined as the coordinated polarity of cells within a tissue axis and is essential for processes such as gastrulation, neural tube closure or hearing. Wnt ligands can be instructive or permissive during PCP-dependent processes, and Wnt pathway mutants are often classified as PCP mutants due to the complexity and the similarities between their phenotypes. Our studies of the zebrafish sensory lateral line reveal that disruptions of the PCP and Wnt pathways have differential effects on hair cell orientations. While mutations in PCP genes cause random orientations of hair cells, mutations in Wnt pathway members induce hair cells to adopt a concentric pattern. We show that PCP signaling is normal in hair cells of Wnt pathway mutants and that the concentric hair cell phenotype is due to altered organization of the surrounding support cells. Thus, the PCP and Wnt pathways work in parallel, as separate pathways to establish proper hair cell orientation. Our data suggest that coordinated support cell organization is established during the formation of lateral line primordia, much earlier than the appearance of hair cells. Together, these finding reveal that hair cell orientation defects are not solely explained by defects in PCP signaling and that some hair cell phenotypes warrant reevaluation.

scholarly journals FGFR1-mediated protocadherin-15 loading mediates cargo specificity during intraflagellar transport in inner ear hair-cell kinocilia

2018 ◽  
Vol 115 (33) ◽  
pp. 8388-8393 ◽  
Author(s):  
Akira Honda ◽  
Tomoko Kita ◽  
Shri Vidhya Seshadri ◽  
Kazuyo Misaki ◽  
Zamal Ahmed ◽  
...  
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Primary Cilia ◽  
Growth Factor Receptor ◽  
Intraflagellar Transport ◽  
Hair Bundle ◽  
Mechanical Stimuli ◽  
Transport Pathway ◽  
Protocadherin 15

The mechanosensory hair cells of the inner ear are required for hearing and balance and have a distinctive apical structure, the hair bundle, that converts mechanical stimuli into electrical signals. This structure comprises a single cilium, the kinocilium, lying adjacent to an ensemble of actin-based projections known as stereocilia. Hair bundle polarity depends on kinociliary protocadherin-15 (Pcdh15) localization. Protocadherin-15 is found only in hair-cell kinocilia, and is not localized to the primary cilia of adjacent supporting cells. Thus, Pcdh15 must be specifically targeted and trafficked into the hair-cell kinocilium. Here we show that kinocilial Pcdh15 trafficking relies on cell type-specific coupling to the generic intraflagellar transport (IFT) transport mechanism. We uncover a role for fibroblast growth factor receptor 1 (FGFR1) in loading Pcdh15 onto kinociliary transport particles in hair cells. We find that on activation, FGFR1 binds and phosphorylates Pcdh15. Moreover, we find a previously uncharacterized role for clathrin in coupling this kinocilia-specific cargo with the anterograde IFT-B complex through the adaptor, DAB2. Our results identify a modified ciliary transport pathway used for Pcdh15 transport into the cilium of the inner ear hair cell and coordinated by FGFR1 activity.

scholarly journals The 133-kDa N-terminal domain enables myosin 15 to maintain mechanotransducing stereocilia and is essential for hearing

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Qing Fang ◽  
Artur A Indzhykulian ◽  
Mirna Mustapha ◽  
Gavin P Riordan ◽  
David F Dolan ◽  
...  
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Knockout Mouse ◽  
Molecular Motor ◽  
Hair Bundle ◽  
Terminal Domain

The precise assembly of inner ear hair cell stereocilia into rows of increasing height is critical for mechanotransduction and the sense of hearing. Yet, how the lengths of actin-based stereocilia are regulated remains poorly understood. Mutations of the molecular motor myosin 15 stunt stereocilia growth and cause deafness. We found that hair cells express two isoforms of myosin 15 that differ by inclusion of an 133-kDa N-terminal domain, and that these isoforms can selectively traffic to different stereocilia rows. Using an isoform-specific knockout mouse, we show that hair cells expressing only the small isoform remarkably develop normal stereocilia bundles. However, a critical subset of stereocilia with active mechanotransducer channels subsequently retracts. The larger isoform with the 133-kDa N-terminal domain traffics to these specialized stereocilia and prevents disassembly of their actin core. Our results show that myosin 15 isoforms can navigate between functionally distinct classes of stereocilia, and are independently required to assemble and then maintain the intricate hair bundle architecture.

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