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Silverman JB, Krystofiak EE, Caplan LR, Lau KS, Tyska MJ. Intestinal tuft cells assemble a cytoskeletal superstructure composed of co-aligned actin bundles and microtubules. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.19.585757. [PMID: 38562898 PMCID: PMC10983963 DOI: 10.1101/2024.03.19.585757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Background & Aims All tissues consist of a distinct set of cell types, which collectively support organ function and homeostasis. Tuft cells are a rare epithelial cell type found in diverse epithelia, where they play important roles in sensing antigens and stimulating downstream immune responses. Exhibiting a unique polarized morphology, tuft cells are defined by an array of giant actin filament bundles that support ∼2 μm of apical membrane protrusion and extend over 7 μm towards the cell's perinuclear region. Despite their established roles in maintaining intestinal epithelial homeostasis, tuft cells remain understudied due to their rarity (e.g. ∼ 1% in the small intestinal epithelium). Details regarding the ultrastructural organization of the tuft cell cytoskeleton, the molecular components involved in building the array of giant actin bundles, and how these cytoskeletal structures support tuft cell biology remain unclear. Methods To begin to answer these questions, we used advanced light and electron microscopy to perform quantitative morphometry of the small intestinal tuft cell cytoskeleton. Results We found that tuft cell core bundles consist of actin filaments that are crosslinked in a parallel "barbed-end out" configuration. These polarized structures are also supported by a unique group of tuft cell enriched actin-binding proteins that are differentially localized along the giant core bundles. Furthermore, we found that tuft cell actin bundles are co-aligned with a highly ordered network of microtubules. Conclusions Tuft cells assemble a cytoskeletal superstructure that is well positioned to serve as a track for subcellular transport along the apical-basolateral axis and in turn, support the dynamic sensing functions that are critical for intestinal epithelial homeostasis. SYNOPSIS This research leveraged advanced light and electron microscopy to perform quantitative morphometry of the intestinal tuft cell cytoskeleton. Three-dimensional reconstructions of segmented image data revealed a co-aligned actin-microtubule superstructure that may play a fundamental role in tuft cell function.
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Miyoshi T, Belyantseva IA, Sajeevadathan M, Friedman TB. Pathophysiology of human hearing loss associated with variants in myosins. Front Physiol 2024; 15:1374901. [PMID: 38562617 PMCID: PMC10982375 DOI: 10.3389/fphys.2024.1374901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 02/21/2024] [Indexed: 04/04/2024] Open
Abstract
Deleterious variants of more than one hundred genes are associated with hearing loss including MYO3A, MYO6, MYO7A and MYO15A and two conventional myosins MYH9 and MYH14. Variants of MYO7A also manifest as Usher syndrome associated with dysfunction of the retina and vestibule as well as hearing loss. While the functions of MYH9 and MYH14 in the inner ear are debated, MYO3A, MYO6, MYO7A and MYO15A are expressed in inner ear hair cells along with class-I myosin MYO1C and are essential for developing and maintaining functional stereocilia on the apical surface of hair cells. Stereocilia are large, cylindrical, actin-rich protrusions functioning as biological mechanosensors to detect sound, acceleration and posture. The rigidity of stereocilia is sustained by highly crosslinked unidirectionally-oriented F-actin, which also provides a scaffold for various proteins including unconventional myosins and their cargo. Typical myosin molecules consist of an ATPase head motor domain to transmit forces to F-actin, a neck containing IQ-motifs that bind regulatory light chains and a tail region with motifs recognizing partners. Instead of long coiled-coil domains characterizing conventional myosins, the tails of unconventional myosins have various motifs to anchor or transport proteins and phospholipids along the F-actin core of a stereocilium. For these myosins, decades of studies have elucidated their biochemical properties, interacting partners in hair cells and variants associated with hearing loss. However, less is known about how myosins traffic in a stereocilium using their motor function, and how each variant correlates with a clinical condition including the severity and onset of hearing loss, mode of inheritance and presence of symptoms other than hearing loss. Here, we cover the domain structures and functions of myosins associated with hearing loss together with advances, open questions about trafficking of myosins in stereocilia and correlations between hundreds of variants in myosins annotated in ClinVar and the corresponding deafness phenotypes.
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, United States
| | - Inna A. Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Mrudhula Sajeevadathan
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, United States
| | - Thomas B. Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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Silverman JB, Vega PN, Tyska MJ, Lau KS. Intestinal Tuft Cells: Morphology, Function, and Implications for Human Health. Annu Rev Physiol 2024; 86:479-504. [PMID: 37863104 PMCID: PMC11193883 DOI: 10.1146/annurev-physiol-042022-030310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2023]
Abstract
Tuft cells are a rare and morphologically distinct chemosensory cell type found throughout many organs, including the gastrointestinal tract. These cells were identified by their unique morphologies distinguished by large apical protrusions. Ultrastructural data have begun to describe the molecular underpinnings of their cytoskeletal features, and tuft cell-enriched cytoskeletal proteins have been identified, although the connection of tuft cell morphology to tuft cell functionality has not yet been established. Furthermore, tuft cells display variations in function and identity between and within tissues, leading to the delineation of distinct tuft cell populations. As a chemosensory cell type, they display receptors that are responsive to ligands specific for their environment. While many studies have demonstrated the tuft cell response to protists and helminths in the intestine, recent research has highlighted other roles of tuft cells as well as implicated tuft cells in other disease processes including inflammation, cancer, and viral infections. Here, we review the literature on the cytoskeletal structure of tuft cells. Additionally, we focus on new research discussing tuft cell lineage, ligand-receptor interactions, tuft cell tropism, and the role of tuft cells in intestinal disease. Finally, we discuss the implication of tuft cell-targeted therapies in human health and how the morphology of tuft cells may contribute to their functionality.
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Affiliation(s)
- Jennifer B Silverman
- Epithelial Biology Center and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; ,
| | - Paige N Vega
- Epithelial Biology Center and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; ,
| | - Matthew J Tyska
- Epithelial Biology Center and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; ,
| | - Ken S Lau
- Epithelial Biology Center and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; ,
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Gong R, Reynolds MJ, Carney KR, Hamilton K, Bidone TC, Alushin GM. Fascin structural plasticity mediates flexible actin bundle construction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.03.574123. [PMID: 38260322 PMCID: PMC10802278 DOI: 10.1101/2024.01.03.574123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Fascin crosslinks actin filaments (F-actin) into bundles that support tubular membrane protrusions including filopodia and stereocilia. Fascin dysregulation drives aberrant cell migration during metastasis, and fascin inhibitors are under development as cancer therapeutics. Here, we use cryo-electron microscopy, cryo-electron tomography coupled with custom denoising, and computational modeling to probe fascin's F-actin crosslinking mechanisms across spatial scales. Our fascin crossbridge structure reveals an asymmetric F-actin binding conformation that is allosterically blocked by the inhibitor G2. Reconstructions of seven-filament hexagonal bundle elements, variability analysis, and simulations show how structural plasticity enables fascin to bridge varied inter-filament orientations, accommodating mismatches between F-actin's helical symmetry and bundle hexagonal packing. Tomography of many-filament bundles and modeling uncovers geometric rules underlying emergent fascin binding patterns, as well as the accumulation of unfavorable crosslinks that limit bundle size. Collectively, this work shows how fascin harnesses fine-tuned nanoscale structural dynamics to build and regulate micron-scale F-actin bundles.
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Affiliation(s)
- Rui Gong
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Matthew J. Reynolds
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Keith R. Carney
- Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
| | - Keith Hamilton
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Tamara C. Bidone
- Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA
| | - Gregory M. Alushin
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
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Kuang X, Zhao W, Wang Q, Sun Z, Xu F, Geng R, Li B, Zheng T, Zheng Q. RNA-seq analysis highlights DNA replication and DNA repair associated with early-onset hearing loss in the cochlea of DBA/2J mice. Life Sci 2024; 337:122350. [PMID: 38103727 DOI: 10.1016/j.lfs.2023.122350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 12/05/2023] [Accepted: 12/09/2023] [Indexed: 12/19/2023]
Abstract
AIMS Age-related hearing loss (ARHL) is a significant health concern, and DBA/2J (D2) and C57BL/6 (B6) mouse strains serve as valuable models for its study. B6 mice, harboring a homozygous ahl allele in Cdh23, manifest high-frequency hearing loss at 3 months. In contrast, D2 mice, carrying the R109H variant of the Fascin-2 gene (Fscn2), experience early-onset hearing loss by 3 weeks. Yet, the underlying molecular mechanisms driving early-onset hearing loss in D2 mice remain elusive. This study aimed to identify novel genes and regulatory pathways as therapeutic targets for early deafness. MAIN METHODS This study employs RNA-sequencing (RNA-seq) to analyze cochlear mRNA expression at two different ages in D2 and B6 mice, respectively. The differentially expressed genes (DEGs) are uniquely associated with D2 mice by Venn diagram analysis. A protein-protein interaction (PPI) network is further constructed, followed by module analysis utilizing MCODE. Enrichment analysis of GO and KEGG pathways revealed biological functions and molecular pathways. The PPI network and VarElect analysis are conducted for genes within these pathways, facilitating the identification of pivotal genes based on scoring criteria. Subsequently, five genes are meticulously selected and validated through qRT-PCR. KEY FINDINGS Notably, 1181 DEGs are uniquely associated with D2 mice by Venn diagram analysis. GO and KEGG pathway enrichment analyses shed light on distinctive pathways in D2 mice, encompassing DNA replication, mismatch repair, base excision repair, and nucleotide excision repair, which are associated with apoptosis. Five genes involved in these pathways were finally selected and validated by qRT-PCR. Their down-regulation with age is consistent with RNA-seq result. SIGNIFICANCE Our study underscores the potential implication of down-regulated genes associated with DNA replication and DNA damage repair in the early-onset hearing loss observed in D2 mice.
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Affiliation(s)
- Xiaojing Kuang
- School of Basic Medicine, Qingdao University, 266000 Qingdao, Shandong, China
| | - Wenben Zhao
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Qin Wang
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Zehua Sun
- Department of Radiology, Qindao University Medical College Affiliated Yantai Yuhuangding Hospital, 264000 Yantai, Shandong, China
| | - Fuyi Xu
- Precision Medicine Research Center, School of Pharmacy, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Ruishuang Geng
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Bo Li
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Tihua Zheng
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China
| | - Qingyin Zheng
- School of Basic Medicine, Qingdao University, 266000 Qingdao, Shandong, China; Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, 264000 Yantai, Shandong, China.
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Xiong Y, Chen M, Wang H, Chen L, Huang H, Xu L. Mutation analysis of GJB2, SLC26A4, GJB3 and mtDNA12SrRNA genes in 251 non-syndromic hearing loss patients in Fujian, China. Int J Pediatr Otorhinolaryngol 2024; 176:111777. [PMID: 38029595 DOI: 10.1016/j.ijporl.2023.111777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 10/23/2023] [Accepted: 11/03/2023] [Indexed: 12/01/2023]
Abstract
OBJECTIVES The molecular etiology of non-syndromic hearing loss (NSHL) in Southeastern China (Fujian) has not been precisely identified. our study selected patients with NSHL and analyzed their causative genes, which helped to improve the accuracy of the diagnosis of hereditary hearing loss (HHL) and its treatment. METHODS 251 unrelated patients who attended the otolaryngology clinic of Fujian Maternal and Child Health Hospital with hearing loss were enrolled to our study. All patients had genetic tests and listening tests, of which 251 were diagnosed with NSHL. In addition, we used whole-exome sequencing (WES) in a patient who has a significant family history of HHL but negative for gene chip testing, as well as in his family members. RESULT Among of 251 patients, Nucleotide changes were found in 63 cases (25.09%), including 34 located in GJB2(13.5%, including 235delC and 299_300delAT), 13 located in SLC26A4(5.18%, including c.919-2G > A and 2168 A > G), 1 located in GJB3(0.4%,538C > T) and 16 located in mtDNA12SrRNA (6.37%,1555 A > G). In addition, we discuss the process of identifying novel PLS1 mutations from 251 patients. CONCLUSION Our results demonstrate the conventional deafness gene mutation in 251 NSHL patients in Fujian, China. Compared with the other area of China, we have a lower detection rate, but GJB2 235delC remains the most common mutation in Fujian. In addition, we discuss the process of discovering novel mutation locus for deafness, which provides an understanding for deafness diagnosis and genetic testing.
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Affiliation(s)
- Yikang Xiong
- The Frist Department of Clinical Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian Province, China
| | - Meihuan Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, 350001, Fujian Province, China
| | - Haiwei Wang
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, 350001, Fujian Province, China
| | - Lingji Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, 350001, Fujian Province, China
| | - Hailong Huang
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, 350001, Fujian Province, China.
| | - Liangpu Xu
- The Frist Department of Clinical Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian Province, China; Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, 350001, Fujian Province, China.
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Paplou VG, Schubert NMA, van Tuinen M, Vijayakumar S, Pyott SJ. Functional, Morphological and Molecular Changes Reveal the Mechanisms Associated with Age-Related Vestibular Loss. Biomolecules 2023; 13:1429. [PMID: 37759828 PMCID: PMC10526133 DOI: 10.3390/biom13091429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/08/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
Age-related loss of vestibular function and hearing are common disorders that arise from the loss of function of the inner ear and significantly decrease quality of life. The underlying pathophysiological mechanisms are poorly understood and difficult to investigate in humans. Therefore, our study examined young (1.5-month-old) and old (24-month-old) C57BL/6 mice, utilizing physiological, histological, and transcriptomic methods. Vestibular sensory-evoked potentials revealed that older mice had reduced wave I amplitudes and delayed wave I latencies, indicating reduced vestibular function. Immunofluorescence and image analysis revealed that older mice exhibited a significant decline in type I sensory hair cell density, particularly in hair cells connected to dimorphic vestibular afferents. An analysis of gene expression in the isolated vestibule revealed the upregulation of immune-related genes and the downregulation of genes associated with ossification and nervous system development. A comparison with the isolated cochlear sensorineural structures showed similar changes in genes related to immune response, chondrocyte differentiation, and myelin formation. These findings suggest that age-related vestibular hypofunction is linked to diminished peripheral vestibular responses, likely due to the loss of a specific subpopulation of hair cells and calyceal afferents. The upregulation of immune- and inflammation-related genes implies that inflammation contributes to these functional and structural changes. Furthermore, the comparison of gene expression between the vestibule and cochlea indicates both shared and distinct mechanisms contributing to age-related vestibular and hearing impairments. Further research is necessary to understand the mechanistic connection between inflammation and age-related balance and hearing disorders and to translate these findings into clinical treatment strategies.
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Affiliation(s)
- Vasiliki Georgia Paplou
- Department of Otorhinolaryngology and Head/Neck Surgery, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands; (V.G.P.); (N.M.A.S.); (M.v.T.)
| | - Nick M. A. Schubert
- Department of Otorhinolaryngology and Head/Neck Surgery, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands; (V.G.P.); (N.M.A.S.); (M.v.T.)
- Graduate School of Medical Sciences Research, School of Behavioural and Cognitive Neurosciences, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Marcel van Tuinen
- Department of Otorhinolaryngology and Head/Neck Surgery, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands; (V.G.P.); (N.M.A.S.); (M.v.T.)
| | - Sarath Vijayakumar
- Department of Biomedical Sciences, School of Medicine, Creighton University, Omaha, NE 68178, USA;
| | - Sonja J. Pyott
- Department of Otorhinolaryngology and Head/Neck Surgery, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands; (V.G.P.); (N.M.A.S.); (M.v.T.)
- Graduate School of Medical Sciences Research, School of Behavioural and Cognitive Neurosciences, University of Groningen, 9713 AV Groningen, The Netherlands
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Park J, Bird JE. The actin cytoskeleton in hair bundle development and hearing loss. Hear Res 2023; 436:108817. [PMID: 37300948 PMCID: PMC10408727 DOI: 10.1016/j.heares.2023.108817] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/18/2023] [Accepted: 05/25/2023] [Indexed: 06/12/2023]
Abstract
Inner ear hair cells assemble mechanosensitive hair bundles on their apical surface that transduce sounds and accelerations. Each hair bundle is comprised of ∼ 100 individual stereocilia that are arranged into rows of increasing height and width; their specific and precise architecture being necessary for mechanoelectrical transduction (MET). The actin cytoskeleton is fundamental to establishing this architecture, not only by forming the structural scaffold shaping each stereocilium, but also by composing rootlets and the cuticular plate that together provide a stable foundation supporting each stereocilium. In concert with the actin cytoskeleton, a large assortment of actin-binding proteins (ABPs) function to cross-link actin filaments into specific topologies, as well as control actin filament growth, severing, and capping. These processes are individually critical for sensory transduction and are all disrupted in hereditary forms of human hearing loss. In this review, we provide an overview of actin-based structures in the hair bundle and the molecules contributing to their assembly and functional properties. We also highlight recent advances in mechanisms driving stereocilia elongation and how these processes are tuned by MET.
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Affiliation(s)
- Jinho Park
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States
| | - Jonathan E Bird
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States.
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Vartanian V, Krey JF, Chatterjee P, Curtis A, Six M, Rice SPM, Jones SM, Sampath H, Allen CN, Ryals RC, Lloyd RS, Barr‐Gillespie PG. Spontaneous allelic variant in deafness-blindness gene Ush1g resulting in an expanded phenotype. GENES, BRAIN, AND BEHAVIOR 2023; 22:e12849. [PMID: 37328946 PMCID: PMC10393423 DOI: 10.1111/gbb.12849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/05/2023] [Accepted: 05/07/2023] [Indexed: 06/18/2023]
Abstract
Relationships between novel phenotypic behaviors and specific genetic alterations are often discovered using target-specific, directed mutagenesis or phenotypic selection following chemical mutagenesis. An alternative approach is to exploit deficiencies in DNA repair pathways that maintain genetic integrity in response to spontaneously induced damage. Mice deficient in the DNA glycosylase NEIL1 show elevated spontaneous mutations, which arise from translesion DNA synthesis past oxidatively induced base damage. Several litters of Neil1 knockout mice included animals that were distinguished by their backwards-walking behavior in open-field environments, while maintaining frantic forward movements in their home cage environment. Other phenotypic manifestations included swim test failures, head tilting and circling. Mapping of the mutation that conferred these behaviors showed the introduction of a stop codon at amino acid 4 of the Ush1g gene. Ush1gbw/bw null mice displayed auditory and vestibular defects that are commonly seen with mutations affecting inner-ear hair-cell function, including a complete lack of auditory brainstem responses and vestibular-evoked potentials. As in other Usher syndrome type I mutant mouse lines, hair cell phenotypes included disorganized and split hair bundles, as well as altered distribution of proteins for stereocilia that localize to the tips of row 1 or row 2. Disruption to the bundle and kinocilium displacement suggested that USH1G is essential for forming the hair cell's kinocilial links. Consistent with other Usher type 1 models, Ush1gbw/bw mice had no substantial retinal degeneration compared with Ush1gbw /+ controls. In contrast to previously described Ush1g alleles, this new allele provides the first knockout model for this gene.
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Affiliation(s)
- Vladimir Vartanian
- Oregon Institute of Occupational Health SciencesOregon Health & Science UniversityPortlandOregonUSA
| | - Jocelyn F. Krey
- Oregon Hearing Research Center and Vollum InstituteOregon Health & Science UniversityPortlandOregonUSA
| | - Paroma Chatterjee
- Oregon Hearing Research Center and Vollum InstituteOregon Health & Science UniversityPortlandOregonUSA
| | - Allison Curtis
- Department of Ophthalmology, Casey Eye InstituteOregon Health & Science UniversityPortlandOregonUSA
| | - Makayla Six
- Department of Ophthalmology, Casey Eye InstituteOregon Health & Science UniversityPortlandOregonUSA
| | - Sean P. M. Rice
- Oregon Institute of Occupational Health Sciences and School of Public HealthOregon Health & Science University‐Portland State UniversityPortlandOregonUSA
| | - Sherri M. Jones
- Department of Special Education and Communication DisordersUniversity of Nebraska‐LincolnLincolnNebraskaUSA
| | - Harini Sampath
- Department of Nutritional Sciences and New Jersey Institute for Food, Nutrition, and HealthRutgers UniversityNew BrunswickNew JerseyUSA
| | - Charles N. Allen
- Oregon Institute of Occupational Health Sciences and Department of Behavioral NeuroscienceOregon Health & Science UniversityPortlandOregonUSA
| | - Renee C. Ryals
- Department of Ophthalmology, Casey Eye InstituteOregon Health & Science UniversityPortlandOregonUSA
| | - R. Stephen Lloyd
- Oregon Institute of Occupational Health SciencesOregon Health & Science UniversityPortlandOregonUSA
- Department of Molecular and Medical GeneticsOregon Health & Science UniversityPortlandOregonUSA
| | - Peter G. Barr‐Gillespie
- Oregon Hearing Research Center and Vollum InstituteOregon Health & Science UniversityPortlandOregonUSA
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Xu L, Wang X, Li J, Chen L, Wang H, Xu S, Zhang Y, Li W, Yao P, Tan M, Zhou S, Chen M, Pan Y, Chen X, Chen X, Liu Y, Lin N, Huang H, Cao H. A novel PLS1 c.981+1G>A variant causes autosomal-dominant hereditary hearing loss in a family. Clin Genet 2023; 103:413-423. [PMID: 36537221 DOI: 10.1111/cge.14283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/03/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022]
Abstract
The fimbrin protein family contains a variety of proteins, among which Plastin1 (PLS1) is an important member. According to recent studies, variations in the coding region of the PLS1 gene are associated with the development of deafness. However, the molecular mechanism of deafness caused by PLS1 gene variants remains unknown. Whole-exome sequencing was performed on hearing-impaired family members and hearing family members to identify pathogenic variants, followed by Sanger sequencing. A minigene assay was conducted to investigate the effect of the variant on PLS1 mRNA splicing. The pathogenicity of the variant was further investigated in zebrafish. RNA-sequencing (RNA-seq) was performed to analyze the dysregulation of downstream signaling pathways caused by knockdown of PLS1 expression. We identified a novel variant, PLS1 c.981+1G>A, in a large Chinese family with hearing loss and showed that the variant is responsible for the occurrence of hearing loss by inducing exon 8 skipping. The variant caused abnormal inner ear phenotypes, characterized by decreases in the mean otolith distance, anterior otolith diameter, posterior otolith diameter, cochlear diameter, and swimming speed and distance in zebrafish. Furthermore, silencing PLS1 expression significantly upregulated the expression of genes in the PI3K-Akt signaling pathway, including Col6a3, Spp1, Itgb3 and hepatocyte growth factor (Hgf). PLS1 c.981+1G>A is a novel pathogenic variant causing hearing loss by inducing exon 8 skipping. Upregulation of the expression of genes in the PI3K-Akt signaling pathway plays an important role in the pathogenesis caused by variants in the PLS1 gene.
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Affiliation(s)
- Liangpu Xu
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Xinrui Wang
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
- Medical Research Center, Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fuzhou, China
- NHC Key Laboratory of Technical Evaluation of Fertility Regulation for Non-human Primates, Fujian Maternity and Child Health Hospital, Fuzhou, China
| | - Jia Li
- BGI Genomics, BGI-Shenzhen, Shenzhen, China
- Hebei Industrial Technology Research Institute of Genomics in Maternal & Child Health, Shijiazhuang BGI Genomics Co., Ltd., Shijiazhuang, China
| | - Lingji Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Haiwei Wang
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
- Medical Research Center, Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fuzhou, China
| | - Shiyi Xu
- The First Clinical Medical College, Guangxi Medical University, Nanning, China
| | - Yanhong Zhang
- Department of Laboratory Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, China
| | - Wei Li
- BGI Genomics, BGI-Shenzhen, Shenzhen, China
| | | | - Meihua Tan
- BGI Genomics, BGI-Shenzhen, Shenzhen, China
| | - Si Zhou
- BGI Genomics, BGI-Shenzhen, Shenzhen, China
- Hebei Industrial Technology Research Institute of Genomics in Maternal & Child Health, Shijiazhuang BGI Genomics Co., Ltd., Shijiazhuang, China
- College of Life Sciences, University of Chinese Academy of Sciences, China
| | - Meihuan Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Yali Pan
- Department of Laboratory Medicine, Medical Technology and Engineering College of Fujian Medical University, Fuzhou, China
| | - Xuemei Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Xiaolan Chen
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Yunliang Liu
- Otolaryngological Department of Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Na Lin
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Hailong Huang
- Medical Genetic Diagnosis and Therapy Center of Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics and Gynecology and Pediatrics, Fujian Provincial Key Laboratory of Prenatal Diagnosis and Birth Defect, Fuzhou, China
| | - Hua Cao
- Medical Research Center, Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fuzhou, China
- NHC Key Laboratory of Technical Evaluation of Fertility Regulation for Non-human Primates, Fujian Maternity and Child Health Hospital, Fuzhou, China
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11
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Krey JF, Chatterjee P, Halford J, Cunningham CL, Perrin BJ, Barr-Gillespie PG. Control of stereocilia length during development of hair bundles. PLoS Biol 2023; 21:e3001964. [PMID: 37011103 PMCID: PMC10101650 DOI: 10.1371/journal.pbio.3001964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 04/13/2023] [Accepted: 03/14/2023] [Indexed: 04/05/2023] Open
Abstract
Assembly of the hair bundle, the sensory organelle of the inner ear, depends on differential growth of actin-based stereocilia. Separate rows of stereocilia, labeled 1 through 3 from tallest to shortest, lengthen or shorten during discrete time intervals during development. We used lattice structured illumination microscopy and surface rendering to measure dimensions of stereocilia from mouse apical inner hair cells during early postnatal development; these measurements revealed a sharp transition at postnatal day 8 between stage III (row 1 and 2 widening; row 2 shortening) and stage IV (final row 1 lengthening and widening). Tip proteins that determine row 1 lengthening did not accumulate simultaneously during stages III and IV; while the actin-bundling protein EPS8 peaked at the end of stage III, GNAI3 peaked several days later-in early stage IV-and GPSM2 peaked near the end of stage IV. To establish the contributions of key macromolecular assemblies to bundle structure, we examined mouse mutants that eliminated tip links (Cdh23v2J or Pcdh15av3J), transduction channels (TmieKO), or the row 1 tip complex (Myo15ash2). Cdh23v2J/v2J and Pcdh15av3J/av3J bundles had adjacent stereocilia in the same row that were not matched in length, revealing that a major role of these cadherins is to synchronize lengths of side-by-side stereocilia. Use of the tip-link mutants also allowed us to distinguish the role of transduction from effects of transduction proteins themselves. While levels of GNAI3 and GPSM2, which stimulate stereocilia elongation, were greatly attenuated at the tips of TmieKO/KO row 1 stereocilia, they accumulated normally in Cdh23v2J/v2J and Pcdh15av3J/av3J stereocilia. These results reinforced the suggestion that the transduction proteins themselves facilitate localization of proteins in the row 1 complex. By contrast, EPS8 concentrates at tips of all TmieKO/KO, Cdh23v2J/v2J, and Pcdh15av3J/av3J stereocilia, correlating with the less polarized distribution of stereocilia lengths in these bundles. These latter results indicated that in wild-type hair cells, the transduction complex prevents accumulation of EPS8 at the tips of shorter stereocilia, causing them to shrink (rows 2 and 3) or disappear (row 4 and microvilli). Reduced rhodamine-actin labeling at row 2 stereocilia tips of tip-link and transduction mutants suggests that transduction's role is to destabilize actin filaments there. These results suggest that regulation of stereocilia length occurs through EPS8 and that CDH23 and PCDH15 regulate stereocilia lengthening beyond their role in gating mechanotransduction channels.
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Affiliation(s)
- Jocelyn F. Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Paroma Chatterjee
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Julia Halford
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Christopher L. Cunningham
- Pittsburgh Hearing Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Benjamin J. Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, United States of America
| | - Peter G. Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
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12
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Sharkova M, Chow E, Erickson T, Hocking JC. The morphological and functional diversity of apical microvilli. J Anat 2023; 242:327-353. [PMID: 36281951 PMCID: PMC9919547 DOI: 10.1111/joa.13781] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 10/03/2022] [Accepted: 10/05/2022] [Indexed: 11/30/2022] Open
Abstract
Sensory neurons use specialized apical processes to perceive external stimuli and monitor internal body conditions. The apical apparatus can include cilia, microvilli, or both, and is adapted for the functions of the particular cell type. Photoreceptors detect light through a large, modified cilium (outer segment), that is supported by a surrounding ring of microvilli-like calyceal processes (CPs). Although first reported 150 years ago, CPs remain poorly understood. As a basis for future study, we therefore conducted a review of existing literature about sensory cell microvilli, which can act either as the primary sensory detector or as support for a cilia-based detector. While all microvilli are finger-like cellular protrusions with an actin core, the processes vary across cell types in size, number, arrangement, dynamics, and function. We summarize the current state of knowledge about CPs and the characteristics of the microvilli found on inner ear hair cells (stereocilia) and cerebral spinal fluid-contacting neurons, with comparisons to the brush border of the intestinal and renal epithelia. The structure, stability, and dynamics of the actin core are regulated by a complement of actin-binding proteins, which includes both common components and unique features when compared across cell types. Further, microvilli are often supported by lateral links, a glycocalyx, and a defined extracellular matrix, each adapted to the function and environment of the cell. Our comparison of microvillar features will inform further research into how CPs support photoreceptor function, and also provide a general basis for investigations into the structure and functions of apical microvilli found on sensory neurons.
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Affiliation(s)
- Maria Sharkova
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Erica Chow
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Timothy Erickson
- Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - Jennifer C Hocking
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.,Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
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13
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Rajan S, Kudryashov DS, Reisler E. Actin Bundles Dynamics and Architecture. Biomolecules 2023; 13:450. [PMID: 36979385 PMCID: PMC10046292 DOI: 10.3390/biom13030450] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/16/2023] [Accepted: 02/20/2023] [Indexed: 03/04/2023] Open
Abstract
Cells use the actin cytoskeleton for many of their functions, including their division, adhesion, mechanosensing, endo- and phagocytosis, migration, and invasion. Actin bundles are the main constituent of actin-rich structures involved in these processes. An ever-increasing number of proteins that crosslink actin into bundles or regulate their morphology is being identified in cells. With recent advances in high-resolution microscopy and imaging techniques, the complex process of bundles formation and the multiple forms of physiological bundles are beginning to be better understood. Here, we review the physiochemical and biological properties of four families of highly conserved and abundant actin-bundling proteins, namely, α-actinin, fimbrin/plastin, fascin, and espin. We describe the similarities and differences between these proteins, their role in the formation of physiological actin bundles, and their properties-both related and unrelated to their bundling abilities. We also review some aspects of the general mechanism of actin bundles formation, which are known from the available information on the activity of the key actin partners involved in this process.
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Affiliation(s)
- Sudeepa Rajan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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14
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Fitz GN, Weck ML, Bodnya C, Perkins OL, Tyska MJ. Protrusion growth driven by myosin-generated force. Dev Cell 2023; 58:18-33.e6. [PMID: 36626869 PMCID: PMC9940483 DOI: 10.1016/j.devcel.2022.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 10/10/2022] [Accepted: 11/29/2022] [Indexed: 01/11/2023]
Abstract
Actin-based protrusions extend from the surface of all eukaryotic cells, where they support diverse activities essential for life. Models of protrusion growth hypothesize that actin filament assembly exerts force for pushing the plasma membrane outward. However, membrane-associated myosin motors are also abundant in protrusions, although their potential for contributing, growth-promoting force remains unexplored. Using an inducible system that docks myosin motor domains to membrane-binding modules with temporal control, we found that application of myosin-generated force to the membrane is sufficient for driving robust protrusion elongation in human, mouse, and pig cell culture models. Protrusion growth scaled with motor accumulation, required barbed-end-directed force, and was independent of cargo delivery or recruitment of canonical elongation factors. Application of growth-promoting force was also supported by structurally distinct myosin motors and membrane-binding modules. Thus, myosin-generated force can drive protrusion growth, and this mechanism is likely active in diverse biological contexts.
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Affiliation(s)
- Gillian N Fitz
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Meredith L Weck
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Caroline Bodnya
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Olivia L Perkins
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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15
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Meenakshi S I, Rao M, Mayor S, Sowdhamini R. A census of actin-associated proteins in humans. Front Cell Dev Biol 2023; 11:1168050. [PMID: 37187613 PMCID: PMC10175787 DOI: 10.3389/fcell.2023.1168050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 03/31/2023] [Indexed: 05/17/2023] Open
Abstract
Actin filaments help in maintaining the cell structure and coordinating cellular movements and cargo transport within the cell. Actin participates in the interaction with several proteins and also with itself to form the helical filamentous actin (F-actin). Actin-binding proteins (ABPs) and actin-associated proteins (AAPs) coordinate the actin filament assembly and processing, regulate the flux between globular G-actin and F-actin in the cell, and help maintain the cellular structure and integrity. We have used protein-protein interaction data available through multiple sources (STRING, BioGRID, mentha, and a few others), functional annotation, and classical actin-binding domains to identify actin-binding and actin-associated proteins in the human proteome. Here, we report 2482 AAPs and present an analysis of their structural and sequential domains, functions, evolutionary conservation, cellular localization, abundance, and tissue-specific expression patterns. This analysis provides a base for the characterization of proteins involved in actin dynamics and turnover in the cell.
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Affiliation(s)
| | - Madan Rao
- National Centre for Biological Sciences, TIFR, Bangalore, India
| | - Satyajit Mayor
- National Centre for Biological Sciences, TIFR, Bangalore, India
| | - Ramanathan Sowdhamini
- National Centre for Biological Sciences, TIFR, Bangalore, India
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
- Institute of Bioinformatics and Applied Biotechnology, Bangalore, India
- *Correspondence: Ramanathan Sowdhamini,
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16
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Abstract
To fulfill the cytoskeleton’s diverse functions in cell mechanics and motility, actin networks with specialized architectures are built by cross-linking proteins. How these cross-linkers specify cytoskeletal network geometry is poorly understood at the level of protein structure. Here, we introduce a machine-learning–enabled pipeline for visualizing cross-linkers bridging cytoskeletal filaments with cryogenic electron microscopy (cryo-EM). We apply our method to T-plastin, a member of the evolutionarily conserved plastin/fimbrin family, revealing a sequence of conformational changes that enables T-plastin to bridge pairs of actin filaments in both parallel and antiparallel orientations. This provides a structural framework for understanding how plastins can generate actin networks featuring mixed filament polarity. To orchestrate cell mechanics, trafficking, and motility, cytoskeletal filaments must assemble into higher-order networks whose local subcellular architecture and composition specify their functions. Cross-linking proteins bridge filaments at the nanoscale to control a network’s μm-scale geometry, thereby conferring its mechanical properties and functional dynamics. While these interfilament linkages are key determinants of cytoskeletal function, their structural mechanisms remain poorly understood. Plastins/fimbrins are an evolutionarily ancient family of tandem calponin-homology domain (CHD) proteins required to construct multiple classes of actin networks, which feature diverse geometries specialized to power cytokinesis, microvilli and stereocilia biogenesis, and persistent cell migration. Here, we focus on the structural basis of actin network assembly by human T-plastin, a ubiquitously expressed isoform necessary for the maintenance of stable cellular protrusions generated by actin polymerization forces. By implementing a machine-learning–enabled cryo-electron microscopy pipeline for visualizing cross-linkers bridging multiple filaments, we uncover a sequential bundling mechanism enabling T-plastin to bridge pairs of actin filaments in both parallel and antiparallel orientations. T-plastin populates distinct structural landscapes in these two bridging orientations that are selectively compatible with actin networks featuring divergent architectures and functions. Our structural, biochemical, and cell biological data highlight inter-CHD linkers as key structural elements underlying flexible but stable cross-linking that are likely to be disrupted by T-plastin mutations that cause hereditary bone diseases.
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17
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Zhai X, Du H, Shen Y, Zhang X, Chen Z, Wang Y, Xu Z. FCHSD2 is required for stereocilia maintenance in mouse cochlear hair cells. J Cell Sci 2022; 135:jcs259912. [PMID: 35892293 DOI: 10.1242/jcs.259912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 07/15/2022] [Indexed: 11/20/2022] Open
Abstract
Stereocilia are F-actin-based protrusions on the apical surface of inner-ear hair cells and are indispensable for hearing and balance perception. The stereocilia of each hair cell are organized into rows of increasing heights, forming a staircase-like pattern. The development and maintenance of stereocilia are tightly regulated, and deficits in these processes lead to stereocilia disorganization and hearing loss. Previously, we showed that the F-BAR protein FCHSD2 is localized along the stereocilia of cochlear hair cells and cooperates with CDC42 to regulate F-actin polymerization and cell protrusion formation in cultured COS-7 cells. In the present work, Fchsd2 knockout mice were established to investigate the role of FCHSD2 in hearing. Our data show that stereocilia maintenance is severely affected in cochlear hair cells of Fchsd2 knockout mice, which leads to progressive hearing loss. Moreover, Fchsd2 knockout mice show increased acoustic vulnerability. Noise exposure causes robust stereocilia degeneration as well as enhanced hearing threshold elevation in Fchsd2 knockout mice. Lastly, Fchsd2/Cdc42 double knockout mice show more severe stereocilia deficits and hearing loss, suggesting that FCHSD2 and CDC42 cooperatively regulate stereocilia maintenance.
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Affiliation(s)
- Xiaoyan Zhai
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Haibo Du
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Yuxin Shen
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Xiujuan Zhang
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Zhengjun Chen
- State Key Laboratory of Cell Biology , Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences (CAS), Shanghai 200031, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China
| | - Yanfei Wang
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Zhigang Xu
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology and Key Laboratory for Experimental Teratology of the Ministry of Education , School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
- Shandong Provincial Collaborative Innovation Center of Cell Biology , Shandong Normal University, Jinan, Shandong 250014, China
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18
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Morales EA, Arnaiz C, Krystofiak ES, Zanic M, Tyska MJ. Mitotic Spindle Positioning (MISP) is an actin bundler that selectively stabilizes the rootlets of epithelial microvilli. Cell Rep 2022; 39:110692. [PMID: 35443169 PMCID: PMC9097542 DOI: 10.1016/j.celrep.2022.110692] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/20/2022] [Accepted: 03/24/2022] [Indexed: 11/11/2022] Open
Abstract
Microvilli are conserved actin-based surface protrusions that have been repurposed throughout evolution to fulfill diverse cell functions. In the case of transporting epithelia, microvilli are supported by a core of actin filaments bundled in parallel by villin, fimbrin, and espin. Remarkably, microvilli biogenesis persists in mice lacking all three of these factors, suggesting the existence of unknown bundlers. We identified Mitotic Spindle Positioning (MISP) as an actin-binding factor that localizes specifically to the rootlet end of the microvillus. MISP promotes rootlet elongation in cells, and purified MISP exhibits potent filament bundling activity in vitro. MISP-bundled filaments also recruit fimbrin, which further elongates and stabilizes bundles. MISP confinement to the rootlet is enforced by ezrin, which prevents decoration of the membrane-wrapped distal end of the core bundle. These discoveries reveal how epithelial cells optimize apical membrane surface area and offer insight on the remarkable robustness of microvilli biogenesis. Morales et al. identify Mitotic Spindle Positioning (MISP) as an actin bundler in the rootlets of epithelial microvilli. MISP cooperates with other bundlers, and its rootlet-specific localization is enforced by membrane-actin linker ezrin. These findings illuminate mechanisms that drive the assembly and compartmentalization of actin bundle-supported protrusions.
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Affiliation(s)
- E Angelo Morales
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Cayetana Arnaiz
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Evan S Krystofiak
- Cell Imaging Shared Resource, Vanderbilt University, Nashville, TN 37232, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA.
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19
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Kim GS, Wang T, Sayyid ZN, Fuhriman J, Jones SM, Cheng AG. Repair of surviving hair cells in the damaged mouse utricle. Proc Natl Acad Sci U S A 2022; 119:e2116973119. [PMID: 35380897 PMCID: PMC9169652 DOI: 10.1073/pnas.2116973119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/21/2022] [Indexed: 11/18/2022] Open
Abstract
Sensory hair cells (HCs) in the utricle are mechanoreceptors required to detect linear acceleration. After damage, the mammalian utricle partially restores the HC population and organ function, although regenerated HCs are primarily type II and immature. Whether native, surviving HCs can repair and contribute to this recovery is unclear. Here, we generated the Pou4f3DTR/+; Atoh1CreERTM/+; Rosa26RtdTomato/+ mouse to fate map HCs prior to ablation. After HC ablation, vestibular evoked potentials were abolished in all animals, with ∼57% later recovering responses. Relative to nonrecovery mice, recovery animals harbored more Atoh1-tdTomato+ surviving HCs. In both groups, surviving HCs displayed markers of both type I and type II subtypes and afferent synapses, despite distorted lamination and morphology. Surviving type II HCs remained innervated in both groups, whereas surviving type I HCs first lacked and later regained calyces in the recovery, but not the nonrecovery, group. Finally, surviving HCs initially displayed immature and subsequently mature-appearing bundles in the recovery group. These results demonstrate that surviving HCs are capable of self-repair and may contribute to the recovery of vestibular function.
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Affiliation(s)
- Grace S. Kim
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Tian Wang
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Zahra N. Sayyid
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Jessica Fuhriman
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
| | - Sherri M. Jones
- Department of Special Education and Communication Disorders, College of Education and Human Sciences, University of Nebraska, Lincoln, NE 68583
| | - Alan G. Cheng
- Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305
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20
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Krey JF, Liu C, Belyantseva IA, Bateschell M, Dumont RA, Goldsmith J, Chatterjee P, Morrill RS, Fedorov LM, Foster S, Kim J, Nuttall AL, Jones SM, Choi D, Friedman TB, Ricci AJ, Zhao B, Barr-Gillespie PG. ANKRD24 organizes TRIOBP to reinforce stereocilia insertion points. J Cell Biol 2022; 221:e202109134. [PMID: 35175278 PMCID: PMC8859912 DOI: 10.1083/jcb.202109134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 01/07/2022] [Accepted: 01/21/2022] [Indexed: 01/04/2023] Open
Abstract
The stereocilia rootlet is a key structure in vertebrate hair cells, anchoring stereocilia firmly into the cell's cuticular plate and protecting them from overstimulation. Using superresolution microscopy, we show that the ankyrin-repeat protein ANKRD24 concentrates at the stereocilia insertion point, forming a ring at the junction between the lower and upper rootlets. Annular ANKRD24 continues into the lower rootlet, where it surrounds and binds TRIOBP-5, which itself bundles rootlet F-actin. TRIOBP-5 is mislocalized in Ankrd24KO/KO hair cells, and ANKRD24 no longer localizes with rootlets in mice lacking TRIOBP-5; exogenous DsRed-TRIOBP-5 restores endogenous ANKRD24 to rootlets in these mice. Ankrd24KO/KO mice show progressive hearing loss and diminished recovery of auditory function after noise damage, as well as increased susceptibility to overstimulation of the hair bundle. We propose that ANKRD24 bridges the apical plasma membrane with the lower rootlet, maintaining a normal distribution of TRIOBP-5. Together with TRIOBP-5, ANKRD24 organizes rootlets to enable hearing with long-term resilience.
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Affiliation(s)
- Jocelyn F. Krey
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Chang Liu
- Department of Otolaryngology—Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN
| | - Inna A. Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD
| | - Michael Bateschell
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Rachel A. Dumont
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Jennifer Goldsmith
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Paroma Chatterjee
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Rachel S. Morrill
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Lev M. Fedorov
- Transgenic Mouse Models, University Shared Resources Program, Oregon Health & Science University, Portland, OR
| | - Sarah Foster
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
| | - Jinkyung Kim
- Department of Otolaryngology—Head & Neck Surgery, Stanford University, Stanford, CA
| | - Alfred L. Nuttall
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
| | - Sherri M. Jones
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln, Lincoln, NE
| | - Dongseok Choi
- OHSU-PSU School of Public Health, Oregon Health & Science University, Portland, OR
| | - Thomas B. Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD
| | - Anthony J. Ricci
- Department of Otolaryngology—Head & Neck Surgery, Stanford University, Stanford, CA
| | - Bo Zhao
- Department of Otolaryngology—Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN
| | - Peter G. Barr-Gillespie
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR
- Vollum Institute, Oregon Health & Science University, Portland, OR
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21
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Miyoshi T, Belyantseva IA, Kitajiri SI, Miyajima H, Nishio SY, Usami SI, Kim BJ, Choi BY, Omori K, Shroff H, Friedman TB. Human deafness-associated variants alter the dynamics of key molecules in hair cell stereocilia F-actin cores. Hum Genet 2022; 141:363-382. [PMID: 34232383 PMCID: PMC11351816 DOI: 10.1007/s00439-021-02304-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 06/15/2021] [Indexed: 12/16/2022]
Abstract
Stereocilia protrude up to 100 µm from the apical surface of vertebrate inner ear hair cells and are packed with cross-linked filamentous actin (F-actin). They function as mechanical switches to convert sound vibration into electrochemical neuronal signals transmitted to the brain. Several genes encode molecular components of stereocilia including actin monomers, actin regulatory and bundling proteins, motor proteins and the proteins of the mechanotransduction complex. A stereocilium F-actin core is a dynamic system, which is continuously being remodeled while maintaining an outwardly stable architecture under the regulation of F-actin barbed-end cappers, severing proteins and crosslinkers. The F-actin cores of stereocilia also provide a pathway for motor proteins to transport cargos including components of tip-link densities, scaffolding proteins and actin regulatory proteins. Deficiencies and mutations of stereocilia components that disturb this "dynamic equilibrium" in stereocilia can induce morphological changes and disrupt mechanotransduction causing sensorineural hearing loss, best studied in mouse and zebrafish models. Currently, at least 23 genes, associated with human syndromic and nonsyndromic hearing loss, encode proteins involved in the development and maintenance of stereocilia F-actin cores. However, it is challenging to predict how variants associated with sensorineural hearing loss segregating in families affect protein function. Here, we review the functions of several molecular components of stereocilia F-actin cores and provide new data from our experimental approach to directly evaluate the pathogenicity and functional impact of reported and novel variants of DIAPH1 in autosomal-dominant DFNA1 hearing loss using single-molecule fluorescence microscopy.
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA.
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
| | - Inna A Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA
| | - Shin-Ichiro Kitajiri
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Hiroki Miyajima
- Department of Otolaryngology, Shinshu University School of Medicine, Matsumoto, 390-8621, Japan
- Department of Otolaryngology, Aizawa Hospital, Matsumoto, 390-8510, Japan
| | - Shin-Ya Nishio
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Shin-Ichi Usami
- Department of Hearing Implant Sciences, Shinshu University School of Medicine, 390-8621, Matsumoto, Japan
| | - Bong Jik Kim
- Department of Otolaryngology-Head and Neck Surgery, Chungnam National University College of Medicine, Chungnam National University Sejong Hospital, Sejong, 30099, South Korea
- Brain Research Institute, Chungnam National University College of Medicine, Daejeon, 35015, South Korea
| | - Byung Yoon Choi
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, 13620, South Korea
| | - Koichi Omori
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Hari Shroff
- Laboratory of High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD, 20892, USA
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22
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Zheng L, Adam SA, García‐Anoveros J, Mitchell BJ, Bartles JR. Espin overexpression causes stereocilia defects and provides an anti-capping effect on actin polymerization. Cytoskeleton (Hoboken) 2022; 79:64-74. [PMID: 35844198 PMCID: PMC9796729 DOI: 10.1002/cm.21719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/01/2022] [Accepted: 07/12/2022] [Indexed: 01/30/2023]
Abstract
Stereocilia are actin-based projections of hair cells that are arranged in a step like array, in rows of increasing height, and that constitute the mechanosensory organelle used for the senses of hearing and balance. In order to function properly, stereocilia must attain precise sizes in different hair cell types and must coordinately form distinct rows with varying lengths. Espins are actin-bundling proteins that have a well-characterized role in stereocilia formation; loss of function mutations in Espin result in shorter stereocilia and deafness in the jerker mouse. Here we describe the generation of an Espin overexpressing transgenic mouse line that results in longer first row stereocilia and discoordination of second-row stereocilia length. Furthermore, Espin overexpression results in the misregulation of other stereocilia factors including GNAI3, GPSM2, EPS8, WHRN, and MYO15A, revealing that GNAI3 and GPSM2 are dispensable for stereocilia overgrowth. Finally, using an in vitro actin polymerization assay we show that espin provides an anti-capping function that requires both the G-actin binding WH2 domain as well as either the C-terminal F-actin binding domain or the internal xAB actin-binding domain. Our results provide a novel function for Espins at the barbed ends of actin filaments distinct from its previous known function of actin bundling that may account for their effects on stereocilia growth.
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Affiliation(s)
- Lili Zheng
- Department of Cell and Developmental BiologyNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA
| | - Stephen A. Adam
- Department of Cell and Developmental BiologyNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA
| | - Jaime García‐Anoveros
- Department of Anesthesiology Neurology and NeuroscienceNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA,Hugh Knowles Center for Clinical and Basic Science in Hearing and its DisordersNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA
| | - Brian J. Mitchell
- Department of Cell and Developmental BiologyNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA
| | - James R. Bartles
- Department of Cell and Developmental BiologyNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA,Hugh Knowles Center for Clinical and Basic Science in Hearing and its DisordersNorthwestern University, Feinberg School of MedicineChicagoIllinoisUSA
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23
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Miyoshi T, Friedman TB, Watanabe N. Fast-dissociating but highly specific antibodies are novel tools in biology, especially useful for multiplex super-resolution microscopy. STAR Protoc 2021; 2:100967. [PMID: 34841279 PMCID: PMC8605432 DOI: 10.1016/j.xpro.2021.100967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Fast-dissociating, highly specific monoclonal antibodies (FDSAs) are single-molecule imaging probes useful for many biological assays including consecutive, multiplexable super-resolution microscopy. We developed a screening assay to characterize the kinetics of antibody-antigen interactions using single-molecule microscopy and established a pipeline to identify FDSAs from thousands of monoclonal candidates. Provided here are detailed protocols to prepare multi-well glass-bottom plates necessary for our assay to identify hybridoma clones secreting FDSAs. Synthesis of fluorescently labeled Fab fragments (Fab probes) from FDSAs is also described. For complete details on the use and execution of this protocol, please refer to Miyoshi et al. (2021).
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Single-Molecule Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
- Department of Pharmacology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD 20892, USA
- Department of Otolaryngology - Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Thomas B. Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, Room 1F-143A, Bethesda, MD 20892, USA
| | - Naoki Watanabe
- Laboratory of Single-Molecule Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
- Department of Pharmacology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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24
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Pacentine IV, Barr-Gillespie PG. Cy3-ATP labeling of unfixed, permeabilized mouse hair cells. Sci Rep 2021; 11:23855. [PMID: 34903829 PMCID: PMC8668996 DOI: 10.1038/s41598-021-03365-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 12/01/2021] [Indexed: 12/02/2022] Open
Abstract
ATP-utilizing enzymes play key roles in hair bundles, the mechanically sensitive organelles of sensory hair cells in the inner ear. We used a fluorescent ATP analog, EDA-ATP-Cy3 (Cy3-ATP), to label ATP-binding proteins in two different preparations of unfixed hair-cell stereocilia of the mouse. In the first preparation, we lightly permeabilized dissected cochleas, then labeled them with Cy3-ATP. Hair cells and their stereocilia remained intact, and stereocilia tips in rows 1 and 2 were labeled particularly strongly with Cy3-ATP. In many cases, vanadate (Vi) traps nucleotides at the active site of myosin isoforms and presents nucleotide dissociation. Co-application with Vi enhanced the tip labeling, which is consistent with myosin isoforms being responsible. By contrast, the actin polymerization inhibitors latrunculin A and cytochalasin D had no effect, suggesting that actin turnover at stereocilia tips was not involved. Cy3-ATP labeling was substantially reduced—but did not disappear altogether—in mutant cochleas lacking MYO15A; by contrast, labeling remained robust in cochleas lacking MYO7A. In the second preparation, used to quantify Cy3-ATP labeling, we labeled vestibular stereocilia that had been adsorbed to glass, which demonstrated that tip labeling was higher in longer stereocilia. We found that tip signal was reduced by ~ 50% in Myo15ash2/sh2 stereocilia as compared to Myo15ash2/+stereocilia. These results suggest that MYO15A accounts for a substantial fraction of the Cy3-ATP tip labeling in vestibular hair cells, and so this novel preparation could be utilized to examine the control of MYO15A ATPase activity in situ.
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Affiliation(s)
- Itallia V Pacentine
- Oregon Hearing Research Center & Vollum Institute, Mail Code L335A, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center & Vollum Institute, Mail Code L335A, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.
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25
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Sayyid ZN, Wang T, Chen L, Jones SM, Cheng AG. Atoh1 Directs Regeneration and Functional Recovery of the Mature Mouse Vestibular System. Cell Rep 2020; 28:312-324.e4. [PMID: 31291569 PMCID: PMC6659123 DOI: 10.1016/j.celrep.2019.06.028] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 02/13/2019] [Accepted: 06/06/2019] [Indexed: 12/02/2022] Open
Abstract
Utricular hair cells (HCs) are mechanoreceptors required for vestibular function. After damage, regeneration of mammalian utricular HCs is limited and regenerated HCs appear immature. Thus, loss of vestibular function is presumed irreversible. Here, we found partial HC replacement and functional recovery in the mature mouse utricle, both enhanced by overexpressing the transcription factor Atoh1. Following damage, long-term fate mapping revealed that support cells non-mitotically and modestly regenerated HCs displaying no or immature bundles. By contrast, Atoh1 overexpression stimulated proliferation and widespread regeneration of HCs exhibiting elongated bundles, patent mechanotransduction channels, and synaptic connections. Finally, although damage without Atoh1 overexpression failed to initiate or sustain a spontaneous functional recovery, Atoh1 overexpression significantly enhanced both the degree and percentage of animals exhibiting sustained functional recovery. Therefore, the mature, damaged utricle has an Atoh1-responsive regenerative program leading to functional recovery, underscoring the potential of a reprogramming approach to sensory regeneration. The mature mouse utricle, which detects linear acceleration, displays limited regeneration, but whether function returns is unknown. Sayyid et al. show that regenerated hair cells appear and mature over months, resulting in a limited, unsustained functional recovery. Atoh1 overexpression enhances regeneration and leads to a sustained recovery of vestibular function.
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Affiliation(s)
- Zahra N Sayyid
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Tian Wang
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Leon Chen
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sherri M Jones
- Department of Special Education and Communication Disorders, College of Education and Human Sciences, University of Nebraska, Lincoln, NE 68583, USA
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
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26
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Chen YS, Kang XR, Zhou ZH, Yang J, Xin Q, Ying CT, Zhang YP, Tao J. MiR-1908/EXO1 and MiR-203a/FOS, regulated by scd1, are associated with fracture risk and bone health in postmenopausal diabetic women. Aging (Albany NY) 2020; 12:9549-9584. [PMID: 32454462 PMCID: PMC7288911 DOI: 10.18632/aging.103227] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 04/13/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Stearoyl-coenzyme A desaturase-1 (SCD1) can inhibit the development of diabetic bone disease by promoting osteogenesis. In this study, we examined whether this regulation by SCD1 is achieved by regulating the expression of related miRNAs. METHODS SCD1 expression levels were observed in human bone-marrow mesenchymal stem cells (BM-MSCs) of patients with type 2 diabetes mellitus (T2DM), and the effect of SCD1 on osteogenesis was observed in human adipose-derived MSCs transfected with the SCD1 lentiviral system. We designed a bioinformatics prediction model to select important differentially expressed miRNAs, and established protein-protein interaction and miRNA-mRNA networks. miRNAs and mRNAs were extracted and their differential expression was detected. The SCD1-miRNA-mRNA network was validated. FINDINGS SCD1 expression in bone marrow was downregulated in patients with T2DM and low-energy fracture, and SCD1 expression promotes BM-MSC osteogenic differentiation. The predictors in the nomogram were seven microRNAs, including hsa-miR-1908 and hsa-miR-203a. SCD1 inhibited the expression of CDKN1A and FOS, but promoted the expression of EXO1 and PLS1. miR-1908 was a regulator of EXO1 expression, and miR-203a was a regulator of FOS expression. INTERPRETATION The regulation of BM-MSCs by SCD1 is a necessary condition for osteogenesis through the miR-203a/FOS and miR-1908/EXO1 regulatory pathways.
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Affiliation(s)
- Yi-sheng Chen
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Xue-ran Kang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China
| | - Zi-hui Zhou
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Jiang Yang
- Department of Neurosurgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Qi Xin
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Chen-ting Ying
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Yun-peng Zhang
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
| | - Jie Tao
- Department of Orthopedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
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27
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Song J, Patterson R, Metlagel Z, Krey JF, Hao S, Wang L, Ng B, Sazzed S, Kovacs J, Wriggers W, He J, Barr-Gillespie PG, Auer M. A cryo-tomography-based volumetric model of the actin core of mouse vestibular hair cell stereocilia lacking plastin 1. J Struct Biol 2020; 210:107461. [PMID: 31962158 PMCID: PMC7067663 DOI: 10.1016/j.jsb.2020.107461] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/11/2020] [Accepted: 01/14/2020] [Indexed: 12/11/2022]
Abstract
Electron cryo-tomography allows for high-resolution imaging of stereocilia in their native state. Because their actin filaments have a higher degree of order, we imaged stereocilia from mice lacking the actin crosslinker plastin 1 (PLS1). We found that while stereocilia actin filaments run 13 nm apart in parallel for long distances, there were gaps of significant size that were stochastically distributed throughout the actin core. Actin crosslinkers were distributed through the stereocilium, but did not occupy all possible binding sites. At stereocilia tips, protein density extended beyond actin filaments, especially on the side of the tip where a tip link is expected to anchor. Along the shaft, repeating density was observed that corresponds to actin-to-membrane connectors. In the taper region, most actin filaments terminated near the plasma membrane. The remaining filaments twisted together to make a tighter bundle than was present in the shaft region; the spacing between them decreased from 13 nm to 9 nm, and the apparent filament diameter decreased from 6.4 to 4.8 nm. Our models illustrate detailed features of distinct structural domains that are present within the stereocilium.
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Affiliation(s)
- Junha Song
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Roma Patterson
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Zoltan Metlagel
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jocelyn F Krey
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Samantha Hao
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Linshanshan Wang
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Brian Ng
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Salim Sazzed
- Department of Computer Science, Old Dominion University, Norfolk, VA, USA
| | - Julio Kovacs
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA, USA
| | - Willy Wriggers
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA, USA
| | - Jing He
- Department of Computer Science, Old Dominion University, Norfolk, VA, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
| | - Manfred Auer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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28
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Myosin-XVa Controls Both Staircase Architecture and Diameter Gradation of Stereocilia Rows in the Auditory Hair Cell Bundles. J Assoc Res Otolaryngol 2020; 21:121-135. [PMID: 32152769 DOI: 10.1007/s10162-020-00745-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 02/04/2020] [Indexed: 02/08/2023] Open
Abstract
Mammalian hair cells develop their mechanosensory bundles through consecutive phases of stereocilia elongation, thickening, and retraction of supernumerary stereocilia. Many molecules involved in stereocilia elongation have been identified, including myosin-XVa. Significantly less is known about molecular mechanisms of stereocilia thickening and retraction. Here, we used scanning electron microscopy (SEM) to quantify postnatal changes in number and diameters of the auditory hair cell stereocilia in shaker-2 mice (Myo15sh2) that lack both "long" and "short" isoforms of myosin-XVa, and in mice lacking only the "long" myosin-XVa isoform (Myo15∆N). Previously, we observed large mechanotransduction current in young postnatal inner (IHC) and outer (OHC) hair cells of both these strains. Stereocilia counts showed nearly identical developmental retraction of supernumerary stereocilia in control heterozygous, Myo15sh2/sh2, and Myo15∆N/∆N mice, suggesting that this retraction is largely unaffected by myosin-XVa deficiency. However, myosin-XVa deficiency does affect stereocilia diameters. In control, the first (tallest) and second row stereocilia grow in diameter simultaneously. However, the third row stereocilia in IHCs grow only until postnatal day 1-2 and then become thinner. In OHCs, they also grow slower than taller stereocilia, forming a stereocilia diameter gradation within a hair bundle. The sh2 mutation disrupts this gradation and makes all stereocilia nearly identical in thickness in both IHCs and OHCs, with only subtle residual diameter differences. All Myo15sh2/sh2 stereocilia grow postnatally including the third row, which is not a part of normal development. Serial sections with focused ion beam (FIB)-SEM confirmed that diameter changes of Myo15sh2/sh2 IHC and OHC stereocilia resulted from corresponding changes of their actin cores. In contrast to Myo15sh2/sh2, Myo15∆N/∆N hair cells develop prominent stereocilia diameter gradation. Thus, besides building the staircase, the short isoform of myosin-XVa is essential for controlling the diameter of the third row stereocilia and formation of the stereocilia diameter gradation in a hair bundle.
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29
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Zhu Y, Scheibinger M, Ellwanger DC, Krey JF, Choi D, Kelly RT, Heller S, Barr-Gillespie PG. Single-cell proteomics reveals changes in expression during hair-cell development. eLife 2019; 8:50777. [PMID: 31682227 PMCID: PMC6855842 DOI: 10.7554/elife.50777] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 11/01/2019] [Indexed: 12/12/2022] Open
Abstract
Hearing and balance rely on small sensory hair cells that reside in the inner ear. To explore dynamic changes in the abundant proteins present in differentiating hair cells, we used nanoliter-scale shotgun mass spectrometry of single cells, each ~1 picoliter, from utricles of embryonic day 15 chickens. We identified unique constellations of proteins or protein groups from presumptive hair cells and from progenitor cells. The single-cell proteomes enabled the de novo reconstruction of a developmental trajectory using protein expression levels, revealing proteins that greatly increased in expression during differentiation of hair cells (e.g., OCM, CRABP1, GPX2, AK1, GSTO1) and those that decreased during differentiation (e.g., TMSB4X, AGR3). Complementary single-cell transcriptome profiling showed corresponding changes in mRNA during maturation of hair cells. Single-cell proteomics data thus can be mined to reveal features of cellular development that may be missed with transcriptomics.
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Affiliation(s)
- Ying Zhu
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, United States
| | - Mirko Scheibinger
- Department of Otolaryngology Head and Neck Surgery, Stanford University, Stanford, United States
| | - Daniel Christian Ellwanger
- Department of Otolaryngology Head and Neck Surgery, Stanford University, Stanford, United States.,Genome Analysis Unit, Amgen Research, Amgen Inc, South San Francisco, United States
| | - Jocelyn F Krey
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, United States.,Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Dongseok Choi
- OHSU-PSU School of Public Health, Oregon Health & Science University, Portland, United States.,Graduate School of Dentistry, Kyung Hee University, Seoul, Republic of Korea
| | - Ryan T Kelly
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, United States.,Department of Chemistry and Biochemistry, Brigham Young University, Provo, United States
| | - Stefan Heller
- Department of Otolaryngology Head and Neck Surgery, Stanford University, Stanford, United States
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, United States.,Vollum Institute, Oregon Health & Science University, Portland, United States
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30
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Diaz-Horta O, Bademci G, Tokgoz-Yilmaz S, Guo S, Zafeer F, Sineni CJ, Duman D, Farooq A, Tekin M. Novel variant p.E269K confirms causative role of PLS1 mutations in autosomal dominant hearing loss. Clin Genet 2019; 96:575-578. [PMID: 31432506 DOI: 10.1111/cge.13626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 08/17/2019] [Indexed: 12/30/2022]
Abstract
Auditory reception relies on the perception of mechanical stimuli by stereocilia and its conversion to electrochemical signal. Mechanosensory stereocilia are abundant in actin, which provides them with structural conformity necessary for perception of auditory stimuli. Out of three major classes of actin-bundling proteins, plastin 1 encoded by PLS1, is highly expressed in stereocilia and is necessary for their regular maintenance. A missense PLS1 variant associated with autosomal dominant hearing loss (HL) in a small family has recently been reported. Here, we present another PLS1 missense variant, c.805G > A (p.E269K), in a Turkish family with autosomal dominant non-syndromic HL confirming the causative role of PLS1 mutations in HL. We propose that HL due to the p.E269K variant is from the loss of a stable PLS1-ACTB interaction.
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Affiliation(s)
- Oscar Diaz-Horta
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida
| | - Guney Bademci
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida
| | - Suna Tokgoz-Yilmaz
- Diagnosis-Rehabilitation Center of Hearing, Balance and Speech-Language Disorders, Ankara University School of Medicine, Ankara, Turkey.,Department of Audiology, Ankara University Health Sciences Faculty, Ankara, Turkey
| | - Shengru Guo
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida
| | - Faraz Zafeer
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida
| | - Claire J Sineni
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida
| | - Duygu Duman
- Department of Audiology, Ankara University Health Sciences Faculty, Ankara, Turkey
| | - Amjad Farooq
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida
| | - Mustafa Tekin
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida.,Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, Florida.,Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, Florida
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32
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Metlagel Z, Krey JF, Song J, Swift MF, Tivol WJ, Dumont RA, Thai J, Chang A, Seifikar H, Volkmann N, Hanein D, Barr-Gillespie PG, Auer M. Electron cryo-tomography of vestibular hair-cell stereocilia. J Struct Biol 2019; 206:149-155. [PMID: 30822456 DOI: 10.1016/j.jsb.2019.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 02/13/2019] [Accepted: 02/17/2019] [Indexed: 11/24/2022]
Abstract
High-resolution imaging of hair-cell stereocilia of the inner ear has contributed substantially to our understanding of auditory and vestibular function. To provide three-dimensional views of the structure of stereocilia cytoskeleton and membranes, we developed a method for rapidly freezing unfixed stereocilia on electron microscopy grids, which allowed subsequent 3D imaging by electron cryo-tomography. Structures of stereocilia tips, shafts, and tapers were revealed, demonstrating that the actin paracrystal was not perfectly ordered. This sample-preparation and imaging procedure will allow for examination of structural features of stereocilia in a near-native state.
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Affiliation(s)
- Zoltan Metlagel
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jocelyn F Krey
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Junha Song
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Mark F Swift
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - William J Tivol
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Rachel A Dumont
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Jasmine Thai
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Alex Chang
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Helia Seifikar
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Niels Volkmann
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - Dorit Hanein
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Manfred Auer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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Krey JF, Barr-Gillespie PG. Molecular Composition of Vestibular Hair Bundles. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033209. [PMID: 29844221 DOI: 10.1101/cshperspect.a033209] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The vertebrate hair bundle, responsible for transduction of mechanical signals into receptor potentials in sensory hair cells, is an evolutionary masterpiece. Composed of actin-filled stereocilia of precisely regulated length, width, and number, the structure of the hair bundle is optimized for sensing auditory and vestibular stimuli. Recent developments in identifying the lipids and proteins constituting the hair bundle, obtained through genetics, biochemistry, and imaging, now permit a description of the consensus composition of vestibular bundles of mouse, rat, and chick.
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Affiliation(s)
- Jocelyn F Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
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34
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Vélez-Ortega AC, Frolenkov GI. Building and repairing the stereocilia cytoskeleton in mammalian auditory hair cells. Hear Res 2019; 376:47-57. [PMID: 30638948 DOI: 10.1016/j.heares.2018.12.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/19/2018] [Accepted: 12/28/2018] [Indexed: 10/27/2022]
Abstract
Despite all recent achievements in identification of the molecules that are essential for the structure and mechanosensory function of stereocilia bundles in the auditory hair cells of mammalian species, we still have only a rudimentary understanding of the mechanisms of stereocilia formation, maintenance, and repair. Important molecular differences distinguishing mammalian auditory hair cells from hair cells of other types and species have been recently revealed. In addition, we are beginning to solve the puzzle of the apparent life-long stability of the stereocilia bundles in these cells. New data link the stability of the cytoskeleton in the mammalian auditory stereocilia with the normal activity of mechanotransduction channels. These data suggest new ideas on how a terminally-differentiated non-regenerating hair cell in the mammalian cochlea may repair and tune its stereocilia bundle throughout the life span of the organism.
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
| | - Gregory I Frolenkov
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
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35
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Khassan O, Jensen KV, Woodman AG, Vogel HJ, Ishida H. Characterization of the EF-Hand Calcium-Binding Domains of Human Plastins. Methods Mol Biol 2019; 1929:245-260. [PMID: 30710278 DOI: 10.1007/978-1-4939-9030-6_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The three human plastins (L-plastin, T-plastin, and I-plastin) are important regulatory Ca2+-binding proteins that belong to the family of actin-binding proteins. Plastins are involved in the regulation of the actin cytoskeleton as well as the cross-linking of actin filaments. In addition to four calponin-homology (CH) domains, all three plastins contain two N-terminal EF-hand Ca2+-binding motifs which together are homologous to a single lobe of the well-known calcium-regulatory protein calmodulin. This part of the protein allows for the regulation of the actin bundling activity in response to elevated calcium levels. In this protocol, we describe the purification of the EF-hand headpiece domains of all three plastins, as well as SPR studies, ITC studies, and NMR interaction studies with different peptides and calcium. In combination, these three experimental techniques provide detailed insights into a novel regulatory mechanism, involving the linker region between the EF-hand domain and the first CH domain of the plastins.
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Affiliation(s)
- Oleg Khassan
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Katharine V Jensen
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Andrew G Woodman
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Hans J Vogel
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.
| | - Hiroaki Ishida
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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36
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Pinette JA, Mao S, Millis BA, Krystofiak ES, Faust JJ, Tyska MJ. Brush border protocadherin CDHR2 promotes the elongation and maximized packing of microvilli in vivo. Mol Biol Cell 2018; 30:108-118. [PMID: 30403560 PMCID: PMC6337912 DOI: 10.1091/mbc.e18-09-0558] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Transporting epithelial cells optimize their morphology for solute uptake by building an apical specialization: a dense array of microvilli that serves to increase membrane surface area. In the intestinal tract, individual cells build thousands of microvilli, which pack tightly to form the brush border. Recent studies implicate adhesion molecule CDHR2 in the regulation of microvillar packing via the formation of adhesion complexes between the tips of adjacent protrusions. To gain insight on how CDHR2 contributes to brush border morphogenesis and enterocyte function under native in vivo conditions, we generated mice lacking CDHR2 expression in the intestinal tract. Although CDHR2 knockout (KO) mice are viable, body weight trends lower and careful examination of tissue, cell, and brush border morphology revealed several perturbations that likely contribute to reduced functional capacity of KO intestine. In the absence of CDHR2, microvilli are significantly shorter, and exhibit disordered packing and a 30% decrease in packing density. These structural perturbations are linked to decreased levels of key solute processing and transporting factors in the brush border. Thus, CDHR2 functions to elongate microvilli and maximize their numbers on the apical surface, which together serve to increase the functional capacity of enterocyte.
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Affiliation(s)
- Julia A Pinette
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Suli Mao
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Bryan A Millis
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Evan S Krystofiak
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - James J Faust
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
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37
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Pelaseyed T, Bretscher A. Regulation of actin-based apical structures on epithelial cells. J Cell Sci 2018; 131:131/20/jcs221853. [PMID: 30333133 DOI: 10.1242/jcs.221853] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Cells of transporting epithelia are characterized by the presence of abundant F-actin-based microvilli on their apical surfaces. Likewise, auditory hair cells have highly reproducible rows of apical stereocilia (giant microvilli) that convert mechanical sound into an electrical signal. Analysis of mutations in deaf patients has highlighted the critical components of tip links between stereocilia, and related structures that contribute to the organization of microvilli on epithelial cells have been found. Ezrin/radixin/moesin (ERM) proteins, which are activated by phosphorylation, provide a critical link between the plasma membrane and underlying actin cytoskeleton in surface structures. Here, we outline recent insights into how microvilli and stereocilia are built, and the roles of tip links. Furthermore, we highlight how ezrin is locally regulated by phosphorylation, and that this is necessary to maintain polarity. Localized phosphorylation is achieved through an intricate coincidence detection mechanism that requires the membrane lipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and the apically localized ezrin kinase, lymphocyte-oriented kinase (LOK, also known as STK10) or Ste20-like kinase (SLK). We also discuss how ezrin-binding scaffolding proteins regulate microvilli and how, despite these significant advances, it remains to be discovered how the cell polarity program ultimately interfaces with these processes.
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Affiliation(s)
- Thaher Pelaseyed
- Institute of Biomedicine, Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Anthony Bretscher
- Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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38
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Postema MM, Grega-Larson NE, Neininger AC, Tyska MJ. IRTKS (BAIAP2L1) Elongates Epithelial Microvilli Using EPS8-Dependent and Independent Mechanisms. Curr Biol 2018; 28:2876-2888.e4. [PMID: 30197089 DOI: 10.1016/j.cub.2018.07.022] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 06/05/2018] [Accepted: 07/09/2018] [Indexed: 11/24/2022]
Abstract
Transporting epithelial cells like those that line the gut build large arrays of actin-supported protrusions called microvilli, which extend from the apical surface into luminal spaces to increase functional surface area. Although critical for maintaining physiological homeostasis, mechanisms controlling the formation of microvilli remain poorly understood. Here, we report that the inverse-bin-amphiphysin-Rvs (I-BAR)-domain-containing protein insulin receptor tyrosine kinase substrate (IRTKS) (also known as BAIAP2L1) promotes the growth of epithelial microvilli. Super-resolution microscopy and live imaging of differentiating epithelial cells revealed that IRTKS localizes to the distal tips of actively growing microvilli via a mechanism that requires its N-terminal I-BAR domain. At microvillar tips, IRTKS promotes elongation through a mechanism involving its C-terminal actin-binding WH2 domain. IRTKS can also drive microvillar elongation using its SH3 domain to recruit the bundling protein EPS8 to microvillar tips. These results provide new insight on mechanisms that control microvillar growth during the differentiation of transporting epithelial cells and help explain why IRTKS is targeted by enteric pathogens that disrupt microvillar structure during infection of the intestinal epithelium.
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Affiliation(s)
- Meagan M Postema
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Nathan E Grega-Larson
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Abigail C Neininger
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA.
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39
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Roy P, Perrin BJ. The stable actin core of mechanosensory stereocilia features continuous turnover of actin cross-linkers. Mol Biol Cell 2018; 29:1856-1865. [PMID: 29874122 PMCID: PMC6085822 DOI: 10.1091/mbc.e18-03-0196] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Stereocilia are mechanosensitive protrusions on the surfaces of sensory hair cells in the inner ear that detect sound, gravity, and head movement. Their cores are composed of parallel actin filaments that are cross-linked and stabilized by several actin-binding proteins, including fascin-2, plastin-1, espin, and XIRP2. The actin filaments are the most stable known, with actin turnover primarily occurring at the stereocilia tips. While stereocilia actin dynamics has been well studied, little is known about the behavior of the actin cross-linking proteins, which are the most abundant type of protein in stereocilia after actin and are critical for stereocilia morphogenesis and maintenance. Here, we developed a novel transgenic mouse to monitor EGFP-fascin-2 incorporation. In contrast to actin, EGFP-fascin-2 readily enters the stereocilia core. We also compared the effect of EGFP-fascin-2 expression on developing and mature stereocilia. When it was induced during hair cell development, we observed increases in both stereocilia length and width. Interestingly, stereocilia size was not affected when EGFP-fascin-2 was induced in adult stereocilia. Regardless of the time of induction, EGFP-fascin-2 displaced both espin and plastin-1 from stereocilia. Altering the actin cross-linker composition, even as the actin filaments exhibit little to no turnover, provides a mechanism for ongoing remodeling and repair important for stereocilia homeostasis.
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Affiliation(s)
- Pallabi Roy
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202
| | - Benjamin J Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202
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40
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Ellwanger DC, Scheibinger M, Dumont RA, Barr-Gillespie PG, Heller S. Transcriptional Dynamics of Hair-Bundle Morphogenesis Revealed with CellTrails. Cell Rep 2018; 23:2901-2914.e13. [PMID: 29874578 PMCID: PMC6089258 DOI: 10.1016/j.celrep.2018.05.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/19/2018] [Accepted: 05/01/2018] [Indexed: 11/30/2022] Open
Abstract
Protruding from the apical surface of inner ear sensory cells, hair bundles carry out mechanotransduction. Bundle growth involves sequential and overlapping cellular processes, which are concealed within gene expression profiles of individual cells. To dissect such processes, we developed CellTrails, a tool for uncovering, analyzing, and visualizing single-cell gene-expression dynamics. Utilizing quantitative gene-expression data for key bundle proteins from single cells of the developing chick utricle, we reconstructed de novo a bifurcating trajectory that spanned from progenitor cells to mature striolar and extrastriolar hair cells. Extraction and alignment of developmental trails and association of pseudotime with bundle length measurements linked expression dynamics of individual genes with bundle growth stages. Differential trail analysis revealed high-resolution dynamics of transcripts that control striolar and extrastriolar bundle development, including those that encode proteins that regulate [Ca2+]i or mediate crosslinking and lengthening of actin filaments.
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Affiliation(s)
- Daniel C Ellwanger
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Mirko Scheibinger
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Rachel A Dumont
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA.
| | - Stefan Heller
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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41
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Avenarius MR, Krey JF, Dumont RA, Morgan CP, Benson CB, Vijayakumar S, Cunningham CL, Scheffer DI, Corey DP, Müller U, Jones SM, Barr-Gillespie PG. Heterodimeric capping protein is required for stereocilia length and width regulation. J Cell Biol 2017; 216:3861-3881. [PMID: 28899994 PMCID: PMC5674897 DOI: 10.1083/jcb.201704171] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 07/21/2017] [Accepted: 08/08/2017] [Indexed: 02/07/2023] Open
Abstract
Control of the dimensions of actin-rich processes like filopodia, lamellipodia, microvilli, and stereocilia requires the coordinated activity of many proteins. Each of these actin structures relies on heterodimeric capping protein (CAPZ), which blocks actin polymerization at barbed ends. Because dimension control of the inner ear's stereocilia is particularly precise, we studied the CAPZB subunit in hair cells. CAPZB, present at ∼100 copies per stereocilium, concentrated at stereocilia tips as hair cell development progressed, similar to the CAPZB-interacting protein TWF2. We deleted Capzb specifically in hair cells using Atoh1-Cre, which eliminated auditory and vestibular function. Capzb-null stereocilia initially developed normally but later shortened and disappeared; surprisingly, stereocilia width decreased concomitantly with length. CAPZB2 expressed by in utero electroporation prevented normal elongation of vestibular stereocilia and irregularly widened them. Together, these results suggest that capping protein participates in stereocilia widening by preventing newly elongating actin filaments from depolymerizing.
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Affiliation(s)
- Matthew R. Avenarius
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR
| | - Jocelyn F. Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR
| | - Rachel A. Dumont
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR
| | - Clive P. Morgan
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR
| | - Connor B. Benson
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR
| | - Sarath Vijayakumar
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln, Lincoln, NE
| | | | | | - David P. Corey
- Department of Neurobiology, Harvard Medical School, Boston, MA
| | - Ulrich Müller
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD
| | - Sherri M. Jones
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln, Lincoln, NE
| | - Peter G. Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR,Correspondence to Peter G. Barr-Gillespie:
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42
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Schwebach CL, Agrawal R, Lindert S, Kudryashova E, Kudryashov DS. The Roles of Actin-Binding Domains 1 and 2 in the Calcium-Dependent Regulation of Actin Filament Bundling by Human Plastins. J Mol Biol 2017; 429:2490-2508. [PMID: 28694070 DOI: 10.1016/j.jmb.2017.06.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 06/30/2017] [Accepted: 06/30/2017] [Indexed: 01/04/2023]
Abstract
The actin cytoskeleton is a complex network controlled by a vast array of intricately regulated actin-binding proteins. Human plastins (PLS1, PLS2, and PLS3) are evolutionary conserved proteins that non-covalently crosslink actin filaments into tight bundles. Through stabilization of such bundles, plastins contribute, in an isoform-specific manner, to the formation of kidney and intestinal microvilli, inner ear stereocilia, immune synapses, endocytic patches, adhesion contacts, and invadosomes of immune and cancer cells. All plastins comprise an N-terminal Ca2+-binding regulatory headpiece domain followed by two actin-binding domains (ABD1 and ABD2). Actin bundling occurs due to simultaneous binding of both ABDs to separate actin filaments. Bundling is negatively regulated by Ca2+, but the mechanism of this inhibition remains unknown. In this study, we found that the bundling abilities of PLS1 and PLS2 were similarly sensitive to Ca2+ (pCa50 ~6.4), whereas PLS3 was less sensitive (pCa50 ~5.9). At the same time, all three isoforms bound to F-actin in a Ca2+-independent manner, suggesting that binding of only one of the ABDs is inhibited by Ca2+. Using limited proteolysis and mass spectrometry, we found that in the presence of Ca2+ the EF-hands of human plastins bound to an immediately adjacent sequence homologous to canonical calmodulin-binding peptides. Furthermore, our data from differential centrifugation, Förster resonance energy transfer, native electrophoresis, and chemical crosslinking suggest that Ca2+ does not affect ABD1 but inhibits the ability of ABD2 to interact with actin. A structural mechanism of signal transmission from Ca2+ to ABD2 through EF-hands remains to be established.
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Affiliation(s)
- Christopher L Schwebach
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA
| | - Richa Agrawal
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA.
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43
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Ding WY, Ong HT, Hara Y, Wongsantichon J, Toyama Y, Robinson RC, Nédélec F, Zaidel-Bar R. Plastin increases cortical connectivity to facilitate robust polarization and timely cytokinesis. J Cell Biol 2017; 216:1371-1386. [PMID: 28400443 PMCID: PMC5412556 DOI: 10.1083/jcb.201603070] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 01/11/2017] [Accepted: 03/08/2017] [Indexed: 01/23/2023] Open
Abstract
Ding et al. characterize the function of the F-actin bundling protein plastin in the Caenorhabditis elegans zygote. They demonstrate that plastin is important for optimal connectivity in the cortical actomyosin network that drives large-scale contractile processes such as polarization and cytokinesis. The cell cortex is essential to maintain animal cell shape, and contractile forces generated within it by nonmuscle myosin II (NMY-2) drive cellular morphogenetic processes such as cytokinesis. The role of actin cross-linking proteins in cortical dynamics is still incompletely understood. Here, we show that the evolutionarily conserved actin bundling/cross-linking protein plastin is instrumental for the generation of potent cortical actomyosin contractility in the Caenorhabditis elegans zygote. PLST-1 was enriched in contractile structures and was required for effective coalescence of NMY-2 filaments into large contractile foci and for long-range coordinated contractility in the cortex. In the absence of PLST-1, polarization was compromised, cytokinesis was delayed or failed, and 50% of embryos died during development. Moreover, mathematical modeling showed that an optimal amount of bundling agents enhanced the ability of a network to contract. We propose that by increasing the connectivity of the F-actin meshwork, plastin enables the cortex to generate stronger and more coordinated forces to accomplish cellular morphogenesis.
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Affiliation(s)
- Wei Yung Ding
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Hui Ting Ong
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Yusuke Hara
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | - Jantana Wongsantichon
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology, and Research), Singapore 138673, Singapore
| | - Yusuke Toyama
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.,Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology, and Research), Singapore 138673, Singapore.,Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore
| | - François Nédélec
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Ronen Zaidel-Bar
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore 117583, Singapore
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