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Wang L, Bu T, Wu X, Li L, Sun F, Cheng CY. Motor proteins, spermatogenesis and testis function. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2024; 141:381-445. [PMID: 38960481 DOI: 10.1016/bs.apcsb.2024.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
The role of motor proteins in supporting intracellular transports of vesicles and organelles in mammalian cells has been known for decades. On the other hand, the function of motor proteins that support spermatogenesis is also well established since the deletion of motor protein genes leads to subfertility and/or infertility. Furthermore, mutations and genetic variations of motor protein genes affect fertility in men, but also a wide range of developmental defects in humans including multiple organs besides the testis. In this review, we seek to provide a summary of microtubule and actin-dependent motor proteins based on earlier and recent findings in the field. Since these two cytoskeletons are polarized structures, different motor proteins are being used to transport cargoes to different ends of these cytoskeletons. However, their involvement in germ cell transport across the blood-testis barrier (BTB) and the epithelium of the seminiferous tubules remains relatively unknown. It is based on recent findings in the field, we have provided a hypothetical model by which motor proteins are being used to support germ cell transport across the BTB and the seminiferous epithelium during the epithelial cycle of spermatogenesis. In our discussion, we have highlighted the areas of research that deserve attention to bridge the gap of research in relating the function of motor proteins to spermatogenesis.
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Affiliation(s)
- Lingling Wang
- The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China; Department of Urology and Andrology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - Tiao Bu
- Department of Urology and Andrology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - Xiaolong Wu
- Department of Urology and Andrology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - Linxi Li
- The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Fei Sun
- Department of Urology and Andrology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China
| | - C Yan Cheng
- The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China; Department of Urology and Andrology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China.
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Yang HW, Lee S, Berry BC, Yang D, Zheng S, Carroll RS, Park PJ, Johnson MD. A role for mutations in AK9 and other genes affecting ependymal cells in idiopathic normal pressure hydrocephalus. Proc Natl Acad Sci U S A 2023; 120:e2300681120. [PMID: 38100419 PMCID: PMC10743366 DOI: 10.1073/pnas.2300681120] [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: 01/12/2023] [Accepted: 11/06/2023] [Indexed: 12/17/2023] Open
Abstract
Idiopathic normal pressure hydrocephalus (iNPH) is an enigmatic neurological disorder that develops after age 60 and is characterized by gait difficulty, dementia, and incontinence. Recently, we reported that heterozygous CWH43 deletions may cause iNPH. Here, we identify mutations affecting nine additional genes (AK9, RXFP2, PRKD1, HAVCR1, OTOG, MYO7A, NOTCH1, SPG11, and MYH13) that are statistically enriched among iNPH patients. The encoded proteins are all highly expressed in choroid plexus and ependymal cells, and most have been associated with cilia. Damaging mutations in AK9, which encodes an adenylate kinase, were detected in 9.6% of iNPH patients. Mice homozygous for an iNPH-associated AK9 mutation displayed normal cilia structure and number, but decreased cilia motility and beat frequency, communicating hydrocephalus, and balance impairment. AK9+/- mice displayed normal brain development and behavior until early adulthood, but subsequently developed communicating hydrocephalus. Together, our findings suggest that heterozygous mutations that impair ventricular epithelial function may contribute to iNPH.
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Affiliation(s)
- Hong Wei Yang
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
| | - Semin Lee
- Brigham and Women’s Hospital, Boston, MA02115
- Harvard Medical School, Boston, MA02115
| | - Bethany C. Berry
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
| | - Dejun Yang
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
| | - Shaokuan Zheng
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
| | - Rona S. Carroll
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
- Brigham and Women’s Hospital, Boston, MA02115
- Harvard Medical School, Boston, MA02115
| | - Peter J. Park
- Brigham and Women’s Hospital, Boston, MA02115
- Harvard Medical School, Boston, MA02115
| | - Mark D. Johnson
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA01655
- Department of Neurological Surgery, University of Massachusetts Memorial Health, Worcester, MA01655
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LUZP1: A new player in the actin-microtubule cross-talk. Eur J Cell Biol 2022; 101:151250. [PMID: 35738212 DOI: 10.1016/j.ejcb.2022.151250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/05/2022] [Accepted: 06/08/2022] [Indexed: 11/23/2022] Open
Abstract
LUZP1 (leucine zipper protein 1) was first described as being important for embryonic development. Luzp1 null mice present defective neural tube closure and cardiovascular problems, which cause perinatal death. Since then, LUZP1 has also been implicated in the etiology of diseases like the 1p36 and the Townes-Brocks syndromes, and the molecular mechanisms involving this protein started being uncovered. Proteomics studies placed LUZP1 in the interactomes of the centrosome-cilium interface, centriolar satellites, and midbody. Concordantly, LUZP1 is an actin and microtubule-associated protein, which localizes to the centrosome, the basal body of primary cilia, the midbody, actin filaments and cellular junctions. LUZP1, like its interactor EPLIN, is an actin-stabilizing protein and a negative regulator of primary cilia formation. Moreover, through the regulation of actin, LUZP1 has been implicated in the regulation of cell cycle progression, cell migration and epithelial cell apical constriction. This review discusses the latest findings concerning LUZP1 molecular functions and implications in disease development.
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Decreased activity of piriform cortex and orbitofrontal hyperactivation in Usher Syndrome, a human disorder of ciliary dysfunction. Brain Imaging Behav 2021; 16:1176-1185. [PMID: 34850367 PMCID: PMC9107447 DOI: 10.1007/s11682-021-00594-6] [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] [Accepted: 10/20/2021] [Indexed: 11/27/2022]
Abstract
Usher syndrome (USH) is a condition characterized by ciliary dysfunction leading to retinal degeneration and hearing/vestibular loss. Putative olfactory deficits in humans have been documented at the psychophysical level and remain to be proven at the neurophysiological level. Thus, we aimed to study USH olfactory impairment using functional magnetic resonance imaging. We analyzed differences in whole-brain responses between 27 USH patients and 26 healthy participants during an olfactory detection task with a bimodal odorant (n-butanol). The main research question was whether between-group differences could be identified using a conservative whole-brain approach and in a ROI-based approach in key olfactory brain regions. Results indicated higher olfactory thresholds in USH patients, thereby confirming the hypothesis of reduced olfactory acuity. Importantly, we found decreased BOLD activity for USH patients in response to odorant stimulation in the right piriform cortex, while right orbitofrontal cortex showed increased activity. We also found decreased activity in other higher-level regions in a whole brain approach. We suggest that the hyper activation in the orbitofrontal cortex possibly occurs as a compensatory mechanism after the under-recruitment of the piriform cortex. This study suggests that olfactory deficits in USH can be objectively assessed using functional neuroimaging which reveals differential patterns of activity both in low- and high-level regions of the olfactory network. 1. Psychophysical olfactory deficits are present in Usher Syndrome, a ciliary disorder. 2. USH patients show decreased BOLD activity in the right piriform olfactory cortex; 3. USH patients show increased activity in the orbitofrontal olfactory cortex; 4. USH patients show patterns of decreased activity in high-level cortical regions; 5. Functional neuroimaging unravels USH olfactory deficits at the population level.
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Sallee JL, Crawford JM, Singh V, Kiehart DP. Mutations in Drosophila crinkled/Myosin VIIA disrupt denticle morphogenesis. Dev Biol 2021; 470:121-135. [PMID: 33248112 PMCID: PMC7855556 DOI: 10.1016/j.ydbio.2020.11.007] [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: 07/28/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 10/22/2022]
Abstract
Actin filament crosslinking, bundling and molecular motor proteins are necessary for the assembly of epithelial projections such as microvilli, stereocilia, hairs, and bristles. Mutations in such proteins cause defects in the shape, structure, and function of these actin - based protrusions. One protein necessary for stereocilia formation, Myosin VIIA, is an actin - based motor protein conserved throughout phylogeny. In Drosophila melanogaster, severe mutations in the MyoVIIA homolog crinkled (ck) are "semi - lethal" with only a very small percentage of flies surviving to adulthood. Such survivors show morphological defects related to actin bundling in hairs and bristles. To better understand ck/MyoVIIA's function in bundled - actin structures, we used dominant female sterile approaches to analyze the loss of maternal and zygotic (M/Z) ck/MyoVIIA in the morphogenesis of denticles, small actin - based projections on the ventral epidermis of Drosophila embryos. M/Z ck mutants displayed severe defects in denticle morphology - actin filaments initiated in the correct location, but failed to elongate and bundle to form normal projections. Using deletion mutant constructs, we demonstrated that both of the C - terminal MyTH4 and FERM domains are necessary for proper denticle formation. Furthermore, we show that ck/MyoVIIA interacts genetically with dusky - like (dyl), a member of the ZPD family of proteins that links the extracellular matrix to the plasma membrane, and when mutated also disrupts normal denticle formation. Loss of either protein alone does not alter the localization of the other; however, loss of the two proteins together dramatically enhances the defects in denticle shape observed when either protein alone was absent. Our data indicate that ck/MyoVIIA plays a key role in the formation and/or organization of actin filament bundles, which drive proper shape of cellular projections.
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Affiliation(s)
- Jennifer L Sallee
- Department of Biology, Duke University, Durham, NC, 27708, USA; Department of Biology, North Central College, Naperville, IL, 60540, USA.
| | | | - Vinay Singh
- Department of Biology, Duke University, Durham, NC, 27708, USA
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Liu R, Billington N, Yang Y, Bond C, Hong A, Siththanandan V, Takagi Y, Sellers JR. A binding protein regulates myosin-7a dimerization and actin bundle assembly. Nat Commun 2021; 12:563. [PMID: 33495456 PMCID: PMC7835385 DOI: 10.1038/s41467-020-20864-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 12/07/2020] [Indexed: 01/17/2023] Open
Abstract
Myosin-7a, despite being monomeric in isolation, plays roles in organizing actin-based cell protrusions such as filopodia, microvilli and stereocilia, as well as transporting cargoes within them. Here, we identify a binding protein for Drosophila myosin-7a termed M7BP, and describe how M7BP assembles myosin-7a into a motile complex that enables cargo translocation and actin cytoskeletal remodeling. M7BP binds to the autoinhibitory tail of myosin-7a, extending the molecule and activating its ATPase activity. Single-molecule reconstitution show that M7BP enables robust motility by complexing with myosin-7a as 2:2 translocation dimers in an actin-regulated manner. Meanwhile, M7BP tethers actin, enhancing complex’s processivity and driving actin-filament alignment during processive runs. Finally, we show that myosin-7a-M7BP complex assembles actin bundles and filopodia-like protrusions while migrating along them in living cells. Together, these findings provide insights into the mechanisms by which myosin-7a functions in actin protrusions. Myosin-7a is found in actin bundles, microvilli and stereocilia, and plays conserved roles in hearing and vision. Here the authors identify M7BP, a myosin-7a binding protein that activates and dimerizes myosin-7a, enabling cargo transport and assembly of actin bundles and filopodia-like protrusions
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Affiliation(s)
- Rong Liu
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Neil Billington
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Yi Yang
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.,Laboratory of Functional Proteomics, College of Veterinary Medicine, Hunan Agricultural University, 410128, Changsha, Hunan, China
| | - Charles Bond
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Amy Hong
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Verl Siththanandan
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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Toms M, Pagarkar W, Moosajee M. Usher syndrome: clinical features, molecular genetics and advancing therapeutics. Ther Adv Ophthalmol 2020; 12:2515841420952194. [PMID: 32995707 PMCID: PMC7502997 DOI: 10.1177/2515841420952194] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 07/27/2020] [Indexed: 01/12/2023] Open
Abstract
Usher syndrome has three subtypes, each being clinically and genetically heterogeneous characterised by sensorineural hearing loss and retinitis pigmentosa (RP), with or without vestibular dysfunction. It is the most common cause of deaf–blindness worldwide with a prevalence of between 4 and 17 in 100 000. To date, 10 causative genes have been identified for Usher syndrome, with MYO7A accounting for >50% of type 1 and USH2A contributing to approximately 80% of type 2 Usher syndrome. Variants in these genes can also cause non-syndromic RP and deafness. Genotype–phenotype correlations have been described for several of the Usher genes. Hearing loss is managed with hearing aids and cochlear implants, which has made a significant improvement in quality of life for patients. While there is currently no available approved treatment for the RP, various therapeutic strategies are in development or in clinical trials for Usher syndrome, including gene replacement, gene editing, antisense oligonucleotides and small molecule drugs.
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Affiliation(s)
- Maria Toms
- UCL Institute of Ophthalmology, London, UK; The Francis Crick Institute, London, UK
| | - Waheeda Pagarkar
- Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK; University College London Hospitals NHS Foundation Trust, London, UK
| | - Mariya Moosajee
- Development, Ageing and Disease, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
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Wang L, Yan M, Wu S, Wu X, Bu T, Wong CK, Ge R, Sun F, Cheng CY. Actin binding proteins, actin cytoskeleton and spermatogenesis – Lesson from toxicant models. Reprod Toxicol 2020; 96:76-89. [DOI: 10.1016/j.reprotox.2020.05.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 05/15/2020] [Accepted: 05/30/2020] [Indexed: 12/16/2022]
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Usami SI, Nishio SY, Moteki H, Miyagawa M, Yoshimura H. Cochlear Implantation From the Perspective of Genetic Background. Anat Rec (Hoboken) 2020; 303:563-593. [PMID: 32027099 PMCID: PMC7064903 DOI: 10.1002/ar.24360] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 12/13/2019] [Indexed: 12/18/2022]
Abstract
While cochlear implantation (CI) technology has greatly improved over the past 40 years, one aspect of CI that continues to pose difficulties is the variability of outcomes due to numerous factors involved in postimplantation performance. The electric acoustic stimulation (EAS) system has expanded indications for CI to include patients with residual hearing, and is currently becoming a standard therapy for these patients. Genetic disorders are known to be the most common cause of congenital/early-onset sensorineural hearing loss, and are also involved in a considerable proportion of cases of late-onset hearing loss. There has been a great deal of progress in the identification of deafness genes over the last two decades. Currently, more than 100 genes have been reported to be associated with non-syndromic hearing loss. Patients possessing a variety of deafness gene mutations have achieved satisfactory auditory performance after CI/EAS, suggesting that identification of the genetic background facilitates prediction of post-CI/EAS performance. When the intra-cochlear etiology is associated with a specific genetic background, there is a potential for good CI performance. Thus, it is essential to determine which region of the cochlea is affected by identifying the responsible genes. This review summarizes the genetic background of the patients receiving CI/EAS, and introduces detailed clinical data and CI/EAS outcomes in representative examples. Anat Rec, 303:563-593, 2020. © 2020 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan.,Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan.,Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Hideaki Moteki
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Maiko Miyagawa
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Hidekane Yoshimura
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan.,Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
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Abstract
OBJECTIVE To describe the genetic and phenotypic spectrum of Usher syndrome after 6 years of studies by next-generation sequencing, and propose an up-to-date classification of Usher genes in patients with both visual and hearing impairments suggesting Usher syndrome, and in patients with seemingly isolated deafness. STUDY DESIGN The systematic review and meta-analysis protocol was based on Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We performed 1) a meta-analysis of data from 11 next-generation sequencing studies in 684 patients with Usher syndrome; 2) a meta-analysis of data from 21 next-generation studies in 2,476 patients with seemingly isolated deafness, to assess the involvement of Usher genes in seemingly nonsyndromic hearing loss, and thus the proportion of patients at high risk of subsequent retinitis pigmentosa (RP); 3) a statistical analysis of differences between parts 1) and 2). RESULTS In patients with both visual and hearing impairments, the biallelic disease-causing mutation rate was assessed for each Usher gene to propose a classification by frequency: USH2A: 50% (341/684) of patients, MYO7A: 21% (144/684), CDH23: 6% (39/684), ADGRV1: 5% (35/684), PCDH15: 3% (21/684), USH1C: 2% (17/684), CLRN1: 2% (14/684), USH1G: 1% (9/684), WHRN: 0.4% (3/684), PDZD7 0.1% (1/684), CIB2 (0/684). In patients with seemingly isolated sensorineural deafness, 7.5% had disease-causing mutations in Usher genes, and are therefore at high risk of developing RP. These new findings provide evidence that usherome dysfunction is the second cause of genetic sensorineural hearing loss after connexin dysfunction. CONCLUSION These results promote generalization of early molecular screening for Usher syndrome in deaf children.
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Sorusch N, Yildirim A, Knapp B, Janson J, Fleck W, Scharf C, Wolfrum U. SANS (USH1G) Molecularly Links the Human Usher Syndrome Protein Network to the Intraflagellar Transport Module by Direct Binding to IFT-B Proteins. Front Cell Dev Biol 2019; 7:216. [PMID: 31637240 PMCID: PMC6787559 DOI: 10.3389/fcell.2019.00216] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 09/18/2019] [Indexed: 01/19/2023] Open
Abstract
The human Usher syndrome (USH) is a retinal ciliopathy, characterized by profound congenital deafness, variable vestibular dysfunction and pre-pubertal onset of retinitis pigmentosa. In the effected sensory cells, USH protein networks are assumed to function in ciliary transport processes. The USH1G protein SANS is a scaffold of the ciliary/periciliary USH protein network of photoreceptor cells. Moreover, SANS is associated with microtubules, the transport routes for protein delivery toward the cilium. To enlighten the role of SANS in ciliary transport processes, we aimed to identify transport related proteins associated with SANS. The intraflagellar transport (IFT) system is a conserved mechanism for bi-directional transport toward and through primary cilia. Thus, we tested the direct binding of SANS to IFT molecules, namely IFT20, IFT57, and IFT74 in 1:1 yeast-two-hybrid assay. The identified SANS-IFT interactions were validated in vitro via independent complementary interaction assays and in cells by applying membrane targeting assays. Quantitative immunofluorescence microscopy revealed the co-localization of SANS with IFT20, IFT52, and IFT57 particularly at ciliary base of wild type mouse photoreceptor cells. Analysis of photoreceptor cells of SANS knock out mice revealed the decrease of IFTs in the ciliary compartment indicating a role of SANS in the proper positioning of IFT-B molecules in primary cilia. Our study demonstrated direct binding of IFT complex B proteins IFT52 and IFT57 to the N-terminal ankyrin repeats and the central domain of SANS. Our data also indicate that pathologic mutations in the N-terminus of SANS lead to the loos of SANS binding to IFT-B molecules. Our findings provide direct evidence for a molecular link between the ciliary USH protein network and the IFT transport module in primary cilia.
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Affiliation(s)
| | | | | | | | | | | | - Uwe Wolfrum
- Molecular Cell Biology, Institute of Molecular Physiology, Johannes Gutenberg University Mainz, Mainz, Germany
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12
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Wen Q, Wu S, Lee WM, Wong CKC, Lui WY, Silvestrini B, Cheng CY. Myosin VIIa Supports Spermatid/Organelle Transport and Cell Adhesion During Spermatogenesis in the Rat Testis. Endocrinology 2019; 160:484-503. [PMID: 30649248 PMCID: PMC6372944 DOI: 10.1210/en.2018-00855] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 01/08/2019] [Indexed: 11/19/2022]
Abstract
The biology of transport of spermatids and spermatid adhesion across the seminiferous epithelium during the epithelial cycle remains largely unexplored. Nonetheless, studies have implicated the role of motor proteins in these cellular events. In this article, we report findings to unravel the role of myosin VIIa, an F-actin-based barbed (+)-end-directed motor protein, to support cellular transport and adhesion in the testis. Using RNA interference to knock down myosin VIIa in Sertoli cells cultured in vitro as a study model was shown to perturb the Sertoli cell tight junction permeability barrier, mediated through disorganization of actin- or microtubule (MT)-based cytoskeletons owing to disruptive changes on the spatiotemporal expression of F-actin or MT-regulatory proteins. Consistent with these in vitro findings, knockdown of myosin VIIa in the testis in vivo also induced disorganization of the actin- and MT-based cytoskeletons across the seminiferous epithelium, mediated by disruptive changes in the spatiotemporal expression of actin- and MT-based regulatory proteins. More important, the transport of spermatids and organelles across the epithelium, as well as cell adhesion, was grossly disrupted. For instance, step 19 spermatids failed to be transported to the adluminal compartment near the tubule lumen to undergo spermiation; in this manner, step 19 spermatids were persistently detected in stage IX and XII tubules, intermingling with step 9 and 12 spermatids, respectively. Also, phagosomes were detected near the tubule lumen in stage I to III tubules when they should have been degraded near the base of the seminiferous epithelium via the lysosomal pathway. In summary, myosin VIIa motor protein was crucial to support cellular transport and adhesion during spermatogenesis.
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Affiliation(s)
- Qing Wen
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York
| | - Siwen Wu
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York
| | - Will M Lee
- School of Biological Sciences, University of Hong Kong, Hong Kong, China
| | - Chris K C Wong
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Wing-yee Lui
- School of Biological Sciences, University of Hong Kong, Hong Kong, China
| | | | - C Yan Cheng
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York
- Correspondence: C. Yan Cheng, PhD, The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10065. E-mail:
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Bigday EV, Samojlov VO. Chemosensory and Mechanosensory Functions of Olfactory Cilia. Biophysics (Nagoya-shi) 2018. [DOI: 10.1134/s0006350918060027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Cilium structure, assembly, and disassembly regulated by the cytoskeleton. Biochem J 2018; 475:2329-2353. [PMID: 30064990 PMCID: PMC6068341 DOI: 10.1042/bcj20170453] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/02/2018] [Accepted: 07/04/2018] [Indexed: 12/17/2022]
Abstract
The cilium, once considered a vestigial structure, is a conserved, microtubule-based organelle critical for transducing extracellular chemical and mechanical signals that control cell polarity, differentiation, and proliferation. The cilium undergoes cycles of assembly and disassembly that are controlled by complex inter-relationships with the cytoskeleton. Microtubules form the core of the cilium, the axoneme, and are regulated by post-translational modifications, associated proteins, and microtubule dynamics. Although actin and septin cytoskeletons are not major components of the axoneme, they also regulate cilium organization and assembly state. Here, we discuss recent advances on how these different cytoskeletal systems affect cilium function, structure, and organization.
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Apodaca G. Role of Polarity Proteins in the Generation and Organization of Apical Surface Protrusions. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a027813. [PMID: 28264821 DOI: 10.1101/cshperspect.a027813] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protruding from the apical surfaces of epithelial cells are specialized structures, including cilia, microplicae, microvilli, and stereocilia. These contribute to epithelial function by cushioning the apical surface, by amplifying its surface area to facilitate nutrient absorption, and by promoting sensory transduction and barrier function. Despite these important roles, and the diseases that result when their formation is perturbed, there remain significant gaps in our understanding of the biogenesis of apical protrusions, or the pathways that promote their organization and orientation once at the apical surface. Here, I review some general aspects of these apical structures, and then discuss our current understanding of their formation and organization with respect to proteins that specify apicobasolateral polarity and planar cell polarity.
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Affiliation(s)
- Gerard Apodaca
- Department of Medicine Renal-Electrolyte Division and the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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16
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Xiong A, Haithcock J, Liu Y, Eusner L, McConnell M, White HD, Belknap B, Forgacs E. The shaker-1 mouse myosin VIIa deafness mutation results in a severely reduced rate of the ATP hydrolysis step. J Biol Chem 2017; 293:819-829. [PMID: 29167268 DOI: 10.1074/jbc.m117.810119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 11/21/2017] [Indexed: 11/06/2022] Open
Abstract
Mutations in the MYO7A gene, encoding the motor protein myosin VIIa, can cause Usher 1B, a deafness/blindness syndrome in humans, and the shaker-1 phenotype, characterized by deafness, head tossing, and circling behavior, in mice. Myosin VIIa is responsible for tension bearing and the transduction mechanism in the stereocilia and for melanosome transport in the retina, in line with the phenotypic outcomes observed in mice. However, the effect of the shaker-1 mutation, a R502P amino acid substitution, on the motor function is unclear. To explore this question, we determined the kinetic properties and the effect on the filopodial tip localization of the recombinant mouse myosin VIIa-5IQ-SAH R502P (myoVIIa-sh1) construct. Interestingly, although residue 502 is localized to a region thought to be involved in interacting with actin, the kinetic parameters for actin binding changed only slightly for the mutant construct. However, the rate constant for ATP hydrolysis (k+H + k-H) was reduced by ∼200-fold from 12 s-1 to 0.05 s-1, making the hydrolysis step the rate-limiting step of the ATPase cycle in the presence and absence of actin. Given that wild-type mouse myosin VIIa is a slow, high-duty ratio, monomeric motor, this altered hydrolysis rate would reduce activity to extremely low levels. Indeed, the translocation to the filopodial tips was hampered by the diminished motor function of a dimeric construct of the shaker-1 mutant. We conclude that the diminished motor activity of this mutant is most likely responsible for impaired hearing in the shaker-1 mice.
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Affiliation(s)
- Ailian Xiong
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Jessica Haithcock
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Yingying Liu
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Lauren Eusner
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Matthew McConnell
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Howard D White
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Betty Belknap
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Eva Forgacs
- From the Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507
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17
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Qu C, Liang F, Long Q, Zhao M, Shang H, Fan L, Wang L, Foster J, Yan D, Liu X. Genetic screening revealed usher syndrome in a paediatric Chinese patient. HEARING BALANCE AND COMMUNICATION 2017; 15:98-106. [PMID: 30800556 DOI: 10.1080/21695717.2017.1321217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Introduction Usher syndrome is the most common cause of hereditary deaf-blindness. Three clinical subtypes have been classified. Usher syndrome type I is the most severe subtype characterized by congenital severe-to-profound hearing loss, retinitis pigmentosa and vestibular dysfunction. Methods One family was analyzed and the analysis included the combination of a custom capture/next-generation sequencing panel of 180 known deafness gene, Sanger sequencing and bioinformatics approaches. Results Compound heterozygous mutations in the MYO7A gene: a known missense mutation c.494C>T (p.Thr165Met) and a novel missense mutation c.6113G>A (p.Gly2038Glu) were identified in a proband. This Chinese hearing-impaired child was misdiagnosed as non-syndromic hearing loss which was later changed to the diagnosis of Usher syndrome type I after comprehensive audiometric, vestibular and ophthalmological examinations at 9 years old. Conclusions Due to the features of genetic heterogeneity and variation in clinical manifestation, molecular diagnosis and ophthalmological examinations by skilled ophthalmologists with knowledge of Usher syndrome should be suggested as a routine assessment which may improve the accuracy and reliability of etiological diagnosis for hearing loss.
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Affiliation(s)
- Chunyan Qu
- China Rehabilitation and Research Center for Deaf Children, Beijing 100029, China
| | - Fenghe Liang
- Department of Otolaryngology-Head and Neck Surgery, Capital Medical University, Beijing Tongren Hospital, Beijing 100730, China
| | - Qin Long
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China
| | - Min Zhao
- China Rehabilitation and Research Center for Deaf Children, Beijing 100029, China
| | - Haiqiong Shang
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan 250021, China
| | - Lynn Fan
- BSc, University of Miami, Miami, FL 33136, USA
| | - Li Wang
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Joseph Foster
- Department of Human Genetics, John P. Hussman Institute for Human Genomics, University of Miami, FL 33136, USA
| | - Denise Yan
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Xuezhong Liu
- Department of Human Genetics, John P. Hussman Institute for Human Genomics, University of Miami, FL 33136, USA.,Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.,Dr. John T. Macdonald Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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18
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Nager AR, Goldstein JS, Herranz-Pérez V, Portran D, Ye F, Garcia-Verdugo JM, Nachury MV. An Actin Network Dispatches Ciliary GPCRs into Extracellular Vesicles to Modulate Signaling. Cell 2016; 168:252-263.e14. [PMID: 28017328 DOI: 10.1016/j.cell.2016.11.036] [Citation(s) in RCA: 244] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 09/14/2016] [Accepted: 11/17/2016] [Indexed: 12/13/2022]
Abstract
Signaling receptors dynamically exit cilia upon activation of signaling pathways such as Hedgehog. Here, we find that when activated G protein-coupled receptors (GPCRs) fail to undergo BBSome-mediated retrieval from cilia back into the cell, these GPCRs concentrate into membranous buds at the tips of cilia before release into extracellular vesicles named ectosomes. Unexpectedly, actin and the actin regulators drebrin and myosin 6 mediate ectosome release from the tip of cilia. Mirroring signal-dependent retrieval, signal-dependent ectocytosis is a selective and effective process that removes activated signaling molecules from cilia. Congruently, ectocytosis compensates for BBSome defects as ectocytic removal of GPR161, a negative regulator of Hedgehog signaling, permits the appropriate transduction of Hedgehog signals in Bbs mutants. Finally, ciliary receptors that lack retrieval determinants such as the anorexigenic GPCR NPY2R undergo signal-dependent ectocytosis in wild-type cells. Our data show that signal-dependent ectocytosis regulates ciliary signaling in physiological and pathological contexts.
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Affiliation(s)
- Andrew R Nager
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
| | - Jaclyn S Goldstein
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
| | - Vicente Herranz-Pérez
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles, Universitat de València, CIBERNED, 46980 Valencia, Spain; Unidad Mixta de Esclerosis Múltiple y Neurorregeneración, IIS Hospital La Fe-UVEG, 46026 Valencia, Spain
| | - Didier Portran
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
| | - Fan Ye
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
| | - Jose Manuel Garcia-Verdugo
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles, Universitat de València, CIBERNED, 46980 Valencia, Spain; Unidad Mixta de Esclerosis Múltiple y Neurorregeneración, IIS Hospital La Fe-UVEG, 46026 Valencia, Spain
| | - Maxence V Nachury
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA.
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Wen Q, Tang EI, Xiao X, Gao Y, Chu DS, Mruk DD, Silvestrini B, Cheng CY. Transport of germ cells across the seminiferous epithelium during spermatogenesis-the involvement of both actin- and microtubule-based cytoskeletons. Tissue Barriers 2016; 4:e1265042. [PMID: 28123928 DOI: 10.1080/21688370.2016.1265042] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/19/2016] [Accepted: 11/21/2016] [Indexed: 12/16/2022] Open
Abstract
The transport of germ cells from the base of the seminiferous epithelium toward the luminal edge of the tubule lumen in the adluminal compartment during the epithelial cycle is an essential cellular event to support spermatogenesis. Thus, fully developed elongated spermatids (i.e., spermatozoa) can be released at spermiation in late stage VIII in rodents versus late stage II in humans. Earlier studies to examine the molecular mechanism(s) that support germ cell transport, most notably the transport of preleptotene spermatocytes across the blood-testis barrier (BTB), and the transport of elongating spermatids across the adluminal compartment during spermiogenesis, is focused on the adhesion protein complexes at the cell-cell interface. It is generally accepted that cell junctions at the Sertoli cell-cell interface at the BTB, including the actin-based tight junction (TJ), basal ectoplasmic specialization (basal ES, a testis-specific adherens junction) and gap junction (GJ), as well as the intermediate filament-based desmosome undergo constant remodeling to accommodate the transport of preleptotene spermatocytes across the barrier. On the other hand, similar junction dynamics (i.e., disassembly, reassembly and stabilization/maintenance) take place at the Sertoli-spermatid interface. Emerging evidence has shown that junction dynamics at the Sertoli cell-cell vs. Sertoli-germ cell interface are supported by the 2 intriguingly coordinated cytoskeletons, namely the F-actin- and microtubule (MT)-based cytoskeletons. Herein, we provide a brief summary and critically evaluate the recent findings. We also provide an updated hypothetical concept regarding germ cell transport in the testis utilizing the MT-conferred tracks and the MT-specific motor proteins. Furthermore, this cellular event is also supported by the F-actin-based cytoskeleton.
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Affiliation(s)
- Qing Wen
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
| | - Elizabeth I Tang
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
| | - Xiang Xiao
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, NY, USA; Department of Reproductive Physiology, Zhejiang Academy of Medical Sciences, Hangzhou, China
| | - Ying Gao
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
| | - Darren S Chu
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
| | - Dolores D Mruk
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
| | | | - C Yan Cheng
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council , New York, NY, USA
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20
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Dad S, Rendtorff ND, Tranebjærg L, Grønskov K, Karstensen HG, Brox V, Nilssen Ø, Roux AF, Rosenberg T, Jensen H, Møller LB. Usher syndrome in Denmark: mutation spectrum and some clinical observations. Mol Genet Genomic Med 2016; 4:527-539. [PMID: 27957503 PMCID: PMC5023938 DOI: 10.1002/mgg3.228] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 12/22/2022] Open
Abstract
Background Usher syndrome (USH) is a genetically heterogeneous deafness‐blindness syndrome, divided into three clinical subtypes: USH1, USH2 and USH3. Methods Mutations in 21 out of 26 investigated Danish unrelated individuals with USH were identified, using a combination of molecular diagnostic methods. Results Before Next Generation Sequencing (NGS) became available mutations in nine individuals (1 USH1, 7 USH2, 1 USH3) were identified by Sanger sequencing of USH1C,USH2A or CLRN1 or by Arrayed Primer EXtension (APEX) method. Mutations in 12 individuals (7 USH1, 5 USH2) were found by targeted NGS of ten known USH genes. Five novel pathogenic variants were identified. We combined our data with previously published, and obtained an overview of the USH mutation spectrum in Denmark, including 100 unrelated individuals; 32 with USH1, 67 with USH2, and 1 with USH3. Macular edema was observed in 44 of 117 individuals. Olfactory function was tested in 12 individuals and found to be within normal range in all. Conclusion Mutations that lead to USH1 were predominantly identified in MYO7A (75%), whereas all mutations in USH2 cases were identified in USH2A. The MYO7A mutation c.93C>A, p.(Cys31*) accounted for 33% of all USH1 mutations and the USH2A c.2299delG, p.(Glu767Serfs*21) variant accounted for 45% of all USH2 mutations in the Danish cohort.
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Affiliation(s)
- Shzeena Dad
- Applied Human Genetics Kennedy Center Department of Clinical Genetics Copenhagen University Rigshospitalet Glostrup Denmark
| | - Nanna Dahl Rendtorff
- Applied Human GeneticsKennedy CenterDepartment of Clinical GeneticsCopenhagen UniversityRigshospitaletGlostrupDenmark; Department of Cellular and Molecular MedicineThe Faculty of Health SciencesUniversity of Copenhagen2200CopenhagenDenmark; Department of Otorhinolaryngology, Head & Neck Surgery and AudiologyBispebjerg Hospital/RigshospitaletCopenhagenDenmark
| | - Lisbeth Tranebjærg
- Applied Human GeneticsKennedy CenterDepartment of Clinical GeneticsCopenhagen UniversityRigshospitaletGlostrupDenmark; Department of Cellular and Molecular MedicineThe Faculty of Health SciencesUniversity of Copenhagen2200CopenhagenDenmark; Department of Otorhinolaryngology, Head & Neck Surgery and AudiologyBispebjerg Hospital/RigshospitaletCopenhagenDenmark
| | - Karen Grønskov
- Applied Human GeneticsKennedy CenterDepartment of Clinical GeneticsCopenhagen UniversityRigshospitaletGlostrupDenmark; Department of Cellular and Molecular MedicineThe Faculty of Health SciencesUniversity of Copenhagen2200CopenhagenDenmark
| | - Helena Gásdal Karstensen
- Department of Cellular and Molecular Medicine The Faculty of Health Sciences University of Copenhagen 2200 Copenhagen Denmark
| | - Vigdis Brox
- Department of Medical Genetics University Hospital of North-Norway N-9038 Tromsø Norway
| | - Øivind Nilssen
- Department of Medical GeneticsUniversity Hospital of North-NorwayN-9038TromsøNorway; Department of Clinical Medicine, Medical GeneticsUniversity of TromsøNO-9037TromsøNorway
| | - Anne-Françoise Roux
- Laboratoire de Génétique MoléculaireCHU MontpellierMontpellierF-34000France; U827InsermMontpellierF-34000France
| | - Thomas Rosenberg
- The National Eye ClinicThe Kennedy CenterDepartment of OphthalmologyCopenhagen University Hospital2600RigshospitaletGlostrupDenmark; Institute of Clinical MedicineThe Faculty of Health SciencesUniversity of Copenhagen2200Copenhagen NDenmark
| | - Hanne Jensen
- The National Eye Clinic The Kennedy Center Department of Ophthalmology Copenhagen University Hospital 2600 Rigshospitalet Glostrup Denmark
| | - Lisbeth Birk Møller
- Applied Human GeneticsKennedy CenterDepartment of Clinical GeneticsCopenhagen UniversityRigshospitaletGlostrupDenmark; Department of Cellular and Molecular MedicineThe Faculty of Health SciencesUniversity of Copenhagen2200CopenhagenDenmark; Department of Science Systems and Models (NSM)Roskilde UniversityDK 4000RoskildeDenmark
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21
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Jansen F, Kalbe B, Scholz P, Mikosz M, Wunderlich KA, Kurtenbach S, Nagel-Wolfrum K, Wolfrum U, Hatt H, Osterloh S. Impact of the Usher syndrome on olfaction. Hum Mol Genet 2015; 25:524-33. [PMID: 26620972 DOI: 10.1093/hmg/ddv490] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/24/2015] [Indexed: 12/21/2022] Open
Abstract
Usher syndrome is a genetically and clinically heterogeneous disease in humans, characterized by sensorineural hearing loss, retinitis pigmentosa and vestibular dysfunction. This disease is caused by mutations in genes encoding proteins that form complex networks in different cellular compartments. Currently, it remains unclear whether the Usher proteins also form networks within the olfactory epithelium (OE). Here, we describe Usher gene expression at the mRNA and protein level in the OE of mice and showed interactions between these proteins and olfactory signaling proteins. Additionally, we analyzed the odor sensitivity of different Usher syndrome mouse models using electro-olfactogram recordings and monitored significant changes in the odor detection capabilities in mice expressing mutant Usher proteins. Furthermore, we observed changes in the expression of signaling proteins that might compensate for the Usher protein deficiency. In summary, this study provides novel insights into the presence and purpose of the Usher proteins in olfactory signal transduction.
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Affiliation(s)
- Fabian Jansen
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Benjamin Kalbe
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Paul Scholz
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Marta Mikosz
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Kirsten A Wunderlich
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Stefan Kurtenbach
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Kerstin Nagel-Wolfrum
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Uwe Wolfrum
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Hanns Hatt
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Sabrina Osterloh
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
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Sauvanet C, Wayt J, Pelaseyed T, Bretscher A. Structure, Regulation, and Functional Diversity of Microvilli on the Apical Domain of Epithelial Cells. Annu Rev Cell Dev Biol 2015; 31:593-621. [DOI: 10.1146/annurev-cellbio-100814-125234] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Cécile Sauvanet
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Jessica Wayt
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Thaher Pelaseyed
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Anthony Bretscher
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
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23
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Bachmann-Gagescu R, Dona M, Hetterschijt L, Tonnaer E, Peters T, de Vrieze E, Mans DA, van Beersum SEC, Phelps IG, Arts HH, Keunen JE, Ueffing M, Roepman R, Boldt K, Doherty D, Moens CB, Neuhauss SCF, Kremer H, van Wijk E. The Ciliopathy Protein CC2D2A Associates with NINL and Functions in RAB8-MICAL3-Regulated Vesicle Trafficking. PLoS Genet 2015; 11:e1005575. [PMID: 26485645 PMCID: PMC4617701 DOI: 10.1371/journal.pgen.1005575] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 09/16/2015] [Indexed: 12/16/2022] Open
Abstract
Ciliopathies are a group of human disorders caused by dysfunction of primary cilia, ubiquitous microtubule-based organelles involved in transduction of extra-cellular signals to the cell. This function requires the concentration of receptors and channels in the ciliary membrane, which is achieved by complex trafficking mechanisms, in part controlled by the small GTPase RAB8, and by sorting at the transition zone located at the entrance of the ciliary compartment. Mutations in the transition zone gene CC2D2A cause the related Joubert and Meckel syndromes, two typical ciliopathies characterized by central nervous system malformations, and result in loss of ciliary localization of multiple proteins in various models. The precise mechanisms by which CC2D2A and other transition zone proteins control protein entrance into the cilium and how they are linked to vesicular trafficking of incoming cargo remain largely unknown. In this work, we identify the centrosomal protein NINL as a physical interaction partner of CC2D2A. NINL partially co-localizes with CC2D2A at the base of cilia and ninl knockdown in zebrafish leads to photoreceptor outer segment loss, mislocalization of opsins and vesicle accumulation, similar to cc2d2a-/- phenotypes. Moreover, partial ninl knockdown in cc2d2a-/- embryos enhances the retinal phenotype of the mutants, indicating a genetic interaction in vivo, for which an illustration is found in patients from a Joubert Syndrome cohort. Similar to zebrafish cc2d2a mutants, ninl morphants display altered Rab8a localization. Further exploration of the NINL-associated interactome identifies MICAL3, a protein known to interact with Rab8 and to play an important role in vesicle docking and fusion. Together, these data support a model where CC2D2A associates with NINL to provide a docking point for cilia-directed cargo vesicles, suggesting a mechanism by which transition zone proteins can control the protein content of the ciliary compartment.
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Affiliation(s)
- Ruxandra Bachmann-Gagescu
- Institute for Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Institute of Medical Genetics, University of Zurich, Zurich, Switzerland
| | - Margo Dona
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
| | - Lisette Hetterschijt
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
| | - Edith Tonnaer
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Theo Peters
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Erik de Vrieze
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
| | - Dorus A. Mans
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Sylvia E. C. van Beersum
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Ian G. Phelps
- Department of Pediatrics, University of Washington, Seattle, Washington, United States of America
| | - Heleen H. Arts
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Jan E. Keunen
- Department of Ophthalmology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Marius Ueffing
- Division of Experimental Ophthalmology and Medical Proteome Center, Centre for Ophthalmology, Eberhard Karls University Tuebingen, Germany
| | - Ronald Roepman
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Karsten Boldt
- Division of Experimental Ophthalmology and Medical Proteome Center, Centre for Ophthalmology, Eberhard Karls University Tuebingen, Germany
| | - Dan Doherty
- Department of Pediatrics, University of Washington, Seattle, Washington, United States of America
| | - Cecilia B. Moens
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | | | - Hannie Kremer
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Erwin van Wijk
- Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands
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Bigday EV, Samoilov VO. Chemotaxis as a mechanism of the locomotor activity of olfactory cilia. Biophysics (Nagoya-shi) 2015. [DOI: 10.1134/s0006350915040041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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25
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Toms M, Bitner-Glindzicz M, Webster A, Moosajee M. Usher syndrome: a review of the clinical phenotype, genes and therapeutic strategies. EXPERT REVIEW OF OPHTHALMOLOGY 2015. [DOI: 10.1586/17469899.2015.1033403] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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26
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Chuang JZ, Hsu YC, Sung CH. Ultrastructural visualization of trans-ciliary rhodopsin cargoes in mammalian rods. Cilia 2015; 4:4. [PMID: 25664179 PMCID: PMC4320831 DOI: 10.1186/s13630-015-0013-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 01/15/2015] [Indexed: 11/28/2022] Open
Abstract
Background Cilia are vital to various cellular and sensory functions. The pathway by which ciliary membrane proteins translocate through the transition zone is not well understood. Direct morphological characterization of ciliary cargoes in transit remains lacking. In the vertebrate photoreceptor, rhodopsin is synthesized and transported from the inner segment to the disc membranes of the outer segment (OS), which is a modified cilium. To date, the membrane topology of the basal OS and the mechanisms by which rhodopsin is transported through the transition zone (i.e., connecting cilium) and by which nascent disc membranes are formed remain controversial. Results Using an antibody recognizing its cytoplasmic C-terminus, we localize rhodopsin on both the plasma membrane and lumen of the connecting cilium by immuno-electron microscopy (EM). We also use transmission EM to visualize the electron-dense enzymatic products derived from the rhodopsin-horseradish peroxidase (HRP) fusion in transfected rodent rods. In the connecting cilium, rhodopsin is not only expressed in the plasma membrane but also in the lumen on two types of membranous carriers, long smooth tubules and small, coated, filament-bound vesicles. Additionally, membrane-bound rhodopsin carriers are also found in close proximity to the nascent discs at the basal OS axoneme and in the distal inner segment. This topology-indicative HRP-rhodopsin reporter shows that the nascent basalmost discs and the mature discs have the same membrane topology, with no indication of evagination or invagination from the basal OS plasma membranes. Serial block face and focus ion beam scanning EM analyses both indicate that the transport carriers enter the connecting cilium lumen from either the basal body lumen or cytoplasmic space between the axonemal microtubules and the ciliary plasma membrane. Conclusions Our results suggest the existence of multiple ciliary gate entry pathways in rod photoreceptors. Rhodopsin is likely transported across the connecting cilium on the plasma membrane and through the lumens on two types of tubulovesicular carriers produced in the inner segment. Our findings agree with a previous model that rhodopsin carriers derived from the cell body may fuse directly onto nascent discs as they grow and mature. Electronic supplementary material The online version of this article (doi:10.1186/s13630-015-0013-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jen-Zen Chuang
- Department of Ophthalmology, Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10065 USA
| | - Ya-Chu Hsu
- Department of Ophthalmology, Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10065 USA
| | - Ching-Hwa Sung
- Department of Ophthalmology, Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10065 USA ; Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10067 USA ; The Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Avenue, LC313, New York, NY 10065 USA
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Mathur P, Yang J. Usher syndrome: Hearing loss, retinal degeneration and associated abnormalities. Biochim Biophys Acta Mol Basis Dis 2014; 1852:406-20. [PMID: 25481835 DOI: 10.1016/j.bbadis.2014.11.020] [Citation(s) in RCA: 222] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 11/25/2014] [Accepted: 11/26/2014] [Indexed: 02/06/2023]
Abstract
Usher syndrome (USH), clinically and genetically heterogeneous, is the leading genetic cause of combined hearing and vision loss. USH is classified into three types, based on the hearing and vestibular symptoms observed in patients. Sixteen loci have been reported to be involved in the occurrence of USH and atypical USH. Among them, twelve have been identified as causative genes and one as a modifier gene. Studies on the proteins encoded by these USH genes suggest that USH proteins interact among one another and function in multiprotein complexes in vivo. Although their exact functions remain enigmatic in the retina, USH proteins are required for the development, maintenance and function of hair bundles, which are the primary mechanosensitive structure of inner ear hair cells. Despite the unavailability of a cure, progress has been made to develop effective treatments for this disease. In this review, we focus on the most recent discoveries in the field with an emphasis on USH genes, protein complexes and functions in various tissues as well as progress toward therapeutic development for USH.
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Affiliation(s)
- Pranav Mathur
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA; Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT 84132, USA
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA; Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT 84132, USA; Department of Otolaryngology Head and Neck Surgery, University of Utah, Salt Lake City, UT 84132, USA.
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Dyka FM, Boye SL, Chiodo VA, Hauswirth WW, Boye SE. Dual adeno-associated virus vectors result in efficient in vitro and in vivo expression of an oversized gene, MYO7A. Hum Gene Ther Methods 2014; 25:166-77. [PMID: 24568220 DOI: 10.1089/hgtb.2013.212] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Usher syndrome 1B (USH1B) is a severe, autosomal recessive, deaf-blind disorder caused by mutations in myosin 7A (MYO7A). Patients are born profoundly deaf and exhibit progressive loss of vision starting in their first decade. MYO7A is expressed in human photoreceptors and retinal pigment epithelium, but disease pathology begins in photoreceptors, highlighting the need to develop a gene replacement strategy that effectively targets this cell type. For its safety and efficacy in clinical trials and ability to transduce postmitotic photoreceptors, we have focused on developing a clinically applicable adeno-associated virus (AAV) platform for delivering full-length MYO7A cDNA (∼6.7 kb). Packaging of full-length MYO7A cDNA in AAV produces vectors with heterogeneous, fragmented genomes ("fAAV") capable of reconstituting full-length cDNA postinfection. We previously showed that fAAV vectors effectively delivered full-length MYO7A in vitro and in vivo. However, fAAV vectors are relatively inefficient and their heterogeneous genomes preclude definitive characterization, a drawback for clinical translatability. The aim of this study was to overcome these limitations by creating dual-AAV-vector platforms for USH1B with defined genomes. Human MYO7A was cloned in AAV vector pairs, each containing genomes <5 kb and intact inverted terminal repeats. One vector contained a promoter and 5' portion of the cDNA and the partner vector contained a 3' portion and polyadenylation signal. "Simple overlap" vectors share a central part of the MYO7A cDNA sequence. "Trans-splicing" and "hybrid" vectors utilize splice donor and acceptor sites with and without an additional central recombinogenic sequence, respectively. Vector pairs expressed full-length MYO7A in vitro and in vivo with equal or higher efficiency than fAAV, with a hybrid platform being most efficient. Importantly, analysis of MYO7A mRNA derived from each dual-vector platform revealed 100% fidelity to the predicted sequence. Our results suggest that dual AAV vectors with defined genetic payloads are a potential treatment option for USH1B.
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Affiliation(s)
- Frank M Dyka
- Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, FL 32610
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29
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Hodel C, Niklaus S, Heidemann M, Klooster J, Kamermans M, Biehlmaier O, Gesemann M, Neuhauss SC. Myosin VIIA is a Marker for the Cone Accessory Outer Segment in Zebrafish. Anat Rec (Hoboken) 2014; 297:1777-84. [DOI: 10.1002/ar.22976] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/25/2014] [Accepted: 05/18/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Corinne Hodel
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
| | - Stephanie Niklaus
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
| | - Martina Heidemann
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
| | - Jan Klooster
- Netherlands Institute for Neuroscience; The Royal Netherlands Academy of Arts and Sciences; Amsterdam The Netherlands
| | - Maarten Kamermans
- Netherlands Institute for Neuroscience; The Royal Netherlands Academy of Arts and Sciences; Amsterdam The Netherlands
| | - Oliver Biehlmaier
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
| | - Matthias Gesemann
- Institute of Molecular Life Sciences; University of Zurich; Zurich Switzerland
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Piatti G, De Santi MM, Brogi M, Castorina P, Ambrosetti U. Emerging ciliopathies: are respiratory cilia compromised in Usher syndrome? Am J Otolaryngol 2014; 35:340-6. [PMID: 24602455 DOI: 10.1016/j.amjoto.2014.01.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/26/2014] [Indexed: 01/19/2023]
Abstract
PURPOSE Usher syndrome is a ciliopathy involving photoreceptors and cochlear hair cells (sensory cilia): since sensory and motor ciliopathies can overlap, we analysed the respiratory cilia (motile) in 17 patients affected by Usher syndrome and 18 healthy control subject. PATIENTS AND METHODS We studied the mucociliary transport time with the saccharine test, ciliary motility and ultrastructure of respiratory cilia obtained by nasal brushing; we also recorded the classical respiratory function values by spirometry. RESULTS All enrolled subjects showed normal respiratory function values. The mean mucociliary transport time with saccharine was 22.33 ± 17.96 min, which is in the range of normal values. The mean ciliary beat frequency of all subjects was 8.81 ± 2.18 Hz, which is a value approaching the lower physiological limit. None of the classical ciliary alterations characterizing the "ciliary primary dyskinesia" was detected, although two patients showed alterations in number and arrangement of peripheral microtubules and one patient had abnormal ciliary roots. CONCLUSIONS Respiratory cilia in Usher patients don't seem to have evident ultrastructural alterations, as expected, but the fact that the ciliary motility appeared slightly reduced could emphasize that a rigid distinction between sensory and motor ciliopathies may not reflect what really occurs.
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Affiliation(s)
- G Piatti
- Department of Pathophysiology and Transplantation, University of Milan, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Italy.
| | - M M De Santi
- Department of Human Pathology and Oncology, University of Siena, Italy
| | - M Brogi
- Department of Human Pathology and Oncology, University of Siena, Italy
| | - P Castorina
- Department of Clinical Sciences and Community, University of Milan, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Italy
| | - U Ambrosetti
- Department of Clinical Sciences and Community, University of Milan, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Italy
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Wasfy MM, Matsui JI, Miller J, Dowling JE, Perkins BD. myosin 7aa(-/-) mutant zebrafish show mild photoreceptor degeneration and reduced electroretinographic responses. Exp Eye Res 2014; 122:65-76. [PMID: 24698764 DOI: 10.1016/j.exer.2014.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 03/18/2014] [Accepted: 03/19/2014] [Indexed: 01/20/2023]
Abstract
Mutations in myosin VIIa (MYO7A) cause Usher Syndrome 1B (USH1B), a disease characterized by the combination of sensorineural hearing loss and visual impairment termed retinitis pigmentosa (RP). Although the shaker-1 mouse model of USH1B exists, only minor defects in the retina have been observed during its lifespan. Previous studies of the zebrafish mariner mutant, which also carries a mutation in myo7aa, revealed balance and hearing defects in the mutants but the retinal phenotype has not been described. We found elevated cell death in the outer nuclear layer (ONL) of myo7aa(-/-) mutants. While myo7aa(-/-) mutants retained visual behaviors in the optokinetic reflex (OKR) assay, electroretinogram (ERG) recordings revealed a significant decrease in both a- and b-wave amplitudes in mutant animals, but not a change in ERG threshold sensitivity. Immunohistochemistry showed mislocalization of rod and blue cone opsins and reduced expression of rod-specific markers in the myo7aa(-/-) ONL, providing further evidence that the photoreceptor degeneration observed represents the initial stages of the RP. Further, constant light exposure resulted in widespread photoreceptor degeneration and the appearance of large holes in the retinal pigment epithelium (RPE). No differences were observed in the retinomotor movements of the photoreceptors or in melanosome migration within the RPE, suggesting that myo7aa(-/-) does not function in these processes in teleosts. These results indicate that the zebrafish myo7aa(-/-) mutant is a useful animal model for the RP seen in humans with USH1B.
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Affiliation(s)
- Meagan M Wasfy
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Jonathan I Matsui
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Jessica Miller
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - John E Dowling
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Brian D Perkins
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
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Smith TS, Spitzbarth B, Li J, Dugger DR, Stern-Schneider G, Sehn E, Bolch SN, McDowell JH, Tipton J, Wolfrum U, Smith WC. Light-dependent phosphorylation of Bardet-Biedl syndrome 5 in photoreceptor cells modulates its interaction with arrestin1. Cell Mol Life Sci 2013; 70:4603-16. [PMID: 23817741 DOI: 10.1007/s00018-013-1403-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/04/2013] [Accepted: 06/10/2013] [Indexed: 01/14/2023]
Abstract
Arrestins are dynamic proteins that move between cell compartments triggered by stimulation of G-protein-coupled receptors. Even more dynamically in vertebrate photoreceptors, arrestin1 (Arr1) moves between the inner and outer segments according to the light conditions. Previous studies have shown that the light-driven translocation of Arr1 in rod photoreceptors is initiated by rhodopsin through a phospholipase C/protein kinase C (PKC) signaling cascade. The purpose of this study is to identify the PKC substrate that regulates the translocation of Arr1. Mass spectrometry was used to identify the primary phosphorylated proteins in extracts prepared from PKC-stimulated mouse eye cups, confirming the finding with in vitro phosphorylation assays. Our results show that Bardet-Biedl syndrome 5 (BBS5) is the principal protein phosphorylated either by phorbol ester stimulation or by light stimulation of PKC. Via immunoprecipitation of BBS5 in rod outer segments, Arr1 was pulled down; phosphorylation of BBS5 reduced this co-precipitation of Arr1. Immunofluorescence and immunoelectron microscopy showed that BBS5 principally localizes along the axonemes of rods and cones, but also in photoreceptor inner segments, and synaptic regions. Our principal findings in this study are threefold. First, we demonstrate that BBS5 is post-translationally regulated by phosphorylation via PKC, an event that is triggered by light in photoreceptor cells. Second, we find a direct interaction between BBS5 and Arr1, an interaction that is modulated by phosphorylation of BBS5. Finally, we show that BBS5 is distributed along the photoreceptor axoneme, co-localizing with Arr1 in the dark. These findings suggest a role for BBS5 in regulating light-dependent translocation of Arr1 and a model describing its role in Arr1 translocation is proposed.
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Affiliation(s)
- Tyler S Smith
- Department of Ophthalmology, University of Florida, Box 100284 JHMHC, Gainesville, FL, 32610-0284, USA
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Papal S, Cortese M, Legendre K, Sorusch N, Dragavon J, Sahly I, Shorte S, Wolfrum U, Petit C, El-Amraoui A. The giant spectrin βV couples the molecular motors to phototransduction and Usher syndrome type I proteins along their trafficking route. Hum Mol Genet 2013; 22:3773-88. [PMID: 23704327 DOI: 10.1093/hmg/ddt228] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Mutations in the myosin VIIa gene cause Usher syndrome type IB (USH1B), characterized by deaf-blindness. A delay of opsin trafficking has been observed in the retinal photoreceptor cells of myosin VIIa-deficient mice. We identified spectrin βV, the mammalian β-heavy spectrin, as a myosin VIIa- and rhodopsin-interacting partner in photoreceptor cells. Spectrin βV displays a polarized distribution from the Golgi apparatus to the base of the outer segment, which, unlike that of other β spectrins, matches the trafficking route of opsin and other phototransduction proteins. Formation of spectrin βV-rhodopsin complex could be detected in the differentiating photoreceptors as soon as their outer segment emerges. A failure of the spectrin βV-mediated coupling between myosin VIIa and opsin molecules thus probably accounts for the opsin transport delay in myosin VIIa-deficient mice. We showed that spectrin βV also associates with two USH1 proteins, sans (USH1G) and harmonin (USH1C). Spectrins are supposed to function as heteromers of α and β subunits, but fluorescence resonance energy transfer and in vitro binding experiments indicated that spectrin βV can also form homodimers, which likely supports its αII-independent βV functions. Finally, consistent with its distribution along the connecting cilia axonemes, spectrin βV binds to several subunits of the microtubule-based motor proteins, kinesin II and the dynein complex. We therefore suggest that spectrin βV homomers couple some USH1 proteins, opsin and other phototransduction proteins to both actin- and microtubule-based motors, thereby contributing to their transport towards the photoreceptor outer disks.
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Affiliation(s)
- Samantha Papal
- Institut Pasteur, Unité de génétique et physiologie de l'audition, Paris, France
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Kravtsov DV, Caputo C, Collaco A, Hoekstra N, Egan ME, Mooseker MS, Ameen NA. Myosin Ia is required for CFTR brush border membrane trafficking and ion transport in the mouse small intestine. Traffic 2012; 13:1072-82. [PMID: 22510086 DOI: 10.1111/j.1600-0854.2012.01368.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 04/12/2012] [Accepted: 04/17/2012] [Indexed: 12/16/2022]
Abstract
In enterocytes of the small intestine, endocytic trafficking of CFTR channels from the brush border membrane (BBM) to the subapical endosomes requires the minus-end motor, myosin VI (Myo6). The subapical localization of Myo6 is dependent on myosin Ia (Myo1a) the major plus-end motor associated with the BBM, suggestive of functional synergy between these two motors. In villus enterocytes of the Myo1a KO mouse small intestine, CFTR accumulated in syntaxin-3 positive subapical endosomes, redistributed to the basolateral domain and was absent from the BBM. In colon, where villi are absent and Myo1a expression is low, CFTR exhibited normal localization to the BBM in the Myo1a KO similar to WT. cAMP-stimulated CFTR anion transport in the small intestine was reduced by 58% in the KO, while anion transport in the colon was comparable to WT. Co-immunoprecipitation confirmed the association of CFTR with Myo1a. These data indicate that Myo1a is an important regulator of CFTR traffic and anion transport in the BBM of villus enterocytes and suggest that Myo1a may power apical CFTR movement into the BBM from subapical endosomes. Alternatively, it may anchor CFTR channels in the BBM of villus enterocytes as was proposed for Myo1a's role in BBM localization of sucrase-isomaltase.
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Affiliation(s)
- Dmitri V Kravtsov
- Department of Pediatrics/Gastroenterology & Hepatology, Yale University School of Medicine, 333 Cedar Street, FMP 408, P.O. Box 208064, New Haven, CT 06520, USA
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Overexpression of S4D mutant of Leishmania donovani ADF/cofilin impairs flagellum assembly by affecting actin dynamics. EUKARYOTIC CELL 2012; 11:752-60. [PMID: 22492507 DOI: 10.1128/ec.00013-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Leishmania, like other eukaryotes, contains large amounts of actin and a number of actin-related and actin binding proteins. Our earlier studies have shown that deletion of the gene corresponding to Leishmania actin-depolymerizing protein (ADF/cofilin) adversely affects flagellum assembly, intracellular trafficking, and cell division. To further analyze this, we have now created ADF/cofilin site-specific point mutants and then examined (i) the actin-depolymerizing, G-actin binding, and actin-bound nucleotide exchange activities of the mutant proteins and (ii) the effect of overexpression of these proteins in wild-type cells. Here we show that S4D mutant protein failed to depolymerize F-actin but weakly bound G-actin and inhibited the exchange of G-actin-bound nucleotide. We further observed that overexpression of this protein impaired flagellum assembly and consequently cell motility by severely impairing the assembly of the paraflagellar rod, without significantly affecting vesicular trafficking or cell growth. Taken together, these results indicate that dynamic actin is essentially required in assembly of the eukaryotic flagellum.
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Ramamurthy B, Cao W, De la Cruz EM, Mooseker MS. Plus-end directed myosins accelerate actin filament sliding by single-headed myosin VI. Cytoskeleton (Hoboken) 2012; 69:59-69. [PMID: 22213699 DOI: 10.1002/cm.21002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 12/19/2011] [Accepted: 12/20/2011] [Indexed: 12/19/2022]
Abstract
Myosin VI (Myo6) is unique among myosins in that it moves toward the minus (pointed) end of the actin filament. Thus to exert tension on, or move cargo along an actin filament, Myo6 is working against potentially multiple plus (barbed)-end myosins. To test the effect of plus-end motors on Myo6, the gliding actin filament assay was used to assess the motility of single-headed Myo6 in the absence and presence of cardiac myosin II (Myo2) and myosin Va (Myo5a). Myo6 alone exhibited a filament gliding velocities of 60.34 ± 13.68 nm/s. Addition of either Myo2 or Myo5a, at densities below that required to promote plus-end movement resulted in an increase in Myo6 velocity (~100-150% increase). Movement in the presence of these plus-end myosins was minus-end directed as determined using polarity tagged filaments. High densities of Myo2 or Myo5a were required to convert to plus-end directed motility indicating that Myo6 is a potent inhibitor of Myo2 and Myo5a. Previous studies have shown that two-headed Myo6 slows and then stalls in an anchored state under load. Consistent with these studies, velocity of a two headed heavy mero myosin form of Myo6 was unaffected by Myo5a at low densities, and was inhibited at high Myo5a densities.
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Affiliation(s)
- Bhagavathi Ramamurthy
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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Wang L, Zou J, Shen Z, Song E, Yang J. Whirlin interacts with espin and modulates its actin-regulatory function: an insight into the mechanism of Usher syndrome type II. Hum Mol Genet 2011; 21:692-710. [PMID: 22048959 DOI: 10.1093/hmg/ddr503] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Whirlin mutations cause retinal degeneration and hearing loss in Usher syndrome type II (USH2) and non-syndromic deafness, DFNB31. Its protein recruits other USH2 causative proteins to form a complex at the periciliary membrane complex in photoreceptors and the ankle link of the stereocilia in hair cells. However, the biological function of this USH2 protein complex is largely unknown. Using a yeast two-hybrid screen, we identified espin, an actin-binding/bundling protein involved in human deafness when defective, as a whirlin-interacting protein. The interaction between these two proteins was confirmed by their coimmunoprecipitation and colocalization in cultured cells. This interaction involves multiple domains of both proteins and only occurs when espin does not bind to actin. Espin was partially colocalized with whirlin in the retina and the inner ear. In whirlin knockout mice, espin expression changed significantly in these two tissues. Further studies found that whirlin increased the mobility of espin and actin at the actin bundles cross-linked by espin and, eventually, affected the dimension of these actin bundles. In whirlin knockout mice, the stereocilia were thickened in inner hair cells. We conclude that the interaction between whirlin and espin and the balance between their expressions are required to maintain the actin bundle network in photoreceptors and hair cells. Disruption of this actin bundle network contributes to the pathogenic mechanism of hearing loss and retinal degeneration caused by whirlin and espin mutations. Espin is a component of the USH2 protein complex and could be a candidate gene for Usher syndrome.
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Affiliation(s)
- Le Wang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA
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Moen RJ, Johnsrud DO, Thomas DD, Titus MA. Characterization of a myosin VII MyTH/FERM domain. J Mol Biol 2011; 413:17-23. [PMID: 21875595 DOI: 10.1016/j.jmb.2011.08.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 08/13/2011] [Accepted: 08/16/2011] [Indexed: 11/28/2022]
Abstract
A group of closely related myosins is characterized by the presence of at least one MyTH/FERM (myosin tail homology; band 4.1, ezrin, radixin, moesin) domain in their C-terminal tails. This domain interacts with a variety of binding partners, and mutations in either the MyTH4 or the FERM domain of myosin VII and myosin XV result in deafness, highlighting the functional importance of each domain. The N-terminal MyTH/FERM region of Dictyostelium myosin VII (M7) has been isolated as a first step toward gaining insight into the function of this domain and its interaction with binding partners. The M7 MyTH4/FERM domain (MF1) binds to both actin and microtubules in vitro, with dissociation constants of 13.7 and 1.7 μM, respectively. Gel filtration and UV spectroscopy reveal that MF1 exists as a monomer in solution and forms a well-folded, compact conformation with a high degree of secondary structure. These results indicate that MF1 forms an integrated structural domain that serves to couple actin filaments and microtubules in specific regions of the cytoskeleton.
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Affiliation(s)
- Rebecca J Moen
- (1)Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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Peng YW, Zallocchi M, Wang WM, Delimont D, Cosgrove D. Moderate light-induced degeneration of rod photoreceptors with delayed transducin translocation in shaker1 mice. Invest Ophthalmol Vis Sci 2011; 52:6421-7. [PMID: 21447681 DOI: 10.1167/iovs.10-6557] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE. Usher syndrome is characterized by congenital deafness associated with retinitis pigmentosa (RP). Mutations in the myosin VIIa gene (MYO7A) cause a common and severe subtype of Usher syndrome (USH1B). Shaker1 mice have mutant MYO7A. They are deaf and have vestibular dysfunction but do not develop photoreceptor degeneration. The goal of this study was to investigate abnormalities of photoreceptors in shaker1 mice. METHODS. Immunocytochemistry and hydroethidine-based detection of intracellular superoxide production were used. Photoreceptor cell densities under various conditions of light/dark exposures were evaluated. RESULTS. In shaker1 mice, the rod transducin translocation is delayed because of a shift of its light activation threshold to a higher level. Even moderate light exposure can induce oxidative damage and significant rod degeneration in shaker1 mice. Shaker1 mice reared under a moderate light/dark cycle develop severe retinal degeneration in less than 6 months. CONCLUSIONS. These findings show that, contrary to earlier studies, shaker1 mice possess a robust retinal phenotype that may link to defective rod protein translocation. Importantly, USH1B animal models are likely vulnerable to light-induced photoreceptor damage, even under moderate light.
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Affiliation(s)
- You-Wei Peng
- National Usher Syndrome Center, Boys Town National Research Hospital, Omaha, Nebraska, USA.
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Heissler SM, Manstein DJ. Functional characterization of the human myosin-7a motor domain. Cell Mol Life Sci 2011; 69:299-311. [PMID: 21687988 PMCID: PMC3249170 DOI: 10.1007/s00018-011-0749-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 05/30/2011] [Accepted: 06/01/2011] [Indexed: 11/26/2022]
Abstract
Myosin-7a participates in auditory and visual processes. Defects in MYO7A, the gene encoding the myosin-7a heavy chain, are causative for Usher syndrome 1B, the most frequent cause of deaf-blindness in humans. In the present study, we performed a detailed kinetic and functional characterization of the isolated human myosin-7a motor domain to elucidate the details of chemomechanical coupling and the regulation of motor function. A rate-limiting, slow ADP release step causes long lifetimes of strong actin-binding intermediates and results in a high duty ratio. Moreover, our results reveal a Mg2+-sensitive regulatory mechanism tuning the kinetic and mechanical properties of the myosin-7a motor domain. We obtained direct evidence that changes in the concentration of free Mg2+ ions affect the motor properties of human myosin-7a using an in vitro motility assay system. Our results suggest that in a cellular environment, compartment-specific fluctuations in free Mg2+ ions can mediate the conditional switching of myosin-7a between cargo moving and tension bearing modes.
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Affiliation(s)
- Sarah M. Heissler
- Institut für Biophysikalische Chemie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dietmar J. Manstein
- Institut für Biophysikalische Chemie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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Haithcock J, Billington N, Choi K, Fordham J, Sellers JR, Stafford WF, White H, Forgacs E. The kinetic mechanism of mouse myosin VIIA. J Biol Chem 2011; 286:8819-28. [PMID: 21212272 DOI: 10.1074/jbc.m110.163592] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin VIIa is crucial in hearing and visual processes. We examined the kinetic and association properties of the baculovirus expressed, truncated mouse myosin VIIa construct containing the head, all 5IQ motifs and the putative coiled coil domain (myosin VIIa-5IQ). The construct appears to be monomeric as determined by analytical ultracentrifugation experiments, and only single headed molecules were detected by negative stain electron microscopy. The relatively high basal steady-state rate of 0.18 s(-1) is activated by actin only by ∼3.5-fold resulting in a V(max) of 0.7 s(-1) and a K(ATPase) of 11.5 μM. There is no single rate-limiting step of the ATP hydrolysis cycle. The ATP hydrolysis step (M·T M·D·P) is slow (12 s(-1)) and the equilibrium constant (K(H)) of 1 suggests significant reversal of hydrolysis. In the presence of actin ADP dissociates with a rate constant of 1.2 s(-1). Phosphate dissociation is relatively fast (>12 s(-1)), but the maximal rate could not be experimentally obtained at actin concentrations ≤ 50 μM because of the weak binding of the myosin VIIa-ADP-P(i) complex to actin. At higher actin concentrations the rate of attached hydrolysis (0.4 s(-1)) becomes significant and partially rate-limiting. Our findings suggest that the myosin VIIa is a "slow", monomeric molecular motor with a duty ratio of 0.6.
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Affiliation(s)
- Jessica Haithcock
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507, USA
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Lange K. Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signaling system at the cell periphery. J Cell Physiol 2010; 226:896-927. [PMID: 20607764 DOI: 10.1002/jcp.22302] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Nakanishi H, Ohtsubo M, Iwasaki S, Hotta Y, Mizuta K, Mineta H, Minoshima S. Hair roots as an mRNA source for mutation analysis of Usher syndrome-causing genes. J Hum Genet 2010; 55:701-3. [DOI: 10.1038/jhg.2010.83] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zallocchi M, Sisson JH, Cosgrove D. Biochemical characterization of native Usher protein complexes from a vesicular subfraction of tracheal epithelial cells. Biochemistry 2010; 49:1236-47. [PMID: 20058854 DOI: 10.1021/bi9020617] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Usher syndrome is the major cause of deaf/blindness in the world. It is a genetic heterogeneous disorder, with nine genes already identified as causative for the disease. We noted expression of all known Usher proteins in bovine tracheal epithelial cells and exploited this system for large-scale biochemical analysis of Usher protein complexes. The dissected epithelia were homogenized in nondetergent buffer and sedimented on sucrose gradients. At least two complexes were evident after the first gradient: one formed by specific isoforms of CDH23, PCDH15, and VLGR-1 and a different one at the top of the gradient that included all of the Usher proteins and rab5, a transport vesicle marker. TEM analysis of these top fractions found them enriched in 100-200 nm vesicles, confirming a vesicular association of the Usher complex(es). Immunoisolation of these vesicles confirmed some of the associations already predicted and identified novel interactions. When the vesicles are lysed in the presence of phenylbutyrate, most of the Usher proteins cosediment into the gradient at a sedimentation coefficient of approximately 50 S, correlating with a predicted molecular mass of 2 x 10(6) Da. Although it is still unclear whether there is only one complex or several independent complexes that are trafficked within distinct vesicular pools, this work shows for the first time that native Usher protein complexes occur in vivo. This complex(es) is present primarily in transport vesicles at the apical pole of tracheal epithelial cells, predicting that Usher proteins may be directionally transported as complexes in hair cells and photoreceptors.
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Affiliation(s)
- Marisa Zallocchi
- Usher Syndrome Center, Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA
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Brown JW, McKnight CJ. Molecular model of the microvillar cytoskeleton and organization of the brush border. PLoS One 2010; 5:e9406. [PMID: 20195380 PMCID: PMC2827561 DOI: 10.1371/journal.pone.0009406] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 02/01/2010] [Indexed: 01/22/2023] Open
Abstract
Background Brush border microvilli are ∼1-µm long finger-like projections emanating from the apical surfaces of certain, specialized absorptive epithelial cells. A highly symmetric hexagonal array of thousands of these uniformly sized structures form the brush border, which in addition to aiding in nutrient absorption also defends the large surface area against pathogens. Here, we present a molecular model of the protein cytoskeleton responsible for this dramatic cellular morphology. Methodology/Principal Findings The model is constructed from published crystallographic and microscopic structures reported by several groups over the last 30+ years. Our efforts resulted in a single, unique, self-consistent arrangement of actin, fimbrin, villin, brush border myosin (Myo1A), calmodulin, and brush border spectrin. The central actin core bundle that supports the microvillus is nearly saturated with fimbrin and villin cross-linkers and has a density similar to that found in protein crystals. The proposed model accounts for all major proteinaceous components, reproduces the experimentally determined stoichiometry, and is consistent with the size and morphology of the biological brush border membrane. Conclusions/Significance The model presented here will serve as a structural framework to explain many of the dynamic cellular processes occurring over several time scales, such as protein diffusion, association, and turnover, lipid raft sorting, membrane deformation, cytoskeletal-membrane interactions, and even effacement of the brush border by invading pathogens. In addition, this model provides a structural basis for evaluating the equilibrium processes that result in the uniform size and structure of the highly dynamic microvilli.
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Affiliation(s)
- Jeffrey W. Brown
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - C. James McKnight
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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A novel allele of myosin VIIa reveals a critical function for the C-terminal FERM domain for melanosome transport in retinal pigment epithelial cells. J Neurosci 2010; 29:15810-8. [PMID: 20016096 DOI: 10.1523/jneurosci.4876-09.2009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mutations in the head and tail domains of the motor protein myosin VIIA (MYO7A) cause deaf-blindness (Usher syndrome type 1B, USH1B) and nonsyndromic deafness (DFNB2, DFNA11). The head domain binds to F-actin and serves as the MYO7A motor domain, but little is known about the function of the tail domain. In a genetic screen, we have identified polka mice, which carry a mutation (c.5742 + 5G > A) that affects splicing of the MYO7A transcript and truncates the MYO7A tail domain at the C-terminal FERM domain. In the inner ear, expression of the truncated MYO7A protein is severely reduced, leading to defects in hair cell development. In retinal pigment epithelial (RPE) cells, the truncated MYO7A protein is expressed at comparative levels to wild-type protein but fails to associate with and transport melanosomes. We conclude that the C-terminal FERM domain of MYO7A is critical for melanosome transport in RPE cells. Our findings also suggest that MYO7A mutations can lead to tissue-specific effects on protein levels, which may explain why some mutations in MYO7A lead to deafness without retinal impairment.
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Gibbs D, Diemer T, Khanobdee K, Hu J, Bok D, Williams DS. Function of MYO7A in the human RPE and the validity of shaker1 mice as a model for Usher syndrome 1B. Invest Ophthalmol Vis Sci 2009; 51:1130-5. [PMID: 19643958 DOI: 10.1167/iovs.09-4032] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To investigate the function of MYO7A in human RPE cells and to test the validity of using shaker1 RPE in preclinical studies on therapies for Usher syndrome 1B by comparing human and mouse cells. METHODS MYO7A was localized by immunofluorescence. Primary cultures of human and mouse RPE cells were used to measure melanosome motility and rod outer segment (ROS) phagocytosis and digestion. MYO7A was knocked down in the human RPE cells by RNAi to test for a mutant phenotype in melanosome motility. RESULTS The distribution of MYO7A in the RPE of human and mouse was found to be comparable, both in vivo and in primary cultures. Primary cultures of human RPE cells phagocytosed and digested ROSs with kinetics comparable to that of primary cultures of mouse RPE cells. Melanosome motility was also comparable, and, after RNAi knockdown, consisted of longer-range fast movements characteristic of melanosomes in shaker1 RPE. CONCLUSIONS The localization and function of MYO7A in human RPE cells is comparable to that in mouse RPE cells. Although shaker1 retinas do not undergo degeneration, correction of mutant phenotypes in the shaker1 RPE represents a valid preclinical test for potential therapeutic treatments.
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Affiliation(s)
- Daniel Gibbs
- Department of Pharmacology, University of California at San Diego School of Medicine, La Jolla, California, USA
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Woolner S, Bement WM. Unconventional myosins acting unconventionally. Trends Cell Biol 2009; 19:245-52. [PMID: 19406643 DOI: 10.1016/j.tcb.2009.03.003] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Revised: 03/26/2009] [Accepted: 03/27/2009] [Indexed: 11/26/2022]
Abstract
Unconventional myosins are proteins that bind actin filaments in an ATP-regulated manner. Because of their association with membranes, they have traditionally been viewed as motors that function primarily to transport membranous organelles along actin filaments. Recently, however, a wealth of roles for myosins that are not obviously related to organelle transport have been uncovered, including organization of F-actin, mitotic spindle regulation and gene transcription. Furthermore, it has also become apparent that the motor domains of different myosins vary strikingly in their biophysical attributes. We suggest that the assumption that most unconventional myosins function primarily as organelle transporters might be misguided.
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Affiliation(s)
- Sarah Woolner
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK.
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Abstract
PURPOSE OF REVIEW The present review addresses the mechanisms, genetics and pathogenesis of Usher syndrome. RECENT FINDINGS Recent molecular findings have provided more information regarding the pathogenesis of this disorder and the wide phenotypic variation in both audiovestibular and/or visual systems. Evidence has begun to emerge supporting a theory of a protein interactome involving the Usher proteins in both the inner ear and the retina. This interactome appears to be important for hair cell development in the ear but its role in the retina remains unclear. SUMMARY Understanding clinical disease progression and molecular pathways is important in the progress towards developing gene therapy to prevent blindness due to Usher syndrome as well as delivering prognostic information to affected individuals.
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