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Sutton DC, Andrews JC, Dolezal DM, Park YJ, Li H, Eberl DF, Yamamoto S, Groves AK. Comparative exploration of mammalian deafness gene homologues in the Drosophila auditory organ shows genetic correlation between insect and vertebrate hearing. PLoS One 2024; 19:e0297846. [PMID: 38412189 PMCID: PMC10898740 DOI: 10.1371/journal.pone.0297846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 01/13/2024] [Indexed: 02/29/2024] Open
Abstract
Johnston's organ, the Drosophila auditory organ, is anatomically very different from the mammalian organ of Corti. However, recent evidence indicates significant cellular and molecular similarities exist between vertebrate and invertebrate hearing, suggesting that Drosophila may be a useful platform to determine the function of the many mammalian deafness genes whose underlying biological mechanisms are poorly characterized. Our goal was a comprehensive screen of all known orthologues of mammalian deafness genes in the fruit fly to better understand conservation of hearing mechanisms between the insect and the fly and ultimately gain insight into human hereditary deafness. We used bioinformatic comparisons to screen previously reported human and mouse deafness genes and found that 156 of them have orthologues in Drosophila melanogaster. We used fluorescent imaging of T2A-GAL4 gene trap and GFP or YFP fluorescent protein trap lines for 54 of the Drosophila genes and found 38 to be expressed in different cell types in Johnston's organ. We phenotypically characterized the function of strong loss-of-function mutants in three genes expressed in Johnston's organ (Cad99C, Msp-300, and Koi) using a courtship assay and electrophysiological recordings of sound-evoked potentials. Cad99C and Koi were found to have significant courtship defects. However, when we tested these genes for electrophysiological defects in hearing response, we did not see a significant difference suggesting the courtship defects were not caused by hearing deficiencies. Furthermore, we used a UAS/RNAi approach to test the function of seven genes and found two additional genes, CG5921 and Myo10a, that gave a statistically significant delay in courtship but not in sound-evoked potentials. Our results suggest that many mammalian deafness genes have Drosophila homologues expressed in the Johnston's organ, but that their requirement for hearing may not necessarily be the same as in mammals.
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Affiliation(s)
- Daniel C. Sutton
- Graduate Program in Genetics & Genomics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Jonathan C. Andrews
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, Texas, United States of America
| | - Dylan M. Dolezal
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Ye Jin Park
- Graduate Program in Development, Disease Models & Therapeutics, Baylor College of Medicine, Houston, Texas, United States of America
- Huffington Center on Aging, One Baylor Plaza, Houston, Texas, United States of America
| | - Hongjie Li
- Graduate Program in Development, Disease Models & Therapeutics, Baylor College of Medicine, Houston, Texas, United States of America
- Huffington Center on Aging, One Baylor Plaza, Houston, Texas, United States of America
| | - Daniel F. Eberl
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Shinya Yamamoto
- Graduate Program in Genetics & Genomics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, Texas, United States of America
- Graduate Program in Development, Disease Models & Therapeutics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Andrew K. Groves
- Graduate Program in Genetics & Genomics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Development, Disease Models & Therapeutics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
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Warren B, Eberl D. What can insects teach us about hearing loss? J Physiol 2024; 602:297-316. [PMID: 38128023 DOI: 10.1113/jp281281] [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: 05/26/2023] [Accepted: 12/05/2023] [Indexed: 12/23/2023] Open
Abstract
Over the last three decades, insects have been utilized to provide a deep and fundamental understanding of many human diseases and disorders. Here, we present arguments for insects as models to understand general principles underlying hearing loss. Despite ∼600 million years since the last common ancestor of vertebrates and invertebrates, we share an overwhelming degree of genetic homology particularly with respect to auditory organ development and maintenance. Despite the anatomical differences between human and insect auditory organs, both share physiological principles of operation. We explain why these observations are expected and highlight areas in hearing loss research in which insects can provide insight. We start by briefly introducing the evolutionary journey of auditory organs, the reasons for using insect auditory organs for hearing loss research, and the tools and approaches available in insects. Then, the first half of the review focuses on auditory development and auditory disorders with a genetic cause. The second half analyses the physiological and genetic consequences of ageing and short- and long-term changes as a result of noise exposure. We finish with complex age and noise interactions in auditory systems. In this review, we present some of the evidence and arguments to support the use of insects to study mechanisms and potential treatments for hearing loss in humans. Obviously, insects cannot fully substitute for all aspects of human auditory function and loss of function, although there are many important questions that can be addressed in an animal model for which there are important ethical, practical and experimental advantages.
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Affiliation(s)
- Ben Warren
- Neurogenetics Group, College of Life Sciences, University of Leicester, Leicester, UK
| | - Daniel Eberl
- Department of Biology, University of Iowa, Iowa City, IA, USA
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Zhang B, Duan H, Kavaler J, Wei L, Eberl DF, Lai EC. A nonneural miRNA cluster mediates hearing via repression of two neural targets. Genes Dev 2023; 37:1041-1051. [PMID: 38110249 PMCID: PMC10760640 DOI: 10.1101/gad.351052.123] [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: 08/07/2023] [Accepted: 11/29/2023] [Indexed: 12/20/2023]
Abstract
We show here that mir-279/996 are absolutely essential for development and function of Johnston's organ (JO), the primary proprioceptive and auditory organ in Drosophila Their deletion results in highly aberrant cell fate determination, including loss of scolopale cells and ectopic neurons, and mutants are electrophysiologically deaf. In vivo activity sensors and mosaic analyses indicate that these seed-related miRNAs function autonomously to suppress neural fate in nonneuronal cells. Finally, genetic interactions pinpoint two neural targets (elav and insensible) that underlie miRNA mutant JO phenotypes. This work uncovers how critical post-transcriptional regulation of specific miRNA targets governs cell specification and function of the auditory system.
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Affiliation(s)
- Binglong Zhang
- Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA
| | - Hong Duan
- Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA
| | - Joshua Kavaler
- Department of Biology, Colby College, Waterville, Maine 04901, USA
| | - Lu Wei
- Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA
| | - Daniel F Eberl
- Department of Biology, University of Iowa, Iowa City, Iowa 52242, USA
| | - Eric C Lai
- Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA;
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Sharma Y, Jacobs JS, Sivan-Loukianova E, Lee E, Kernan MJ, Eberl DF. The retrograde IFT dynein is required for normal function of diverse mechanosensory cilia in Drosophila. Front Mol Neurosci 2023; 16:1263411. [PMID: 37808471 PMCID: PMC10556659 DOI: 10.3389/fnmol.2023.1263411] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/07/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction Cilia biogenesis relies on intraflagellar transport (IFT), a conserved transport mechanism which functions bi-directionally to bring protein complexes to the growing ciliary tip and recycle signaling and transport proteins between the cilium and cell body. In Drosophila, anterograde IFT is critical for assembly of sensory cilia in the neurons of both chordotonal (ch) organs, which have relatively long ciliary axonemes, and external sensory (es) organs, which have short axonemal segments with microtubules in distal sensory segments forming non-axonemal bundles. We previously isolated the beethoven (btv) mutant in a mutagenesis screen for auditory mutants. Although many btv mutant flies are deaf, some retain a small residual auditory function as determined both by behavior and by auditory electrophysiology. Results Here we molecularly characterize the btv gene and demonstrate that it encodes the IFT-associated dynein-2 heavy chain Dync2h1. We also describe morphological changes in Johnston's organ as flies age to 30 days, and we find that morphological and electrophysiological phenotypes in this ch organ of btv mutants become more severe with age. We show that NompB protein, encoding the conserved IFT88 protein, an IFT complex B component, fails to be cleared from chordotonal cilia in btv mutants, instead accumulating in the distorted cilia. In macrochaete bristles, a class of es organ, btv mutants show a 50% reduction in mechanoreceptor potentials. Discussion Thus, the btv-encoded Dync2h1 functions as the retrograde IFT motor in the assembly of long ciliary axonemes in ch organs and is also important for normal function of the short ciliary axonemes in es organs.
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Affiliation(s)
- Yashoda Sharma
- Department of Biology, The University of Iowa, Iowa City, IA, United States
| | - Julie S. Jacobs
- Department of Biology, The University of Iowa, Iowa City, IA, United States
| | | | - Eugene Lee
- Department of Neurobiology and Behavior, State University of New York, Stony Brook, NY, United States
| | - Maurice J. Kernan
- Department of Neurobiology and Behavior, State University of New York, Stony Brook, NY, United States
| | - Daniel F. Eberl
- Department of Biology, The University of Iowa, Iowa City, IA, United States
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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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Johnson SL, Blount JR, Libohova K, Ranxhi B, Paulson HL, Tsou WL, Todi SV. Differential toxicity of ataxin-3 isoforms in Drosophila models of Spinocerebellar Ataxia Type 3. Neurobiol Dis 2019; 132:104535. [PMID: 31310802 DOI: 10.1016/j.nbd.2019.104535] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 12/28/2022] Open
Abstract
The most commonly inherited dominant ataxia, Spinocerebellar Ataxia Type 3 (SCA3), is caused by a CAG repeat expansion that encodes an abnormally long polyglutamine (polyQ) repeat in the disease protein ataxin-3, a deubiquitinase. Two major full-length isoforms of ataxin-3 exist, both of which contain the same N-terminal portion and polyQ repeat, but differ in their C-termini; one (denoted here as isoform 1) contains a motif that binds ataxin-3's substrate, ubiquitin, whereas the other (denoted here as isoform 2) has a hydrophobic tail. Most SCA3 studies have focused on isoform 1, the predominant version in mammalian brain, yet both isoforms are present in brain and a better understanding of their relative pathogenicity in vivo is needed. We took advantage of the fruit fly, Drosophila melanogaster to model SCA3 and to examine the toxicity of each ataxin-3 isoform. Our assays reveal isoform 1 to be markedly more toxic than isoform 2 in all fly tissues. Reduced toxicity from isoform 2 is due to much lower protein levels as a result of its expedited degradation. Additional studies indicate that isoform 1 is more aggregation-prone than isoform 2 and that the C-terminus of isoform 2 is critical for its enhanced proteasomal degradation. According to our results, although both full-length, pathogenic ataxin-3 isoforms are toxic, isoform 1 is likely the primary contributor to SCA3 due to its presence at higher levels. Isoform 2, as a result of rapid degradation that is dictated by its tail, is unlikely to be a key player in this disease. Our findings provide new insight into the biology of this ataxia and the cellular processing of the underlying disease protein.
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Affiliation(s)
- Sean L Johnson
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Jessica R Blount
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Kozeta Libohova
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Bedri Ranxhi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Henry L Paulson
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Wei-Ling Tsou
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - Sokol V Todi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA; Department of Neurology, Wayne State University School of Medicine, Detroit, MI, USA.
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Li C, Liu J, Lü P, Ma S, Zhu K, Gao L, Li B, Chen K. Identification, expression and function of myosin heavy chain family genes in Tribolium castaneum. Genomics 2019; 111:719-728. [DOI: 10.1016/j.ygeno.2018.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 04/12/2018] [Accepted: 04/13/2018] [Indexed: 02/07/2023]
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Blount JR, Meyer DN, Akemann C, Johnson SL, Gurdziel K, Baker TR, Todi SV. Unanchored ubiquitin chains do not lead to marked alterations in gene expression in Drosophila melanogaster. Biol Open 2019; 8:bio.043372. [PMID: 31097444 PMCID: PMC6550069 DOI: 10.1242/bio.043372] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The small protein modifier ubiquitin regulates various aspects of cellular biology through its chemical conjugation onto proteins. Ubiquitination of proteins presents itself in numerous iterations, from a single mono-ubiquitination event to chains of poly-ubiquitin. Ubiquitin chains can be attached onto other proteins or can exist as unanchored species, i.e. free from another protein. Unanchored ubiquitin chains are thought to be deleterious to the cell and rapidly disassembled into mono-ubiquitin. We recently examined the toxicity and utilization of unanchored poly-ubiquitin in Drosophila melanogaster. We found that free poly-ubiquitin species are largely innocuous to flies and that free poly-ubiquitin can be controlled by being degraded by the proteasome or by being conjugated onto another protein as a single unit. Here, to explore whether an organismal defense is mounted against unanchored chains, we conducted RNA-Seq analyses to examine the transcriptomic impact of free poly-ubiquitin in the fly. We found ∼90 transcripts whose expression is altered in the presence of different types of unanchored poly-ubiquitin. The set of genes identified was essentially devoid of ubiquitin-, proteasome-, or autophagy-related components. The seeming absence of a large and multipronged response to unanchored poly-ubiquitin supports the conclusion that these species need not be toxic in vivo and underscores the need to re-examine the role of free ubiquitin chains in the cell. Summary: Our Drosophila studies indicate the lack of a marked, coordinated response towards unanchored poly-ubiquitin in flies, suggesting that untethered ubiquitin chains are not necessarily problematic in intact organisms.
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Affiliation(s)
- Jessica R Blount
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Danielle N Meyer
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Camille Akemann
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Sean L Johnson
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Katherine Gurdziel
- Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Tracie R Baker
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA .,Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48201, USA
| | - Sokol V Todi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA .,Department of Neurology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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Genome-wide identification and characterization of myosin genes in the silkworm, Bombyx mori. Gene 2019; 691:45-55. [PMID: 30611842 DOI: 10.1016/j.gene.2018.12.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 11/18/2018] [Accepted: 12/01/2018] [Indexed: 11/21/2022]
Abstract
Myosins are a large family of actin filament-based motor proteins with a broad range of functions such as intracellular membrane trafficking, endocytosis, exocytosis, organellar transport, growth cone motility, cytokinesis, and cell locomotion. They are found in many organisms from fungi to humans. The myosin gene family in Bombyx mori is poorly studied, even though the molecular functions of these genes in vertebrates and insects, such as Drosophila, are well known. We identified 16 myosin genes from B. mori and identified the myosin genes in 12 vertebrates, eight insects, three nematodes, and seven protozoa. The number of myosin genes in vertebrates is double the number in invertebrates. The number of myosin isoforms in classes I and II is larger in vertebrates compared to invertebrates. B. mori myosin genes can be classified into 11 classes. Compared to B. mori, some myosin classes are not present in other insects. Classes I, II, XVIII, and XXI appear to be important for insect survival because they are conserved among nine insects. The relatively large sizes of B. mori myosin genes are due to their longer introns. Reverse transcription PCR (RT-PCR) and quantitative real-time PCR (qRT-PCR) analysis demonstrated that many B. mori myosin genes have tissue-specific expression and exhibit temporal-specific activity during metamorphosis. These data provide insights into evolutionary and functional aspects of B. mori myosin genes that could be useful for the study of homologous myosins in other Lepidoptera species.
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11
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Sabiha B, Ali J, Yousafzai YM, Haider SA. Novel deleterious mutation in MYO7A, TH and EVC2 in two Pakistani brothers with familial deafness. Pak J Med Sci 2018; 35:17-22. [PMID: 30881389 PMCID: PMC6408642 DOI: 10.12669/pjms.35.1.98] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Objective In Pakistan, 74% of consanguineous marriages are among the first cousins. Continuity of consanguineous marriages over generations increases the risk of recessive diseases such as deafness. The objective of this study was to investigate genetic origin of Pakistani deaf brothers with parents of consanguineous marriage. Methods DNA was extracted from the blood through Qiagen kit. Paired-end sequencing library was prepared according to protocol of Illumina's TruSight Rapid Capture kit and TruSight Inherited Disease Panel. Library was normalized and used for Next Generation Sequencing through MiSeq. NGS data were analyzed using various bioinformatics tools. Results Both brothers were found to have novel deleterious mutation in MYO7A (c.2476G>A) while the younger brother had additional novel deleterious mutation in TH (c.43C>T) and EVC2 (c.2614C>T) genes. Conclusion It is concluded that in addition to novel mutations in MYO7A, TH and EVC2, the CDH23 and GJB2 can also be responsible for deafness in the family with consanguineous marriages.
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Affiliation(s)
- Bibi Sabiha
- Bibi Sabiha, Center for Genomic Sciences, Rehman Medical College, Phase-V, Hayatabad, Peshawar, KP, Pakistan
| | - Johar Ali
- Johar Ali, Center for Genomic Sciences, Rehman Medical College, Phase-V, Hayatabad, Peshawar, KP, Pakistan
| | - Yasar Mehmood Yousafzai
- Yasar Mehmood Yousafzai, Institute of Basic Medical Sciences, Khyber Medical University, Peshawar, Pakistan
| | - Syed Adnan Haider
- Syed Adnan Haider, Center for Genomic Sciences, Rehman Medical College, Phase-V, Hayatabad, Peshawar, KP, Pakistan
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Li C, Lu Y, Ma S, Lü P, Li B, Chen K. Crinkled employs wingless pathway for wing development in Tribolium castaneum. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2018; 99:e21496. [PMID: 29984841 DOI: 10.1002/arch.21496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Crinkled is associated with embryonic denticle formation and auditory organ development in Drosophila melanogaster. However, the functions of Crinkled have not been fully investigated. Additionally, the genes that participate in the Crinkled pathway are unknown. Phylogenetic analysis indicates that crinkled exhibits a one-to-one orthologous relationship in insects. In Tribolium castaneum, the crinkled gene is 6,498 bp in length and consists of six exons. Crinkled expression peaked during two phases in Tribolium: late embryonic and pupal stages. High levels of crinkled mRNA were detected in the fat body, head, epidermis, ovary, and accessory gland of late adults. Knockdown of crinkled using RNA interference (RNAi) severely affected wing morphogenesis in T. castaneum. We further showed that crinkled silencing reduced forked expression through wingless and shaven-baby, and RNAi of forked phenocopied the effects of crinkled knockdown in T. castaneum. This study investigated the development role of crinkled in postembryonic stages and indicated that forked mediates the functions of crinkled during wing morphogenesis in T. castaneum.
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Affiliation(s)
- Chengjun Li
- Institute of Life Sciences, Jiangsu University, Zhenjiang, China
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Yaoyao Lu
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Shangshang Ma
- Institute of Life Sciences, Jiangsu University, Zhenjiang, China
| | - Peng Lü
- Institute of Life Sciences, Jiangsu University, Zhenjiang, China
| | - Bin Li
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Keping Chen
- Institute of Life Sciences, Jiangsu University, Zhenjiang, China
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13
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Blount JR, Libohova K, Marsh GB, Sutton JR, Todi SV. Expression and Regulation of Deubiquitinase-Resistant, Unanchored Ubiquitin Chains in Drosophila. Sci Rep 2018; 8:8513. [PMID: 29855490 PMCID: PMC5981470 DOI: 10.1038/s41598-018-26364-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 05/10/2018] [Indexed: 01/03/2023] Open
Abstract
The modifier protein, ubiquitin (Ub) regulates various cellular pathways by controlling the fate of substrates to which it is conjugated. Ub moieties are also conjugated to each other, forming chains of various topologies. In cells, poly-Ub is attached to proteins and also exists in unanchored form. Accumulation of unanchored poly-Ub is thought to be harmful and quickly dispersed through dismantling by deubiquitinases (DUBs). We wondered whether disassembly by DUBs is necessary to control unanchored Ub chains in vivo. We generated Drosophila melanogaster lines that express Ub chains non-cleavable into mono-Ub by DUBs. These chains are rapidly modified with different linkages and represent various types of unanchored species. We found that unanchored poly-Ub is not devastating in Drosophila, under normal conditions or during stress. The DUB-resistant, free Ub chains are degraded by the proteasome, at least in part through the assistance of VCP and its cofactor, p47. Also, unanchored poly-Ub that cannot be cleaved by DUBs can be conjugated en bloc, in vivo. Our results indicate that unanchored poly-Ub species need not be intrinsically toxic; they can be controlled independently of DUB-based disassembly by being degraded, or through conjugation onto other proteins.
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Affiliation(s)
- Jessica R Blount
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Kozeta Libohova
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Gregory B Marsh
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Joanna R Sutton
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Sokol V Todi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA. .,Department of Neurology, Wayne State University School of Medicine, Detroit, MI, USA.
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14
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Li T, Bellen HJ, Groves AK. Using Drosophila to study mechanisms of hereditary hearing loss. Dis Model Mech 2018; 11:11/6/dmm031492. [PMID: 29853544 PMCID: PMC6031363 DOI: 10.1242/dmm.031492] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Johnston's organ - the hearing organ of Drosophila - has a very different structure and morphology to that of the hearing organs of vertebrates. Nevertheless, it is becoming clear that vertebrate and invertebrate auditory organs share many physiological, molecular and genetic similarities. Here, we compare the molecular and cellular features of hearing organs in Drosophila with those of vertebrates, and discuss recent evidence concerning the functional conservation of Usher proteins between flies and mammals. Mutations in Usher genes cause Usher syndrome, the leading cause of human deafness and blindness. In Drosophila, some Usher syndrome proteins appear to physically interact in protein complexes that are similar to those described in mammals. This functional conservation highlights a rational role for Drosophila as a model for studying hearing, and for investigating the evolution of auditory organs, with the aim of advancing our understanding of the genes that regulate human hearing and the pathogenic mechanisms that lead to deafness.
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Affiliation(s)
- Tongchao Li
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Hugo J Bellen
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA .,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
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15
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Tsou WL, Qiblawi SH, Hosking RR, Gomez CM, Todi SV. Polyglutamine length-dependent toxicity from α1ACT in Drosophila models of spinocerebellar ataxia type 6. Biol Open 2016; 5:1770-1775. [PMID: 27979829 PMCID: PMC5200913 DOI: 10.1242/bio.021667] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disease that results from abnormal expansion of a polyglutamine (polyQ) repeat. SCA6 is caused by CAG triplet repeat expansion in the gene CACNA1A, resulting in a polyQ tract of 19-33 in patients. CACNA1A, a bicistronic gene, encodes the α1A calcium channel subunit and the transcription factor, α1ACT. PolyQ expansion in α1ACT causes degeneration in mice. We recently described the first Drosophila models of SCA6 that express α1ACT with a normal (11Q) or hyper-expanded (70Q) polyQ. Here, we report additional α1ACT transgenic flies, which express full-length α1ACT with a 33Q repeat. We show that α1ACT33Q is toxic in Drosophila, but less so than the 70Q version. When expressed everywhere, α1ACT33Q-expressing adults die earlier than flies expressing the normal allele. α1ACT33Q causes retinal degeneration and leads to aggregated species in an age-dependent manner, but at a slower pace than the 70Q counterpart. According to western blots, α1ACT33Q localizes less readily in the nucleus than α1ACT70Q, providing clues into the importance of polyQ tract length on α1ACT localization and its site of toxicity. We expect that these new lines will be highly valuable for future work on SCA6.
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Affiliation(s)
- Wei-Ling Tsou
- Department of Pharmacology, Wayne State University, Detroit, MI 48201, USA
| | - Sultan H Qiblawi
- Department of Pharmacology, Wayne State University, Detroit, MI 48201, USA
| | - Ryan R Hosking
- Department of Pharmacology, Wayne State University, Detroit, MI 48201, USA
| | | | - Sokol V Todi
- Department of Pharmacology, Wayne State University, Detroit, MI 48201, USA .,Department of Neurology, Wayne State University, Detroit, MI 48201, USA
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16
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Abstract
Studying the auditory system of the fruit fly can reveal how hearing works in mammals.
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Affiliation(s)
- Yi-Nan Lee
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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17
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Li T, Giagtzoglou N, Eberl DF, Jaiswal SN, Cai T, Godt D, Groves AK, Bellen HJ. The E3 ligase Ubr3 regulates Usher syndrome and MYH9 disorder proteins in the auditory organs of Drosophila and mammals. eLife 2016; 5. [PMID: 27331610 PMCID: PMC4978524 DOI: 10.7554/elife.15258] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/21/2016] [Indexed: 01/08/2023] Open
Abstract
Myosins play essential roles in the development and function of auditory organs and multiple myosin genes are associated with hereditary forms of deafness. Using a forward genetic screen in Drosophila, we identified an E3 ligase, Ubr3, as an essential gene for auditory organ development. Ubr3 negatively regulates the mono-ubiquitination of non-muscle Myosin II, a protein associated with hearing loss in humans. The mono-ubiquitination of Myosin II promotes its physical interaction with Myosin VIIa, a protein responsible for Usher syndrome type IB. We show that ubr3 mutants phenocopy pathogenic variants of Myosin II and that Ubr3 interacts genetically and physically with three Usher syndrome proteins. The interactions between Myosin VIIa and Myosin IIa are conserved in the mammalian cochlea and in human retinal pigment epithelium cells. Our work reveals a novel mechanism that regulates protein complexes affected in two forms of syndromic deafness and suggests a molecular function for Myosin IIa in auditory organs.
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Affiliation(s)
- Tongchao Li
- Program in Developmental Biology, Baylor College of Medicine, Houston, United States
| | - Nikolaos Giagtzoglou
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Department of Neurology, Baylor College of Medicine, Houston, United States
| | - Daniel F Eberl
- Department of Biology, University of Iowa, Iowa City, United States
| | - Sonal Nagarkar Jaiswal
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, United States
| | - Tiantian Cai
- Department of Neuroscience, Baylor College of Medicine, Houston, United States
| | - Dorothea Godt
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Department of Neuroscience, Baylor College of Medicine, Houston, United States
| | - Hugo J Bellen
- Program in Developmental Biology, Baylor College of Medicine, Houston, United States.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, United States.,Department of Neuroscience, Baylor College of Medicine, Houston, United States
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18
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Glowinski C, Liu RHS, Chen X, Darabie A, Godt D. Myosin VIIA regulates microvillus morphogenesis and interacts with cadherin Cad99C in Drosophila oogenesis. J Cell Sci 2014; 127:4821-32. [PMID: 25236597 DOI: 10.1242/jcs.099242] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Microvilli and related actin-based protrusions permit multiple interactions between cells and their environment. How the shape, length and arrangement of microvilli are determined remains largely unclear. To address this issue and explore the cooperation of the two main components of a microvillus, the central F-actin bundle and the enveloping plasma membrane, we investigated the expression and function of Myosin VIIA (Myo7A), which is encoded by crinkled (ck), and its interaction with cadherin Cad99C in the microvilli of the Drosophila follicular epithelium. Myo7A is present in the microvilli and terminal web of follicle cells, and associates with several other F-actin-rich structures in the ovary. Loss of Myo7A caused brush border defects and a reduction in the amount of the microvillus regulator Cad99C. We show that Myo7A and Cad99C form a molecular complex and that the cytoplasmic tail of Cad99C recruits Myo7A to microvilli. Our data indicate that Myo7A regulates the structure and spacing of microvilli, and interacts with Cad99C in vivo. A comparison of the mutant phenotypes suggests that Myo7A and Cad99C have co-dependent and independent functions in microvilli.
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Affiliation(s)
- Cory Glowinski
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 2M6, Canada
| | - Ri-Hua Sandy Liu
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 2M6, Canada
| | - Xi Chen
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 2M6, Canada
| | - Audrey Darabie
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 2M6, Canada
| | - Dorothea Godt
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 2M6, Canada
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19
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Boekhoff-Falk G, Eberl DF. The Drosophila auditory system. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 3:179-91. [PMID: 24719289 DOI: 10.1002/wdev.128] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 08/28/2013] [Accepted: 09/10/2013] [Indexed: 11/10/2022]
Abstract
Development of a functional auditory system in Drosophila requires specification and differentiation of the chordotonal sensilla of Johnston's organ (JO) in the antenna, correct axonal targeting to the antennal mechanosensory and motor center in the brain, and synaptic connections to neurons in the downstream circuit. Chordotonal development in JO is functionally complicated by structural, molecular, and functional diversity that is not yet fully understood, and construction of the auditory neural circuitry is only beginning to unfold. Here, we describe our current understanding of developmental and molecular mechanisms that generate the exquisite functions of the Drosophila auditory system, emphasizing recent progress and highlighting important new questions arising from research on this remarkable sensory system.
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Affiliation(s)
- Grace Boekhoff-Falk
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
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20
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Tsou WL, Burr AA, Ouyang M, Blount JR, Scaglione KM, Todi SV. Ubiquitination regulates the neuroprotective function of the deubiquitinase ataxin-3 in vivo. J Biol Chem 2013; 288:34460-9. [PMID: 24106274 DOI: 10.1074/jbc.m113.513903] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Deubiquitinases (DUBs) are proteases that regulate various cellular processes by controlling protein ubiquitination. Cell-based studies indicate that the regulation of the activity of DUBs is important for homeostasis and is achieved by multiple mechanisms, including through their own ubiquitination. However, the physiological significance of the ubiquitination of DUBs to their functions in vivo is unclear. Here, we report that ubiquitination of the DUB ataxin-3 at lysine residue 117, which markedly enhances its protease activity in vitro, is critical for its ability to suppress toxic protein-dependent degeneration in Drosophila melanogaster. Compared with ataxin-3 with only Lys-117 present, ataxin-3 that does not become ubiquitinated performs significantly less efficiently in suppressing or delaying the onset of toxic protein-dependent degeneration in flies. According to further studies, the C terminus of Hsc70-interacting protein (CHIP), an E3 ubiquitin ligase that ubiquitinates ataxin-3 in vitro, is dispensable for its ubiquitination in vivo and is not required for the neuroprotective function of this DUB in Drosophila. Our work also suggests that ataxin-3 suppresses degeneration by regulating toxic protein aggregation rather than stability.
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Affiliation(s)
- Wei-Ling Tsou
- From the Departments of Pharmacology and Neurology and
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21
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Heckman CA, Plummer HK. Filopodia as sensors. Cell Signal 2013; 25:2298-311. [PMID: 23876793 DOI: 10.1016/j.cellsig.2013.07.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 07/04/2013] [Accepted: 07/09/2013] [Indexed: 12/19/2022]
Abstract
Filopodia are sensors on both excitable and non-excitable cells. The sensing function is well documented in neurons and blood vessels of adult animals and is obvious during dorsal closure in embryonic development. Nerve cells extend neurites in a bidirectional fashion with growth cones at the tips where filopodia are concentrated. Their sensing of environmental cues underpins the axon's ability to "guide," bypassing non-target cells and moving toward the target to be innervated. This review focuses on the role of filopodia structure and dynamics in the detection of environmental cues, including both the extracellular matrix (ECM) and the surfaces of neighboring cells. Other protrusions including the stereocilia of the inner ear and epididymus, the invertebrate Type I mechanosensors, and the elongated processes connecting osteocytes, share certain principles of organization with the filopodia. Actin bundles, which may be inside or outside of the excitable cell, function to transduce stress from physical perturbations into ion signals. There are different ways of detecting such perturbations. Osteocyte processes contain an actin core and are physically anchored on an extracellular structure by integrins. Some Type I mechanosensors have bridge proteins that anchor microtubules to the membrane, but bundles of actin in accessory cells exert stress on this complex. Hair cells of the inner ear rely on attachments between the actin-based protrusions to activate ion channels, which then transduce signals to afferent neurons. In adherent filopodia, the focal contacts (FCs) integrated with ECM proteins through integrins may regulate integrin-coupled ion channels to achieve signal transduction. Issues that are not understood include the role of Ca(2+) influx in filopodia dynamics and how integrins coordinate or gate signals arising from perturbation of channels by environmental cues.
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Affiliation(s)
- C A Heckman
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403-0212, USA.
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22
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Duncan JS, Fritzsch B. Evolution of Sound and Balance Perception: Innovations that Aggregate Single Hair Cells into the Ear and Transform a Gravistatic Sensor into the Organ of Corti. Anat Rec (Hoboken) 2012; 295:1760-74. [DOI: 10.1002/ar.22573] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/24/2012] [Indexed: 01/20/2023]
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23
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Abstract
Most animals exhibit innate auditory behaviors driven by genetically hardwired neural circuits. In Drosophila, acoustic information is relayed by Johnston organ neurons from the antenna to the antennal mechanosensory and motor center (AMMC) in the brain. Here, by using structural connectivity analysis, we identified five distinct types of auditory projection neurons (PNs) interconnecting the AMMC, inferior ventrolateral protocerebrum (IVLP), and ventrolateral protocerebrum (VLP) regions of the central brain. These auditory PNs are also functionally distinct; AMMC-B1a, AMMC-B1b, and AMMC-A2 neurons differ in their responses to sound (i.e., they are narrowly tuned or broadly tuned); one type of audioresponsive IVLP commissural PN connecting the two hemispheres is GABAergic; and one type of IVLP-VLP PN acts as a generalist responding to all tested audio frequencies. Our findings delineate an auditory processing pathway involving AMMC→IVLP→VLP in the Drosophila brain.
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24
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Eberl DF, Kernan MJ. Recording sound-evoked potentials from the Drosophila antennal nerve. Cold Spring Harb Protoc 2011; 2011:prot5576. [PMID: 21363940 DOI: 10.1101/pdb.prot5576] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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25
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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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26
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Etournay R, Lepelletier L, Boutet de Monvel J, Michel V, Cayet N, Leibovici M, Weil D, Foucher I, Hardelin JP, Petit C. Cochlear outer hair cells undergo an apical circumference remodeling constrained by the hair bundle shape. Development 2010; 137:1373-83. [PMID: 20332152 DOI: 10.1242/dev.045138] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Epithelial cells acquire diverse shapes relating to their different functions. This is particularly relevant for the cochlear outer hair cells (OHCs), whose apical and basolateral shapes accommodate the functioning of these cells as mechano-electrical and electromechanical transducers, respectively. We uncovered a circumferential shape transition of the apical junctional complex (AJC) of OHCs, which occurs during the early postnatal period in the mouse, prior to hearing onset. Geometric analysis of the OHC apical circumference using immunostaining of the AJC protein ZO1 and Fourier-interpolated contour detection characterizes this transition as a switch from a rounded-hexagon to a non-convex circumference delineating two lateral lobes at the neural side of the cell, with a negative curvature in between. This shape tightly correlates with the 'V'-configuration of the OHC hair bundle, the apical mechanosensitive organelle that converts sound-evoked vibrations into variations in cell membrane potential. The OHC apical circumference remodeling failed or was incomplete in all the mouse mutants affected in hair bundle morphogenesis that we tested. During the normal shape transition, myosin VIIa and myosin II (A and B isoforms) displayed polarized redistributions into and out of the developing lobes, respectively, while Shroom2 and F-actin transiently accumulated in the lobes. Defects in these redistributions were observed in the mutants, paralleling their apical circumference abnormalities. Our results point to a pivotal role for actomyosin cytoskeleton tensions in the reshaping of the OHC apical circumference. We propose that this remodeling contributes to optimize the mechanical coupling between the basal and apical poles of mature OHCs.
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Affiliation(s)
- Raphaël Etournay
- Unité de Génétique et Physiologie de l'Audition, INSERM UMRS587-Université Paris VI, Institut Pasteur, 25 rue du Dr Roux, Paris Cedex 15, France
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27
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FERM proteins in animal morphogenesis. Curr Opin Genet Dev 2009; 19:357-67. [PMID: 19596566 DOI: 10.1016/j.gde.2009.05.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Accepted: 05/29/2009] [Indexed: 01/19/2023]
Abstract
Proteins containing a FERM domain are ubiquitous components of the cytocortex of animal cells where they are engaged in structural, transport, and signaling functions. Recent years have seen a wealth of genetic studies in model organisms that explore FERM protein function in development and tissue organization. In addition, mutations in several FERM protein-encoding genes have been associated with human diseases. This review will provide a brief overview of the FERM domain structure and the FERM protein superfamily and then discuss recent advances in our understanding of the mechanism of function and developmental requirement of several FERM proteins including Moesin, Myosin-VIIA, Myosin-XV, Coracle/Band4.1 as well as Yurt and its vertebrate homologs Mosaic Eyes and EPB41L5/YMO1/Limulus.
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28
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Demontis F, Dahmann C. Characterization of the Drosophila ortholog of the human Usher Syndrome type 1G protein sans. PLoS One 2009; 4:e4753. [PMID: 19270738 PMCID: PMC2649435 DOI: 10.1371/journal.pone.0004753] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 02/09/2009] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND The Usher syndrome (USH) is the most frequent deaf-blindness hereditary disease in humans. Deafness is attributed to the disorganization of stereocilia in the inner ear. USH1, the most severe subtype, is associated with mutations in genes encoding myosin VIIa, harmonin, cadherin 23, protocadherin 15, and sans. Myosin VIIa, harmonin, cadherin 23, and protocadherin 15 physically interact in vitro and localize to stereocilia tips in vivo, indicating that they form functional complexes. Sans, in contrast, localizes to vesicle-like structures beneath the apical membrane of stereocilia-displaying hair cells. How mutations in sans result in deafness and blindness is not well understood. Orthologs of myosin VIIa and protocadherin 15 have been identified in Drosophila melanogaster and their genetic analysis has identified essential roles in auditory perception and microvilli morphogenesis, respectively. PRINCIPAL FINDINGS Here, we have identified and characterized the Drosophila ortholog of human sans. Drosophila Sans is expressed in tubular organs of the embryo, in lens-secreting cone cells of the adult eye, and in microvilli-displaying follicle cells during oogenesis. Sans mutants are viable, fertile, and mutant follicle cells appear to form microvilli, indicating that Sans is dispensable for fly development and microvilli morphogenesis in the follicle epithelium. In follicle cells, Sans protein localizes, similar to its vertebrate ortholog, to intracellular punctate structures, which we have identified as early endosomes associated with the syntaxin Avalanche. CONCLUSIONS Our work is consistent with an evolutionary conserved function of Sans in vesicle trafficking. Furthermore it provides a significant basis for further understanding of the role of this Usher syndrome ortholog in development and disease.
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Affiliation(s)
- Fabio Demontis
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Christian Dahmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- * E-mail:
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