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Klann M, Schacht MI, Benton MA, Stollewerk A. Functional analysis of sense organ specification in the Tribolium castaneum larva reveals divergent mechanisms in insects. BMC Biol 2021; 19:22. [PMID: 33546687 PMCID: PMC7866635 DOI: 10.1186/s12915-021-00948-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 01/04/2021] [Indexed: 12/27/2022] Open
Abstract
Abstract Insects and other arthropods utilise external sensory structures for mechanosensory, olfactory, and gustatory reception. These sense organs have characteristic shapes related to their function, and in many cases are distributed in a fixed pattern so that they are identifiable individually. In Drosophila melanogaster, the identity of sense organs is regulated by specific combinations of transcription factors. In other arthropods, however, sense organ subtypes cannot be linked to the same code of gene expression. This raises the questions of how sense organ diversity has evolved and whether the principles underlying subtype identity in D. melanogaster are representative of other insects. Here, we provide evidence that such principles cannot be generalised, and suggest that sensory organ diversification followed the recruitment of sensory genes to distinct sensory organ specification mechanism. Results We analysed sense organ development in a nondipteran insect, the flour beetle Tribolium castaneum, by gene expression and RNA interference studies. We show that in contrast to D. melanogaster, T. castaneum sense organs cannot be categorised based on the expression or their requirement for individual or combinations of conserved sense organ transcription factors such as cut and pox neuro, or members of the Achaete-Scute (Tc ASH, Tc asense), Atonal (Tc atonal, Tc cato, Tc amos), and neurogenin families (Tc tap). Rather, our observations support an evolutionary scenario whereby these sensory genes are required for the specification of sense organ precursors and the development and differentiation of sensory cell types in diverse external sensilla which do not fall into specific morphological and functional classes. Conclusions Based on our findings and past research, we present an evolutionary scenario suggesting that sense organ subtype identity has evolved by recruitment of a flexible sensory gene network to the different sense organ specification processes. A dominant role of these genes in subtype identity has evolved as a secondary effect of the function of these genes in individual or subsets of sense organs, probably modulated by positional cues. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-00948-y.
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Affiliation(s)
- Marleen Klann
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.,Marine Eco-Evo-Devo Unit, Okinawa Institute for Science and Technology (OIST), 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan
| | - Magdalena Ines Schacht
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Matthew Alan Benton
- Department of Zoology, University of Cambridge, Downing St, Cambridge, CB2 3EJ, UK
| | - Angelika Stollewerk
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
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2
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Teuscher M, Ströhlein N, Birkenbach M, Schultheis D, Schoppmeier M. TC003132 is essential for the follicle stem cell lineage in telotrophic Tribolium oogenesis. Front Zool 2017; 14:26. [PMID: 28533810 PMCID: PMC5438533 DOI: 10.1186/s12983-017-0212-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 05/11/2017] [Indexed: 12/31/2022] Open
Abstract
Background Stem cells are undifferentiated cells with a potential for self-renewal, which are essential to support normal development and homeostasis. To gain insight into the molecular mechanisms underlying adult stem cell biology and organ evolution, we use the telotrophic ovary of the beetle Tribolium. To this end, we participated in a large-scale RNAi screen in the red flour beetle Tribolium, which identified functions in embryonic and postembryonic development for more than half of the Tribolium genes. Results We identified TC003132 as candidate gene for the follicle stem cell linage in telotrophic Tribolium oogenesis. TC003132 belongs to the Casein Kinase 2 substrate family (CK2S), which in humans is associated with the proliferative activity of different cancers. Upon TC003132 RNAi, central pre-follicular cells are lost, which results in termination of oogenesis. Given that also Notch-signalling is required to promote the mitotic activity of central pre-follicular cells, we performed epistasis experiments with Notch and cut. In addition, we identified a putative follicle stem cell population by monitoring the mitotic pattern of wild type and TC003132 depleted follicle cells by EdU incorporations. In TC003132 RNAi these putative FSCs cease the expression of differentiation makers and are eventually lost. Conclusions TC003132 depleted pre-follicular cells neither react to mitosis or endocycle stimulating signals, suggesting that TC003132 provides competence for differentiation cues. This may resemble the situation in C. elegans were CK2 is required to maintain the balance between proliferation and differentiation in the germ line. Since the earliest effect of TC003132 RNAi is characterized by the loss of putative FSCs, we posit that TC003132 crucially contributes to the proliferation or maintenance of follicle stem cells in the telotrophic Tribolium ovary. Electronic supplementary material The online version of this article (doi:10.1186/s12983-017-0212-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthias Teuscher
- Department Biology, Developmental Biology Unit, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Nadi Ströhlein
- Department Biology, Developmental Biology Unit, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Markus Birkenbach
- Department Biology, Developmental Biology Unit, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Dorothea Schultheis
- Present address: Institute of Neuropathology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Michael Schoppmeier
- Department Biology, Developmental Biology Unit, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
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3
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Cachero S, Simpson TI, zur Lage PI, Ma L, Newton FG, Holohan EE, Armstrong JD, Jarman AP. The gene regulatory cascade linking proneural specification with differentiation in Drosophila sensory neurons. PLoS Biol 2011; 9:e1000568. [PMID: 21283833 PMCID: PMC3023811 DOI: 10.1371/journal.pbio.1000568] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 11/05/2010] [Indexed: 12/20/2022] Open
Abstract
In neurogenesis, neural cell fate specification is generally triggered by proneural transcription factors. Whilst the role of proneural factors in fate specification is well studied, the link between neural specification and the cellular pathways that ultimately must be activated to construct specialised neurons is usually obscure. High-resolution temporal profiling of gene expression reveals the events downstream of atonal proneural gene function during the development of Drosophila chordotonal (mechanosensory) neurons. Among other findings, this reveals the onset of expression of genes required for construction of the ciliary dendrite, a key specialisation of mechanosensory neurons. We determine that atonal activates this cellular differentiation pathway in several ways. Firstly, atonal directly regulates Rfx, a well-known highly conserved ciliogenesis transcriptional regulator. Unexpectedly, differences in Rfx regulation by proneural factors may underlie variations in ciliary dendrite specialisation in different sensory neuronal lineages. In contrast, fd3F encodes a novel forkhead family transcription factor that is exclusively expressed in differentiating chordotonal neurons. fd3F regulates genes required for specialized aspects of chordotonal dendrite physiology. In addition to these intermediate transcriptional regulators, we show that atonal directly regulates a novel gene, dilatory, that is directly associated with ciliogenesis during neuronal differentiation. Our analysis demonstrates how early cell fate specification factors can regulate structural and physiological differentiation of neuronal cell types. It also suggests a model for how subtype differentiation in different neuronal lineages may be regulated by different proneural factors. In addition, it provides a paradigm for how transcriptional regulation may modulate the ciliogenesis pathway to give rise to structurally and functionally specialised ciliary dendrites.
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Affiliation(s)
- Sebastián Cachero
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - T. Ian Simpson
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Petra I. zur Lage
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Lina Ma
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Fay G. Newton
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Eimear E. Holohan
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - J. Douglas Armstrong
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Andrew P. Jarman
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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4
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Ebacher DJS, Todi SV, Eberl DF, Boekhoff-Falk GE. Cut mutant Drosophila auditory organs differentiate abnormally and degenerate. Fly (Austin) 2009; 1:86-94. [PMID: 18820445 DOI: 10.4161/fly.4242] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The Drosophila antenna is a sophisticated structure that functions in both olfaction and audition. Previous studies have identified Homothorax, Extradenticle, and Distal-less, three homeodomain transcription factors, as required for specification of antennal identity. Antennal expression of cut is activated by Homothorax and Extradenticle, and repressed by Distal-less. cut encodes the Drosophila homolog of human CAAT-displacement protein, a cell cycle-regulated homeodomain transcription factor. Cut is required for normal development of external mechanosensory structures and Malphigian tubules (kidney analogs). The role of cut in the Drosophila auditory organ, Johnston's organ, has not been characterized. We have employed the FLP/FRT system to generate cut null clones in developing Johnston's organ. In cut mutants, the scolopidial subunits that constitute Johnston's organ differentiate abnormally and subsequently degenerate. Electrophysiological experiments confirm that adult Drosophila with cut null antennae are deaf. We find that cut acts in parallel to atonal, spalt-major, and spalt-related, which encode other transcription factors required for Johnston's organ differentiation. We speculate that Cut functions in conjunction with these factors to regulate transcription of as yet unidentified targets.
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Affiliation(s)
- Dominic J S Ebacher
- Department of Anatomy, University of Wisconsin, Madison, Wisconsin 53706, USA
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5
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Ghiradella HT, Butler MW. Many variations on a few themes: a broader look at development of iridescent scales (and feathers). J R Soc Interface 2009; 6 Suppl 2:S243-51. [PMID: 19141432 PMCID: PMC2706475 DOI: 10.1098/rsif.2008.0372.focus] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/04/2008] [Accepted: 12/05/2008] [Indexed: 01/27/2023] Open
Abstract
Iridescent structures are some of the most visually stunning phenomena in biological organisms. Insects and birds have in common the display of such colours in their non-living investiture, the scales and bristles in insects and the feathers in birds. The biological mechanisms underlying the formation of these structures, at least in insects, appear quite conservative in that the same architect, the eukaryotic cell, can produce not only the iridescent structure but, with some tweaking of the genome, other structures as well, a fact that may be of particular interest to materials scientists and industrial parties seeking to biomimic these forms. Here, we review two examples, one on the cellular and the other on the subcellular level of this developmental flexibility in insects. We then go on to review what is known about iridescent feather development in birds. We suggest that, in view of the increasing evidence that genes and pathways are conserved among taxa, the work on insects may perhaps suggest perspectives or directions of potential use in the study of birds.
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Affiliation(s)
- Helen T Ghiradella
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY 12222, USA.
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6
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Kernan MJ. Mechanotransduction and auditory transduction in Drosophila. Pflugers Arch 2007; 454:703-20. [PMID: 17436012 DOI: 10.1007/s00424-007-0263-x] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 03/22/2007] [Indexed: 11/28/2022]
Abstract
Insects are utterly reliant on sensory mechanotransduction, the process of converting physical stimuli into neuronal receptor potentials. The senses of proprioception, touch, and hearing are involved in almost every aspect of an adult insect's complex behavioral repertoire and are mediated by a diverse array of specialized sensilla and sensory neurons. The physiology and morphology of several of these have been described in detail; genetic approaches in Drosophila, combining behavioral screens and sensory electrophysiology with forward and reverse genetic techniques, have now revealed specific proteins involved in their differentiation and operation. These include three different TRP superfamily ion channels that are required for transduction in tactile bristles, chordotonal stretch receptors, and polymodal nociceptors. Transduction also depends on the normal differentiation and mechanical integrity of the modified cilia that form the neuronal sensory endings, the accessory structures that transmit stimuli to them and, in bristles, a specialized receptor lymph and transepithelial potential. Flies hear near-field sounds with a vibration-sensitive, antennal chordotonal organ. Biomechanical analyses of wild-type antennae reveal non-linear, active mechanical properties that increase their sensitivity to weak stimuli. The effects of mechanosensory and ciliary mutations on antennal mechanics show that the sensory cilia are the active motor elements and indicate distinct roles for TRPN and TRPV channels in auditory transduction and amplification.
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Affiliation(s)
- Maurice J Kernan
- Department of Neurobiology and Behavior and Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794-5230, USA.
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7
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Eberl DF, Boekhoff-Falk G. Development of Johnston's organ in Drosophila. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2007; 51:679-87. [PMID: 17891726 PMCID: PMC3417114 DOI: 10.1387/ijdb.072364de] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Hearing is a specialized mechanosensory modality that is refined during evolution to meet the particular requirements of different organisms. In the fruitfly, Drosophila, hearing is mediated by Johnston's organ, a large chordotonal organ in the antenna that is exquisitely sensitive to the near-field acoustic signal of courtship songs generated by male wing vibration. We summarize recent progress in understanding the molecular genetic determinants of Johnston's organ development and discuss surprising differences from other chordotonal organs that likely facilitate hearing. We outline novel discoveries of active processes that generate motion of the antenna for acute sensitivity to the stimulus. Finally, we discuss further research directions that would probe remaining questions in understanding Johnston's organ development, function and evolution.
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Affiliation(s)
- Daniel F Eberl
- Department of Biology, University of Iowa, Iowa City, IA 52242-1324, USA.
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8
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Sun J, Deng WM. Notch-dependent downregulation of the homeodomain gene cut is required for the mitotic cycle/endocycle switch and cell differentiation in Drosophila follicle cells. Development 2005; 132:4299-308. [PMID: 16141223 PMCID: PMC3891799 DOI: 10.1242/dev.02015] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During Drosophila mid-oogenesis, follicular epithelial cells switch from the mitotic cycle to the specialized endocycle in which the M phase is skipped. The switch, along with cell differentiation in follicle cells, is induced by Notch signaling. We show that the homeodomain gene cut functions as a linker between Notch and genes that are involved in cell-cycle progression. Cut was expressed in proliferating follicle cells but not in cells in the endocycle. Downregulation of Cut expression was controlled by the Notch pathway and was essential for follicle cells to differentiate and to enter the endocycle properly. cut-mutant follicle cells entered the endocycle and differentiated prematurely in a cell-autonomous manner. By contrast, prolonged expression of Cut caused defects in the mitotic cycle/endocycle switch. These cells continued to express an essential mitotic cyclin, Cyclin A, which is normally degraded by the Fizzy-related-APC/C ubiquitin proteosome system during the endocycle. Cut promoted Cyclin A expression by negatively regulating Fizzy-related. Our data suggest that Cut functions in regulating both cell differentiation and the cell cycle, and that downregulation of Cut by Notch contributes to the mitotic cycle/endocycle switch and cell differentiation in follicle cells.
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9
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Boekhoff-Falk G. Hearing in Drosophila: development of Johnston's organ and emerging parallels to vertebrate ear development. Dev Dyn 2005; 232:550-8. [PMID: 15704117 DOI: 10.1002/dvdy.20207] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In this review, I describe recent progress toward understanding the developmental genetics governing formation of the Drosophila auditory apparatus. The Drosophila auditory organ, Johnston's organ, is housed in the antenna. Intriguingly, key genes needed for specification or function of auditory cell types in the Drosophila antenna also are required for normal development or function of the vertebrate ear. These genes include distal-less, spalt and spalt-related, atonal, crinkled, nanchung and inactive, and prestin, and their vertebrate counterparts Dlx, spalt-like (sall), atonal homolog (ath), myosin VIIA, TRPV, and prestin, respectively. In addition, Drosophila auditory neurons recently were shown to serve actuating as well as transducing roles, much like their hair cell counterparts of the vertebrate cochlea. The emerging genetic and physiologic parallels have come as something of a surprise, because conventional wisdom holds that vertebrate and invertebrate hearing organs have separate evolutionary origins. The new findings raise the possibility that auditory organs are more ancient than previously thought and indicate that Drosophila is likely to be a powerful model system in which to gain insights regarding the etiologies of human deafness disorders.
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Affiliation(s)
- Grace Boekhoff-Falk
- Department of Anatomy, University of Wisconsin-Madison, Medical School, Madison, Wisconsin 53706, USA.
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10
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Krupp JJ, Yaich LE, Wessells RJ, Bodmer R. Identification of genetic loci that interact with cut during Drosophila wing-margin development. Genetics 2005; 170:1775-95. [PMID: 15956666 PMCID: PMC1449764 DOI: 10.1534/genetics.105.043125] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The Drosophila selector gene cut is a hierarchal regulator of external sensory organ identity and is required to pattern the sensory and nonsensory cells of the wing margin. Cut performs the latter function, in part, by maintaining expression of the secreted morphogen encoded by wingless (wg). We find that Cut is required for wing-margin sensory organ specification in addition to and independently of Wg maintenance. In addition, we performed a genetic modifier screen to identify other genes that interact with cut in the regulation of wing-margin patterning. In total, 45 genetic loci (35 gain-of-function and 10 loss-of-function loci) were identified by virtue of their ability to suppress the wing-margin defects resulting from gypsy retrotransposon-mediated insulation of the cut wing-margin enhancer. Further genetic characterization identified several subgroups of candidate cut interacting loci. One group consists of putative regulators of gypsy insulator activity. A second group is potentially required for the regulation of Cut expression and/or activity and includes longitudinals lacking, a gene that encodes a family of BTB-domain zinc-finger transcription factors. A third group, which includes a component of the Brahma chromatin remodeling complex encoded by moira, affects the level of Cut expression in two opposing ways by suppressing the gypsy-mediated ct(K) phenotype and enhancing the non-gypsy ct(53d) phenotype. This suggests that the Brahma complex modulates both enhancer-controlled transcription and gypsy-mediated gene insulation of the cut locus.
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11
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Abstract
This study identifies the cuticular metathoracic structures in earless cockroaches that are the homologs to the peripheral auditory components in their sister taxon, praying mantids, and defines the nature of the cuticular transition from earless to eared in the Dictyoptera. The single, midline ear of mantids comprises an auditory chamber with complex walls that contain the tympana and chordotonal transduction elements. The corresponding area in cockroaches, between the furcasternum and coxae, has many socketed hairs arranged in discrete fields and the Nerve 7 chordotonal organ, the homolog of the mantis tympanal organ. The Nerve 7 chordotonal organ attaches at the apex of the lateral ventropleurite (LVp), which has the same shape and general structure as an auditory chamber wall. High-speed video shows that when the coxa moves toward the midline, the LVp rotates medially to stimulate socketed hairs, and also moves like a triangular hinge giving the chordotonal organ maximal in-out stimulation. Formation of the mantis auditory chamber from the LVp and adjacent structures would involve only enlargement, a shift toward the midline, and a mild rotation. Almost all proprioceptive function would be lost, which may constitute the major cost of building and maintaining the mantis ear. Isolation from leg movement dictates the position of the mantis ear in the midline and the rigid frame, formed by the cuticular knobs, which protects the chordotonal organs.
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Affiliation(s)
- David D Yager
- Department of Psychology and Neuroscience, Cognitive Science Program, University of Maryland, College Park, Maryland 20742, USA.
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12
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Abstract
Synaptic specificity is the culmination of several processes, beginning with the establishment of neuronal subtype identity, followed by navigation of the axon to the correct subdivision of neuropil, and finally, the cell-cell recognition of appropriate synaptic partners. In this review we summarize the work on sensory neurons in crickets, cockroaches, moths, and fruit flies that establishes some of the principles and molecular mechanisms involved in the control of synaptic specificity. The identity of a sensory neuron is controlled by combinatorial expression of transcription factors, the products of patterning and proneural genes. In the nervous system, sensory axon projections are anatomically segregated according to modality, stimulus quality, and cell-body position. A variety of cell-surface and intracellular signaling molecules are used to achieve this. Synaptic target recognition is also controlled by transcription factors such as Engrailed and may be, in part, mediated by cadherin-like molecules.
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Affiliation(s)
- Jonathan M Blagburn
- Institute of Neurobiology, Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, Puerto Rico 00901-1123.
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13
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Willingham AT, Keil T. A tissue specific cytochrome P450 required for the structure and function of Drosophila sensory organs. Mech Dev 2004; 121:1289-97. [PMID: 15327788 DOI: 10.1016/j.mod.2004.04.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2004] [Revised: 03/24/2004] [Accepted: 04/21/2004] [Indexed: 11/21/2022]
Abstract
Cytochrome P450s have generally been acknowledged as broadly tuned detoxifying enzymes. However, emerging evidence argues P450s have an integral role in cell signaling and developmental processes, via their metabolism of retinoic acid, arachidonic acid, steroids, and other cellular ligands. To study the morphogenesis of Drosophila sensory organs, we examined mutants with impaired mechanosensation and discovered one, nompH, encodes the cytochrome P450 CYP303a1. We now report the characterization of nompH, a mutant defective in the function of peripheral chemo- and mechanoreceptor cells, and demonstrate CYP303a1 is essential for the development and structure of external sensory organs which mediate the reception of vital mechanosensory and chemosensory stimuli. Notably this P450 is expressed only in sensory bristles, localizing in the apical region of the socket cell. The wide diversity of the P450 family and the growing number of P450s with developmental phenotypes suggests the exquisite tissue and subcellular specificity of CYP303a1 illustrates an important aspect of P450 function; namely, a strategy to process critical developmental signals in a tissue- and cell-specific manner.
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Affiliation(s)
- Aarron T Willingham
- Division of Biology, University of California, San Diego, La Jolla, CA 92093-0649, USA.
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14
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Lai EC, Orgogozo V. A hidden program in Drosophila peripheral neurogenesis revealed: fundamental principles underlying sensory organ diversity. Dev Biol 2004; 269:1-17. [PMID: 15081353 DOI: 10.1016/j.ydbio.2004.01.032] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Revised: 01/22/2004] [Accepted: 01/26/2004] [Indexed: 11/19/2022]
Abstract
How is cell fate diversity reliably achieved during development? Insect sensory organs have been a favorable model system for investigating this question for over 100 years. They are constructed using defined cell lineages that generate a maximum of cell diversity with a minimum number of cell divisions, and display tremendous variety in their morphologies, constituent cell types, and functions. An unexpected realization of the past 5 years is that very diverse sensory organs in Drosophila are produced by astonishingly similar cell lineages, and that their diversity can be largely attributed to only a small repertoire of developmental processes. These include changes in terminal cell differentiation, cell death, cell proliferation, cell recruitment, cell-cell interactions, and asymmetric segregation of cell fate determinants during mitosis. We propose that most Drosophila sensory organs are built from an archetypal lineage, and we speculate about how this stereotyped pattern of cell divisions may have been built during evolution.
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Affiliation(s)
- Eric C Lai
- Howard Hughes Medical Institute, 545 Life Sciences Addition, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
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15
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Grueber WB, Jan LY, Jan YN. Different levels of the homeodomain protein cut regulate distinct dendrite branching patterns of Drosophila multidendritic neurons. Cell 2003; 112:805-18. [PMID: 12654247 DOI: 10.1016/s0092-8674(03)00160-0] [Citation(s) in RCA: 237] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Functionally similar neurons can share common dendrite morphology, but how different neurons are directed into similar forms is not understood. Here, we show in embryonic and larval development that the level of Cut immunoreactivity in individual dendritic arborization (da) sensory neurons correlates with distinct patterns of terminal dendrites: high Cut in neurons with extensive unbranched terminal protrusions (dendritic spikes), medium levels in neurons with expansive and complex arbors, and low or nondetectable Cut in neurons with simple dendrites. Loss of Cut reduced dendrite growth and class-specific terminal branching, whereas overexpression of Cut or a mammalian homolog in lower-level neurons resulted in transformations toward the branch morphology of high-Cut neurons. Thus, different levels of a homeoprotein can regulate distinct patterns of dendrite branching.
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Affiliation(s)
- Wesley B Grueber
- Howard Hughes Medical Institute and Department of Physiology, University of California, San Francisco, 533 Parnassus Avenue, Room U226, San Francisco, CA 94143, USA
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Caldwell JC, Eberl DF. Towards a molecular understanding of Drosophila hearing. JOURNAL OF NEUROBIOLOGY 2002; 53:172-89. [PMID: 12382274 PMCID: PMC1805767 DOI: 10.1002/neu.10126] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The Drosophila auditory system is presented as a powerful new genetic model system for understanding the molecular aspects of development and physiology of hearing organs. The fly's ear resides in the antenna, with Johnston's organ serving as the mechanoreceptor. New approaches using electrophysiology and laser vibrometry have provided useful tools to apply to the study of mutations that disrupt hearing. The fundamental developmental processes that generate the peripheral nervous system are fairly well understood, although specific variations of these processes for chordotonal organs (CHO) and especially for Johnston's organ require more scrutiny. In contrast, even the fundamental physiologic workings of mechanosensitive systems are still poorly understood, but rapid recent progress is beginning to shed light. The identification and analysis of mutations that affect auditory function are summarized here, and prospects for the role of the Drosophila auditory system in understanding both insect and vertebrate hearing are discussed.
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Affiliation(s)
- Jason C Caldwell
- Department of Biological Sciences, The University of Iowa, Iowa City, Iowa, 52242-1324, USA
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17
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Brewster R, Hardiman K, Deo M, Khan S, Bodmer R. The selector gene cut represses a neural cell fate that is specified independently of the Achaete-Scute-Complex and atonal. Mech Dev 2001; 105:57-68. [PMID: 11429282 DOI: 10.1016/s0925-4773(01)00375-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The peripheral nervous system (PNS) of Drosophila offers a powerful system to precisely identify individual cells and dissect their genetic pathways of development. The mode of specification of a subset of larval PNS cells, the multiple dendritic (md) neurons (or type II neurons), is complex and still poorly understood. Within the dorsal thoracic and abdominal segments, two md neurons, dbd and dda1, apparently require the proneural gene amos but not atonal (ato) or Achaete-Scute-Complex (ASC) genes. ASC normally acts via the neural selector gene cut to specify appropriate sensory organ identities. Here, we show that dbd- and dda1-type differentiation is suppressed by cut in dorsal ASC-dependent md neurons. Thus, cut is not only required to promote an ASC-dependent mode of differentiation, but also represses an ASC- and ato-independent fate that leads to dbd and dda1 differentiation.
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Affiliation(s)
- R Brewster
- Department of Biology, The University of Michigan, 830 North University, 48109-1048, Ann Arbor, MI, USA
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18
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Chung YD, Zhu J, Han Y, Kernan MJ. nompA encodes a PNS-specific, ZP domain protein required to connect mechanosensory dendrites to sensory structures. Neuron 2001; 29:415-28. [PMID: 11239432 DOI: 10.1016/s0896-6273(01)00215-x] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in the no-mechanoreceptor-potential A (nompA) gene, which eliminate transduction in Drosophila mechanosensory organs, disrupt contacts between neuronal sensory endings and cuticular structures. nompA encodes a transmembrane protein with a large, modular extracellular segment that includes a zona pellucida (ZP) domain and several plasminogen N-terminal (PAN) modules. It is specifically expressed in type I sense organs of the peripheral nervous system by the support cells that ensheath the neuronal sensory process. A green fluorescent protein (GFP)-NompA fusion protein is localized to the dendritic cap, an extracellular matrix that covers the ciliary outer segment of the sensory process and that shows organizational defects in nompA mutants. The structure and location of NompA suggest that it forms part of a mechanical linkage required to transmit mechanical stimuli to the transduction apparatus.
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Affiliation(s)
- Y D Chung
- Department of Neurobiology and Behavior and, The State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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19
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Abstract
To test the effects of mechanosensory mutations on hearing in Drosophila, we have recorded sound-evoked potentials originating from ciliated sensory neurons in Johnston's organ, the chordotonal organ that is the sensory element of the fly's antennal ear. Electrodes inserted close to the antennal nerve were used to record extracellular compound potentials evoked by near-field sound stimuli. Sound-evoked potentials are absent in atonal mutant flies, which lack Johnston's organ. Mutations in many genes involved in mechanotransduction by tactile bristles also eliminate or reduce the Johnston's organ response, indicating that related transduction mechanisms operate in each type of mechanosensory organ. In addition, the sound-evoked response is affected by two mutations that do not affect bristle mechanotransduction, beethoven (btv) and touch-insensitive-larvaB (tilB). btv shows defects in the ciliary dilation, an elaboration of the axoneme that is characteristic of chordotonal cilia. tilB, which also causes male sterility, shows structural defects in sperm flagellar axonemes. This suggests that in addition to the shared transduction mechanism, axonemal integrity and possibly ciliary motility are required for signal amplification or transduction by chordotonal sensory neurons.
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20
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Abstract
What is the nature of the genetic programme that allows neurons to extend their axons and connect to other neurons with a high degree of specificity? Work on the sensory neurons of the fly has shown how the control of neuronal identity is embedded in the general developmental programme of the organism. The ongoing analysis of pathfinding mutants suggests plausible mechanisms for the translation of neuronal identity into axonal behaviour.
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Affiliation(s)
- A Ghysen
- Laboratoire de Neurogénétique, INSERM E0012 Université Montpellier II, cc103, place E. Bataillon, 34095 Montpellier, France. aghysen@univ-montp2
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21
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Abstract
This paper reviews the structure and function of insect mechanoreceptors with respect to their cellular, subcellular, and cuticular organization. Four types are described and their function is discussed: 1, the bristles; 2, the trichobothria; 3, the campaniform sensilla; and 4, the scolopidia. Usually, bristles respond to touch, trichobothria to air currents and sound, campaniform sensilla to deformation of the cuticle, and scolopidia to stretch. Mechanoreceptors are composed of four cells: a bipolar sensory neuron, which is enveloped by the thecogen, the trichogen, and the tormogen cells. Apically, the neuron gives off a ciliary dendrite which is attached to the stimulus-transmitting cuticular structures. In types 1-3, the tip of the dendrite contains a highly organized cytoskeletal complex of microtubules, the "tubular body," which is connected to the dendritic membrane via short rods, the "membrane-integrated cones" (MICs). The dendritic membrane is attached to the cuticle via fine attachment fibers. The hair-type sensilla (types 1, 2) are constructed as first-order levers, which transmit deflection of the hair directly to the dendrite tip. In campaniform sensilla (type 3), there is a cuticular dome instead of a hair and the dendrite is stimulated by deformation of the cuticle. In these three types, a slight lateral compression of the dendrite tip is most probably the effective stimulus. In scolopidia, the dendritic membrane is most probably stimulated by stretch. On the subcellular level, connectors between the cytoskeleton, the dendritic membrane, and extracellular (cuticular) structures are present in all four types and are thought to be engaged in membrane depolarization.
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Affiliation(s)
- T A Keil
- Arbeitsgruppe Kaissling, Max-Planck-Institut für Verhaltensphysiologie, Seewiesen, Germany
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