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Guan C, Shaikh M, Warnecke A, Vona B, Albert JT. A burden shared: The evolutionary case for studying human deafness in Drosophila. Hear Res 2024; 450:109047. [PMID: 38896942 DOI: 10.1016/j.heares.2024.109047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 05/09/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024]
Abstract
Hearing impairment is the most prevalent sensory disease in humans and can have dramatic effects on the development, and preservation, of our cognitive abilities and social interactions. Currently 20 % of the world's population suffer from a form of hearing impairment; this is predicted to rise to 25 % by 2050. Despite this staggering disease load, and the vast damage it inflicts on the social, medical and economic fabric of humankind, our ability to predict, or prevent, the loss of hearing is very poor indeed. We here make the case for a paradigm shift in our approach to studying deafness. By exploiting more forcefully the molecular-genetic conservation between human hearing and hearing in morphologically distinct models, such as the fruit fly Drosophila melanogaster, we believe, a deeper understanding of hearing and deafness can be achieved. An understanding that moves beyond the surface of the 'deafness genes' to probe the underlying bedrock of hearing, which is shared across taxa, and partly shared across modalities. When it comes to understanding the workings (and failings) of human sensory function, a simple fruit fly has a lot to offer and a fly eye might sometimes be a powerful model for a human ear. Particularly the use of fly avatars, in which specific molecular (genetic or proteomic) states of humans (e.g. specific patients) are experimentally reproduced, in order to study the corresponding molecular mechanisms (e.g. specific diseases) in a controlled yet naturalistic environment, is a tool that promises multiple unprecedented insights. The use of the fly - and fly avatars - would benefit humans and will help enhance the power of other scientific models, such as the mouse.
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Affiliation(s)
- Chonglin Guan
- Sensory Physiology & Behaviour Group, Department for Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany; Cluster of Excellence Hearing4all, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany
| | - Muhammad Shaikh
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1 × 8EE, UK
| | - Athanasia Warnecke
- Hannover Medical School, Department of Otorhinolaryngology, Head & Neck Surgery, Hannover, Germany; Cluster of Excellence Hearing4all, MHH Hannover, Germany
| | - Barbara Vona
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany; Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, 37075 Göttingen, Germany.
| | - Joerg T Albert
- Sensory Physiology & Behaviour Group, Department for Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany; Cluster of Excellence Hearing4all, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Str. 9-11, 26111 Oldenburg, Germany; Ear Institute, University College London, 332 Gray's Inn Road, London, WC1 × 8EE, UK.
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2
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Anselmi C, Fuller GK, Stolfi A, Groves AK, Manni L. Sensory cells in tunicates: insights into mechanoreceptor evolution. Front Cell Dev Biol 2024; 12:1359207. [PMID: 38550380 PMCID: PMC10973136 DOI: 10.3389/fcell.2024.1359207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 03/04/2024] [Indexed: 04/04/2024] Open
Abstract
Tunicates, the sister group of vertebrates, offer a unique perspective for evolutionary developmental studies (Evo-Devo) due to their simple anatomical organization. Moreover, the separation of tunicates from vertebrates predated the vertebrate-specific genome duplications. As adults, they include both sessile and pelagic species, with very limited mobility requirements related mainly to water filtration. In sessile species, larvae exhibit simple swimming behaviors that are required for the selection of a suitable substrate on which to metamorphose. Despite their apparent simplicity, tunicates display a variety of mechanoreceptor structures involving both primary and secondary sensory cells (i.e., coronal sensory cells). This review encapsulates two decades of research on tunicate mechanoreception focusing on the coronal organ's sensory cells as prime candidates for understanding the evolution of vertebrate hair cells of the inner ear and the lateral line organ. The review spans anatomical, cellular and molecular levels emphasizing both similarity and differences between tunicate and vertebrate mechanoreception strategies. The evolutionary significance of mechanoreception is discussed within the broader context of Evo-Devo studies, shedding light on the intricate pathways that have shaped the sensory system in chordates.
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Affiliation(s)
- Chiara Anselmi
- Hopkins Marine Station, Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Pacific Grove, CA, United States
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, United States
| | - Gwynna K. Fuller
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Alberto Stolfi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Andrew K. Groves
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, Padova, Italy
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3
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Edens BM, Bronner ME. Making developmental sense of the senses, their origin and function. Curr Top Dev Biol 2024; 159:132-167. [PMID: 38729675 DOI: 10.1016/bs.ctdb.2024.01.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
The primary senses-touch, taste, sight, smell, and hearing-connect animals with their environments and with one another. Aside from the eyes, the primary sense organs of vertebrates and the peripheral sensory pathways that relay their inputs arise from two transient stem cell populations: the neural crest and the cranial placodes. In this chapter we consider the senses from historical and cultural perspectives, and discuss the senses as biological faculties. We begin with the embryonic origin of the neural crest and cranial placodes from within the neural plate border of the ectodermal germ layer. Then, we describe the major chemical (i.e. olfactory and gustatory) and mechanical (i.e. vestibulo-auditory and somatosensory) senses, with an emphasis on the developmental interactions between neural crest and cranial placodes that shape their structures and functions.
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Affiliation(s)
- Brittany M Edens
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Marianne E Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States.
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4
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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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5
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Shu M, Hong D, Lin H, Zhang J, Luo Z, Du Y, Sun Z, Yin M, Yin Y, Liu L, Bao S, Liu Z, Lu F, Huang J, Dai J. Single-cell chromatin accessibility identifies enhancer networks driving gene expression during spinal cord development in mouse. Dev Cell 2022; 57:2761-2775.e6. [PMID: 36495874 DOI: 10.1016/j.devcel.2022.11.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/22/2022] [Accepted: 11/16/2022] [Indexed: 12/14/2022]
Abstract
Spinal cord development is precisely orchestrated by spatiotemporal gene regulatory programs. However, the underlying epigenetic mechanisms remain largely elusive. Here, we profiled single-cell chromatin accessibility landscapes in mouse neural tubes spanning embryonic days 9.5-13.5. We identified neuronal-cell-cluster-specific cis-regulatory elements in neural progenitors and neurons. Furthermore, we applied a novel computational method, eNet, to build enhancer networks by integrating single-cell chromatin accessibility and gene expression data and identify the hub enhancers within enhancer networks. It was experimentally validated in vivo for Atoh1 that knockout of the hub enhancers, but not the non-hub enhancers, markedly decreased Atoh1 expression and reduced dp1/dI1 cells. Together, our work provides insights into the epigenetic regulation of spinal cord development and a proof-of-concept demonstration of enhancer networks as a general mechanism in transcriptional regulation.
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Affiliation(s)
- Muya Shu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Danni Hong
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Hongli Lin
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Jixiang Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhengnan Luo
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Yi Du
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Zheng Sun
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Man Yin
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Yanyun Yin
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Lifang Liu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Shilai Bao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100101, China
| | - Falong Lu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China.
| | - Jialiang Huang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian 361102, China; National Institute for Data Science in Health and Medicine, Xiamen University, Xiamen, Fujian 361102, China.
| | - Jianwu Dai
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China.
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Blockley A, Ogle D, Woodrow C, Montealegre-Z F, Warren B. Physiological changes throughout an insect ear due to age and noise - a longitudinal study. iScience 2022; 25:104746. [PMID: 36034233 PMCID: PMC9400085 DOI: 10.1016/j.isci.2022.104746] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 11/20/2022] Open
Abstract
Hearing loss is not unique to humans and is experienced by all animals in the face of wild and eclectic differences in ear morphology. Here, we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria to rigorously quantify changes in the auditory system due to noise exposure and age. In this exploratory study, we analyzed tympanal displacements, morphology of the auditory Müller’s organ and measured activity of the auditory nerve, the transduction current, and electrophysiological properties of individual auditory receptors. This work shows that hearing loss manifests as a complex disorder due to differential effects of age and noise on several processes and cell types within the ear. The “middle-aged deafness” pattern of hearing loss found in locusts mirrors that found for humans exposed to noise early in their life suggesting a fundamental interaction of the use of an auditory system (noise) and its aging. Locusts routinely exposed to noise follow same pattern of hearing loss as humans Parts of the auditory system are affected by noise, age, or both noise and age Hearing loss is a multifaceted disorder caused by defects in distinct ear processes
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GFI1 regulates hair cell differentiation by acting as an off-DNA transcriptional co-activator of ATOH1, and a DNA-binding repressor. Sci Rep 2022; 12:7793. [PMID: 35551236 PMCID: PMC9098437 DOI: 10.1038/s41598-022-11931-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 05/03/2022] [Indexed: 11/08/2022] Open
Abstract
GFI1 is a zinc finger transcription factor that is necessary for the differentiation and survival of hair cells in the cochlea. Deletion of Gfi1 in mice significantly reduces the expression of hundreds of hair cell genes: this is a surprising result, as GFI1 normally acts as a transcriptional repressor by recruiting histone demethylases and methyltransferases to its targets. To understand the mechanisms by which GFI1 promotes hair cell differentiation, we used CUT&RUN to identify the direct targets of GFI1 and ATOH1 in hair cells. We found that GFI1 regulates hair cell differentiation in two distinct ways—first, GFI1 and ATOH1 can bind to the same regulatory elements in hair cell genes, but while ATOH1 directly binds its target DNA motifs in many of these regions, GFI1 does not. Instead, it appears to enhance ATOH1’s transcriptional activity by acting as part of a complex in which it does not directly bind DNA. Second, GFI1 can act in its more typical role as a direct, DNA-binding transcriptional repressor in hair cells; here it represses non-hair cell genes, including many neuronal genes. Together, our results illuminate the function of GFI1 in hair cell development and hair cell reprogramming strategies.
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8
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Ecovoiu AA, Ratiu AC, Micheu MM, Chifiriuc MC. Inter-Species Rescue of Mutant Phenotype-The Standard for Genetic Analysis of Human Genetic Disorders in Drosophila melanogaster Model. Int J Mol Sci 2022; 23:2613. [PMID: 35269756 PMCID: PMC8909942 DOI: 10.3390/ijms23052613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 02/23/2022] [Accepted: 02/24/2022] [Indexed: 11/16/2022] Open
Abstract
Drosophila melanogaster (the fruit fly) is arguably a superstar of genetics, an astonishing versatile experimental model which fueled no less than six Nobel prizes in medicine. Nowadays, an evolving research endeavor is to simulate and investigate human genetic diseases in the powerful D. melanogaster platform. Such a translational experimental strategy is expected to allow scientists not only to understand the molecular mechanisms of the respective disorders but also to alleviate or even cure them. In this regard, functional gene orthology should be initially confirmed in vivo by transferring human or vertebrate orthologous transgenes in specific mutant backgrounds of D. melanogaster. If such a transgene rescues, at least partially, the mutant phenotype, then it qualifies as a strong candidate for modeling the respective genetic disorder in the fruit fly. Herein, we review various examples of inter-species rescue of relevant mutant phenotypes of the fruit fly and discuss how these results recommend several human genes as candidates to study and validate genetic variants associated with human diseases. We also consider that a wider implementation of this evolutionist exploratory approach as a standard for the medicine of genetic disorders would allow this particular field of human health to advance at a faster pace.
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Affiliation(s)
- Alexandru Al. Ecovoiu
- Department of Genetics, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania;
| | - Attila Cristian Ratiu
- Department of Genetics, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania;
| | - Miruna Mihaela Micheu
- Department of Cardiology, Clinical Emergency Hospital of Bucharest, 014461 Bucharest, Romania;
| | - Mariana Carmen Chifiriuc
- The Research Institute of the University of Bucharest and Faculty of Biology, University of Bucharest, 050095 Bucharest, Romania;
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9
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Warren B, Nowotny M. Bridging the Gap Between Mammal and Insect Ears – A Comparative and Evolutionary View of Sound-Reception. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.667218] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Insects must wonder why mammals have ears only in their head and why they evolved only one common principle of ear design—the cochlea. Ears independently evolved at least 19 times in different insect groups and therefore can be found in completely different body parts. The morphologies and functional characteristics of insect ears are as wildly diverse as the ecological niches they exploit. In both, insects and mammals, hearing organs are constrained by the same biophysical principles and their respective molecular processes for mechanotransduction are thought to share a common evolutionary origin. Due to this, comparative knowledge of hearing across animal phyla provides crucial insight into fundamental processes of auditory transduction, especially at the biomechanical and molecular level. This review will start by comparing hearing between insects and mammals in an evolutionary context. It will then discuss current findings about sound reception will help to bridge the gap between both research fields.
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Elliott KL, Pavlínková G, Chizhikov VV, Yamoah EN, Fritzsch B. Development in the Mammalian Auditory System Depends on Transcription Factors. Int J Mol Sci 2021; 22:ijms22084189. [PMID: 33919542 PMCID: PMC8074135 DOI: 10.3390/ijms22084189] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 12/16/2022] Open
Abstract
We review the molecular basis of several transcription factors (Eya1, Sox2), including the three related genes coding basic helix–loop–helix (bHLH; see abbreviations) proteins (Neurog1, Neurod1, Atoh1) during the development of spiral ganglia, cochlear nuclei, and cochlear hair cells. Neuronal development requires Neurog1, followed by its downstream target Neurod1, to cross-regulate Atoh1 expression. In contrast, hair cells and cochlear nuclei critically depend on Atoh1 and require Neurod1 expression for interactions with Atoh1. Upregulation of Atoh1 following Neurod1 loss changes some vestibular neurons’ fate into “hair cells”, highlighting the significant interplay between the bHLH genes. Further work showed that replacing Atoh1 by Neurog1 rescues some hair cells from complete absence observed in Atoh1 null mutants, suggesting that bHLH genes can partially replace one another. The inhibition of Atoh1 by Neurod1 is essential for proper neuronal cell fate, and in the absence of Neurod1, Atoh1 is upregulated, resulting in the formation of “intraganglionic” HCs. Additional genes, such as Eya1/Six1, Sox2, Pax2, Gata3, Fgfr2b, Foxg1, and Lmx1a/b, play a role in the auditory system. Finally, both Lmx1a and Lmx1b genes are essential for the cochlear organ of Corti, spiral ganglion neuron, and cochlear nuclei formation. We integrate the mammalian auditory system development to provide comprehensive insights beyond the limited perception driven by singular investigations of cochlear neurons, cochlear hair cells, and cochlear nuclei. A detailed analysis of gene expression is needed to understand better how upstream regulators facilitate gene interactions and mammalian auditory system development.
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Affiliation(s)
- Karen L. Elliott
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA;
| | - Gabriela Pavlínková
- Institute of Biotechnology of the Czech Academy of Sciences, 25250 Vestec, Czechia;
| | - Victor V. Chizhikov
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA;
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, NV 89557, USA;
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA;
- Correspondence:
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11
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Fernández-Hernández I, Marsh EB, Bonaguidi MA. Mechanosensory neuron regeneration in adult Drosophila. Development 2021; 148:dev.187534. [PMID: 33597190 DOI: 10.1242/dev.187534] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 02/09/2021] [Indexed: 01/01/2023]
Abstract
Auditory and vestibular mechanosensory hair cells do not regenerate following injury or aging in the adult mammalian inner ear, inducing irreversible hearing loss and balance disorders for millions of people. Research on model systems showing replacement of mechanosensory cells can provide mechanistic insights into developing new regenerative therapies. Here, we developed lineage tracing systems to reveal the generation of mechanosensory neurons in the Johnston's organ (JO) of intact adult Drosophila, which are the functional counterparts to hair cells in vertebrates. New JO neurons develop cilia and target central brain circuitry. Unexpectedly, mitotic recombination clones point to JO neuron self-replication as a likely source of neuronal plasticity. This mechanism is further enhanced upon treatment with experimental and ototoxic compounds. Our findings introduce a new platform to expedite research on mechanisms and compounds mediating mechanosensory cell regeneration, with nascent implications for hearing and balance restoration.
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Affiliation(s)
- Ismael Fernández-Hernández
- Department of Stem Cell Biology and Regenerative Medicine, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Evan B Marsh
- Department of Stem Cell Biology and Regenerative Medicine, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Michael A Bonaguidi
- Department of Stem Cell Biology and Regenerative Medicine, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA .,Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.,Department of Gerontology, Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA.,Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 USA
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12
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Homeostatic maintenance and age-related functional decline in the Drosophila ear. Sci Rep 2020; 10:7431. [PMID: 32366993 PMCID: PMC7198581 DOI: 10.1038/s41598-020-64498-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/13/2020] [Indexed: 01/12/2023] Open
Abstract
Age-related hearing loss (ARHL) is a threat to future human wellbeing. Multiple factors contributing to the terminal auditory decline have been identified; but a unified understanding of ARHL - or the homeostatic maintenance of hearing before its breakdown - is missing. We here present an in-depth analysis of homeostasis and ageing in the antennal ears of the fruit fly Drosophila melanogaster. We show that Drosophila, just like humans, display ARHL. By focusing on the phase of dynamic stability prior to the eventual hearing loss we discovered a set of evolutionarily conserved homeostasis genes. The transcription factors Onecut (closest human orthologues: ONECUT2, ONECUT3), Optix (SIX3, SIX6), Worniu (SNAI2) and Amos (ATOH1, ATOH7, ATOH8, NEUROD1) emerged as key regulators, acting upstream of core components of the fly’s molecular machinery for auditory transduction and amplification. Adult-specific manipulation of homeostatic regulators in the fly’s auditory neurons accelerated - or protected against - ARHL.
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13
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Warren B, Fenton GE, Klenschi E, Windmill JFC, French AS. Physiological Basis of Noise-Induced Hearing Loss in a Tympanal Ear. J Neurosci 2020; 40:3130-3140. [PMID: 32144181 PMCID: PMC7141877 DOI: 10.1523/jneurosci.2279-19.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/19/2019] [Accepted: 12/08/2019] [Indexed: 11/30/2022] Open
Abstract
Acoustic overexposure, such as listening to loud music too often, results in noise-induced hearing loss. The pathologies of this prevalent sensory disorder begin within the ear at synapses of the primary auditory receptors, their postsynaptic partners and their supporting cells. The extent of noise-induced damage, however, is determined by overstimulation of primary auditory receptors, upstream of where the pathologies manifest. A systematic characterization of the electrophysiological function of the upstream primary auditory receptors is warranted to understand how noise exposure impacts on downstream targets, where the pathologies of hearing loss begin. Here, we used the experimentally-accessible locust ear (male, Schistocerca gregaria) to characterize a decrease in the auditory receptor's ability to respond to sound after noise exposure. Surprisingly, after noise exposure, the electrophysiological properties of the auditory receptors remain unchanged, despite a decrease in the ability to transduce sound. This auditory deficit stems from changes in a specialized receptor lymph that bathes the auditory receptors, revealing striking parallels with the mammalian auditory system.SIGNIFICANCE STATEMENT Noise exposure is the largest preventable cause of hearing loss. It is the auditory receptors that bear the initial brunt of excessive acoustic stimulation, because they must convert excessive sound-induced movements into electrical signals, but remain functional afterward. Here we use the accessible ear of an invertebrate to, for the first time in any animal, characterize changes in auditory receptors after noise overexposure. We find that their decreased ability to transduce sound into electrical signals is, most probably, due to changes in supporting (scolopale) cells that maintain the ionic composition of the ear. An emerging doctrine in hearing research is that vertebrate primary auditory receptors are surprisingly robust, something that we show rings true for invertebrate ears too.
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Affiliation(s)
- Ben Warren
- Department of Neuroscience, Psychology and Behavior, University of Leicester, Leicester, LE1 7RH, United Kingdom,
| | - Georgina E Fenton
- Department of Neuroscience, Psychology and Behavior, University of Leicester, Leicester, LE1 7RH, United Kingdom
| | - Elizabeth Klenschi
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XW, United Kingdom, and
| | - James F C Windmill
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XW, United Kingdom, and
| | - Andrew S French
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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14
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Warren B, Fenton GE, Klenschi E, Windmill JFC, French AS. Physiological Basis of Noise-Induced Hearing Loss in a Tympanal Ear. J Neurosci 2020. [PMID: 32144181 DOI: 10.3760/cma.j.cn112137-20200803-02267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Acoustic overexposure, such as listening to loud music too often, results in noise-induced hearing loss. The pathologies of this prevalent sensory disorder begin within the ear at synapses of the primary auditory receptors, their postsynaptic partners and their supporting cells. The extent of noise-induced damage, however, is determined by overstimulation of primary auditory receptors, upstream of where the pathologies manifest. A systematic characterization of the electrophysiological function of the upstream primary auditory receptors is warranted to understand how noise exposure impacts on downstream targets, where the pathologies of hearing loss begin. Here, we used the experimentally-accessible locust ear (male, Schistocerca gregaria) to characterize a decrease in the auditory receptor's ability to respond to sound after noise exposure. Surprisingly, after noise exposure, the electrophysiological properties of the auditory receptors remain unchanged, despite a decrease in the ability to transduce sound. This auditory deficit stems from changes in a specialized receptor lymph that bathes the auditory receptors, revealing striking parallels with the mammalian auditory system.SIGNIFICANCE STATEMENT Noise exposure is the largest preventable cause of hearing loss. It is the auditory receptors that bear the initial brunt of excessive acoustic stimulation, because they must convert excessive sound-induced movements into electrical signals, but remain functional afterward. Here we use the accessible ear of an invertebrate to, for the first time in any animal, characterize changes in auditory receptors after noise overexposure. We find that their decreased ability to transduce sound into electrical signals is, most probably, due to changes in supporting (scolopale) cells that maintain the ionic composition of the ear. An emerging doctrine in hearing research is that vertebrate primary auditory receptors are surprisingly robust, something that we show rings true for invertebrate ears too.
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Affiliation(s)
- Ben Warren
- Department of Neuroscience, Psychology and Behavior, University of Leicester, Leicester, LE1 7RH, United Kingdom,
| | - Georgina E Fenton
- Department of Neuroscience, Psychology and Behavior, University of Leicester, Leicester, LE1 7RH, United Kingdom
| | - Elizabeth Klenschi
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XW, United Kingdom, and
| | - James F C Windmill
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XW, United Kingdom, and
| | - Andrew S French
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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15
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Schatton A, Agoro J, Mardink J, Leboulle G, Scharff C. Identification of the neurotransmitter profile of AmFoxP expressing neurons in the honeybee brain using double-label in situ hybridization. BMC Neurosci 2018; 19:69. [PMID: 30400853 PMCID: PMC6219247 DOI: 10.1186/s12868-018-0469-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 10/29/2018] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND FoxP transcription factors play crucial roles for the development and function of vertebrate brains. In humans the neurally expressed FOXPs, FOXP1, FOXP2, and FOXP4 are implicated in cognition, including language. Neural FoxP expression is specific to particular brain regions but FoxP1, FoxP2 and FoxP4 are not limited to a particular neuron or neurotransmitter type. Motor- or sensory activity can regulate FoxP2 expression, e.g. in the striatal nucleus Area X of songbirds and in the auditory thalamus of mice. The DNA-binding domain of FoxP proteins is highly conserved within metazoa, raising the possibility that cellular functions were preserved across deep evolutionary time. We have previously shown in bee brains that FoxP is expressed in eleven specific neuron populations, seven tightly packed clusters and four loosely arranged groups. RESULTS The present study examined the co-expression of honeybee FoxP (AmFoxP) with markers for glutamatergic, GABAergic, cholinergic and monoaminergic transmission. We found that AmFoxP could co-occur with any one of those markers. Interestingly, AmFoxP clusters and AmFoxP groups differed with respect to homogeneity of marker co-expression; within a cluster, all neurons co-expressed the same neurotransmitter marker, within a group co-expression varied. We also assessed qualitatively whether age or housing conditions providing different sensory and motor experiences affected the AmFoxP neuron populations, but found no differences. CONCLUSIONS Based on the neurotransmitter homogeneity we conclude that AmFoxP neurons within the clusters might have a common projection and function whereas the AmFoxP groups are more diverse and could be further sub-divided. The obtained information about the neurotransmitters co-expressed in the AmFoxP neuron populations facilitated the search of similar neurons described in the literature. These comparisons revealed e.g. a possible function of AmFoxP neurons in the central complex. Our findings provide opportunities to focus future functional studies on invertebrate FoxP expressing neurons. In a broader context, our data will contribute to the ongoing efforts to discern in which cases relationships between molecular and phenotypic signatures are linked evolutionary.
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Affiliation(s)
- Adriana Schatton
- Department of Animal Behavior, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Julia Agoro
- Department of Animal Behavior, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
- Department of Neurobiology, Freie Universität Berlin, Königin-Luise-Straße 28-30, 14195 Berlin, Germany
| | - Janis Mardink
- Department of Animal Behavior, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Gérard Leboulle
- Department of Neurobiology, Freie Universität Berlin, Königin-Luise-Straße 28-30, 14195 Berlin, Germany
| | - Constance Scharff
- Department of Animal Behavior, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
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16
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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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17
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Baker NE, Brown NL. All in the family: proneural bHLH genes and neuronal diversity. Development 2018; 145:145/9/dev159426. [PMID: 29720483 DOI: 10.1242/dev.159426] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Proneural basic Helix-Loop-Helix (bHLH) proteins are required for neuronal determination and the differentiation of most neural precursor cells. These transcription factors are expressed in vastly divergent organisms, ranging from sponges to primates. Here, we review proneural bHLH gene evolution and function in the Drosophila and vertebrate nervous systems, arguing that the Drosophila gene atonal provides a useful platform for understanding proneural gene structure and regulation. We also discuss how functional equivalency experiments using distinct proneural genes can reveal how proneural gene duplication and divergence are interwoven with neuronal complexity.
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Affiliation(s)
- Nicholas E Baker
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 USA
| | - Nadean L Brown
- Department of Cell Biology and Human Anatomy, University of California, One Shields Avenue, Davis, CA 95616 USA
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18
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Humanized Flies and Resources for Cross-Species Study. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1076:277-288. [DOI: 10.1007/978-981-13-0529-0_15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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19
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Wangler MF, Yamamoto S, Chao HT, Posey JE, Westerfield M, Postlethwait J, Hieter P, Boycott KM, Campeau PM, Bellen HJ. Model Organisms Facilitate Rare Disease Diagnosis and Therapeutic Research. Genetics 2017; 207:9-27. [PMID: 28874452 PMCID: PMC5586389 DOI: 10.1534/genetics.117.203067] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 07/06/2017] [Indexed: 12/29/2022] Open
Abstract
Efforts to identify the genetic underpinnings of rare undiagnosed diseases increasingly involve the use of next-generation sequencing and comparative genomic hybridization methods. These efforts are limited by a lack of knowledge regarding gene function, and an inability to predict the impact of genetic variation on the encoded protein function. Diagnostic challenges posed by undiagnosed diseases have solutions in model organism research, which provides a wealth of detailed biological information. Model organism geneticists are by necessity experts in particular genes, gene families, specific organs, and biological functions. Here, we review the current state of research into undiagnosed diseases, highlighting large efforts in North America and internationally, including the Undiagnosed Diseases Network (UDN) (Supplemental Material, File S1) and UDN International (UDNI), the Centers for Mendelian Genomics (CMG), and the Canadian Rare Diseases Models and Mechanisms Network (RDMM). We discuss how merging human genetics with model organism research guides experimental studies to solve these medical mysteries, gain new insights into disease pathogenesis, and uncover new therapeutic strategies.
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Affiliation(s)
- Michael F Wangler
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas 77030
- Department of Pediatrics, Baylor College of Medicine (BCM), Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, Texas 77030
| | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, Texas 77030
- Department of Neuroscience, Baylor College of Medicine (BCM), Houston, Texas 77030
| | - Hsiao-Tuan Chao
- Department of Pediatrics, Baylor College of Medicine (BCM), Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
- Department of Pediatrics, Section of Child Neurology, Baylor College of Medicine (BCM), Houston, Texas 77030
| | - Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas 77030
| | - Monte Westerfield
- Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403
| | - John Postlethwait
- Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403
| | - Philip Hieter
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4C, Canada
| | - Kym M Boycott
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ontario K1H 8L1, Canada
| | - Philippe M Campeau
- Department of Pediatrics, University of Montreal, Quebec H3T 1C5, Canada
| | - Hugo J Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, Texas 77030
- Department of Neuroscience, Baylor College of Medicine (BCM), Houston, Texas 77030
- Howard Hughes Medical Institute, Baylor College of Medicine (BCM), Houston, Texas 77030
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20
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An Atoh1-S193A Phospho-Mutant Allele Causes Hearing Deficits and Motor Impairment. J Neurosci 2017; 37:8583-8594. [PMID: 28729444 DOI: 10.1523/jneurosci.0295-17.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 06/20/2017] [Accepted: 06/29/2017] [Indexed: 12/21/2022] Open
Abstract
Atonal homolog 1 (Atoh1) is a basic helix-loop-helix (bHLH) transcription factor that is essential for the genesis, survival, and maturation of a variety of neuronal and non-neuronal cell populations, including those involved in proprioception, interoception, balance, respiration, and hearing. Such diverse functions require fine regulation at the transcriptional and protein levels. Here, we show that serine 193 (S193) is phosphorylated in Atoh1's bHLH domain in vivo Knock-in mice of both sexes bearing a GFP-tagged phospho-dead S193A allele on a null background (Atoh1S193A/lacZ) exhibit mild cerebellar foliation defects, motor impairments, partial pontine nucleus migration defects, cochlear hair cell degeneration, and profound hearing loss. We also found that Atoh1 heterozygous mice of both sexes (Atoh1lacZ/+) have adult-onset deafness. These data indicate that different cell types have different degrees of vulnerability to loss of Atoh1 function and that hypomorphic Atoh1 alleles should be considered in human hearing loss.SIGNIFICANCE STATEMENT The discovery that Atonal homolog 1 (Atoh1) governs the development of the sensory hair cells in the inner ear led to therapeutic efforts to restore these cells in cases of human deafness. Because prior studies of Atoh1-heterozygous mice did not examine or report on hearing loss in mature animals, it has not been clinical practice to sequence ATOH1 in people with deafness. Here, in seeking to understand how phosphorylation of Atoh1 modulates its effects in vivo, we discovered that inner ear hair cells are much more vulnerable to loss of Atoh1 function than other Atoh1-positive cell types and that heterozygous mice actually develop hearing loss late in life. This opens up the possibility that missense mutations in ATOH1 could increase human vulnerability to loss of hair cells because of aging or trauma.
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21
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Costa A, Powell LM, Lowell S, Jarman AP. Atoh1 in sensory hair cell development: constraints and cofactors. Semin Cell Dev Biol 2017; 65:60-68. [DOI: 10.1016/j.semcdb.2016.10.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 09/26/2016] [Accepted: 10/13/2016] [Indexed: 11/28/2022]
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22
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Weinberger S, Topping MP, Yan J, Claeys A, Geest ND, Ozbay D, Hassan T, He X, Albert JT, Hassan BA, Ramaekers A. Evolutionary changes in transcription factor coding sequence quantitatively alter sensory organ development and function. eLife 2017; 6. [PMID: 28406397 PMCID: PMC5432213 DOI: 10.7554/elife.26402] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 03/27/2017] [Indexed: 11/16/2022] Open
Abstract
Animals are characterized by a set of highly conserved developmental regulators. Changes in the cis-regulatory elements of these regulators are thought to constitute the major driver of morphological evolution. However, the role of coding sequence evolution remains unresolved. To address this question, we used the Atonal family of proneural transcription factors as a model. Drosophila atonal coding sequence was endogenously replaced with that of atonal homologues (ATHs) at key phylogenetic positions, non-ATH proneural genes, and the closest homologue to ancestral proneural genes. ATHs and the ancestral-like coding sequences rescued sensory organ fate in atonal mutants, in contrast to non-ATHs. Surprisingly, different ATH factors displayed different levels of proneural activity as reflected by the number and functionality of sense organs. This proneural potency gradient correlated directly with ATH protein stability, including in response to Notch signaling, independently of mRNA levels or codon usage. This establishes a distinct and ancient function for ATHs and demonstrates that coding sequence evolution can underlie quantitative variation in sensory development and function. DOI:http://dx.doi.org/10.7554/eLife.26402.001
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Affiliation(s)
- Simon Weinberger
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Program in Molecular and Developmental Genetics, Doctoral School for Biomedical Sciences, University of Leuven School Group Biomedicine, Leuven, Belgium
| | - Matthew P Topping
- Ear Institute, University College London, London, United Kingdom.,Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom
| | - Jiekun Yan
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Annelies Claeys
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Natalie De Geest
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Duru Ozbay
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Talah Hassan
- Ear Institute, University College London, London, United Kingdom
| | - Xiaoli He
- Ear Institute, University College London, London, United Kingdom
| | - Joerg T Albert
- Ear Institute, University College London, London, United Kingdom.,Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom.,Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Program in Molecular and Developmental Genetics, Doctoral School for Biomedical Sciences, University of Leuven School Group Biomedicine, Leuven, Belgium.,Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Inserm, CNRS, Paris, France
| | - Ariane Ramaekers
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Inserm, CNRS, Paris, France
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23
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Bandyopadhyay M, Arbet S, Bishop CP, Bidwai AP. Drosophila Protein Kinase CK2: Genetics, Regulatory Complexity and Emerging Roles during Development. Pharmaceuticals (Basel) 2016; 10:E4. [PMID: 28036067 PMCID: PMC5374408 DOI: 10.3390/ph10010004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/12/2016] [Accepted: 12/19/2016] [Indexed: 01/06/2023] Open
Abstract
CK2 is a Ser/Thr protein kinase that is highly conserved amongst all eukaryotes. It is a well-known oncogenic kinase that regulates vital cell autonomous functions and animal development. Genetic studies in the fruit fly Drosophila are providing unique insights into the roles of CK2 in cell signaling, embryogenesis, organogenesis, neurogenesis, and the circadian clock, and are revealing hitherto unknown complexities in CK2 functions and regulation. Here, we review Drosophila CK2 with respect to its structure, subunit diversity, potential mechanisms of regulation, developmental abnormalities linked to mutations in the gene encoding CK2 subunits, and emerging roles in multiple aspects of eye development. We examine the Drosophila CK2 "interaction map" and the eye-specific "transcriptome" databases, which raise the prospect that this protein kinase has many additional targets in the developing eye. We discuss the possibility that CK2 functions during early retinal neurogenesis in Drosophila and mammals bear greater similarity than has been recognized, and that this conservation may extend to other developmental programs. Together, these studies underscore the immense power of the Drosophila model organism to provide new insights and avenues to further investigate developmentally relevant targets of this protein kinase.
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Affiliation(s)
| | - Scott Arbet
- Department of Biology, West Virginia University, Morgantown, WV 26506, USA.
| | - Clifton P Bishop
- Department of Biology, West Virginia University, Morgantown, WV 26506, USA.
| | - Ashok P Bidwai
- Department of Biology, West Virginia University, Morgantown, WV 26506, USA.
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24
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Arendt D, Benito-Gutierrez E, Brunet T, Marlow H. Gastric pouches and the mucociliary sole: setting the stage for nervous system evolution. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0286. [PMID: 26554050 PMCID: PMC4650134 DOI: 10.1098/rstb.2015.0286] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Prerequisite for tracing nervous system evolution is understanding of the body plan, feeding behaviour and locomotion of the first animals in which neurons evolved. Here, a comprehensive scenario is presented for the diversification of cell types in early metazoans, which enhanced feeding efficiency and led to the emergence of larger animals that were able to move. Starting from cup-shaped, gastraea-like animals with outer and inner choanoflagellate-like cells, two major innovations are discussed that set the stage for nervous system evolution. First, the invention of a mucociliary sole entailed a switch from intra- to extracellular digestion and increased the concentration of nutrients flowing into the gastric cavity. In these animals, an initial nerve net may have evolved via division of labour from mechanosensory-contractile cells in the lateral body wall, enabling coordinated movement of the growing body that involved both mucociliary creeping and changes of body shape. Second, the inner surface of the animals folded into metameric series of gastric pouches, which optimized nutrient resorption and allowed larger body sizes. The concomitant acquisition of bilateral symmetry may have allowed more directed locomotion and, with more demanding coordinative tasks, triggered the evolution of specialized nervous subsystems. Animals of this organizational state would have resembled Ediacarian fossils such as Dickinsonia and may have been close to the cnidarian–bilaterian ancestor. In the bilaterian lineage, the mucociliary sole was used mostly for creeping, or frequently lost. One possible remnant is the enigmatic Reissner's fibre in the ventral neural tube of cephalochordates and vertebrates.
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Affiliation(s)
- Detlev Arendt
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69012 Heidelberg, Germany Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
| | | | - Thibaut Brunet
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69012 Heidelberg, Germany
| | - Heather Marlow
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69012 Heidelberg, Germany
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25
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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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26
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Quan XJ, Yuan L, Tiberi L, Claeys A, De Geest N, Yan J, van der Kant R, Xie W, Klisch T, Shymkowitz J, Rousseau F, Bollen M, Beullens M, Zoghbi H, Vanderhaeghen P, Hassan B. Post-translational Control of the Temporal Dynamics of Transcription Factor Activity Regulates Neurogenesis. Cell 2016; 164:460-75. [DOI: 10.1016/j.cell.2015.12.048] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 10/12/2015] [Accepted: 12/22/2015] [Indexed: 11/28/2022]
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27
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Jahan I, Pan N, Kersigo J, Fritzsch B. Neurog1 can partially substitute for Atoh1 function in hair cell differentiation and maintenance during organ of Corti development. Development 2015. [PMID: 26209643 DOI: 10.1242/dev.123091] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Atoh1, a basic helix-loop-helix (bHLH) transcription factor (TF), is essential for the differentiation of hair cells (HCs), mechanotransducers that convert sound into auditory signals in the mammalian organ of Corti (OC). Previous work demonstrated that replacing mouse Atoh1 with the fly ortholog atonal rescues HC differentiation, indicating functional replacement by other bHLH genes. However, replacing Atoh1 with Neurog1 resulted in reduced HC differentiation compared with transient Atoh1 expression in a 'self-terminating' Atoh1 conditional null mouse (Atoh1-Cre; Atoh1(f/f)). We now show that combining Neurog1 in one allele with removal of floxed Atoh1 in a self-terminating conditional mutant (Atoh1-Cre; Atoh1(f/kiNeurog1)) mouse results in significantly more differentiated inner HCs and outer HCs that have a prolonged longevity of 9 months compared with Atoh1 self-terminating littermates. Stereocilia bundles are partially disorganized, disoriented and not HC type specific. Replacement of Atoh1 with Neurog1 maintains limited expression of Pou4f3 and Barhl1 and rescues HCs quantitatively, but not qualitatively. OC patterning and supporting cell differentiation are also partially disrupted. Diffusible factors involved in patterning are reduced (Fgf8) and factors involved in cell-cell interactions are affected (Jag1, Hes5). Despite the presence of many HCs with stereocilia these mice are deaf, possibly owing to HC and OC patterning defects. This study provides a novel approach to disrupt OC development through modulating the HC-specific intracellular TF network. The resulting disorganized OC indicates that normally differentiated HCs act as 'self-organizers' for OC development and that Atoh1 plays a crucial role to initiate HC stereocilia differentiation independently of HC viability.
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Affiliation(s)
- Israt Jahan
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Ning Pan
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Jennifer Kersigo
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Bernd Fritzsch
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
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Rebeiz M, Patel NH, Hinman VF. Unraveling the Tangled Skein: The Evolution of Transcriptional Regulatory Networks in Development. Annu Rev Genomics Hum Genet 2015; 16:103-31. [PMID: 26079281 DOI: 10.1146/annurev-genom-091212-153423] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The molecular and genetic basis for the evolution of anatomical diversity is a major question that has inspired evolutionary and developmental biologists for decades. Because morphology takes form during development, a true comprehension of how anatomical structures evolve requires an understanding of the evolutionary events that alter developmental genetic programs. Vast gene regulatory networks (GRNs) that connect transcription factors to their target regulatory sequences control gene expression in time and space and therefore determine the tissue-specific genetic programs that shape morphological structures. In recent years, many new examples have greatly advanced our understanding of the genetic alterations that modify GRNs to generate newly evolved morphologies. Here, we review several aspects of GRN evolution, including their deep preservation, their mechanisms of alteration, and how they originate to generate novel developmental programs.
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Affiliation(s)
- Mark Rebeiz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260;
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Naval-Sánchez M, Potier D, Hulselmans G, Christiaens V, Aerts S. Identification of Lineage-Specific Cis-Regulatory Modules Associated with Variation in Transcription Factor Binding and Chromatin Activity Using Ornstein-Uhlenbeck Models. Mol Biol Evol 2015; 32:2441-55. [PMID: 25944915 PMCID: PMC4540964 DOI: 10.1093/molbev/msv107] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Scoring the impact of noncoding variation on the function of cis-regulatory regions, on their chromatin state, and on the qualitative and quantitative expression levels of target genes is a fundamental problem in evolutionary genomics. A particular challenge is how to model the divergence of quantitative traits and to identify relationships between the changes across the different levels of the genome, the chromatin activity landscape, and the transcriptome. Here, we examine the use of the Ornstein-Uhlenbeck (OU) model to infer selection at the level of predicted cis-regulatory modules (CRMs), and link these with changes in transcription factor binding and chromatin activity. Using publicly available cross-species ChIP-Seq and STARR-Seq data we show how OU can be applied genome-wide to identify candidate transcription factors for which binding site and CRM turnover is correlated with changes in regulatory activity. Next, we profile open chromatin in the developing eye across three Drosophila species. We identify the recognition motifs of the chromatin remodelers, Trithorax-like and Grainyhead as mostly correlating with species-specific changes in open chromatin. In conclusion, we show in this study that CRM scores can be used as quantitative traits and that motif discovery approaches can be extended towards more complex models of divergence.
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Affiliation(s)
- Marina Naval-Sánchez
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Delphine Potier
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Gert Hulselmans
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Valerie Christiaens
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Stein Aerts
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
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30
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Davie K, Jacobs J, Atkins M, Potier D, Christiaens V, Halder G, Aerts S. Discovery of transcription factors and regulatory regions driving in vivo tumor development by ATAC-seq and FAIRE-seq open chromatin profiling. PLoS Genet 2015; 11:e1004994. [PMID: 25679813 PMCID: PMC4334524 DOI: 10.1371/journal.pgen.1004994] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 01/08/2015] [Indexed: 01/24/2023] Open
Abstract
Genomic enhancers regulate spatio-temporal gene expression by recruiting specific combinations of transcription factors (TFs). When TFs are bound to active regulatory regions, they displace canonical nucleosomes, making these regions biochemically detectable as nucleosome-depleted regions or accessible/open chromatin. Here we ask whether open chromatin profiling can be used to identify the entire repertoire of active promoters and enhancers underlying tissue-specific gene expression during normal development and oncogenesis in vivo. To this end, we first compare two different approaches to detect open chromatin in vivo using the Drosophila eye primordium as a model system: FAIRE-seq, based on physical separation of open versus closed chromatin; and ATAC-seq, based on preferential integration of a transposon into open chromatin. We find that both methods reproducibly capture the tissue-specific chromatin activity of regulatory regions, including promoters, enhancers, and insulators. Using both techniques, we screened for regulatory regions that become ectopically active during Ras-dependent oncogenesis, and identified 3778 regions that become (over-)activated during tumor development. Next, we applied motif discovery to search for candidate transcription factors that could bind these regions and identified AP-1 and Stat92E as key regulators. We validated the importance of Stat92E in the development of the tumors by introducing a loss of function Stat92E mutant, which was sufficient to rescue the tumor phenotype. Additionally we tested if the predicted Stat92E responsive regulatory regions are genuine, using ectopic induction of JAK/STAT signaling in developing eye discs, and observed that similar chromatin changes indeed occurred. Finally, we determine that these are functionally significant regulatory changes, as nearby target genes are up- or down-regulated. In conclusion, we show that FAIRE-seq and ATAC-seq based open chromatin profiling, combined with motif discovery, is a straightforward approach to identify functional genomic regulatory regions, master regulators, and gene regulatory networks controlling complex in vivo processes.
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Affiliation(s)
- Kristofer Davie
- Laboratory of Computational Biology, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - Jelle Jacobs
- Laboratory of Computational Biology, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - Mardelle Atkins
- Laboratory of Growth Control and Cancer Research, Center for Human Genetics, KU Leuven, Leuven, Belgium
- VIB Center for the Biology of Disease, Laboratory for Molecular Cancer Biology, Leuven, Belgium
| | - Delphine Potier
- Laboratory of Computational Biology, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - Valerie Christiaens
- Laboratory of Computational Biology, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - Georg Halder
- Laboratory of Growth Control and Cancer Research, Center for Human Genetics, KU Leuven, Leuven, Belgium
- VIB Center for the Biology of Disease, Laboratory for Molecular Cancer Biology, Leuven, Belgium
| | - Stein Aerts
- Laboratory of Computational Biology, Center for Human Genetics, KU Leuven, Leuven, Belgium
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Cheatle Jarvela AM, Hinman VF. Evolution of transcription factor function as a mechanism for changing metazoan developmental gene regulatory networks. EvoDevo 2015; 6:3. [PMID: 25685316 PMCID: PMC4327956 DOI: 10.1186/2041-9139-6-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 12/18/2014] [Indexed: 11/10/2022] Open
Abstract
The form that an animal takes during development is directed by gene regulatory networks (GRNs). Developmental GRNs interpret maternally deposited molecules and externally supplied signals to direct cell-fate decisions, which ultimately leads to the arrangements of organs and tissues in the organism. Genetically encoded modifications to these networks have generated the wide range of metazoan diversity that exists today. Most studies of GRN evolution focus on changes to cis-regulatory DNA, and it was historically theorized that changes to the transcription factors that bind to these cis-regulatory modules (CRMs) contribute to this process only rarely. A growing body of evidence suggests that changes to the coding regions of transcription factors play a much larger role in the evolution of developmental gene regulatory networks than originally imagined. Just as cis-regulatory changes make use of modular binding site composition and tissue-specific modules to avoid pleiotropy, transcription factor coding regions also predominantly evolve in ways that limit the context of functional effects. Here, we review the recent works that have led to this unexpected change in the field of Evolution and Development (Evo-Devo) and consider the implications these studies have had on our understanding of the evolution of developmental processes.
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Affiliation(s)
- Alys M Cheatle Jarvela
- Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213 USA
| | - Veronica F Hinman
- Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213 USA
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Mapping Gene Regulatory Networks in Drosophila Eye Development by Large-Scale Transcriptome Perturbations and Motif Inference. Cell Rep 2014; 9:2290-303. [DOI: 10.1016/j.celrep.2014.11.038] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 10/24/2014] [Accepted: 11/22/2014] [Indexed: 11/20/2022] Open
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Fritzsch B, Jahan I, Pan N, Elliott KL. Evolving gene regulatory networks into cellular networks guiding adaptive behavior: an outline how single cells could have evolved into a centralized neurosensory system. Cell Tissue Res 2014; 359:295-313. [PMID: 25416504 DOI: 10.1007/s00441-014-2043-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 10/20/2014] [Indexed: 12/18/2022]
Abstract
Understanding the evolution of the neurosensory system of man, able to reflect on its own origin, is one of the major goals of comparative neurobiology. Details of the origin of neurosensory cells, their aggregation into central nervous systems and associated sensory organs and their localized patterning leading to remarkably different cell types aggregated into variably sized parts of the central nervous system have begun to emerge. Insights at the cellular and molecular level have begun to shed some light on the evolution of neurosensory cells, partially covered in this review. Molecular evidence suggests that high mobility group (HMG) proteins of pre-metazoans evolved into the definitive Sox [SRY (sex determining region Y)-box] genes used for neurosensory precursor specification in metazoans. Likewise, pre-metazoan basic helix-loop-helix (bHLH) genes evolved in metazoans into the group A bHLH genes dedicated to neurosensory differentiation in bilaterians. Available evidence suggests that the Sox and bHLH genes evolved a cross-regulatory network able to synchronize expansion of precursor populations and their subsequent differentiation into novel parts of the brain or sensory organs. Molecular evidence suggests metazoans evolved patterning gene networks early, which were not dedicated to neuronal development. Only later in evolution were these patterning gene networks tied into the increasing complexity of diffusible factors, many of which were already present in pre-metazoans, to drive local patterning events. It appears that the evolving molecular basis of neurosensory cell development may have led, in interaction with differentially expressed patterning genes, to local network modifications guiding unique specializations of neurosensory cells into sensory organs and various areas of the central nervous system.
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, University of Iowa, CLAS, 143 BB, Iowa City, IA, 52242, USA,
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Cai T, Groves AK. The Role of Atonal Factors in Mechanosensory Cell Specification and Function. Mol Neurobiol 2014; 52:1315-1329. [PMID: 25339580 DOI: 10.1007/s12035-014-8925-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/07/2014] [Indexed: 10/24/2022]
Abstract
Atonal genes are basic helix-loop-helix transcription factors that were first identified as regulating the formation of mechanoreceptors and photoreceptors in Drosophila. Isolation of vertebrate homologs of atonal genes has shown these transcription factors to play diverse roles in the development of neurons and their progenitors, gut epithelial cells, and mechanosensory cells in the inner ear and skin. In this article, we review the molecular function and regulation of atonal genes and their targets, with particular emphasis on the function of Atoh1 in the development, survival, and function of hair cells of the inner ear. We discuss cell-extrinsic signals that induce Atoh1 expression and the transcriptional networks that regulate its expression during development. Finally, we discuss recent work showing how identification of Atoh1 target genes in the cerebellum, spinal cord, and gut can be used to propose candidate Atoh1 targets in tissues such as the inner ear where cell numbers and biochemical material are limiting.
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Affiliation(s)
- Tiantian Cai
- Program in Developmental Biology, Baylor College of Medicine, Houston, USA
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, Houston, USA. .,Department of Neuroscience, Baylor College of Medicine, Houston, USA. .,Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA.
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35
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Cheatle Jarvela AM, Brubaker L, Vedenko A, Gupta A, Armitage BA, Bulyk ML, Hinman VF. Modular evolution of DNA-binding preference of a Tbrain transcription factor provides a mechanism for modifying gene regulatory networks. Mol Biol Evol 2014; 31:2672-88. [PMID: 25016582 PMCID: PMC4166925 DOI: 10.1093/molbev/msu213] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gene regulatory networks (GRNs) describe the progression of transcriptional states that take a single-celled zygote to a multicellular organism. It is well documented that GRNs can evolve extensively through mutations to cis-regulatory modules (CRMs). Transcription factor proteins that bind these CRMs may also evolve to produce novelty. Coding changes are considered to be rarer, however, because transcription factors are multifunctional and hence are more constrained to evolve in ways that will not produce widespread detrimental effects. Recent technological advances have unearthed a surprising variation in DNA-binding abilities, such that individual transcription factors may recognize both a preferred primary motif and an additional secondary motif. This provides a source of modularity in function. Here, we demonstrate that orthologous transcription factors can also evolve a changed preference for a secondary binding motif, thereby offering an unexplored mechanism for GRN evolution. Using protein-binding microarray, surface plasmon resonance, and in vivo reporter assays, we demonstrate an important difference in DNA-binding preference between Tbrain protein orthologs in two species of echinoderms, the sea star, Patiria miniata, and the sea urchin, Strongylocentrotus purpuratus. Although both orthologs recognize the same primary motif, only the sea star Tbr also has a secondary binding motif. Our in vivo assays demonstrate that this difference may allow for greater evolutionary change in timing of regulatory control. This uncovers a layer of transcription factor binding divergence that could exist for many pairs of orthologs. We hypothesize that this divergence provides modularity that allows orthologous transcription factors to evolve novel roles in GRNs through modification of binding to secondary sites.
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Affiliation(s)
| | - Lisa Brubaker
- Department of Biological Sciences, Carnegie Mellon University
| | - Anastasia Vedenko
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
| | - Anisha Gupta
- Department of Chemistry, Carnegie Mellon University
| | | | - Martha L Bulyk
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
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Raft S, Groves AK. Segregating neural and mechanosensory fates in the developing ear: patterning, signaling, and transcriptional control. Cell Tissue Res 2014; 359:315-32. [PMID: 24902666 DOI: 10.1007/s00441-014-1917-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 05/08/2014] [Indexed: 12/21/2022]
Abstract
The vertebrate inner ear is composed of multiple sensory receptor epithelia, each of which is specialized for detection of sound, gravity, or angular acceleration. Each receptor epithelium contains mechanosensitive hair cells, which are connected to the brainstem by bipolar sensory neurons. Hair cells and their associated neurons are derived from the embryonic rudiment of the inner ear epithelium, but the precise spatial and temporal patterns of their generation, as well as the signals that coordinate these events, have only recently begun to be understood. Gene expression, lineage tracing, and mutant analyses suggest that both neurons and hair cells are generated from a common domain of neural and sensory competence in the embryonic inner ear rudiment. Members of the Shh, Wnt, and FGF families, together with retinoic acid signals, regulate transcription factor genes within the inner ear rudiment to establish the axial identity of the ear and regionalize neurogenic activity. Close-range signaling, such as that of the Notch pathway, specifies the fate of sensory regions and individual cell types. We also describe positive and negative interactions between basic helix-loop-helix and SoxB family transcription factors that specify either neuronal or sensory fates in a context-dependent manner. Finally, we review recent work on inner ear development in zebrafish, which demonstrates that the relative timing of neurogenesis and sensory epithelial formation is not phylogenetically constrained.
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Affiliation(s)
- Steven Raft
- Section on Sensory Cell Regeneration and Development, National Institute on Deafness and Other Communication Disorders National Institutes of Health, 35 Convent Drive, Bethesda, MD, 20892, USA,
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37
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Evolution of vertebrate mechanosensory hair cells and inner ears: toward identifying stimuli that select mutation driven altered morphologies. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2013; 200:5-18. [PMID: 24281353 DOI: 10.1007/s00359-013-0865-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/16/2013] [Accepted: 10/18/2013] [Indexed: 12/31/2022]
Abstract
Among the major distance senses of vertebrates, the ear is unique in its complex morphological changes during evolution. Conceivably, these changes enable the ear to adapt toward sensing various physically well-characterized stimuli. This review develops a scenario that integrates sensory cell with organ evolution. We propose that molecular and cellular evolution of the vertebrate hair cells occurred prior to the formation of the vertebrate ear. We previously proposed that the genes driving hair cell differentiation were aggregated in the otic region through developmental re-patterning that generated a unique vertebrate embryonic structure, the otic placode. In agreement with the presence of graviceptive receptors in many vertebrate outgroups, it is likely that the vertebrate ear originally functioned as a simple gravity-sensing organ. Based on the rare occurrence of angular acceleration receptors in vertebrate outgroups, we further propose that the canal system evolved with a more sophisticated ear morphogenesis. This evolving morphogenesis obviously turned the initial otocyst into a complex set of canals and recesses, harboring multiple sensory epithelia each adapted to the acquisition of a specific aspect of a given physical stimulus. As support for this evolutionary progression, we provide several details of the molecular basis of ear development.
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38
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Physiological, anatomical, and behavioral changes after acoustic trauma in Drosophila melanogaster. Proc Natl Acad Sci U S A 2013; 110:15449-54. [PMID: 24003166 DOI: 10.1073/pnas.1307294110] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Noise-induced hearing loss (NIHL) is a growing health issue, with costly treatment and lost quality of life. Here we establish Drosophila melanogaster as an inexpensive, flexible, and powerful genetic model system for NIHL. We exposed flies to acoustic trauma and quantified physiological and anatomical effects. Trauma significantly reduced sound-evoked potential (SEP) amplitudes and increased SEP latencies in control genotypes. SEP amplitude but not latency effects recovered after 7 d. Although trauma produced no gross morphological changes in the auditory organ (Johnston's organ), mitochondrial cross-sectional area was reduced 7 d after exposure. In nervana 3 heterozygous flies, which slightly compromise ion homeostasis, trauma had exaggerated effects on SEP amplitude and mitochondrial morphology, suggesting a key role for ion homeostasis in resistance to acoustic trauma. Thus, Drosophila exhibit acoustic trauma effects resembling those found in vertebrates, including inducing metabolic stress in sensory cells. This report of noise trauma in Drosophila is a foundation for studying molecular and genetic sequelae of NIHL.
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Fritzsch B, Pan N, Jahan I, Duncan JS, Kopecky BJ, Elliott KL, Kersigo J, Yang T. Evolution and development of the tetrapod auditory system: an organ of Corti-centric perspective. Evol Dev 2013; 15:63-79. [PMID: 23331918 DOI: 10.1111/ede.12015] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The tetrapod auditory system transmits sound through the outer and middle ear to the organ of Corti or other sound pressure receivers of the inner ear where specialized hair cells translate vibrations of the basilar membrane into electrical potential changes that are conducted by the spiral ganglion neurons to the auditory nuclei. In other systems, notably the vertebrate limb, a detailed connection between the evolutionary variations in adaptive morphology and the underlying alterations in the genetic basis of development has been partially elucidated. In this review, we attempt to correlate evolutionary and partially characterized molecular data into a cohesive perspective of the evolution of the mammalian organ of Corti out of the tetrapod basilar papilla. We propose a stepwise, molecularly partially characterized transformation of the ancestral, vestibular developmental program of the vertebrate ear. This review provides a framework to decipher both discrete steps in development and the evolution of unique functional adaptations of the auditory system. The combined analysis of evolution and development establishes a powerful cross-correlation where conclusions derived from either approach become more meaningful in a larger context which is not possible through exclusively evolution or development centered perspectives. Selection may explain the survival of the fittest auditory system, but only developmental genetics can explain the arrival of the fittest auditory system. [Modified after (Wagner 2011)].
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, University of Iowa, CLAS, 143 BB, Iowa City, IA, 52242, USA. bernd‐
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40
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Jarman AP, Groves AK. The role of Atonal transcription factors in the development of mechanosensitive cells. Semin Cell Dev Biol 2013; 24:438-47. [PMID: 23548731 DOI: 10.1016/j.semcdb.2013.03.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 01/04/2013] [Accepted: 03/21/2013] [Indexed: 11/29/2022]
Abstract
Mechanosensation is an evolutionarily ancient sensory modality seen in all main animal groups. Mechanosensation can be mediated by sensory neurons or by dedicated receptor cells that form synapses with sensory neurons. Evidence over the last 15-20 years suggests that both classes of mechanosensory cells can be specified by the atonal class of basic helix-loop-helix transcription factors. In this review we discuss recent work addressing how atonal factors specify mechanosensitive cells in vertebrates and invertebrates, and how the redeployment of these factors underlies the regeneration of mechanosensitive cells in some vertebrate groups.
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Affiliation(s)
- Andrew P Jarman
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom.
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41
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Abstract
Basic helix-loop-helix (bHLH) transcription factors (TFs) are crucial for inner ear neurosensory development. The proneural TF Atoh1 regulates the differentiation of hair cells (HCs) whereas Neurog1 and Neurod1 regulate specification and differentiation of neurons, respectively, but also affect HC development. Expression of Delta and Jagged ligands in nascent HCs and Notch receptors in supporting cells induce supporting cell differentiation through the regulation of neurogenic bHLH TFs (such as Hes1, Hes5) and suppression of limited Atoh1 expression. In sensorineural hearing loss, HCs are lost followed by supporting cells and progressive degeneration of neurons, at least in rodents. Regaining complete hearing may require reconstituting the organ of Corti from scratch, including the two types of HCs, inner and outer hair cells with the precise sorting of two types of afferent (type I and II) and efferent (lateral and medial olivo-cochlear) innervation. We review effects of bHLH TF dosage and their cross-regulation to differentiate HC types in the organ of Corti. We categorize findings of specific gene expressions in HCs: 1. as markers without meaning for the regeneration task, 2. as stabilizers who are needed to maintain or complete differentiation, and 3. as decision-making genes, expressed and acting early enough to be useful in this process. Only one TF has been characterized that fits the last aspect: Atoh1. We propose that temporal and intensity variations of Atoh1 are naturally modulated to differentiate specific types of HCs. Importantly, the molecular means to modify the Atoh1 expression are at least partially understood and can be readily implemented in the attempts to regenerate specific types of HCs.
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42
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Naval-Sánchez M, Potier D, Haagen L, Sánchez M, Munck S, Van de Sande B, Casares F, Christiaens V, Aerts S. Comparative motif discovery combined with comparative transcriptomics yields accurate targetome and enhancer predictions. Genome Res 2012; 23:74-88. [PMID: 23070853 PMCID: PMC3530685 DOI: 10.1101/gr.140426.112] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The identification of transcription factor binding sites, enhancers, and transcriptional target genes often relies on the integration of gene expression profiling and computational cis-regulatory sequence analysis. Methods for the prediction of cis-regulatory elements can take advantage of comparative genomics to increase signal-to-noise levels. However, gene expression data are usually derived from only one species. Here we investigate tissue-specific cross-species gene expression profiling by high-throughput sequencing, combined with cross-species motif discovery. First, we compared different methods for expression level quantification and cross-species integration using Tag-seq data. Using the optimal pipeline, we derived a set of genes with conserved expression during retinal determination across Drosophila melanogaster, Drosophila yakuba, and Drosophila virilis. These genes are enriched for binding sites of eye-related transcription factors including the zinc-finger Glass, a master regulator of photoreceptor differentiation. Validation of predicted Glass targets using RNA-seq in homozygous glass mutants confirms that the majority of our predictions are expressed downstream from Glass. Finally, we tested nine candidate enhancers by in vivo reporter assays and found eight of them to drive GFP in the eye disc, of which seven colocalize with the Glass protein, namely, scrt, chp, dpr10, CG6329, retn, Lim3, and dmrt99B. In conclusion, we show for the first time the combined use of cross-species expression profiling with cross-species motif discovery as a method to define a core developmental program, and we augment the candidate Glass targetome from a single known target gene, lozenge, to at least 62 conserved transcriptional targets.
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Affiliation(s)
- Marina Naval-Sánchez
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, 3000 Leuven, Belgium
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Okray Z, Hassan BA. Genetic approaches in Drosophila for the study neurodevelopmental disorders. Neuropharmacology 2012; 68:150-6. [PMID: 23067575 DOI: 10.1016/j.neuropharm.2012.09.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 08/31/2012] [Accepted: 09/07/2012] [Indexed: 12/16/2022]
Abstract
The fruit fly Drosophila melanogaster is one of the premier genetic model organisms used in biomedical research today owing to the extraordinary power of its genetic tool-kit. Made famous by numerous seminal discoveries of basic developmental mechanisms and behavioral genetics, the power of fruit fly genetics is becoming increasingly applied to questions directly relevant to human health. In this review we discuss how Drosophila research is applied to address major questions in neurodevelopmental disorders. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.
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Affiliation(s)
- Zeynep Okray
- Laboratory of Neurogenetics, VIB Center for the Biology of Disease, VIB, Herestraat 49, Leuven, Belgium
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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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Pan N, Kopecky B, Jahan I, Fritzsch B. Understanding the evolution and development of neurosensory transcription factors of the ear to enhance therapeutic translation. Cell Tissue Res 2012; 349:415-32. [PMID: 22688958 DOI: 10.1007/s00441-012-1454-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/18/2012] [Indexed: 01/08/2023]
Abstract
Reconstructing a functional organ of Corti is the ultimate target towards curing hearing loss. Despite the impressive technical gains made over the last few years, many complications remain ahead for the two main restoration avenues: in vitro transformation of pluripotent cells into hair cell-like cells and adenovirus-mediated gene therapy. Most notably, both approaches require a more complete understanding of the molecular networks that ensure specific cell types form in the correct places to allow proper function of the restored organ of Corti. Important to this understanding are the basic helix-loop-helix (bHLH) transcription factors (TFs) that are highly diverse and serve to increase functional complexity but their evolutionary implementation in the inner ear neurosensory development is less conspicuous. To this end, we review the evolutionary and developmentally dynamic interactions of the three bHLH TFs that have been identified as the main players in neurosensory evolution and development, Neurog1, Neurod1 and Atoh1. These three TFs belong to the neurogenin/atonal family and evolved from a molecular precursor that likely regulated single sensory cell development in the ectoderm of metazoan ancestors but are now also expressed in other parts of the body, including the brain. They interact extensively via intracellular and intercellular cross-regulation to establish the two main neurosensory cell types of the ear, the hair cells and sensory neurons. Furthermore, the level and duration of their expression affect the specification of hair cell subtypes (inner hair cells vs. outer hair cells). We propose that appropriate manipulation of these TFs through their characterized binding sites may offer a solution by itself, or in conjunction with the two other approaches currently pursued by others, to restore the organ of Corti.
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Affiliation(s)
- Ning Pan
- Department of Biology, University of Iowa, College of Liberal Arts and Sciences, Iowa City, IA 52242, USA
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Atoh1, an essential transcription factor in neurogenesis and intestinal and inner ear development: function, regulation, and context dependency. J Assoc Res Otolaryngol 2012; 13:281-93. [PMID: 22370966 DOI: 10.1007/s10162-012-0317-4] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 02/06/2012] [Indexed: 01/07/2023] Open
Abstract
Atoh1 (also known as Math1, Hath1, and Cath1 in mouse, human, and chicken, respectively) is a proneural basic helix-loop-helix (bHLH) transcription factor that is required in a variety of developmental contexts. Atoh1 is involved in differentiation of neurons, secretory cells in the gut, and mechanoreceptors including auditory hair cells. Together with the two closely related bHLH genes, Neurog1 and NeuroD1, Atoh1 regulates neurosensory development in the ear as well as neurogenesis in the cerebellum. Atoh1 activity in the cochlea is both necessary and sufficient to drive auditory hair cell differentiation, in keeping with its known role as a regulator of various genes that are markers of terminal differentiation. Atoh1 is known in other fields as an oncogene and a tumor suppressor involved in regulation of cell cycle control and apoptosis. Aberrant Atoh1 activity in adult tissue is implicated in cancer progression, specifically in medullablastoma and adenomatous polyposis carcinoma. We demonstrate through protein sequence comparison that Atoh1 contains conserved phosphorylation sites outside the bHLH domain, which may allow regulation through post-translational modification. With such diverse roles, tight regulation of Atoh1 at both the transcriptional and protein level is essential.
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Jahan I, Pan N, Kersigo J, Calisto LE, Morris KA, Kopecky B, Duncan JS, Beisel KW, Fritzsch B. Expression of Neurog1 instead of Atoh1 can partially rescue organ of Corti cell survival. PLoS One 2012; 7:e30853. [PMID: 22292060 PMCID: PMC3265522 DOI: 10.1371/journal.pone.0030853] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 12/21/2011] [Indexed: 11/19/2022] Open
Abstract
In the mammalian inner ear neurosensory cell fate depends on three closely related transcription factors, Atoh1 for hair cells and Neurog1 and Neurod1 for neurons. We have previously shown that neuronal cell fate can be altered towards hair cell fate by eliminating Neurod1 mediated repression of Atoh1 expression in neurons. To test whether a similar plasticity is present in hair cell fate commitment, we have generated a knockin (KI) mouse line (Atoh1KINeurog1) in which Atoh1 is replaced by Neurog1. Expression of Neurog1 under Atoh1 promoter control alters the cellular gene expression pattern, differentiation and survival of hair cell precursors in both heterozygous (Atoh1+/KINeurog1) and homozygous (Atoh1KINeurog1/KINeurog1) KI mice. Homozygous KI mice develop patches of organ of Corti precursor cells that express Neurog1, Neurod1, several prosensory genes and neurotrophins. In addition, these patches of cells receive afferent and efferent processes. Some cells among these patches form multiple microvilli but no stereocilia. Importantly, Neurog1 expressing mutants differ from Atoh1 null mutants, as they have intermittent formation of organ of Corti-like patches, opposed to a complete ‘flat epithelium’ in the absence of Atoh1. In heterozygous KI mice co-expression of Atoh1 and Neurog1 results in change in fate and patterning of some hair cells and supporting cells in addition to the abnormal hair cell polarity in the later stages of development. This differs from haploinsufficiency of Atoh1 (Pax2cre; Atoh1f/+), indicating the effect of Neurog1 expression in developing hair cells. Our data suggest that Atoh1KINeurog1 can provide some degree of functional support for survival of organ of Corti cells. In contrast to the previously demonstrated fate plasticity of neurons to differentiate as hair cells, hair cell precursors can be maintained for a limited time by Neurog1 but do not transdifferentiate as neurons.
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Affiliation(s)
- Israt Jahan
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
| | - Ning Pan
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
| | - Jennifer Kersigo
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
| | - Lilian E. Calisto
- Creighton University, Department of Biomedical Sciences, Omaha, Nebraska, United States of America
| | - Ken A. Morris
- Creighton University, Department of Biomedical Sciences, Omaha, Nebraska, United States of America
| | - Benjamin Kopecky
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
| | - Jeremy S. Duncan
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
| | - Kirk W. Beisel
- Creighton University, Department of Biomedical Sciences, Omaha, Nebraska, United States of America
| | - Bernd Fritzsch
- University of Iowa, Department of Biology, Iowa City, Iowa, United States of America
- * E-mail:
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Complementary function and integrated wiring of the evolutionarily distinct Drosophila olfactory subsystems. J Neurosci 2011; 31:13357-75. [PMID: 21940430 DOI: 10.1523/jneurosci.2360-11.2011] [Citation(s) in RCA: 324] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To sense myriad environmental odors, animals have evolved multiple, large families of divergent olfactory receptors. How and why distinct receptor repertoires and their associated circuits are functionally and anatomically integrated is essentially unknown. We have addressed these questions through comprehensive comparative analysis of the Drosophila olfactory subsystems that express the ionotropic receptors (IRs) and odorant receptors (ORs). We identify ligands for most IR neuron classes, revealing their specificity for select amines and acids, which complements the broader tuning of ORs for esters and alcohols. IR and OR sensory neurons exhibit glomerular convergence in segregated, although interconnected, zones of the primary olfactory center, but these circuits are extensively interdigitated in higher brain regions. Consistently, behavioral responses to odors arise from an interplay between IR- and OR-dependent pathways. We integrate knowledge on the different phylogenetic and developmental properties of these receptors and circuits to propose models for the functional contributions and evolution of these distinct olfactory subsystems.
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Pontier SM, Schweisguth F. Glycosphingolipids in signaling and development: From liposomes to model organisms. Dev Dyn 2011; 241:92-106. [DOI: 10.1002/dvdy.22766] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2011] [Indexed: 01/05/2023] Open
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Abstract
Neural basic helix-loop-helix (bHLH) transcription factors are crucial in regulating the differentiation and neuronal subtype specification of neurons. Precisely how these transcription factors direct such processes is largely unknown due to the lack of bona fide targets in vivo. Genetic evidence suggests that bHLH factors have shared targets in their common differentiation role, but unique targets with respect to their distinct roles in neuronal subtype specification. However, whether neuronal subtype-specific targets exist remains an unsolved question. To address this question, we focused on Atoh1 (Math1), a bHLH transcription factor that specifies distinct neuronal subtypes of the proprioceptive pathway in mammals including the dI1 (dorsal interneuron 1) population of the developing spinal cord. We identified transcripts unique to the Atoh1-derived lineage using microarray analyses of specific bHLH-sorted populations from mouse. Chromatin immunoprecipitation-sequencing experiments followed by enhancer reporter analyses identified five direct neuronal subtype-specific targets of Atoh1 in vivo along with their Atoh1-responsive enhancers. These targets, Klf7, Rab15, Rassf4, Selm, and Smad7, have diverse functions that range from transcription factors to regulators of endocytosis and signaling pathways. Only Rab15 and Selm are expressed across several different Atoh1-specified neuronal subtypes including external granule cells (external granule cell layer) in the developing cerebellum, hair cells of the inner ear, and Merkel cells. Our work establishes on a molecular level that neuronal differentiation bHLH transcription factors have distinct lineage-specific targets.
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