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Kanata E, Duffié R, Schulz EG. Establishment and maintenance of random monoallelic expression. Development 2024; 151:dev201741. [PMID: 38813842 PMCID: PMC11166465 DOI: 10.1242/dev.201741] [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: 05/31/2024]
Abstract
This Review elucidates the regulatory principles of random monoallelic expression by focusing on two well-studied examples: the X-chromosome inactivation regulator Xist and the olfactory receptor gene family. Although the choice of a single X chromosome or olfactory receptor occurs in different developmental contexts, common gene regulatory principles guide monoallelic expression in both systems. In both cases, an event breaks the symmetry between genetically and epigenetically identical copies of the gene, leading to the expression of one single random allele, stabilized through negative feedback control. Although many regulatory steps that govern the establishment and maintenance of monoallelic expression have been identified, key pieces of the puzzle are still missing. We provide an overview of the current knowledge and models for the monoallelic expression of Xist and olfactory receptors. We discuss their similarities and differences, and highlight open questions and approaches that could guide the study of other monoallelically expressed genes.
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Affiliation(s)
- Eleni Kanata
- Systems Epigenetics, Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Rachel Duffié
- Department of Biochemistry and Molecular Biophysics, Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Edda G. Schulz
- Systems Epigenetics, Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
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2
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Abbas G, Vyas R, Noble JC, Lin B, Lane RP. Transformation of an olfactory placode-derived cell into one with stem cell characteristics by disrupting epigenetic barriers. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.03.592460. [PMID: 38746208 PMCID: PMC11092772 DOI: 10.1101/2024.05.03.592460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
The mammalian olfactory neuronal lineage is regenerative, and accordingly, maintains a population of pluripotent cells that replenish olfactory sensory neurons and other olfactory cell types during the life of the animal. Moreover, in response to acute injury, the early transit amplifying cells along the olfactory sensory neuronal lineage are able to de-differentiate to shift resources in support of tissue restoration. In order to further explore plasticity of various cellular stages along the olfactory sensory neuronal lineage, we challenged the epigenetic stability of two olfactory placode-derived cell lines that model immature olfactory sensory neuronal stages. We found that perturbation of the Ehmt2 chromatin modifier transformed the growth properties, morphology, and gene expression profiles towards states with several stem cell characteristics. This transformation was dependent on continued expression of the large T-antigen, and was enhanced by Sox2 over-expression. These findings may provide momentum for exploring inherent cellular plasticity within early cell types of the olfactory lineage, as well as potentially add to our knowledge of cellular reprogramming. SUMMARY STATEMENT Discovering how epigenetic modifications influence olfactory neuronal lineage plasticity offers insights into regenerative potential and cellular reprogramming.
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3
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Ordway AJ, Helt RN, Johnston RJ. Transcriptional priming and chromatin regulation during stochastic cell fate specification. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230046. [PMID: 38432315 PMCID: PMC10909510 DOI: 10.1098/rstb.2023.0046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 01/19/2024] [Indexed: 03/05/2024] Open
Abstract
Stochastic cell fate specification, in which a cell chooses between two or more fates with a set probability, diversifies cell subtypes in development. Although this is a vital process across species, a common mechanism for these cell fate decisions remains elusive. This review examines two well-characterized stochastic cell fate decisions to identify commonalities between their developmental programmes. In the fly eye, two subtypes of R7 photoreceptors are specified by the stochastic ON/OFF expression of a transcription factor, spineless. In the mouse olfactory system, olfactory sensory neurons (OSNs) randomly select to express one copy of an olfactory receptor (OR) gene out of a pool of 2800 alleles. Despite the differences in these sensory systems, both stochastic fate choices rely on the dynamic interplay between transcriptional priming, chromatin regulation and terminal gene expression. The coupling of transcription and chromatin modifications primes gene loci in undifferentiated neurons, enabling later expression during terminal differentiation. Here, we compare these mechanisms, examine broader implications for gene regulation during development and posit key challenges moving forward. This article is part of a discussion meeting issue 'Causes and consequences of stochastic processes in development and disease'.
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Affiliation(s)
- Alison J. Ordway
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Rina N. Helt
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Robert J. Johnston
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
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4
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Yusuf N, Monahan K. Epigenetic programming of stochastic olfactory receptor choice. Genesis 2024; 62:e23593. [PMID: 38562011 PMCID: PMC11003729 DOI: 10.1002/dvg.23593] [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: 11/27/2023] [Revised: 03/01/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024]
Abstract
The mammalian sense of smell relies upon a vast array of receptor proteins to detect odorant compounds present in the environment. The proper deployment of these receptor proteins in olfactory sensory neurons is orchestrated by a suite of epigenetic processes that remodel the olfactory genes in differentiating neuronal progenitors. The goal of this review is to elucidate the central role of gene regulatory processes acting in neuronal progenitors of olfactory sensory neurons that lead to a singular expression of an odorant receptor in mature olfactory sensory neurons. We begin by describing the principal features of odorant receptor gene expression in mature olfactory sensory neurons. Next, we delineate our current understanding of how these features emerge from multiple gene regulatory mechanisms acting in neuronal progenitors. Finally, we close by discussing the key gaps in our understanding of how these regulatory mechanisms work and how they interact with each other over the course of differentiation.
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Affiliation(s)
- Nusrath Yusuf
- Division of Life Sciences-Molecular Biology and Biochemistry Department, Rutgers University-New Brunswick, New Brunswick, New Jersey, USA
| | - Kevin Monahan
- Division of Life Sciences-Molecular Biology and Biochemistry Department, Rutgers University-New Brunswick, New Brunswick, New Jersey, USA
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5
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Raja R, Dumontier E, Phen A, Cloutier JF. Insertion of a neomycin selection cassette in the Amigo1 locus alters gene expression in the olfactory epithelium leading to region-specific defects in olfactory receptor neuron development. Genesis 2024; 62:e23594. [PMID: 38590146 DOI: 10.1002/dvg.23594] [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: 12/04/2023] [Revised: 03/08/2024] [Accepted: 03/18/2024] [Indexed: 04/10/2024]
Abstract
During development of the nervous system, neurons connect to one another in a precisely organized manner. Sensory systems provide a good example of this organization, whereby the composition of the outside world is represented in the brain by neuronal maps. Establishing correct patterns of neural circuitry is crucial, as inaccurate map formation can lead to severe disruptions in sensory processing. In rodents, olfactory stimuli modulate a wide variety of behaviors essential for survival. The formation of the olfactory glomerular map is dependent on molecular cues that guide olfactory receptor neuron axons to broad regions of the olfactory bulb and on cell adhesion molecules that promote axonal sorting into specific synaptic units in this structure. Here, we demonstrate that the cell adhesion molecule Amigo1 is expressed in a subpopulation of olfactory receptor neurons, and we investigate its role in the precise targeting of olfactory receptor neuron axons to the olfactory bulb using a genetic loss-of-function approach in mice. While ablation of Amigo1 did not lead to alterations in olfactory sensory neuron axonal targeting, our experiments revealed that the presence of a neomycin resistance selection cassette in the Amigo1 locus can lead to off-target effects that are not due to loss of Amigo1 expression, including unexpected altered gene expression in olfactory receptor neurons and reduced glomerular size in the ventral region of the olfactory bulb. Our results demonstrate that insertion of a neomycin selection cassette into the mouse genome can have specific deleterious effects on the development of the olfactory system and highlight the importance of removing antibiotic resistance cassettes from genetic loss-of-function mouse models when studying olfactory system development.
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Affiliation(s)
- Reesha Raja
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, Québec, Canada
| | - Emilie Dumontier
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
| | - Alina Phen
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
| | - Jean-François Cloutier
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, Québec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada
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6
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Hirota J. Molecular mechanisms of differentiation and class choice of olfactory sensory neurons. Genesis 2024; 62:e23587. [PMID: 38454646 DOI: 10.1002/dvg.23587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/10/2024] [Accepted: 01/29/2024] [Indexed: 03/09/2024]
Abstract
The sense of smell is intricately linked to essential animal behaviors necessary for individual survival and species preservation. During vertebrate evolution, odorant receptors (ORs), responsible for detecting odor molecules, have evolved to adapt to changing environments, transitioning from aquatic to terrestrial habitats and accommodating increasing complex chemical environments. These evolutionary pressures have given rise to the largest gene family in vertebrate genomes. Vertebrate ORs are phylogenetically divided into two major classes; class I and class II. Class I OR genes, initially identified in fish and frog, have persisted across vertebrate species. On the other hand, class II OR genes are unique to terrestrial animals, accounting for ~90% of mammalian OR genes. In mice, each olfactory sensory neuron (OSN) expresses a single functional allele of a single OR gene from either the class I or class II OR repertoire. This one neuron-one receptor rule is established through two sequential steps: specification of OR class and subsequent exclusive OR expression from the corresponding OR class. Consequently, OSNs acquire diverse neuronal identities during the process of OSN differentiation, enabling animals to detect a wide array of odor molecules. This review provides an overview of the OSN differentiation process through which OSN diversity is achieved, primarily using the mouse as a model animal.
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Affiliation(s)
- Junji Hirota
- Department of Life Science and Technology, Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- Center for Integrative Biosciences, Tokyo Institute of Technology, Yokohama, Japan
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Mohanty SK, Maryam S, Gautam V, Mittal A, Gupta K, Arora R, Bhadra W, Mishra T, Sengupta D, Ahuja G. Transcriptional advantage influence odorant receptor gene choice. Brief Funct Genomics 2022; 22:281-290. [DOI: 10.1093/bfgp/elac052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/13/2022] [Accepted: 11/17/2022] [Indexed: 12/24/2022] Open
Abstract
Abstract
Odorant receptors (ORs) obey mutual exclusivity and monoallelic mode of expression. Efforts are ongoing to decipher the molecular mechanism that drives the ‘one-neuron-one-receptor’ rule of olfaction. Recently, single-cell profiling of olfactory sensory neurons (OSNs) revealed the expression of multiple ORs in the immature neurons, suggesting that the OR gene choice mechanism is much more complex than previously described by the silence-all-and-activate-one model. These results also led to the genesis of two possible mechanistic models i.e. winner-takes-all and stochastic selection. We developed Reverse Cell Tracking (RCT), a novel computational framework that facilitates OR-guided cellular backtracking by leveraging Uniform Manifold Approximation and Projection embeddings from RNA Velocity Workflow. RCT-based trajectory backtracking, coupled with statistical analysis, revealed the OR gene choice bias for the transcriptionally advanced (highest expressed) OR during neuronal differentiation. Interestingly, the observed selection bias was uniform for all ORs across different spatial zones or their relative expression within the olfactory organ. We validated these findings on independent datasets and further confirmed that the OR gene selection may be regulated by Upf3b. Lastly, our RNA dynamics-based tracking of the differentiation cascade revealed a transition cell state that harbors mixed molecular identities of immature and mature OSNs, and their relative abundance is regulated by Upf3b.
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Affiliation(s)
- Sanjay Kumar Mohanty
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Sidrah Maryam
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Vishakha Gautam
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Aayushi Mittal
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Krishan Gupta
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computer Science and Engineering, , Okhla, Phase III, New Delhi 110020, India
| | - Radhika Arora
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Wrik Bhadra
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
| | - Tripti Mishra
- Pathfinder Research and Training Foundation , Uttar Pradesh 201308, India
| | - Debarka Sengupta
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computer Science and Engineering, , Okhla, Phase III, New Delhi 110020, India
| | - Gaurav Ahuja
- Indraprastha Institute of Information Technology-Delhi (IIIT-Delhi) Department of Computational Biology, , Okhla, Phase III, New Delhi 110020, India
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8
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Hussainy M, Korsching SI, Tresch A. Pseudotime analysis reveals novel regulatory factors for multigenic onset and monogenic transition of odorant receptor expression. Sci Rep 2022; 12:16183. [PMID: 36171231 PMCID: PMC9519747 DOI: 10.1038/s41598-022-20106-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 09/08/2022] [Indexed: 12/02/2022] Open
Abstract
During their maturation from horizontal basal stem cells, olfactory sensory neurons (OSNs) are known to select exactly one out of hundreds of olfactory receptors (ORs) and express it on their surface, a process called monogenic selection. Monogenic expression is preceded by a multigenic phase during which several OR genes are expressed in a single OSN. Here, we perform pseudotime analysis of a single cell RNA-Seq dataset of murine olfactory epithelium to precisely align the multigenic and monogenic expression phases with the cell types occurring during OSN differentiation. In combination with motif analysis of OR gene cluster-associated enhancer regions, we identify known and novel transcription (co-)factors (Ebf1, Lhx2, Ldb1, Fos and Ssbp2) and chromatin remodelers (Kdm1a, Eed and Zmynd8) associated with OR expression. The inferred temporal order of their activity suggests novel mechanisms contributing to multigenic OR expression and monogenic selection.
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Affiliation(s)
- Mohammad Hussainy
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany.,Institute of Genetics, Faculty of Mathematics and Natural Sciences, University of Cologne, Cologne, Germany
| | - Sigrun I Korsching
- Institute of Genetics, Faculty of Mathematics and Natural Sciences, University of Cologne, Cologne, Germany
| | - Achim Tresch
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany. .,Cologne Excellence Cluster On Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany. .,Center for Data and Simulation Science, University of Cologne, Cologne, Germany.
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9
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Establishment of H3K9-methylated heterochromatin and its functions in tissue differentiation and maintenance. Nat Rev Mol Cell Biol 2022; 23:623-640. [PMID: 35562425 PMCID: PMC9099300 DOI: 10.1038/s41580-022-00483-w] [Citation(s) in RCA: 115] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2022] [Indexed: 12/14/2022]
Abstract
Heterochromatin is characterized by dimethylated or trimethylated histone H3 Lys9 (H3K9me2 or H3K9me3, respectively) and is found at transposable elements, satellite repeats and genes, where it ensures their transcriptional silencing. The histone methyltransferases (HMTs) that methylate H3K9 — in mammals Suppressor of variegation 3–9 homologue 1 (SUV39H1), SUV39H2, SET domain bifurcated 1 (SETDB1), SETDB2, G9A and G9A-like protein (GLP) — and the ‘readers’ of H3K9me2 or H3K9me3 are highly conserved and show considerable redundancy. Despite their redundancy, genetic ablation or mistargeting of an individual H3K9 methyltransferase can correlate with impaired cell differentiation, loss of tissue identity, premature aging and/or cancer. In this Review, we discuss recent advances in understanding the roles of the known H3K9-specific HMTs in ensuring transcriptional homeostasis during tissue differentiation in mammals. We examine the effects of H3K9-methylation-dependent gene repression in haematopoiesis, muscle differentiation and neurogenesis in mammals, and compare them with mechanistic insights obtained from the study of model organisms, notably Caenorhabditis elegans and Drosophila melanogaster. In all these organisms, H3K9-specific HMTs have both unique and redundant roles that ensure the maintenance of tissue integrity by restricting the binding of transcription factors to lineage-specific promoters and enhancer elements. Histone H3 Lys9 (H3K9)-methylated heterochromatin ensures transcriptional silencing of repetitive elements and genes, and its deregulation leads to impaired cell and tissue identity, premature aging and cancer. Recent studies in mammals clarified the roles H3K9-specific histone methyltransferases in ensuring transcriptional homeostasis during tissue differentiation.
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10
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Williams DL, Sikora VM, Hammer MA, Amin S, Brinjikji T, Brumley EK, Burrows CJ, Carrillo PM, Cromer K, Edwards SJ, Emri O, Fergle D, Jenkins MJ, Kaushik K, Maydan DD, Woodard W, Clowney EJ. May the Odds Be Ever in Your Favor: Non-deterministic Mechanisms Diversifying Cell Surface Molecule Expression. Front Cell Dev Biol 2022; 9:720798. [PMID: 35087825 PMCID: PMC8787164 DOI: 10.3389/fcell.2021.720798] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 11/24/2021] [Indexed: 12/30/2022] Open
Abstract
How does the information in the genome program the functions of the wide variety of cells in the body? While the development of biological organisms appears to follow an explicit set of genomic instructions to generate the same outcome each time, many biological mechanisms harness molecular noise to produce variable outcomes. Non-deterministic variation is frequently observed in the diversification of cell surface molecules that give cells their functional properties, and is observed across eukaryotic clades, from single-celled protozoans to mammals. This is particularly evident in immune systems, where random recombination produces millions of antibodies from only a few genes; in nervous systems, where stochastic mechanisms vary the sensory receptors and synaptic matching molecules produced by different neurons; and in microbial antigenic variation. These systems employ overlapping molecular strategies including allelic exclusion, gene silencing by constitutive heterochromatin, targeted double-strand breaks, and competition for limiting enhancers. Here, we describe and compare five stochastic molecular mechanisms that produce variety in pathogen coat proteins and in the cell surface receptors of animal immune and neuronal cells, with an emphasis on the utility of non-deterministic variation.
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Affiliation(s)
- Donnell L. Williams
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Veronica Maria Sikora
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Max A. Hammer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Sayali Amin
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Taema Brinjikji
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Emily K. Brumley
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Connor J. Burrows
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Paola Michelle Carrillo
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Kirin Cromer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Summer J. Edwards
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Olivia Emri
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniel Fergle
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - M. Jamal Jenkins
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Krishangi Kaushik
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniella D. Maydan
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Wrenn Woodard
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - E. Josephine Clowney
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
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11
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Olfactory receptor choice: a case study for gene regulation in a multi-enhancer system. Curr Opin Genet Dev 2021; 72:101-109. [PMID: 34896807 DOI: 10.1016/j.gde.2021.11.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/25/2021] [Accepted: 11/11/2021] [Indexed: 12/14/2022]
Abstract
The mammalian genome possesses >2000 olfactory receptor (OR) alleles regulated by 63 known OR-Enhancer elements, yet each olfactory sensory neuron (OSN) expresses only a single OR allele. Choreographed changes to OSN nuclear architecture are evidently necessary for OR expression. Additionally, the insulated organization of OR-enhancers around an OR allele is a hallmark of the chosen OR. However, the biology guiding OR choice itself is unclear. Innovations in single-cell and biophysics-based analysis of nuclear architecture are revising previous models of the nucleus to include its dynamic and probabilistic nature. In this review, we ground current knowledge of OR gene regulation in these emerging theories to speculate on mechanisms that may give rise to diverse and singular OR expression.
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12
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Abbas G, Tang S, Noble J, Lane RP. Olfactory receptor coding sequences cause silencing of episomal constructs in multiple cell lines. Mol Cell Neurosci 2021; 117:103681. [PMID: 34742908 PMCID: PMC8669572 DOI: 10.1016/j.mcn.2021.103681] [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: 12/29/2020] [Revised: 10/26/2021] [Accepted: 10/29/2021] [Indexed: 10/19/2022] Open
Abstract
The mammalian olfactory system consists of sensory neurons with specialized odorant-binding capability accomplished by mutually exclusive odorant receptor (OR) expression. Mutually exclusive OR expression is a complex multi-step process regulated by a number of cis and trans factors, including pan-silencing of all OR genes preceding the robust and stable expression of the one OR selected in each sensory neuron. We transfected two olfactory-placode-derived cell lines modeling immature odorant sensory neurons, as well as the GD25 fibroblast cell line, with episomes containing CMV-driven GFP and TK-driven hygromycin reporter genes. We inserted various coding sequences, along with an IRES, immediately upstream of the GFP gene to produce bicistronic mRNAs driven from the local CMV promoter. We found that the presence of several OR coding sequences resulted in significantly diminished episomal expression of GFP in all three cell lines. These findings suggest that OR coding sequences have intrinsic self-silencing capability that might facilitate mutually exclusive OR expression in olfactory sensory neurons by making it less likely that multiple ORs acquire an above-threshold level of expression at once.
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Affiliation(s)
- Ghazia Abbas
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Spencer Tang
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Joyce Noble
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Robert P Lane
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA.
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13
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Ciptasari U, van Bokhoven H. The phenomenal epigenome in neurodevelopmental disorders. Hum Mol Genet 2021; 29:R42-R50. [PMID: 32766754 PMCID: PMC7530535 DOI: 10.1093/hmg/ddaa175] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/16/2020] [Accepted: 07/30/2020] [Indexed: 12/12/2022] Open
Abstract
Disruption of chromatin structure due to epimutations is a leading genetic etiology of neurodevelopmental disorders, collectively known as chromatinopathies. We show that there is an increasing level of convergence from the high diversity of genes that are affected by mutations to the molecular networks and pathways involving the respective proteins, the disrupted cellular and subcellular processes, and their consequence for higher order cellular network function. This convergence is ultimately reflected by specific phenotypic features shared across the various chromatinopathies. Based on these observations, we propose that the commonly disrupted molecular and cellular anomalies might provide a rational target for the development of symptomatic interventions for defined groups of genetically distinct neurodevelopmental disorders.
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Affiliation(s)
- Ummi Ciptasari
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud university medical center, 6500 HB Nijmegen, The Netherlands
| | - Hans van Bokhoven
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.,Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behavior, Radboud university medical center, 6500 HB Nijmegen, The Netherlands
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14
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Billiard S, Castric V, Llaurens V. The integrative biology of genetic dominance. Biol Rev Camb Philos Soc 2021; 96:2925-2942. [PMID: 34382317 PMCID: PMC9292577 DOI: 10.1111/brv.12786] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 07/29/2021] [Accepted: 07/30/2021] [Indexed: 11/29/2022]
Abstract
Dominance is a basic property of inheritance systems describing the link between a diploid genotype at a single locus and the resulting phenotype. Models for the evolution of dominance have long been framed as an opposition between the irreconcilable views of Fisher in 1928 supporting the role of largely elusive dominance modifiers and Wright in 1929, who viewed dominance as an emerging property of the structure of enzymatic pathways. Recent theoretical and empirical advances however suggest that these opposing views can be reconciled, notably using models investigating the regulation of gene expression and developmental processes. In this more comprehensive framework, phenotypic dominance emerges from departures from linearity between any levels of integration in the genotype‐to‐phenotype map. Here, we review how these different models illuminate the emergence and evolution of dominance. We then detail recent empirical studies shedding new light on the diversity of molecular and physiological mechanisms underlying dominance and its evolution. By reconciling population genetics and functional biology, we hope our review will facilitate cross‐talk among research fields in the integrative study of dominance evolution.
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Affiliation(s)
- Sylvain Billiard
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France
| | - Vincent Castric
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France
| | - Violaine Llaurens
- Institut de Systématique, Evolution et Biodiversité, CNRS/MNHN/Sorbonne Université/EPHE, Museum National d'Histoire Naturelle, CP50, 57 rue Cuvier, 75005, Paris, France
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15
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Weirich S, Khella MS, Jeltsch A. Structure, Activity and Function of the Suv39h1 and Suv39h2 Protein Lysine Methyltransferases. Life (Basel) 2021; 11:life11070703. [PMID: 34357075 PMCID: PMC8303541 DOI: 10.3390/life11070703] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/01/2021] [Accepted: 07/13/2021] [Indexed: 12/26/2022] Open
Abstract
SUV39H1 and SUV39H2 were the first protein lysine methyltransferases that were identified more than 20 years ago. Both enzymes introduce di- and trimethylation at histone H3 lysine 9 (H3K9) and have important roles in the maintenance of heterochromatin and gene repression. They consist of a catalytically active SET domain and a chromodomain, which binds H3K9me2/3 and has roles in enzyme targeting and regulation. The heterochromatic targeting of SUV39H enzymes is further enhanced by the interaction with HP1 proteins and repeat-associated RNA. SUV39H1 and SUV39H2 recognize an RKST motif with additional residues on both sides, mainly K4 in the case of SUV39H1 and G12 in the case of SUV39H2. Both SUV39H enzymes methylate different non-histone proteins including RAG2, DOT1L, SET8 and HupB in the case of SUV39H1 and LSD1 in the case of SUV39H2. Both enzymes are expressed in embryonic cells and have broad expression profiles in the adult body. SUV39H1 shows little tissue preference except thymus, while SUV39H2 is more highly expressed in the brain, testis and thymus. Both enzymes are connected to cancer, having oncogenic or tumor-suppressive roles depending on the tumor type. In addition, SUV39H2 has roles in the brain during early neurodevelopment.
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Affiliation(s)
- Sara Weirich
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany; (S.W.); (M.S.K.)
| | - Mina S. Khella
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany; (S.W.); (M.S.K.)
- Biochemistry Department, Faculty of Pharmacy, Ain Shams University, African Union Organization Street, Abbassia, Cairo 11566, Egypt
| | - Albert Jeltsch
- Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany; (S.W.); (M.S.K.)
- Correspondence:
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16
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Shah A, Ratkowski M, Rosa A, Feinstein P, Bozza T. Olfactory expression of trace amine-associated receptors requires cooperative cis-acting enhancers. Nat Commun 2021; 12:3797. [PMID: 34145232 PMCID: PMC8213819 DOI: 10.1038/s41467-021-23824-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 05/18/2021] [Indexed: 11/28/2022] Open
Abstract
Olfactory sensory neurons express a large family of odorant receptors (ORs) and a small family of trace amine-associated receptors (TAARs). While both families are subject to so-called singular expression (expression of one allele of one gene), the mechanisms underlying TAAR gene choice remain obscure. Here, we report the identification of two conserved sequence elements in the mouse TAAR cluster (T-elements) that are required for TAAR gene expression. We observed that cell-type-specific expression of a TAAR-derived transgene required either T-element. Moreover, deleting either element reduced or abolished expression of a subset of TAAR genes, while deleting both elements abolished olfactory expression of all TAARs in cis with the mutation. The T-elements exhibit several features of known OR enhancers but also contain highly conserved, unique sequence motifs. Our data demonstrate that TAAR gene expression requires two cooperative cis-acting enhancers and suggest that ORs and TAARs share similar mechanisms of singular expression.
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Affiliation(s)
- Ami Shah
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
| | - Madison Ratkowski
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
| | - Alessandro Rosa
- The Graduate Center Programs in Biochemistry, Biology and CUNY Neuroscience Collaborative, New York, NY, USA
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Paul Feinstein
- The Graduate Center Programs in Biochemistry, Biology and CUNY Neuroscience Collaborative, New York, NY, USA
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Thomas Bozza
- Department of Neurobiology, Northwestern University, Evanston, IL, USA.
- Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA.
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17
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Mutzel V, Schulz EG. Dosage Sensing, Threshold Responses, and Epigenetic Memory: A Systems Biology Perspective on Random X-Chromosome Inactivation. Bioessays 2021; 42:e1900163. [PMID: 32189388 DOI: 10.1002/bies.201900163] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/27/2020] [Indexed: 02/06/2023]
Abstract
X-chromosome inactivation ensures dosage compensation between the sexes in mammals by randomly choosing one out of the two X chromosomes in females for inactivation. This process imposes a plethora of questions: How do cells count their X chromosome number and ensure that exactly one stays active? How do they randomly choose one of two identical X chromosomes for inactivation? And how do they stably maintain this state of monoallelic expression? Here, different regulatory concepts and their plausibility are evaluated in the context of theoretical studies that have investigated threshold behavior, ultrasensitivity, and bistability through mathematical modeling. It is discussed how a twofold difference between a single and a double dose of X-linked genes might be converted to an all-or-nothing response and how mutually exclusive expression can be initiated and maintained. Finally, candidate factors that might mediate the proposed regulatory principles are reviewed.
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Affiliation(s)
- Verena Mutzel
- Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, Berlin, 14195, Germany
| | - Edda G Schulz
- Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, Berlin, 14195, Germany
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18
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Jafari S, Henriksson J, Yan H, Alenius M. Stress and odorant receptor feedback during a critical period after hatching regulates olfactory sensory neuron differentiation in Drosophila. PLoS Biol 2021; 19:e3001101. [PMID: 33793547 PMCID: PMC8043390 DOI: 10.1371/journal.pbio.3001101] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 04/13/2021] [Accepted: 03/02/2021] [Indexed: 11/19/2022] Open
Abstract
Here, we reveal that the regulation of Drosophila odorant receptor (OR) expression during the pupal stage is permissive and imprecise. We found that directly after hatching an OR feedback mechanism both directs and refines OR expression. We demonstrate that, as in mice, dLsd1 and Su(var)3-9 balance heterochromatin formation to direct OR expression. We show that the expressed OR induces dLsd1 and Su(var)3-9 expression, linking OR level and possibly function to OR expression. OR expression refinement shows a restricted duration, suggesting that a gene regulatory critical period brings olfactory sensory neuron differentiation to an end. Consistent with a change in differentiation, stress during the critical period represses dLsd1 and Su(var)3-9 expression and makes the early permissive OR expression permanent. This induced permissive gene regulatory state makes OR expression resilient to stress later in life. Hence, during a critical period OR feedback, similar to in mouse OR selection, defines adult OR expression in Drosophila.
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Affiliation(s)
- Shadi Jafari
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Johan Henriksson
- Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Hua Yan
- Department of Biology, University of Florida, Gainesville, Florida, United States of America
| | - Mattias Alenius
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Molecular Biology, Umeå University, Umeå, Sweden
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Genetic and Non-Genetic Mechanisms Underlying Cancer Evolution. Cancers (Basel) 2021; 13:cancers13061380. [PMID: 33803675 PMCID: PMC8002988 DOI: 10.3390/cancers13061380] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 03/10/2021] [Indexed: 12/14/2022] Open
Abstract
Simple Summary Our manuscript summarizes the up-to-date data on the complex and dynamic nature of adaptation mechanisms and evolutionary processes taking place during cancer initiation, development and progression. Although for decades cancer has been viewed as a process governed by genetic mechanisms, it is becoming more and more clear that non-genetic mechanisms may play an equally important role in cancer evolution. In this review, we bring together these fundamental concepts and discuss how those tightly interconnected mechanisms lead to the establishment of highly adaptive quickly evolving cancers. Furthermore, we argue that in depth understanding of cancer progression from the evolutionary perspective may allow the prediction and direction of the evolutionary path of cancer populations towards drug sensitive phenotypes and thus facilitate the development of more effective anti-cancer approaches. Abstract Cancer development can be defined as a process of cellular and tissular microevolution ultimately leading to malignancy. Strikingly, though this concept has prevailed in the field for more than a century, the precise mechanisms underlying evolutionary processes occurring within tumours remain largely uncharacterized and rather cryptic. Nevertheless, although our current knowledge is fragmentary, data collected to date suggest that most tumours display features compatible with a diverse array of evolutionary paths, suggesting that most of the existing macro-evolutionary models find their avatar in cancer biology. Herein, we discuss an up-to-date view of the fundamental genetic and non-genetic mechanisms underlying tumour evolution with the aim of concurring into an integrated view of the evolutionary forces at play throughout the emergence and progression of the disease and into the acquisition of resistance to diverse therapeutic paradigms. Our ultimate goal is to delve into the intricacies of genetic and non-genetic networks underlying tumour evolution to build a framework where both core concepts are considered non-negligible and equally fundamental.
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20
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LINE-1 specific nuclear organization in mice olfactory sensory neurons. Mol Cell Neurosci 2020; 105:103494. [PMID: 32387751 DOI: 10.1016/j.mcn.2020.103494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 03/31/2020] [Accepted: 04/05/2020] [Indexed: 12/21/2022] Open
Abstract
Long interspersed nuclear elements-1 (LINE-1) are mobile DNA elements that comprise the majority of interspersed repeats in the mammalian genome. During the last decade, these transposable sequences have been described as controlling elements involved in transcriptional regulation and genome plasticity. Recently, LINE-1 have been implicated in neurogenesis, but to date little is known about their nuclear organization in neurons. The olfactory epithelium is a site of continuous neurogenesis, and loci of olfactory receptor genes are enriched in LINE-1 copies. Olfactory neurons have a unique inverted nuclear architecture and constitutive heterochromatin forms a block in the center of the nuclei. Our DNA FISH images show that, even though LINE-1 copies are dispersed throughout the mice genome, they are clustered forming a cap around the central heterochromatin block and frequently occupy the same position as facultative heterochromatin in olfactory neurons nuclei. This specific LINE-1 organization could not be observed in other olfactory epithelium cell types. Analyses of H3K27me3 and H3K9me3 ChIP-seq data from olfactory epithelium revealed that LINE-1 copies located at OR gene loci show different enrichment for these heterochromatin marks. We also found that LINE-1 are transcribed in mouse olfactory epithelium. These results suggest that LINE-1 play a role in the olfactory neurons' nuclear architecture. SIGNIFICANCE STATEMENT: LINE-1 are mobile DNA elements and comprise almost 20% of mice and human genomes. These retrotransposons have been implicated in neurogenesis. We show for the first time that LINE-1 retrotransposons have a specific nuclear organization in olfactory neurons, forming aggregates concentric to the heterochromatin block and frequently occupying the same region as facultative heterochromatin. We found that LINE-1 at olfactory receptor gene loci are differently enriched for H3K9me3 and H3K27me3, but LINE-1 transcripts could be detected in the olfactory epithelium. We speculate that these retrotransposons play an active role in olfactory neurons' nuclear architecture.
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21
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Singh PB, Newman AG. On the relations of phase separation and Hi-C maps to epigenetics. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191976. [PMID: 32257349 PMCID: PMC7062049 DOI: 10.1098/rsos.191976] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 02/03/2020] [Indexed: 05/10/2023]
Abstract
The relationship between compartmentalization of the genome and epigenetics is long and hoary. In 1928, Heitz defined heterochromatin as the largest differentiated chromatin compartment in eukaryotic nuclei. Müller's discovery of position-effect variegation in 1930 went on to show that heterochromatin is a cytologically visible state of heritable (epigenetic) gene repression. Current insights into compartmentalization have come from a high-throughput top-down approach where contact frequency (Hi-C) maps revealed the presence of compartmental domains that segregate the genome into heterochromatin and euchromatin. It has been argued that the compartmentalization seen in Hi-C maps is owing to the physiochemical process of phase separation. Oddly, the insights provided by these experimental and conceptual advances have remained largely silent on how Hi-C maps and phase separation relate to epigenetics. Addressing this issue directly in mammals, we have made use of a bottom-up approach starting with the hallmarks of constitutive heterochromatin, heterochromatin protein 1 (HP1) and its binding partner the H3K9me2/3 determinant of the histone code. They are key epigenetic regulators in eukaryotes. Both hallmarks are also found outside mammalian constitutive heterochromatin as constituents of larger (0.1-5 Mb) heterochromatin-like domains and smaller (less than 100 kb) complexes. The well-documented ability of HP1 proteins to function as bridges between H3K9me2/3-marked nucleosomes contributes to polymer-polymer phase separation that packages epigenetically heritable chromatin states during interphase. Contacts mediated by HP1 'bridging' are likely to have been detected in Hi-C maps, as evidenced by the B4 heterochromatic subcompartment that emerges from contacts between large KRAB-ZNF heterochromatin-like domains. Further, mutational analyses have revealed a finer, innate, compartmentalization in Hi-C experiments that probably reflect contacts involving smaller domains/complexes. Proteins that bridge (modified) DNA and histones in nucleosomal fibres-where the HP1-H3K9me2/3 interaction represents the most evolutionarily conserved paradigm-could drive and generate the fundamental compartmentalization of the interphase nucleus. This has implications for the mechanism(s) that maintains cellular identity, be it a terminally differentiated fibroblast or a pluripotent embryonic stem cell.
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Affiliation(s)
- Prim B. Singh
- Nazarbayev University School of Medicine, 5/1 Kerei, Zhanibek Khandar Street, Nur-Sultan Z05K4F4, Kazakhstan
- Epigenetics Laboratory, Department of Natural Sciences, Novosibirsk State University, Pirogov Street 2, Novosibirsk 630090, Russian Federation
| | - Andrew G. Newman
- Institute of Cell and Neurobiology, Charité—Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, Berlin, Germany
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22
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Finn EH, Misteli T. Molecular basis and biological function of variability in spatial genome organization. Science 2019; 365:365/6457/eaaw9498. [PMID: 31488662 DOI: 10.1126/science.aaw9498] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 07/22/2019] [Indexed: 12/14/2022]
Abstract
The complex three-dimensional organization of genomes in the cell nucleus arises from a wide range of architectural features including DNA loops, chromatin domains, and higher-order compartments. Although these features are universally present in most cell types and tissues, recent single-cell biochemistry and imaging approaches have demonstrated stochasticity in transcription and high variability of chromatin architecture in individual cells. We review the occurrence, mechanistic basis, and functional implications of stochasticity in genome organization. We summarize recent observations on cell- and allele-specific variability of genome architecture, discuss the nature of extrinsic and intrinsic sources of variability in genome organization, and highlight potential implications of structural heterogeneity for genome function.
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Affiliation(s)
| | - Tom Misteli
- National Cancer Institute, Bethesda, MD 20892, USA.
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23
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Bashkirova E, Lomvardas S. Olfactory receptor genes make the case for inter-chromosomal interactions. Curr Opin Genet Dev 2019; 55:106-113. [PMID: 31491591 DOI: 10.1016/j.gde.2019.07.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 07/04/2019] [Accepted: 07/07/2019] [Indexed: 12/11/2022]
Abstract
The partitioning of the interphase nucleus into chromosome territories generally precludes DNA from making specific and reproducible inter-chromosomal contacts. However, with the development of powerful genomic and imaging tools for the analysis of the 3D genome, and with their application on an increasing number of cell types, it becomes apparent that regulated, specific, and functionally important inter-chromosomal contacts exist. Widespread and stereotypic inter-chromosomal interactions are at the center of chemosensation, where they regulate the singular and stochastic expression of olfactory receptor genes. In olfactory sensory neurons (OSNs) coalescence of multiple intergenic enhancers to a multi-chromosomal hub orchestrates the expression of a single OR allele, whereas convergence of the remaining OR genes from 18 chromosomes into a few heterochromatic compartments mediates their effective transcriptional silencing. In this review we describe the role of interchromosomal interactions in OR gene choice, and we describe other biological systems where such genomic interactions may contribute to regulatory robustness and transcriptional diversification.
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Affiliation(s)
- Elizaveta Bashkirova
- Department of Biochemistry and Molecular Biophysics, Roy Vangelos Columbia University Medical Center, New York, NY 10032, United States
| | - Stavros Lomvardas
- Department of Biochemistry and Molecular Biophysics, Roy Vangelos Columbia University Medical Center, New York, NY 10032, United States; Department of Neuroscience, Roy Vangelos Columbia University Medical Center, Columbia University, New York, NY 10032, United States; Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY 10027, United States; Kavli Institute for Neurosciences at Columbia University, New York, NY 10027, United States.
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24
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Iacono G, Dubos A, Méziane H, Benevento M, Habibi E, Mandoli A, Riet F, Selloum M, Feil R, Zhou H, Kleefstra T, Kasri NN, van Bokhoven H, Herault Y, Stunnenberg HG. Increased H3K9 methylation and impaired expression of Protocadherins are associated with the cognitive dysfunctions of the Kleefstra syndrome. Nucleic Acids Res 2019; 46:4950-4965. [PMID: 29554304 PMCID: PMC6007260 DOI: 10.1093/nar/gky196] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 03/09/2018] [Indexed: 12/13/2022] Open
Abstract
Kleefstra syndrome, a disease with intellectual disability, autism spectrum disorders and other developmental defects is caused in humans by haploinsufficiency of EHMT1. Although EHMT1 and its paralog EHMT2 were shown to be histone methyltransferases responsible for deposition of the di-methylated H3K9 (H3K9me2), the exact nature of epigenetic dysfunctions in Kleefstra syndrome remains unknown. Here, we found that the epigenome of Ehmt1+/- adult mouse brain displays a marked increase of H3K9me2/3 which correlates with impaired expression of protocadherins, master regulators of neuronal diversity. Increased H3K9me3 was present already at birth, indicating that aberrant methylation patterns are established during embryogenesis. Interestingly, we found that Ehmt2+/- mice do not present neither the marked increase of H3K9me2/3 nor the cognitive deficits found in Ehmt1+/- mice, indicating an evolutionary diversification of functions. Our finding of increased H3K9me3 in Ehmt1+/- mice is the first one supporting the notion that EHMT1 can quench the deposition of tri-methylation by other Histone methyltransferases, ultimately leading to impaired neurocognitive functioning. Our insights into the epigenetic pathophysiology of Kleefstra syndrome may offer guidance for future developments of therapeutic strategies for this disease.
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Affiliation(s)
- Giovanni Iacono
- Radboud University, Department of Molecular Biology, Faculty of Science, 6500 HB Nijmegen, the Netherlands
- To whom correspondence should be addressed. Tel: +31 24 3610524; . Correspondence may also be addressed to Giovanni Iacono.
| | - Aline Dubos
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris, 1 rue Laurent Fries, 67404 Illkirch, France
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Illkirch, France
- Centre National de la Recherche Scientifique, UMR7104, Illkirch, France
- Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Hamid Méziane
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Marco Benevento
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, the Netherlands
| | - Ehsan Habibi
- Radboud University, Department of Molecular Biology, Faculty of Science, 6500 HB Nijmegen, the Netherlands
| | - Amit Mandoli
- Radboud University, Department of Molecular Biology, Faculty of Science, 6500 HB Nijmegen, the Netherlands
| | - Fabrice Riet
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Mohammed Selloum
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Robert Feil
- Institute of Molecular Genetics (IGMM), UMR5535, Centre National de Recherche Scientifique (CNRS), 1919 Route de Mende, 34293 Montpellier, France
- The University of Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
| | - Huiqing Zhou
- Radboud University, Department of Molecular Biology, Faculty of Science, 6500 HB Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
| | - Tjitske Kleefstra
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, the Netherlands
| | - Nael Nadif Kasri
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, the Netherlands
| | - Hans van Bokhoven
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, 6525 AJ Nijmegen, the Netherlands
| | - Yann Herault
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris, 1 rue Laurent Fries, 67404 Illkirch, France
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Illkirch, France
- Centre National de la Recherche Scientifique, UMR7104, Illkirch, France
- Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Hendrik G Stunnenberg
- Radboud University, Department of Molecular Biology, Faculty of Science, 6500 HB Nijmegen, the Netherlands
- To whom correspondence should be addressed. Tel: +31 24 3610524; . Correspondence may also be addressed to Giovanni Iacono.
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Abstract
The epigenetic control of gene expression could be affected by addition and/or removal of post-translational modifications such as phosphorylation, acetylation and methylation of histone proteins, as well as methylation of DNA (5-methylation on cytosines). Misregulation of these modifications is associated with altered gene expression, resulting in various disease conditions. G9a belongs to the protein lysine methyltransferases that specifically methylates the K9 residue of histone H3, leading to suppression of several tumor suppressor genes. In this review, G9a functions, role in various diseases, structural biology aspects for inhibitor design, structure-activity relationship among the reported inhibitors are discussed which could aid in the design and development of potent G9a inhibitors for cancer treatment in the future.
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26
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Scandaglia M, Barco A. Contribution of spurious transcription to intellectual disability disorders. J Med Genet 2019; 56:491-498. [PMID: 30745423 DOI: 10.1136/jmedgenet-2018-105668] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 12/17/2018] [Accepted: 01/18/2019] [Indexed: 12/31/2022]
Abstract
During the development of multicellular organisms, chromatin-modifying enzymes orchestrate the establishment of gene expression programmes that characterise each differentiated cell type. These enzymes also contribute to the maintenance of cell type-specific transcription profiles throughout life. But what happens when epigenomic regulation goes awry? Genomic screens in experimental models of intellectual disability disorders (IDDs) caused by mutations in epigenetic machinery-encoding genes have shown that transcriptional dysregulation constitutes a hallmark of these conditions. Here, we underscore the connections between a subset of chromatin-linked IDDs and spurious transcription in brain cells. We also propose that aberrant gene expression in neurons, including both the ectopic transcription of non-neuronal genes and the activation of cryptic promoters, may importantly contribute to the pathoaetiology of these disorders.
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Affiliation(s)
- Marilyn Scandaglia
- Molecular Neurobiology and Neuropathology Unit, Instituto de Neurociencias (UMH-CSIC), San Juan de Alicante, Alicante, Spain
| | - Angel Barco
- Molecular Neurobiology and Neuropathology Unit, Instituto de Neurociencias (UMH-CSIC), San Juan de Alicante, Alicante, Spain
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27
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Maßberg D, Hatt H. Human Olfactory Receptors: Novel Cellular Functions Outside of the Nose. Physiol Rev 2018; 98:1739-1763. [PMID: 29897292 DOI: 10.1152/physrev.00013.2017] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Olfactory receptors (ORs) are not exclusively expressed in the olfactory sensory neurons; they are also observed outside of the olfactory system in all other human tissues tested to date, including the testis, lung, intestine, skin, heart, and blood. Within these tissues, certain ORs have been determined to be exclusively expressed in only one tissue, whereas other ORs are more widely distributed in many different tissues throughout the human body. For most of the ectopically expressed ORs, limited data are available for their functional roles. They have been shown to be involved in the modulation of cell-cell recognition, migration, proliferation, the apoptotic cycle, exocytosis, and pathfinding processes. Additionally, there is a growing body of evidence that they have the potential to serve as diagnostic and therapeutic tools, as ORs are highly expressed in different cancer tissues. Interestingly, in addition to the canonical signaling pathways activated by ORs in olfactory sensory neurons, alternative pathways have been demonstrated in nonolfactory tissues. In this review, the existing data concerning the expression, as well as the physiological and pathophysiological functions, of ORs outside of the nose are highlighted to provide insights into future lines of research.
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Affiliation(s)
- Désirée Maßberg
- Ruhr-University Bochum, Department of Cell Physiology , Bochum , Germany
| | - Hanns Hatt
- Ruhr-University Bochum, Department of Cell Physiology , Bochum , Germany
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28
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Spatial Determination of Neuronal Diversification in the Olfactory Epithelium. J Neurosci 2018; 39:814-832. [PMID: 30530861 DOI: 10.1523/jneurosci.3594-17.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 11/21/2018] [Accepted: 11/23/2018] [Indexed: 01/31/2023] Open
Abstract
Neurons in the murine olfactory epithelium (OE) differ by the olfactory receptor they express as well as other molecular phenotypes that are regionally restricted. These patterns can be precisely regenerated following epithelial injury, suggesting that spatial cues within the tissue can direct neuronal diversification. Nonetheless, the permanency and mechanism of this spatial patterning remain subject to debate. Via transplantation of stem and progenitor cells from dorsal OE into ventral OE, we demonstrate that, in mice of both sexes, nonautonomous spatial cues can direct the spatially circumscribed differentiation of olfactory sensory neurons. The vast majority of dorsal transplant-derived neurons express the ventral marker OCAM (NCAM2) and lose expression of NQO1 to match their new location. Single-cell analysis also demonstrates that OSNs adopt a fate defined by their new position following progenitor cell transplant, such that a ventral olfactory receptor is expressed after stem and progenitor cell engraftment. Thus, spatially constrained differentiation of olfactory sensory neurons is plastic, and any bias toward an epigenetic memory of place can be overcome.SIGNIFICANCE STATEMENT Spatially restricted differentiation of olfactory sensory neurons is both key to normal olfactory function and a challenging example of biological specificity. That the stem cells of the olfactory epithelium reproduce the organization of the olfactory periphery to a very close approximation during lesion-induced regeneration begs the question of whether stem cell-autonomous genomic architecture or environmental cues are responsible. The plasticity demonstrated after transfer to a novel location suggests that cues external to the transplanted stem and progenitor cells confer neuronal identity. Thus, a necessary prerequisite is satisfied for using engraftment of olfactory stem and progenitor cells as a cellular therapeutic intervention to reinvigorate neurogenesis whose exhaustion contributes to the waning of olfaction with age.
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29
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Noble JC, Meredith D, Lane RP. Frequent and biased odorant receptor (OR) re-selection in an olfactory placode-derived cell line. PLoS One 2018; 13:e0204604. [PMID: 30256852 PMCID: PMC6157871 DOI: 10.1371/journal.pone.0204604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/11/2018] [Indexed: 11/18/2022] Open
Abstract
We previously characterized a clonal olfactory placode-derived cell line (OP6) as a model system for studying odorant receptor (OR) choice, where individual OP6 cells, similar to olfactory sensory neurons in vivo, transcribe one allele ("monoallelic") of one OR gene ("monogenic"). The OP6 cell line provides a unique opportunity to investigate intrinsic properties of OR regulation that cannot easily be investigated in vivo. First, whereas OR-expressing cells in vivo are post-mitotic, OP6 cells are immortalized, raising interesting questions about the stability of epigenetic states associated with OR selection/silencing as OP6 cells progress through the cell cycle. Second, OP6 cells have been isolated away from extrinsic developmental cues, and therefore, any long-term OR selection biases are likely to arise from intrinsic epigenetic states that persist in the absence of developmental context. In this study, we investigated OR re-selection frequency and selection biases within clonal OP6 cell populations. We found no evidence of OR stability through the cell cycle: our results were most consistent with OR re-selection events transpiring at least once per cell division, suggesting that chromatin states associated with OR selection in this system might not be maintained in the subsequent generation. In contrast, we found strong evidence for OR selection biases maintained over prolonged culturing across a diverse set of OP6 cell lineages, suggesting the persistence of intrinsic epigenetic states that advantage some OR loci over others. Together, our data suggest that in the absence of instructive cues, intrinsic epigenetic states influencing OR eligibility, but not those determining OR choice, might persist through the cell cycle.
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Affiliation(s)
- J. C. Noble
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
| | - Diane Meredith
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
| | - Robert P. Lane
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
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30
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Tan L, Xie XS. A Near-Complete Spatial Map of Olfactory Receptors in the Mouse Main Olfactory Epithelium. Chem Senses 2018; 43:427-432. [PMID: 29796642 PMCID: PMC6454507 DOI: 10.1093/chemse/bjy030] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Different regions of the mammalian nose smell different odors. In the mouse olfactory system, spatially regulated expression of >1000 olfactory receptors (ORs) along the dorsomedial-ventrolateral (DV) axis forms a topological map in the main olfactory epithelium (MOE). However, the locations of most ORs along the DV axis are currently unknown. By sequencing mRNA of 12 isolated MOE pieces, we mapped out the DV locations-as quantified by "zone indices" on a scale of 1-5-of 1033 OR genes with an estimated error of 0.3 zone indices. Our map covered 81% of all intact OR genes and 99.4% of the total OR mRNA abundance. Spatial regulation tended to vary gradually along chromosomes. We further identified putative non-OR genes that may exhibit spatial expression along the DV axis.
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Affiliation(s)
- Longzhi Tan
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Systems Biology PhD Program, Harvard Medical School, Boston, MA, USA
| | - Xiaoliang Sunney Xie
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
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31
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Sokpor G, Abbas E, Rosenbusch J, Staiger JF, Tuoc T. Transcriptional and Epigenetic Control of Mammalian Olfactory Epithelium Development. Mol Neurobiol 2018. [PMID: 29532253 DOI: 10.1007/s12035-018-0987-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The postnatal mammalian olfactory epithelium (OE) represents a major aspect of the peripheral olfactory system. It is a pseudostratified tissue that originates from the olfactory placode and is composed of diverse cells, some of which are specialized receptor neurons capable of transducing odorant stimuli to afford the perception of smell (olfaction). The OE is known to offer a tractable miniature model for studying the systematic generation of neurons and glia that typify neural tissue development. During OE development, stem/progenitor cells that will become olfactory sensory neurons and/or non-neuronal cell types display fine spatiotemporal expression of neuronal and non-neuronal genes that ensures their proper proliferation, differentiation, survival, and regeneration. Many factors, including transcription and epigenetic factors, have been identified as key regulators of the expression of such requisite genes to permit normal OE morphogenesis. Typically, specific interactive regulatory networks established between transcription and epigenetic factors/cofactors orchestrate histogenesis in the embryonic and adult OE. Hence, investigation of these regulatory networks critical for OE development promises to disclose strategies that may be employed in manipulating the stepwise transition of olfactory precursor cells to become fully differentiated and functional neuronal and non-neuronal cell types. Such strategies potentially offer formidable means of replacing injured or degenerated neural cells as therapeutics for nervous system perturbations. This review recapitulates the developmental cellular diversity of the olfactory neuroepithelium and discusses findings on how the precise and cooperative molecular control by transcriptional and epigenetic machinery is indispensable for OE ontogeny.
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Affiliation(s)
- Godwin Sokpor
- Institute of Neuroanatomy, University Medical Center, Georg-August-University Goettingen, 37075, Goettingen, Germany
| | - Eman Abbas
- Institute of Neuroanatomy, University Medical Center, Georg-August-University Goettingen, 37075, Goettingen, Germany.,Zoology Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Joachim Rosenbusch
- Institute of Neuroanatomy, University Medical Center, Georg-August-University Goettingen, 37075, Goettingen, Germany
| | - Jochen F Staiger
- Institute of Neuroanatomy, University Medical Center, Georg-August-University Goettingen, 37075, Goettingen, Germany.,DFG Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37075, Goettingen, Germany
| | - Tran Tuoc
- Institute of Neuroanatomy, University Medical Center, Georg-August-University Goettingen, 37075, Goettingen, Germany. .,DFG Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37075, Goettingen, Germany.
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Monahan K, Schieren I, Cheung J, Mumbey-Wafula A, Monuki ES, Lomvardas S. Cooperative interactions enable singular olfactory receptor expression in mouse olfactory neurons. eLife 2017; 6. [PMID: 28933695 PMCID: PMC5608512 DOI: 10.7554/elife.28620] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 08/28/2017] [Indexed: 12/16/2022] Open
Abstract
The monogenic and monoallelic expression of only one out of >1000 mouse olfactory receptor (ORs) genes requires the formation of large heterochromatic chromatin domains that sequester the OR gene clusters. Within these domains, intergenic transcriptional enhancers evade heterochromatic silencing and converge into interchromosomal hubs that assemble over the transcriptionally active OR. The significance of this nuclear organization in OR choice remains elusive. Here, we show that transcription factors Lhx2 and Ebf specify OR enhancers by binding in a functionally cooperative fashion to stereotypically spaced motifs that defy heterochromatin. Specific displacement of Lhx2 and Ebf from OR enhancers resulted in pervasive, long-range, and trans downregulation of OR transcription, whereas pre-assembly of a multi-enhancer hub increased the frequency of OR choice in cis. Our data provide genetic support for the requirement and sufficiency of interchromosomal interactions in singular OR choice and generate general regulatory principles for stochastic, mutually exclusive gene expression programs.
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Affiliation(s)
- Kevin Monahan
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Ira Schieren
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Jonah Cheung
- New York Structural Biology Center, New York, United States
| | - Alice Mumbey-Wafula
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Edwin S Monuki
- Department of Pathology and Laboratory Medicine, School of Medicine, University of California Irvine, Irvine, United States
| | - Stavros Lomvardas
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States.,Department of Neuroscience, Columbia University, New York, United States.,Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, United States
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33
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Papait R, Serio S, Pagiatakis C, Rusconi F, Carullo P, Mazzola M, Salvarani N, Miragoli M, Condorelli G. Histone Methyltransferase G9a Is Required for Cardiomyocyte Homeostasis and Hypertrophy. Circulation 2017; 136:1233-1246. [PMID: 28778944 DOI: 10.1161/circulationaha.117.028561] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 07/21/2017] [Indexed: 02/01/2023]
Abstract
BACKGROUND Correct gene expression programming of the cardiomyocyte underlies the normal functioning of the heart. Alterations to this can lead to the loss of cardiac homeostasis, triggering heart dysfunction. Although the role of some histone methyltransferases in establishing the transcriptional program of postnatal cardiomyocytes during heart development has been shown, the function of this class of epigenetic enzymes is largely unexplored in the adult heart. In this study, we investigated the role of G9a/Ehmt2, a histone methyltransferase that defines a repressive epigenetic signature, in defining the transcriptional program for cardiomyocyte homeostasis and cardiac hypertrophy. METHODS We investigated the function of G9a in normal and stressed cardiomyocytes with the use of a conditional, cardiac-specific G9a knockout mouse, a specific G9a inhibitor, and high-throughput approaches for the study of the epigenome (chromatin immunoprecipitation sequencing) and transcriptome (RNA sequencing); traditional methods were used to assess cardiac function and cardiovascular disease. RESULTS We found that G9a is required for cardiomyocyte homeostasis in the adult heart by mediating the repression of key genes regulating cardiomyocyte function via dimethylation of H3 lysine 9 and interaction with enhancer of zeste homolog 2, the catalytic subunit of polycomb repressive complex 2, and MEF2C-dependent gene expression by forming a complex with this transcription factor. The G9a-MEF2C complex was found to be required also for the maintenance of heterochromatin needed for the silencing of developmental genes in the adult heart. Moreover, G9a promoted cardiac hypertrophy by repressing antihypertrophic genes. CONCLUSIONS Taken together, our findings demonstrate that G9a orchestrates critical epigenetic changes in cardiomyocytes in physiological and pathological conditions, thereby providing novel therapeutic avenues for cardiac pathologies associated with dysregulation of these mechanisms.
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Affiliation(s)
- Roberto Papait
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli).
| | - Simone Serio
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Christina Pagiatakis
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Francesca Rusconi
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Pierluigi Carullo
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Marta Mazzola
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Nicolò Salvarani
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Michele Miragoli
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli)
| | - Gianluigi Condorelli
- From Department of Cardiovascular Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy (R.P., S.S., C.P., F.R., P.C., N.S., M. Miragoli, G.C.); Genetic and Biomedical Research Institute, National Research Council of Italy, Rozzano, Milan, Italy (R.P., F.R., P.C., N.S., G.C.); Humanitas University, Rozzano, Milan, Italy (M. Mazzola, G.C.); School of Medicine, University of Verona, Italy (M. Mazzola); and Department of Medicine and Surgery, University of Parma, Italy (M. Miragoli).
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Gigante CM, Dibattista M, Dong FN, Zheng X, Yue S, Young SG, Reisert J, Zheng Y, Zhao H. Lamin B1 is required for mature neuron-specific gene expression during olfactory sensory neuron differentiation. Nat Commun 2017; 8:15098. [PMID: 28425486 PMCID: PMC5411488 DOI: 10.1038/ncomms15098] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 02/28/2017] [Indexed: 01/29/2023] Open
Abstract
B-type lamins are major constituents of the nuclear lamina in all metazoan cells, yet have specific roles in the development of certain cell types. Although they are speculated to regulate gene expression in developmental contexts, a direct link between B-type lamins and developmental gene expression in an in vivo system is currently lacking. Here, we identify lamin B1 as a key regulator of gene expression required for the formation of functional olfactory sensory neurons. By using targeted knockout in olfactory epithelial stem cells in adult mice, we show that lamin B1 deficient neurons exhibit attenuated response to odour stimulation. This deficit can be explained by decreased expression of genes involved in mature neuron function, along with increased expression of genes atypical of the olfactory lineage. These results support that the broadly expressed lamin B1 regulates expression of a subset of genes involved in the differentiation of a specific cell type.
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Affiliation(s)
- Crystal M. Gigante
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Michele Dibattista
- Monell Chemical Senses Center, Philadelphia, Pennsylvania 19104, USA
- Department of Basic Medical Sciences, Neuroscience and Sensory Organs, University of Bari ‘A. Moro', Bari 70121, Italy
| | - Frederick N. Dong
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Xiaobin Zheng
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Sibiao Yue
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Stephen G. Young
- Department of Medicine, Molecular Biology Institute and Department of Human Genetics, University of California, Los Angeles, California 90095, USA
| | - Johannes Reisert
- Monell Chemical Senses Center, Philadelphia, Pennsylvania 19104, USA
| | - Yixian Zheng
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Haiqing Zhao
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Lysine-specific demethylase-1 (LSD1) depletion disrupts monogenic and monoallelic odorant receptor (OR) expression in an olfactory neuronal cell line. Mol Cell Neurosci 2017; 82:1-11. [PMID: 28414096 DOI: 10.1016/j.mcn.2017.04.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 04/05/2017] [Accepted: 04/13/2017] [Indexed: 11/22/2022] Open
Abstract
Function of the mammalian olfactory system depends on specialized olfactory sensory neurons (OSNs) that each express only one allele ("monoallelic") of one odorant receptor (OR) gene ("monogenic"). The lysine-specific demethylase-1 (LSD1) protein removes activating H3K4 or silencing H3K9 methylation marks in a variety of developmental contexts, and is thought to be important for proper OR regulation. Most of the focus in the field has been on a potential "activating" function for LSD1; e.g., in the demethylation of H3K9 associated with the expressed OR allele. Here we show that depletion of LSD1 in an immortalized olfactory-placode-derived cell line (OP6) results in multigenic and multiallelic OR transcription per cell, while not seemingly disrupting the ability of these cells to activate new OR genes during clonal expansion. These results are consistent with LSD1 having a role in silencing additional OR alleles, as opposed to being required for the activation of OR alleles, within the OP6 cellular context.
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36
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Jung H, Chae YC, Kim JY, Jeong OS, Kook H, Seo SB. Regulatory role of G9a and LSD1 in the Transcription of Olfactory Receptors during Leukaemia Cell Differentiation. Sci Rep 2017; 7:46182. [PMID: 28387360 PMCID: PMC5384044 DOI: 10.1038/srep46182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/10/2017] [Indexed: 01/31/2023] Open
Abstract
Recent studies have reported the ectopic expression of olfactory receptors (ORs) in non-olfactory tissues, however, their physiological roles were not well elucidated. ORs are expressed in and function in different types of cancers. Here, we identified that the H3K9me2 levels of several OR promoters decreased during differentiation in the HL-60, human myeloid leukaemia cell line, by all-trans-retinoic acid (ATRA). We found that the differential OR promoters H3K9me2 levels were regulated by G9a and LSD1, resulting in the decrease of ORs transcription during HL-60 differentiation. G9a and LSD1 could regulate the expression of ORs in several non-olfactory cells via the methylation and demethylation of H3K9me2. In addition, we demonstrated that knockdown of OR significantly reduced cell proliferation. Therefore, the epigenetic regulation of ORs transcription is critical for carcinogenesis.
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Affiliation(s)
- Hyeonsoo Jung
- Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Yun-Cheol Chae
- Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Ji-Young Kim
- Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Oh-Seok Jeong
- Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Hoon Kook
- Environmental Health Center for Childhood Leukaemia and Cancer, Department of Pediatrics, Chonnam National University Hwasun Hospital, Hwasun 519-809, Republic of Korea
| | - Sang-Beom Seo
- Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
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37
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Sneppen K. Models of life: epigenetics, diversity and cycles. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:042601. [PMID: 28106010 DOI: 10.1088/1361-6633/aa5aeb] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This review emphasizes aspects of biology that can be understood through repeated applications of simple causal rules. The selected topics include perspectives on gene regulation, phage lambda development, epigenetics, microbial ecology, as well as model approaches to diversity and to punctuated equilibrium in evolution. Two outstanding features are repeatedly described. One is the minimal number of rules to sustain specific states of complex systems for a long time. The other is the collapse of such states and the subsequent dynamical cycle of situations that restitute the system to a potentially new metastable state.
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Affiliation(s)
- Kim Sneppen
- Center for Models of Life, Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark
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38
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Sharma R, Ishimaru Y, Davison I, Ikegami K, Chien MS, You H, Chi Q, Kubota M, Yohda M, Ehlers M, Matsunami H. Olfactory receptor accessory proteins play crucial roles in receptor function and gene choice. eLife 2017; 6. [PMID: 28262096 PMCID: PMC5362263 DOI: 10.7554/elife.21895] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 02/16/2017] [Indexed: 11/13/2022] Open
Abstract
Each of the olfactory sensory neurons (OSNs) chooses to express a single G protein-coupled olfactory receptor (OR) from a pool of hundreds. Here, we show the receptor transporting protein (RTP) family members play a dual role in both normal OR trafficking and determining OR gene choice probabilities. Rtp1 and Rtp2 double knockout mice (RTP1,2DKO) show OR trafficking defects and decreased OSN activation. Surprisingly, we discovered a small subset of the ORs are expressed in larger numbers of OSNs despite the presence of fewer total OSNs in RTP1,2DKO. Unlike typical ORs, some overrepresented ORs show robust cell surface expression in heterologous cells without the co-expression of RTPs. We present a model in which developing OSNs exhibit unstable OR expression until they choose to express an OR that exits the ER or undergo cell death. Our study sheds light on the new link between OR protein trafficking and OR transcriptional regulation.
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Affiliation(s)
- Ruchira Sharma
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Yoshiro Ishimaru
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Ian Davison
- Department of Biology, Boston University, Boston, United States
| | - Kentaro Ikegami
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Ming-Shan Chien
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Helena You
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Quiyi Chi
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Momoka Kubota
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States
| | - Masafumi Yohda
- Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Michael Ehlers
- Department of Neurobiology, Duke University Medical Center, Durham, United States.,Biogen Inc, Cambridge, United States
| | - Hiroaki Matsunami
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Durham, United States
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39
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Landscape of monoallelic DNA accessibility in mouse embryonic stem cells and neural progenitor cells. Nat Genet 2017; 49:377-386. [PMID: 28112738 DOI: 10.1038/ng.3769] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 12/14/2016] [Indexed: 12/12/2022]
Abstract
We developed an allele-specific assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) to genotype and profile active regulatory DNA across the genome. Using a mouse hybrid F1 system, we found that monoallelic DNA accessibility across autosomes was pervasive, developmentally programmed and composed of several patterns. Genetically determined accessibility was enriched at distal enhancers, but random monoallelically accessible (RAMA) elements were enriched at promoters and may act as gatekeepers of monoallelic mRNA expression. Allelic choice at RAMA elements was stable across cell generations and bookmarked through mitosis. RAMA elements in neural progenitor cells were biallelically accessible in embryonic stem cells but premarked with bivalent histone modifications; one allele was silenced during differentiation. Quantitative analysis indicated that allelic choice at the majority of RAMA elements is consistent with a stochastic process; however, up to 30% of RAMA elements may deviate from the expected pattern, suggesting a regulated or counting mechanism.
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40
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Heterochromatin and the molecular mechanisms of ‘parent-of-origin’ effects in animals. J Biosci 2016; 41:759-786. [DOI: 10.1007/s12038-016-9650-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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41
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Lhx2 Determines Odorant Receptor Expression Frequency in Mature Olfactory Sensory Neurons. eNeuro 2016; 3:eN-NWR-0230-16. [PMID: 27822500 PMCID: PMC5086798 DOI: 10.1523/eneuro.0230-16.2016] [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: 08/07/2016] [Revised: 10/04/2016] [Accepted: 10/10/2016] [Indexed: 02/08/2023] Open
Abstract
A developmental program of epigenetic repression prepares each mammalian olfactory sensory neuron (OSN) to strongly express one allele from just one of hundreds of odorant receptor (OR) genes, but what completes this process of OR gene choice by driving the expression of this allele is incompletely understood. Conditional deletion experiments in mice demonstrate that Lhx2 is necessary for normal expression frequencies of nearly all ORs and all trace amine-associated receptors, irrespective of whether the deletion of Lhx2 is initiated in immature or mature OSNs. Given previous evidence that Lhx2 binds OR gene control elements, these findings indicate that Lhx2 is directly involved in driving OR expression. The data also support the conclusion that OR expression is necessary to allow immature OSNs to complete differentiation and become mature. In contrast to the robust effects of conditional deletion of Lhx2, the loss of Emx2 has much smaller effects and more often causes increased expression frequencies. Lhx2:Emx2 double mutants show opposing effects on Olfr15 expression that reveal independent effects of these two transcription factors. While Lhx2 is necessary for OR expression that supports OR gene choice, Emx2 can act differently; perhaps by helping to control the availability of OR genes for expression.
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42
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Nagai MH, Armelin-Correa LM, Malnic B. Monogenic and Monoallelic Expression of Odorant Receptors. Mol Pharmacol 2016; 90:633-639. [PMID: 27587538 DOI: 10.1124/mol.116.104745] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/31/2016] [Indexed: 02/06/2023] Open
Abstract
Odorant receptors (ORs) belong to a large gene family of rhodopsin-like G protein-coupled receptors (GPCRs). The mouse OR gene family is composed of ∼1000 OR genes, and the human OR gene family is composed of ∼400 OR genes. The OR genes are spread throughout the genome, and can be found in clusters or as solitary genes in almost all chromosomes. These chemosensory GPCRs are expressed in highly specialized cells, the olfactory sensory neurons of the nose. Each one of these neurons expresses a single OR gene out of the complete repertoire of genes. In addition, only one of the two homologous alleles of the chosen OR gene, the maternal or the paternal, is expressed per neuron. Here we review recent findings that help to elucidate the mechanisms underlying monogenic and monoallelic expression of OR genes.
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Affiliation(s)
- Maíra H Nagai
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
| | | | - Bettina Malnic
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
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43
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Achieving diverse and monoallelic olfactory receptor selection through dual-objective optimization design. Proc Natl Acad Sci U S A 2016; 113:E2889-98. [PMID: 27162367 DOI: 10.1073/pnas.1601722113] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multiple-objective optimization is common in biological systems. In the mammalian olfactory system, each sensory neuron stochastically expresses only one out of up to thousands of olfactory receptor (OR) gene alleles; at the organism level, the types of expressed ORs need to be maximized. Existing models focus only on monoallele activation, and cannot explain recent observations in mutants, especially the reduced global diversity of expressed ORs in G9a/GLP knockouts. In this work we integrated existing information on OR expression, and constructed a comprehensive model that has all its components based on physical interactions. Analyzing the model reveals an evolutionarily optimized three-layer regulation mechanism, which includes zonal segregation, epigenetic barrier crossing coupled to a negative feedback loop that mechanistically differs from previous theoretical proposals, and a previously unidentified enhancer competition step. This model not only recapitulates monoallelic OR expression, but also elucidates how the olfactory system maximizes and maintains the diversity of OR expression, and has multiple predictions validated by existing experimental results. Through making an analogy to a physical system with thermally activated barrier crossing and comparative reverse engineering analyses, the study reveals that the olfactory receptor selection system is optimally designed, and particularly underscores cooperativity and synergy as a general design principle for multiobjective optimization in biology.
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Abdus-Saboor I, Al Nufal MJ, Agha MV, Ruinart de Brimont M, Fleischmann A, Shykind BM. An Expression Refinement Process Ensures Singular Odorant Receptor Gene Choice. Curr Biol 2016; 26:1083-90. [PMID: 27040780 DOI: 10.1016/j.cub.2016.02.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/25/2015] [Accepted: 02/12/2016] [Indexed: 12/11/2022]
Abstract
Odorant receptor (OR) gene choice in mammals is a paradigmatic example of monogenic and monoallelic transcriptional selection, in which each olfactory sensory neuron (OSN) chooses to express one OR allele from over 1,000 encoded in the genome [1-3]. This process, critical for generation of the circuit from nose to brain [4-6], is thought to occur in two steps: a slow initial phase that randomly activates a single OR allele, followed by a rapid feedback that halts subsequent expression [7-14]. Inherent in this model is a finite failure rate wherein multiple OR alleles may be activated prior to feedback suppression [15, 16]. Confronted with more than one receptor, the neuron would need to activate a refinement mechanism to eliminate multigenic OR expression and resolve unique neuronal identity [16], critical to the generation of the circuit from nose to olfactory bulb. Here we used a genetic approach in mice to reveal a new facet of OR regulation that corrects adventitious activation of multiple OR alleles, restoring monogenic OR expression and unique neuronal identity. Using the tetM71tg model system, in which the M71 OR is expressed in >95% of mature OSNs and potently suppresses the expression of the endogenous OR repertoire [10], we provide clear evidence of a post-selection refinement (PSR) process that winnows down the number of ORs. We further demonstrate that PSR efficiency is linked to OR expression level, suggesting an underlying competitive process and shedding light on OR gene switching and the fundamental mechanism of singular OR choice.
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Affiliation(s)
- Ishmail Abdus-Saboor
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Mohammed J Al Nufal
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Maha V Agha
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Marion Ruinart de Brimont
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France
| | - Alexander Fleischmann
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France
| | - Benjamin M Shykind
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar.
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Kilinc S, Savarino A, Coleman JH, Schwob JE, Lane RP. Lysine-specific demethylase-1 (LSD1) is compartmentalized at nuclear chromocenters in early post-mitotic cells of the olfactory sensory neuronal lineage. Mol Cell Neurosci 2016; 74:58-70. [PMID: 26947098 DOI: 10.1016/j.mcn.2016.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 01/29/2016] [Accepted: 03/02/2016] [Indexed: 12/12/2022] Open
Abstract
Mammalian olfaction depends on the development of specialized olfactory sensory neurons (OSNs) that each express one odorant receptor (OR) protein from a large family of OR genes encoded in the genome. The lysine-specific demethylase-1 (LSD1) protein removes activating H3K4 or silencing H3K9 methylation marks at gene promoters and is required for proper OR regulation. We show that LSD1 protein exhibits variable organization within nuclei of developing OSNs, and tends to consolidate into a single dominant compartment at the edges of chromocenters within nuclei of early post-mitotic cells of the mouse olfactory epithelium (MOE). Using an immortalized cell line derived from developing olfactory placode, we show that consolidation of LSD1 appears to be cell-cycle regulated, with a peak occurrence in early G1. LSD1 co-compartmentalizes with CoREST, a protein known to collaborate with LSD1 to carry out a variety of chromatin-modifying functions. We show that LSD1 compartments co-localize with 1-3 OR loci at the exclusion of most OR genes, and commonly associate with Lhx2, a transcription factor involved in OR regulation. Together, our data suggests that LSD1 is sequestered into a distinct nuclear space that might restrict a histone-modifying function to a narrow developmental time window and/or range of OR gene targets.
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Affiliation(s)
- Seda Kilinc
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA.
| | - Alyssa Savarino
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Julie H Coleman
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - James E Schwob
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Robert P Lane
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06457, USA.
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Calfún C, Domínguez C, Pérez-Acle T, Whitlock KE. Changes in Olfactory Receptor Expression Are Correlated With Odor Exposure During Early Development in the zebrafish (Danio rerio). Chem Senses 2016; 41:301-12. [PMID: 26892307 DOI: 10.1093/chemse/bjw002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We have previously shown that exposure to phenyl ethyl alcohol (PEA) causes an increase in the expression of the transcription factor otx2 in the olfactory epithelium (OE) of juvenile zebrafish, and this change is correlated with the formation of an odor memory of PEA. Here, we show that the changes in otx2 expression are specific to βPEA: exposure to αPEA did not affect otx2 expression. We identified 34 olfactory receptors (ORs) representing 16 families on 4 different chromosomes as candidates for direct regulation of OR expression via Otx2. Subsequent in silico analysis uncovered Hnf3b binding sites closely associated with Otx2 binding sites in the regions flanking the ORs. Analysis by quantitative polymerase chain reaction and RNA-seq of OR expression in developing zebrafish exposed to different isoforms of PEA showed that a subset of ORs containing both Otx2/Hnf3b binding sites were downregulated only in βPEA-exposed juveniles and this change persisted through adult life. Localization of OR expression by in situ hybridization indicates the downregulation occurs at the level of RNA and not the number of cells expressing a given receptor. Finally, analysis of immediate early gene expression in the OE did not reveal changes in c-fos expression in response to either αPEA or βPEA.
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Affiliation(s)
- Cristian Calfún
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso 2360102, Chile, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2360102, Chile
| | - Calixto Domínguez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso 2360102, Chile, Center for Bioinformatics and Genome Biology, Fundación Ciencia & Vida, Av. Zañartu 1482, Santiago 7750000, Chile and
| | - Tomás Pérez-Acle
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso 2360102, Chile, Computational Biology Lab, Fundación Ciencia & Vida, Av. Zañartu 1482, Santiago 7750000, Chile
| | - Kathleen E Whitlock
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso 2360102, Chile, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2360102, Chile,
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47
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Affiliation(s)
- Anne Tromelin
- CNRS; UMR6265 Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
- INRA; UMR1324 Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
- Université de Bourgogne; UMR Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
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48
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The role of chromatin repressive marks in cognition and disease: A focus on the repressive complex GLP/G9a. Neurobiol Learn Mem 2015; 124:88-96. [DOI: 10.1016/j.nlm.2015.06.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 06/23/2015] [Accepted: 06/25/2015] [Indexed: 11/23/2022]
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Abstract
The sense of smell collects vital information about the environment by detecting a multitude of chemical odorants. Breadth and sensitivity are provided by a huge number of chemosensory receptor proteins, including more than 1,400 olfactory receptors (ORs). Organizing the sensory information generated by these receptors so that it can be processed and evaluated by the central nervous system is a major challenge. This challenge is overcome by monogenic and monoallelic expression of OR genes. The single OR expressed by each olfactory sensory neuron determines the neuron's odor sensitivity and the axonal connections it will make to downstream neurons in the olfactory bulb. The expression of a single OR per neuron is accomplished by coupling a slow chromatin-mediated activation process to a fast negative-feedback signal that prevents activation of additional ORs. Singular OR activation is likely orchestrated by a network of interchromosomal enhancer interactions and large-scale changes in nuclear architecture.
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Affiliation(s)
- Kevin Monahan
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, and Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY 10032; ,
| | - Stavros Lomvardas
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, and Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY 10032; ,
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50
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Whitlock KE. The loss of scents: do defects in olfactory sensory neuron development underlie human disease? ACTA ACUST UNITED AC 2015; 105:114-25. [PMID: 26111003 DOI: 10.1002/bdrc.21094] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 05/12/2015] [Indexed: 12/20/2022]
Abstract
The olfactory system is a fascinating and beguiling sensory system: olfactory sensory neurons detect odors underlying behaviors essential for mate choice, food selection, and escape from predators, among others. These sensory neurons are unique in that they have dendrites contacting the outside world, yet their first synapse lies in the central nervous system. The information entering the central nervous system is used to create odor memories that play a profound role in recognition of individuals, places, and appropriate foods. Here, the structure of the olfactory epithelium is given as an overview to discuss the origin of the olfactory placode, the plasticity of the olfactory sensory neurons, and finally the origins of the gonadotropin-releasing hormone neuroendocrine cells. For the purposes of this review, the development of the peripheral sensory system will be analyzed, incorporating recently published studies highlighting the potential novelties in development mechanisms. Specifically, an emerging model where the olfactory epithelium and olfactory bulb develop simultaneously from a continuous neurectoderm patterned at the end of gastrulation, and the multiple origins of the gonadotropin-releasing hormone neuroendocrine cells associated with the olfactory sensory system development will be presented. Advances in the understanding of the basic mechanisms underlying olfactory sensory system development allows for a more thorough understanding of the potential causes of human disease.
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Affiliation(s)
- Kathleen E Whitlock
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaiso, Valparaiso, Chile
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