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Ito A, Miller C, Imamura F. Suppression of BMP signaling restores mitral cell development impaired by FGF signaling deficits in mouse olfactory bulb. Mol Cell Neurosci 2024; 128:103913. [PMID: 38056728 PMCID: PMC10939902 DOI: 10.1016/j.mcn.2023.103913] [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: 10/02/2023] [Revised: 11/17/2023] [Accepted: 11/29/2023] [Indexed: 12/08/2023] Open
Abstract
Fibroblast growth factors (FGFs) and bone morphogenic proteins (BMPs) play various important roles in the development of the central nervous system. However, the roles of FGF and BMP signaling in the development of the olfactory bulb (OB) are largely unknown. In this study, we first showed the expression of FGF receptors (FGFRs) and BMP receptors (BMPRs) in OB RGCs, radial glial cells (RGCs) in the developing OB, which generate the OB projection neurons, mitral and tufted cells. When the FGF signaling was inhibited by a dominant-negative form of FGFR1 (dnFGFR1), OB RGCs accelerated their state transition to mitral cell precursors without affecting their transcription cascade and fate. However, the mitral cell precursors could not radially migrate to form the mitral cell layer (MCL). In addition, FGF signaling inhibition reduced the expression of a BMP antagonist, Noggin, in the developing OB. When BMP signaling was suppressed by the ectopic expression of Noggin or a dominant-negative form of BMPR1a (dnBMPR1a) in the developing OB, the defect in MCL formation caused by the dnFGFR1 was rescued. However, the dnBMPR1a did not rescue the accelerated state transition of OB RGCs. These results demonstrate that FGF signaling is important for OB RGCs to maintain their self-renewal state and MCL formation. Moreover, the suppression of BMP signaling is required for mitral cells to form the MCL. This study sheds new light on the roles of FGFs and BMPs in OB development.
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Affiliation(s)
- Ayako Ito
- Department of Pharmacology, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033, USA
| | - Claire Miller
- Department of Pharmacology, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033, USA
| | - Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033, USA.
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2
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Leung RF, George AM, Roussel EM, Faux MC, Wigle JT, Eisenstat DD. Genetic Regulation of Vertebrate Forebrain Development by Homeobox Genes. Front Neurosci 2022; 16:843794. [PMID: 35546872 PMCID: PMC9081933 DOI: 10.3389/fnins.2022.843794] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/14/2022] [Indexed: 01/19/2023] Open
Abstract
Forebrain development in vertebrates is regulated by transcription factors encoded by homeobox, bHLH and forkhead gene families throughout the progressive and overlapping stages of neural induction and patterning, regional specification and generation of neurons and glia from central nervous system (CNS) progenitor cells. Moreover, cell fate decisions, differentiation and migration of these committed CNS progenitors are controlled by the gene regulatory networks that are regulated by various homeodomain-containing transcription factors, including but not limited to those of the Pax (paired), Nkx, Otx (orthodenticle), Gsx/Gsh (genetic screened), and Dlx (distal-less) homeobox gene families. This comprehensive review outlines the integral role of key homeobox transcription factors and their target genes on forebrain development, focused primarily on the telencephalon. Furthermore, links of these transcription factors to human diseases, such as neurodevelopmental disorders and brain tumors are provided.
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Affiliation(s)
- Ryan F. Leung
- Murdoch Children’s Research Institute, The Royal Children’s Hospital Melbourne, Parkville, VIC, Australia
- Department of Paediatrics, University of Melbourne, Parkville, VIC, Australia
| | - Ankita M. George
- Murdoch Children’s Research Institute, The Royal Children’s Hospital Melbourne, Parkville, VIC, Australia
| | - Enola M. Roussel
- Murdoch Children’s Research Institute, The Royal Children’s Hospital Melbourne, Parkville, VIC, Australia
| | - Maree C. Faux
- Murdoch Children’s Research Institute, The Royal Children’s Hospital Melbourne, Parkville, VIC, Australia
- Department of Paediatrics, University of Melbourne, Parkville, VIC, Australia
- Department of Surgery, Royal Melbourne Hospital, The University of Melbourne, Parkville, VIC, Australia
| | - Jeffrey T. Wigle
- Department of Biochemistry and Medical Genetics, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
- Institute of Cardiovascular Sciences, St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB, Canada
| | - David D. Eisenstat
- Murdoch Children’s Research Institute, The Royal Children’s Hospital Melbourne, Parkville, VIC, Australia
- Department of Paediatrics, University of Melbourne, Parkville, VIC, Australia
- Department of Medical Genetics, University of Alberta, Edmonton, AB, Canada
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
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3
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Zeppilli S, Ackels T, Attey R, Klimpert N, Ritola KD, Boeing S, Crombach A, Schaefer AT, Fleischmann A. Molecular characterization of projection neuron subtypes in the mouse olfactory bulb. eLife 2021; 10:e65445. [PMID: 34292150 PMCID: PMC8352594 DOI: 10.7554/elife.65445] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 07/21/2021] [Indexed: 12/14/2022] Open
Abstract
Projection neurons (PNs) in the mammalian olfactory bulb (OB) receive input from the nose and project to diverse cortical and subcortical areas. Morphological and physiological studies have highlighted functional heterogeneity, yet no molecular markers have been described that delineate PN subtypes. Here, we used viral injections into olfactory cortex and fluorescent nucleus sorting to enrich PNs for high-throughput single nucleus and bulk RNA deep sequencing. Transcriptome analysis and RNA in situ hybridization identified distinct mitral and tufted cell populations with characteristic transcription factor network topology, cell adhesion, and excitability-related gene expression. Finally, we describe a new computational approach for integrating bulk and snRNA-seq data and provide evidence that different mitral cell populations preferentially project to different target regions. Together, we have identified potential molecular and gene regulatory mechanisms underlying PN diversity and provide new molecular entry points into studying the diverse functional roles of mitral and tufted cell subtypes.
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Affiliation(s)
- Sara Zeppilli
- Department of Neuroscience, Division of Biology and Medicine, and the Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, and CNRS UMR 7241 and INSERM U1050ParisFrance
| | - Tobias Ackels
- The Francis Crick Institute, Sensory Circuits and Neurotechnology LaboratoryLondonUnited Kingdom
- Department of Neuroscience, Physiology & Pharmacology, University College LondonLondonUnited Kingdom
| | - Robin Attey
- Department of Neuroscience, Division of Biology and Medicine, and the Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
| | - Nell Klimpert
- Department of Neuroscience, Division of Biology and Medicine, and the Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
| | - Kimberly D Ritola
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Stefan Boeing
- The Francis Crick Institute, Bioinformatics and BiostatisticsLondonUnited Kingdom
- The Francis Crick Institute, Scientific Computing - Digital Development TeamLondonUnited Kingdom
| | - Anton Crombach
- Inria Antenne Lyon La DouaVilleurbanneFrance
- Université de Lyon, INSA-Lyon, LIRIS, UMR 5205VilleurbanneFrance
| | - Andreas T Schaefer
- The Francis Crick Institute, Sensory Circuits and Neurotechnology LaboratoryLondonUnited Kingdom
- Department of Neuroscience, Physiology & Pharmacology, University College LondonLondonUnited Kingdom
| | - Alexander Fleischmann
- Department of Neuroscience, Division of Biology and Medicine, and the Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, and CNRS UMR 7241 and INSERM U1050ParisFrance
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4
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Garcia-Calero E, López-González L, Martínez-de-la-Torre M, Fan CM, Puelles L. Sim1-expressing cells illuminate the origin and course of migration of the nucleus of the lateral olfactory tract in the mouse amygdala. Brain Struct Funct 2021; 226:519-562. [PMID: 33492553 PMCID: PMC7910384 DOI: 10.1007/s00429-020-02197-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/16/2020] [Indexed: 12/14/2022]
Abstract
We focus this report on the nucleus of the lateral olfactory tract (NLOT), a superficial amygdalar nucleus receiving olfactory input. Mixed with its Tbr1-expressing layer 2 pyramidal cell population (NLOT2), there are Sim1-expressing cells whose embryonic origin and mode of arrival remain unclear. We examined this population with Sim1-ISH and a Sim1-tauLacZ mouse line. An alar hypothalamic origin is apparent at the paraventricular area, which expresses Sim1 precociously. This progenitor area shows at E10.5 a Sim1-expressing dorsal prolongation that crosses the telencephalic stalk and follows the terminal sulcus, reaching the caudomedial end of the pallial amygdala. We conceive this Sim1-expressing hypothalamo-amygdalar corridor (HyA) as an evaginated part of the hypothalamic paraventricular area, which participates in the production of Sim1-expressing cells. From E13.5 onwards, Sim1-expressing cells migrated via the HyA penetrate the posterior pallial amygdalar radial unit and associate therein to the incipient Tbr1-expressing migration stream which swings medially past the amygdalar anterior basolateral nucleus (E15.5), crosses the pallio-subpallial boundary (E16.5), and forms the NLOT2 within the anterior amygdala by E17.5. We conclude that the Tbr1-expressing NLOT2 cells arise strictly within the posterior pallial amygdalar unit, involving a variety of required gene functions we discuss. Our results are consistent with the experimental data on NLOT2 origin reported by Remedios et al. (Nat Neurosci 10:1141–1150, 2007), but we disagree on their implication in this process of the dorsal pallium, observed to be distant from the amygdala.
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Affiliation(s)
- Elena Garcia-Calero
- University of Murcia, IMIB-Arrixaca Institute of Biomedical Research, 30120, El Palmar, Murcia, Spain.
| | - Lara López-González
- University of Murcia, IMIB-Arrixaca Institute of Biomedical Research, 30120, El Palmar, Murcia, Spain
| | | | - Chen-Ming Fan
- Department of Embryology, Carnegie Institution for Science, 3520 San Martin Drive, Baltimore, MD, 21218, USA
| | - Luis Puelles
- University of Murcia, IMIB-Arrixaca Institute of Biomedical Research, 30120, El Palmar, Murcia, Spain
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5
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Symmank J, Gölling V, Gerstmann K, Zimmer G. The Transcription Factor LHX1 Regulates the Survival and Directed Migration of POA-derived Cortical Interneurons. Cereb Cortex 2020; 29:1644-1658. [PMID: 29912395 DOI: 10.1093/cercor/bhy063] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 02/22/2018] [Accepted: 02/23/2018] [Indexed: 12/17/2022] Open
Abstract
The delicate balance of excitation and inhibition is crucial for proper function of the cerebral cortex, relying on the accurate number and subtype composition of inhibitory gamma-aminobutyric (GABA)-expressing interneurons. Various intrinsic and extrinsic factors precisely orchestrate their multifaceted development including the long-range migration from the basal telencephalon to cortical targets as well as interneuron survival throughout the developmental period. Particularly expressed guidance receptors were described to channel the migration of cortical interneurons deriving from the medial ganglionic eminence (MGE) and the preoptic area (POA) along distinct routes. Hence, unveiling the regulatory genetic networks controlling subtype-specific gene expression profiles is key to understand interneuron-specific developmental programs and to reveal causes for associated disorders. In contrast to MGE-derived interneurons, little is known about the transcriptional networks in interneurons born in the POA. Here, we provide first evidence for the LIM-homeobox transcription factor LHX1 as a crucial key player in the post-mitotic development of POA-derived cortical interneurons. By transcriptional regulation of related genes, LHX1 modulates their survival as well as the subtype-specific expression of guidance receptors of the Eph/ephrin family, thereby affecting directional migration and layer distribution in the adult cortex.
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Affiliation(s)
- Judit Symmank
- Institute of Human Genetics, University Hospital Jena, Jena, Germany
| | - Vanessa Gölling
- Institute of Human Genetics, University Hospital Jena, Jena, Germany
| | - Katrin Gerstmann
- Institute of Human Genetics, University Hospital Jena, Jena, Germany
| | - Geraldine Zimmer
- Institute of Human Genetics, University Hospital Jena, Jena, Germany
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6
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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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7
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Abstract
A hundred years after Lhx2 ortholog apterous was identified as a critical regulator of wing development in Drosophila, LIM-HD gene family members have proved to be versatile and powerful components of the molecular machinery that executes the blueprint of embryogenesis across vertebrate and invertebrate species. Here, we focus on the spatio-temporally varied functions of LIM-homeodomain transcription factor LHX2 in the developing mouse forebrain. Right from its earliest known role in telencephalic and eye field patterning, to the control of the neuron-glia cell fate switch, and the regulation of axon pathfinding and dendritic arborization in late embryonic stages, LHX2 has been identified as a fundamental, temporally dynamic, always necessary, and often sufficient factor in a range of critical developmental phenomena. While Lhx2 mutant phenotypes have been characterized in detail in multiple brain structures, only recently have we advanced in our understanding of the molecular mechanisms by which this factor acts. Common themes emerge from how this multifunctional molecule controls a range of developmental steps in distinct forebrain structures. Examining these shared features, and noting unique aspects of LHX2 function is likely to inform our understanding of how a single factor can bring about a diversity of effects and play central and critical roles across systems and stages. The parallels in LHX2 and APTEROUS functions, and the protein complexes they participate in, offer insights into evolutionary strategies that conserve tool kits and deploy them to play new, yet familiar roles in species separated by hundreds of millions of years.
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Affiliation(s)
- Shen-Ju Chou
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India.
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8
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Kinare V, Shetty AS, Suresh A, Tole S. PAX6 can substitute for LHX2 and override NFIA-induced astrogliogenesis in developing hippocampus in vivo. J Biosci 2018; 43:75-83. [PMID: 29485116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the developing central nervous system, transcription factors play a crucial role in the regulation of cell fate. Previously we demonstrated that LHX2 is a critical regulator of the neuron-glia cell fate switch in the developing mouse hippocampus. Here, we test LHX2 target gene Pax6 for a role in this process. We report that Pax6 overexpression is able to suppress the enhanced astrogliogenesis arising due to loss of functional LHX2. Furthermore, we show that like Lhx2, Pax6 is also able to suppress induced astrogliogenesis caused by overexpression of progliogenic factor Nfia. This demonstrates that overexpression of Pax6 can substitute for Lhx2 in the regulation of the neuronal versus glial cell fate in the developing hippocampus, and therefore, supports a role for PAX6 as a mediator of LHX2 function in this process.
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Affiliation(s)
- Veena Kinare
- Department of Life Sciences, Sophia College for Women, Mumbai, India
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9
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Ruiz-Reig N, Andrés B, Huilgol D, Grove EA, Tissir F, Tole S, Theil T, Herrera E, Fairén A. Lateral Thalamic Eminence: A Novel Origin for mGluR1/Lot Cells. Cereb Cortex 2018; 27:2841-2856. [PMID: 27178193 DOI: 10.1093/cercor/bhw126] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A unique population of cells, called "lot cells," circumscribes the path of the lateral olfactory tract (LOT) in the rodent brain and acts to restrict its position at the lateral margin of the telencephalon. Lot cells were believed to originate in the dorsal pallium (DP). We show that Lhx2 null mice that lack a DP show a significant increase in the number of mGluR1/lot cells in the piriform cortex, indicating a non-DP origin of these cells. Since lot cells present common developmental features with Cajal-Retzius (CR) cells, we analyzed Wnt3a- and Dbx1-reporter mouse lines and found that mGluR1/lot cells are not generated in the cortical hem, ventral pallium, or septum, the best characterized sources of CR cells. Finally, we identified a novel origin for the lot cells by combining in utero electroporation assays and histochemical characterization. We show that mGluR1/lot cells are specifically generated in the lateral thalamic eminence and that they express mitral cell markers, although a minority of them express ΔNp73 instead. We conclude that most mGluR1/lot cells are prospective mitral cells migrating to the accessory olfactory bulb (OB), whereas mGluR1+, ΔNp73+ cells are CR cells that migrate through the LOT to the piriform cortex and the OB.
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Affiliation(s)
- Nuria Ruiz-Reig
- Instituto de Neurociencias (Consejo Superior de Investigaciones Científicas - Universidad Miguel Hernández, CSIC - UMH), San Juan de Alicante, Spain
| | - Belén Andrés
- Instituto de Neurociencias (Consejo Superior de Investigaciones Científicas - Universidad Miguel Hernández, CSIC - UMH), San Juan de Alicante, Spain
| | - Dhananjay Huilgol
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.,Current address: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | | | - Fadel Tissir
- Université catholique de Louvain, Institute of Neuroscience, Brussels, Belgium
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Thomas Theil
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Eloisa Herrera
- Instituto de Neurociencias (Consejo Superior de Investigaciones Científicas - Universidad Miguel Hernández, CSIC - UMH), San Juan de Alicante, Spain
| | - Alfonso Fairén
- Instituto de Neurociencias (Consejo Superior de Investigaciones Científicas - Universidad Miguel Hernández, CSIC - UMH), San Juan de Alicante, Spain
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10
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Kinare V, Shetty AS, Suresh A, Tole S. PAX6 can substitute for LHX2 and override NFIA-induced astrogliogenesis in developing hippocampus in vivo. J Biosci 2018. [DOI: 10.1007/s12038-018-9731-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Huilgol D, Tole S. Cell migration in the developing rodent olfactory system. Cell Mol Life Sci 2016; 73:2467-90. [PMID: 26994098 PMCID: PMC4894936 DOI: 10.1007/s00018-016-2172-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 02/08/2016] [Accepted: 03/01/2016] [Indexed: 02/06/2023]
Abstract
The components of the nervous system are assembled in development by the process of cell migration. Although the principles of cell migration are conserved throughout the brain, different subsystems may predominantly utilize specific migratory mechanisms, or may display unusual features during migration. Examining these subsystems offers not only the potential for insights into the development of the system, but may also help in understanding disorders arising from aberrant cell migration. The olfactory system is an ancient sensory circuit that is essential for the survival and reproduction of a species. The organization of this circuit displays many evolutionarily conserved features in vertebrates, including molecular mechanisms and complex migratory pathways. In this review, we describe the elaborate migrations that populate each component of the olfactory system in rodents and compare them with those described in the well-studied neocortex. Understanding how the components of the olfactory system are assembled will not only shed light on the etiology of olfactory and sexual disorders, but will also offer insights into how conserved migratory mechanisms may have shaped the evolution of the brain.
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Affiliation(s)
- Dhananjay Huilgol
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
- Cold Spring Harbor Laboratory, Cold Spring Harbor, USA
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
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12
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Amaniti EM, Kelman A, Mason JO, Theil T. Cerebral Cortex Expression of Gli3 Is Required for Normal Development of the Lateral Olfactory Tract. PLoS One 2015; 10:e0141525. [PMID: 26509897 PMCID: PMC4624982 DOI: 10.1371/journal.pone.0141525] [Citation(s) in RCA: 2] [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: 09/29/2014] [Accepted: 10/09/2015] [Indexed: 02/03/2023] Open
Abstract
Formation of the lateral olfactory tract (LOT) and innervation of the piriform cortex represent fundamental steps to allow the transmission of olfactory information to the cerebral cortex. Several transcription factors, including the zinc finger transcription factor Gli3, influence LOT formation by controlling the development of mitral cells from which LOT axons emanate and/or by specifying the environment through which these axons navigate. Gli3 null and hypomorphic mutants display severe defects throughout the territory covered by the developing lateral olfactory tract, making it difficult to identify specific roles for Gli3 in its development. Here, we used Emx1Cre;Gli3fl/fl conditional mutants to investigate LOT formation and colonization of the olfactory cortex in embryos in which loss of Gli3 function is restricted to the dorsal telencephalon. These mutants form an olfactory bulb like structure which does not protrude from the telencephalic surface. Nevertheless, mitral cells are formed and their axons enter the piriform cortex though the LOT is shifted medially. Mitral axons also innervate a larger target area consistent with an enlargement of the piriform cortex and form aberrant projections into the deeper layers of the piriform cortex. No obvious differences were found in the expression patterns of key guidance cues. However, we found that an expansion of the piriform cortex temporally coincides with the arrival of LOT axons, suggesting that Gli3 affects LOT positioning and target area innervation through controlling the development of the piriform cortex.
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Affiliation(s)
- Eleni-Maria Amaniti
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, United Kingdom
| | - Alexandra Kelman
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, United Kingdom
| | - John O. Mason
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, United Kingdom
| | - Thomas Theil
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, United Kingdom
- * E-mail:
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13
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Squarzoni P, Thion MS, Garel S. Neuronal and microglial regulators of cortical wiring: usual and novel guideposts. Front Neurosci 2015; 9:248. [PMID: 26236185 PMCID: PMC4505395 DOI: 10.3389/fnins.2015.00248] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 06/30/2015] [Indexed: 12/17/2022] Open
Abstract
Neocortex functioning relies on the formation of complex networks that begin to be assembled during embryogenesis by highly stereotyped processes of cell migration and axonal navigation. The guidance of cells and axons is driven by extracellular cues, released along by final targets or intermediate targets located along specific pathways. In particular, guidepost cells, originally described in the grasshopper, are considered discrete, specialized cell populations located at crucial decision points along axonal trajectories that regulate tract formation. These cells are usually early-born, transient and act at short-range or via cell-cell contact. The vast majority of guidepost cells initially identified were glial cells, which play a role in the formation of important axonal tracts in the forebrain, such as the corpus callosum, anterior, and post-optic commissures as well as optic chiasm. In the last decades, tangential migrating neurons have also been found to participate in the guidance of principal axonal tracts in the forebrain. This is the case for several examples such as guideposts for the lateral olfactory tract (LOT), corridor cells, which open an internal path for thalamo-cortical axons and Cajal-Retzius cells that have been involved in the formation of the entorhino-hippocampal connections. More recently, microglia, the resident macrophages of the brain, were specifically observed at the crossroads of important neuronal migratory routes and axonal tract pathways during forebrain development. We furthermore found that microglia participate to the shaping of prenatal forebrain circuits, thereby opening novel perspectives on forebrain development and wiring. Here we will review the last findings on already known guidepost cell populations and will discuss the role of microglia as a potentially new class of atypical guidepost cells.
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Affiliation(s)
- Paola Squarzoni
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
| | - Morgane S Thion
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
| | - Sonia Garel
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
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14
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Abstract
The three-layered piriform cortex, an integral part of the olfactory system, processes odor information relayed by olfactory bulb mitral cells. Specifically, mitral cell axons form the lateral olfactory tract (LOT) by targeting lateral olfactory tract (lot) guidepost cells in the piriform cortex. While lot cells and other piriform cortical neurons share a pallial origin, the factors that specify their precise phenotypes are poorly understood. Here we show that in mouse, the proneural genes Neurog1 and Neurog2 are coexpressed in the ventral pallium, a progenitor pool that first gives rise to Cajal-Retzius (CR) cells, which populate layer I of all cortical domains, and later to layer II/III neurons of the piriform cortex. Using loss-of-function and gain-of-function approaches, we find that Neurog1 has a unique early role in reducing CR cell neurogenesis by tempering Neurog2's proneural activity. In addition, Neurog1 and Neurog2 have redundant functions in the ventral pallium, acting in two phases to first specify a CR cell fate and later to specify layer II/III piriform cortex neuronal identities. In the early phase, Neurog1 and Neurog2 are also required for lot cell differentiation, which we reveal are a subset of CR neurons, the loss of which prevents mitral cell axon innervation and LOT formation. Consequently, mutation of Trp73, a CR-specific cortical gene, results in lot cell and LOT axon displacement. Neurog1 and Neurog2 thus have unique and redundant functions in the piriform cortex, controlling the timing of differentiation of early-born CR/lot cells and specifying the identities of later-born layer II/III neurons.
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15
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Gordon PJ, Yun S, Clark AM, Monuki ES, Murtaugh LC, Levine EM. Lhx2 balances progenitor maintenance with neurogenic output and promotes competence state progression in the developing retina. J Neurosci 2013; 33:12197-207. [PMID: 23884928 PMCID: PMC3721834 DOI: 10.1523/jneurosci.1494-13.2013] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/29/2013] [Accepted: 06/13/2013] [Indexed: 11/21/2022] Open
Abstract
The LIM-Homeodomain transcription factor Lhx2 is an essential organizer of early eye development and is subsequently expressed in retinal progenitor cells (RPCs). To determine its requirement in RPCs, we performed a temporal series of conditional inactivations in mice with the early RPC driver Pax6 α-Cre and the tamoxifen-inducible Hes1(CreERT2) driver. Deletion of Lhx2 caused a significant reduction of the progenitor population and a corresponding increase in neurogenesis. Precursor fate choice correlated with the time of inactivation; early and late inactivation led to the overproduction of retinal ganglion cells (RGCs) and rod photoreceptors, respectively. In each case, however, the overproduction was selective, occurring at the expense of other cell types and indicating a role for Lhx2 in generating cell type diversity. RPCs that persisted in the absence of Lhx2 continued to generate RGC precursors beyond their normal production window, suggesting that Lhx2 facilitates a transition in competence state. These results identify Lhx2 as a key regulator of RPC properties that contribute to the ordered production of multiple cell types during retinal tissue formation.
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Affiliation(s)
- Patrick J. Gordon
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center
- Interdepartmental Program in Neuroscience, and
| | - Sanghee Yun
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center
| | - Anna M. Clark
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center
| | - Edwin S. Monuki
- Department of Pathology and Laboratory Medicine, University of California, Irvine, California 92697
| | - L. Charles Murtaugh
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84132, and
| | - Edward M. Levine
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center
- Department of Neurobiology and Anatomy
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Hou PS, Chuang CY, Kao CF, Chou SJ, Stone L, Ho HN, Chien CL, Kuo HC. LHX2 regulates the neural differentiation of human embryonic stem cells via transcriptional modulation of PAX6 and CER1. Nucleic Acids Res 2013; 41:7753-70. [PMID: 23804753 PMCID: PMC3763550 DOI: 10.1093/nar/gkt567] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The LIM homeobox 2 transcription factor Lhx2 is known to control crucial aspects of neural development in various species. However, its function in human neural development is still elusive. Here, we demonstrate that LHX2 plays a critical role in human neural differentiation, using human embryonic stem cells (hESCs) as a model. In hESC-derived neural progenitors (hESC-NPs), LHX2 was found to be expressed before PAX6, and co-expressed with early neural markers. Conditional ectopic expression of LHX2 promoted neural differentiation, whereas disruption of LHX2 expression in hESCs significantly impaired neural differentiation. Furthermore, we have demonstrated that LHX2 regulates neural differentiation at two levels: first, it promotes expression of PAX6 by binding to its active enhancers, and second, it attenuates BMP and WNT signaling by promoting expression of the BMP and WNT antagonist Cerberus 1 gene (CER1), to inhibit non-neural differentiation. These findings indicate that LHX2 regulates the transcription of downstream intrinsic and extrinsic molecules that are essential for early neural differentiation in human.
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Affiliation(s)
- Pei-Shan Hou
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 100, Taiwan, Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei 100, Taiwan and Graduate Institute of Clinical Genomics, College of Medicine, National Taiwan University, Taipei 100, Taiwan
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17
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Dual origins of the mammalian accessory olfactory bulb revealed by an evolutionarily conserved migratory stream. Nat Neurosci 2013; 16:157-65. [PMID: 23292680 DOI: 10.1038/nn.3297] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/05/2012] [Indexed: 11/09/2022]
Abstract
The accessory olfactory bulb (AOB) is a critical olfactory structure that has been implicated in mediating social behavior. It receives input from the vomeronasal organ and projects to targets in the amygdaloid complex. Its anterior and posterior components (aAOB and pAOB) display molecular, connectional and functional segregation in processing reproductive and defensive and aggressive behaviors, respectively. We observed a dichotomy in the development of the projection neurons of the aAOB and pAOB in mice. We found that they had distinct sites of origin and that different regulatory molecules were required for their specification and migration. aAOB neurons arose locally in the rostral telencephalon, similar to main olfactory bulb neurons. In contrast, pAOB neurons arose caudally, from the neuroepithelium of the diencephalic-telencephalic boundary, from which they migrated rostrally to reach their destination. This unusual origin and migration is conserved in Xenopus, providing an insight into the origin of a key component of this system in evolution.
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Shaker T, Dennis D, Kurrasch DM, Schuurmans C. Neurog1 and Neurog2 coordinately regulate development of the olfactory system. Neural Dev 2012; 7:28. [PMID: 22906231 PMCID: PMC3444899 DOI: 10.1186/1749-8104-7-28] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 08/03/2012] [Indexed: 01/23/2023] Open
Abstract
Background Proneural genes encode basic helix–loop–helix transcription factors that specify distinct neuronal identities in different regions of the nervous system. In the embryonic telencephalon, the proneural genes Neurog1 and Neurog2 specify a dorsal regional identity and glutamatergic projection neuron phenotype in the presumptive neocortex, but their roles in cell fate specification in the olfactory bulb, which is also partly derived from dorsal telencephalic progenitors, have yet to be assessed. Given that olfactory bulb development is guided by interactions with the olfactory epithelium in the periphery, where proneural genes are also expressed, we investigated the roles of Neurog1 and Neurog2 in the coordinated development of these two olfactory structures. Results Neurog1/2 are co-expressed in olfactory bulb progenitors, while only Neurog1 is widely expressed in progenitors for olfactory sensory neurons in the olfactory epithelium. Strikingly, only a remnant of an olfactory bulb forms in Neurog1−/−;Neurog2−/− double mutants, while this structure is smaller but distinguishable in Neurog1−/− single mutants and morphologically normal in Neurog2−/− single mutants. At the cellular level, fewer glutamatergic mitral and juxtaglomerular cells differentiate in Neurog1−/−;Neurog2−/− double-mutant olfactory bulbs. Instead, ectopic olfactory bulb interneurons are derived from dorsal telencephalic lineages in Neurog1−/−;Neurog2−/− double mutants and to a lesser extent in Neurog2−/− single mutants. Conversely, cell fate specification is normal in Neurog1−/− olfactory bulbs, but aberrant patterns of cell proliferation and neuronal migration are observed in Neurog1−/− single and Neurog1−/−;Neurog2−/− double mutants, probably contributing to their altered morphologies. Finally, in Neurog1−/− and Neurog1−/−;Neurog2−/− embryos, olfactory sensory neurons in the epithelium, which normally project to the olfactory bulb to guide its morphogenesis, fail to innervate the olfactory bulb. Conclusions We have identified a cell autonomous role for Neurog1/2 in specifying the glutamatergic identity of olfactory bulb neurons. Furthermore, Neurog1 (and not Neurog2) is required to guide olfactory sensory neuron innervation of the olfactory bulb, the loss of which results in defects in olfactory bulb proliferation and tissue morphogenesis. We thus conclude that Neurog1/2 together coordinate development of the olfactory system, which depends on tissue interactions between the olfactory bulb and epithelium.
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Affiliation(s)
- Tarek Shaker
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Health Sciences Centre, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
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19
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Berghard A, Hägglund AC, Bohm S, Carlsson L. Lhx2-dependent specification of olfactory sensory neurons is required for successful integration of olfactory, vomeronasal, and GnRH neurons. FASEB J 2012; 26:3464-72. [PMID: 22581782 DOI: 10.1096/fj.12-206193] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Inactivation of the LIM-homeodomain 2 gene (Lhx2) results in a severe defect in specification of olfactory sensory neurons (OSNs). However, the ramifications of lack of Lhx2-dependent OSN specification for formation of the primary olfactory pathway have not been addressed, since mutant mice die in utero. We have analyzed prenatal and postnatal consequences of conditionally inactivating Lhx2 selectively in OSNs. A cell-autonomous effect is that OSN axons cannot innervate their target, the olfactory bulb. Moreover, the lack of Lhx2 in OSNs causes unpredicted, non-cell-autonomous phenotypes. First, the olfactory bulb shows pronounced hypoplasia in adults, and the data suggest that innervation by correctly specified OSNs is necessary for adult bulb size and organization. Second, absence of an olfactory nerve in the conditional mutant reveals that the vomeronasal nerve is dependent on olfactory nerve formation. Third, the lack of a proper vomeronasal nerve prevents migration of gonadotropin-releasing hormone (GnRH) cells the whole distance to their final positions in the hypothalamus during embryo development. As adults, the conditional mutants do not pass puberty, and these findings support the view of an exclusive nasal origin of GnRH neurons in the mouse. Thus, Lhx2 in OSNs is required for functional development of three separate systems.
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Affiliation(s)
- Anna Berghard
- Department of Molecular Biology, Byggn 6L, Umea University, SE90187 Umeå, Sweden.
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20
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Abstract
Vertebrate eyes begin as a small patch of cells at the most anterior end of the early brain called the eye field. If these cells are removed from an amphibian embryo, the eyes do not form. If the eye field is transplanted to another location on the embryo or cultured in a dish, it forms eyes. These simple cut and paste experiments were performed at the beginning of the last century and helped to define the embryonic origin of the vertebrate eye. The genes necessary for eye field specification and eventual eye formation, by contrast, have only recently been identified. These genes and the molecular mechanisms regulating the initial formation of the Xenopus laevis eye field are the subjects of this review.
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Affiliation(s)
- Michael E Zuber
- Center for Vision Research, SUNY Eye Institute, Departments of Ophthalmology and Biochemistry & Molecular Biology, Upstate Medical University, Syracuse, New York, USA
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21
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de Castro F. Wiring Olfaction: The Cellular and Molecular Mechanisms that Guide the Development of Synaptic Connections from the Nose to the Cortex. Front Neurosci 2009; 3:52. [PMID: 20582279 PMCID: PMC2858608 DOI: 10.3389/neuro.22.004.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 11/04/2009] [Indexed: 12/27/2022] Open
Abstract
Within the central nervous system, the olfactory system fascinates by its developmental and physiological particularities, and is one of the most studied models to understand the mechanisms underlying the guidance of growing axons to their appropriate targets. A constellation of contact-mediated (laminins, CAMs, ephrins, etc.) and secreted mechanisms (semaphorins, slits, growth factors, etc.) are known to play different roles in the establishment of synaptic interactions between the olfactory epithelium, olfactory bulb (OB) and olfactory cortex. Specific mechanisms of this system (including the amazing family of about 1000 different olfactory receptors) have been also proposed. In the last years, different reviews have focused in partial sights, specially in the mechanisms involved in the formation of the olfactory nerve, but a detailed review of the mechanisms implicated in the development of the connections among the different olfactory structures (olfactory epithelium, OB, olfactory cortex) remains to be written. In the present work, we afford this systematic review: the different cellular and molecular mechanisms which rule the formation of the olfactory nerve, the lateral olfactory tract and the intracortical connections, as well as the few data available regarding the accessory olfactory system. These mechanisms are compared, and the implications of the differences and similarities discussed in this fundamental scenario of ontogeny.
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Affiliation(s)
- Fernando de Castro
- Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos Toledo, Spain
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22
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Zhao Y, Mailloux CM, Hermesz E, Palkóvits M, Westphal H. A role of the LIM-homeobox gene Lhx2 in the regulation of pituitary development. Dev Biol 2009; 337:313-23. [PMID: 19900438 DOI: 10.1016/j.ydbio.2009.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Revised: 10/29/2009] [Accepted: 11/02/2009] [Indexed: 11/24/2022]
Abstract
The mammalian pituitary gland originates from two separate germinal tissues during embryonic development. The anterior and intermediate lobes of the pituitary are derived from Rathke's pouch, a pocket formed by an invagination of the oral ectoderm. The posterior lobe is derived from the infundibulum, which is formed by evagination of the neuroectoderm in the ventral diencephalon. Previous studies have shown that development of Rathke's pouch and the generation of distinct populations of hormone-producing endocrine cell lineages in the anterior/intermediate pituitary lobes is regulated by a number of transcription factors expressed in the pouch and by inductive signals from the ventral diencephalon/infundibulum. However, little is known about factors that regulate the development of the posterior pituitary lobe. In this study, we show that the LIM-homeobox gene Lhx2 is extensively expressed in the developing ventral diencephalon, including the infundibulum and the posterior lobe of the pituitary. Deletion of Lhx2 gene results in persistent cell proliferation, a complete failure of evagination of the neuroectoderm in the ventral diencephalon, and defects in the formation of the distinct morphological features of the infundibulum and the posterior pituitary lobe. Rathke's pouch is formed and endocrine cell lineages are generated in the anterior/intermediate pituitary lobes of the Lhx2 mutant. However, the shape and organization of the pouch and the anterior/intermediate pituitary lobes are severely altered due to the defects in development of the infundibulum and the posterior lobe. Our study thus reveals an essential role for Lhx2 in the regulation of posterior pituitary development and suggests a mechanism whereby development of the posterior lobe may affect the development of the anterior and intermediate lobes of the pituitary gland.
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Affiliation(s)
- Yangu Zhao
- Laboratory of Mammalian Genes and Development, Program on Genomics of Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA
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Abstract
Neurons acquire their molecular, neurochemical, and connectional features during development as a result of complex regulatory mechanisms. Here, we show that a ubiquitous, multifunctional protein cofactor, Chip, plays a critical role in a set of neurons in Drosophila that control the well described posteclosion behavior. Newly eclosed flies normally expand their wings and display tanning and hardening of their cuticle. Using multiple approaches to interfere with Chip function, we find that these processes do not occur without normal activity of this protein. Furthermore, we identified the nature of the deficit to be an absence of Bursicon in the hemolymph of newly eclosed flies, whereas the responsivity to Bursicon in these flies remains normal. Chip interacts with transcription factors of the LIM-HD (LIM-homeodomain) family, and we identified one member, dIslet, as a potential partner of Chip in this process. Our findings provide the first evidence of transcriptional mechanisms involved in the development of the neuronal circuit that regulates posteclosion behavior in Drosophila.
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Wilson SI, Shafer B, Lee KJ, Dodd J. A molecular program for contralateral trajectory: Rig-1 control by LIM homeodomain transcription factors. Neuron 2008; 59:413-24. [PMID: 18701067 DOI: 10.1016/j.neuron.2008.07.020] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 06/03/2008] [Accepted: 07/14/2008] [Indexed: 12/21/2022]
Abstract
Despite increasing evidence for transcriptional control of neural connectivity, how transcription factors regulate discrete steps in axon guidance remains obscure. Projection neurons in the dorsal spinal cord relay sensory signals to higher brain centers. Some projection neurons send their axons ipsilaterally, whereas others, commissural neurons, send axons contralaterally. We show that two closely related LIM homeodomain proteins, Lhx2 and Lhx9, are expressed by a set of commissural relay neurons (dI1c neurons) and are required for the dI1c axon projection. Midline crossing by dI1c axons is lost in Lhx2/9 double mutants, a defect that results from loss of expression of Rig-1 from dI1c axons. Lhx2 binds to a conserved motif in the Rig-1 gene, suggesting that Lhx2/9 regulate directly the expression of Rig-1. Our findings reveal a link between the transcriptional programs that define neuronal subtype identity and the expression of receptors that guide distinctive aspects of their trajectory.
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Affiliation(s)
- Sara I Wilson
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
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Semaphorin 3F confines ventral tangential migration of lateral olfactory tract neurons onto the telencephalon surface. J Neurosci 2008; 28:4414-22. [PMID: 18434520 DOI: 10.1523/jneurosci.0372-08.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Ventral tangential migration of neurons is the most prominent mode of neuronal translocation during earliest neurogenesis in the mouse telencephalon. A typical example of the neurons that adopt this migration mode is guidepost neurons in the lateral olfactory tract designated as lot cells. These neurons are generated from the neocortical neuroepithelium and migrate tangentially down to the ventral edge of the neocortex abutting the ganglionic eminence, on which the future lateral olfactory tract develops. We show here that this migration stream is repelled by a secreted axon guidance molecule, semaphorin 3F through interaction with its specific receptor, neuropilin-2. Accordingly, in mutant mice for semaphorin 3F or neuropilin-2, lot cells ectopically penetrated into the deep brain domain, which normally expresses semaphorin 3F. These results reveal that semaphorin 3F is an important regulator of the ventral tangential migration stream, confining the migrating neurons on the telencephalon surface by repelling from the deeper domain.
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