101
|
Wang JW, Stifani S. Roles of Runx Genes in Nervous System Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 962:103-116. [PMID: 28299654 DOI: 10.1007/978-981-10-3233-2_8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Runt-related (Runx) transcription factors play essential roles during development and adult tissue homeostasis and are responsible for several human diseases. They regulate a variety of biological mechanisms in numerous cell lineages. Recent years have seen significant progress in our understanding of the functions performed by Runx proteins in the developing and postnatal mammalian nervous system. In both central and peripheral nervous systems, Runx1 and Runx3 display remarkably specific expression in mostly non-overlapping groups of postmitotic neurons. In the central nervous system, Runx1 is involved in the development of selected motor neurons controlling neural circuits mediating vital functions such as chewing, swallowing, breathing, and locomotion. In the peripheral nervous system, Runx1 and Runx3 play essential roles during the development of sensory neurons involved in circuits mediating pain, itch, thermal sensation and sense of relative position. Runx1 and Runx3 orchestrate complex gene expression programs controlling neuronal subtype specification and axonal connectivity. Runx1 is also important in the olfactory system, where it regulates the progenitor-to-neuron transition in undifferentiated neural progenitor cells in the olfactory epithelium as well as the proliferation and developmental maturation of specific glial cells termed olfactory ensheathing cells. Moreover, upregulated Runx expression is associated with brain injury and disease. Increasing knowledge of the functions of Runx proteins in the developing and postnatal nervous system is therefore expected to improve our understanding of nervous system development, homeostasis and disease.
Collapse
Affiliation(s)
- Jae Woong Wang
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, QC, H3A2B4, Canada
| | - Stefano Stifani
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, QC, H3A2B4, Canada.
| |
Collapse
|
102
|
New Insights Into the Roles of Retinoic Acid Signaling in Nervous System Development and the Establishment of Neurotransmitter Systems. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 330:1-84. [PMID: 28215529 DOI: 10.1016/bs.ircmb.2016.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Secreted chiefly from the underlying mesoderm, the morphogen retinoic acid (RA) is well known to contribute to the specification, patterning, and differentiation of neural progenitors in the developing vertebrate nervous system. Furthermore, RA influences the subtype identity and neurotransmitter phenotype of subsets of maturing neurons, although relatively little is known about how these functions are mediated. This review provides a comprehensive overview of the roles played by RA signaling during the formation of the central and peripheral nervous systems of vertebrates and highlights its effects on the differentiation of several neurotransmitter systems. In addition, the evolutionary history of the RA signaling system is discussed, revealing both conserved properties and alternate modes of RA action. It is proposed that comparative approaches should be employed systematically to expand our knowledge of the context-dependent cellular mechanisms controlled by the multifunctional signaling molecule RA.
Collapse
|
103
|
Hessinger C, Technau GM, Rogulja-Ortmann A. The Drosophila Hox gene Ultrabithorax acts in both muscles and motoneurons to orchestrate formation of specific neuromuscular connections. Development 2016; 144:139-150. [PMID: 27913640 PMCID: PMC5278631 DOI: 10.1242/dev.143875] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/17/2016] [Indexed: 12/29/2022]
Abstract
Hox genes are known to specify motoneuron pools in the developing vertebrate spinal cord and to control motoneuronal targeting in several species. However, the mechanisms controlling axial diversification of muscle innervation patterns are still largely unknown. We present data showing that the Drosophila Hox gene Ultrabithorax (Ubx) acts in the late embryo to establish target specificity of ventrally projecting RP motoneurons. In abdominal segments A2 to A7, RP motoneurons innervate the ventrolateral muscles VL1-4, with VL1 and VL2 being innervated in a Wnt4-dependent manner. In Ubx mutants, these motoneurons fail to make correct contacts with muscle VL1, a phenotype partially resembling that of the Wnt4 mutant. We show that Ubx regulates expression of Wnt4 in muscle VL2 and that it interacts with the Wnt4 response pathway in the respective motoneurons. Ubx thus orchestrates the interaction between two cell types, muscles and motoneurons, to regulate establishment of the ventrolateral neuromuscular network. Summary: Ultrabithorax controls correct innervation of ventrolateral muscles by coordinating Wnt4 ligand expression in muscles with the signalling pathway response in motoneurons.
Collapse
|
104
|
Cortical interneuron specification: the juncture of genes, time and geometry. Curr Opin Neurobiol 2016; 42:17-24. [PMID: 27889625 DOI: 10.1016/j.conb.2016.10.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/20/2016] [Accepted: 10/28/2016] [Indexed: 01/23/2023]
Abstract
A fundamental question in developmental neuroscience is how hundreds of diverse cell types are generated to form specialized brain regions. The ganglionic eminences (GEs) are embryonic brain structures located in the ventral telencephalon that produce many inhibitory GABA (γ-Aminobutyric acid)-ergic cell types, including long-range projection neurons and local interneurons (INs), which disperse widely throughout the brain. While much has been discovered about the origin and wiring of these cells, a major question remains: how do neurons originating in the GEs become specified during development as one differentiated subtype versus another? This review will cover recent work that has advanced our knowledge of the mechanisms governing cortical interneuron subtype specification, particularly progenitors' spatial origin, birthdates, lineage, and mode of division.
Collapse
|
105
|
Campbell RF, Walthall WW. Meis/UNC-62 isoform dependent regulation of CoupTF-II/UNC-55 and GABAergic motor neuron subtype differentiation. Dev Biol 2016; 419:250-261. [PMID: 27634571 DOI: 10.1016/j.ydbio.2016.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 08/24/2016] [Accepted: 09/09/2016] [Indexed: 11/28/2022]
Abstract
Gene regulatory networks orchestrate the assembly of functionally related cells within a cellular network. Subtle differences often exist among functionally related cells within such networks. How differences are created among cells with similar functions has been difficult to determine due to the complexity of both the gene and the cellular networks. In Caenorhabditis elegans, the DD and VD motor neurons compose a cross-inhibitory, GABAergic network that coordinates dorsal and ventral muscle contractions during locomotion. The Pitx2 homologue, UNC-30, acts as a terminal selector gene to create similarities and the Coup-TFII homologue, UNC-55, is necessary for creating differences between the two motor neuron classes. What is the organizing gene regulatory network responsible for initiating the expression of UNC-55 and thus creating differences between the DD and VD motor neurons? We show that the unc-55 promoter has modules that contain Meis/UNC-62 binding sites. These sites can be subdivided into regions that are capable of activating or repressing UNC-55 expression in different motor neurons. Interestingly, different isoforms of UNC-62 are responsible for the activation and the stabilization of unc-55 transcription. Furthermore, specific isoforms of UNC-62 are required for proper synaptic patterning of the VD motor neurons. Isoform specific regulation of differentiating neurons is a relatively unexplored area of research and presents a mechanism for creating differences among functionally related cells within a network.
Collapse
MESH Headings
- Animals
- Animals, Genetically Modified
- CRISPR-Cas Systems
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans/physiology
- Caenorhabditis elegans Proteins/biosynthesis
- Caenorhabditis elegans Proteins/physiology
- GABAergic Neurons/cytology
- Gene Expression Regulation, Developmental
- Gene Regulatory Networks/genetics
- Genes, Reporter
- Homeodomain Proteins/physiology
- Motor Neurons/classification
- Motor Neurons/cytology
- Neurogenesis/genetics
- Promoter Regions, Genetic/genetics
- Protein Isoforms/physiology
- RNA, Helminth/biosynthesis
- RNA, Helminth/genetics
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/physiology
- Receptors, Cytoplasmic and Nuclear/biosynthesis
- Receptors, Cytoplasmic and Nuclear/physiology
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Transcription Factors
- Transcription, Genetic/genetics
- RNA, Guide, CRISPR-Cas Systems
Collapse
Affiliation(s)
- Richard F Campbell
- Department of Biology, Georgia State University, Atlanta, GA 30303, United States
| | - Walter W Walthall
- Department of Biology, Georgia State University, Atlanta, GA 30303, United States.
| |
Collapse
|
106
|
Abstract
Restless legs syndrome (RLS) is a complex disorder that involves sensory and motor systems. The major pathophysiology of RLS is low iron concentration in the substantia nigra containing the cell bodies of dopamine neurons that project to the striatum, an area that is crucial for modulating movement. People who have RLS often present with normal iron values outside the brain; recent studies implicate several genes are involved in the syndrome. Like most complex diseases, animal models usually do not faithfully capture the full phenotypic spectrum of "disease," which is a uniquely human construct. Nonetheless, animal models have proven useful in helping to unravel the complex pathophysiology of diseases such as RLS and suggesting novel treatment paradigms. For example, hypothesis-independent genome-wide association studies (GWAS) have identified several genes as increasing the risk for RLS, including BTBD9. Independently, the murine homolog Btbd9 was identified as a candidate gene for iron regulation in the midbrain in mice. The relevance of the phenotype of another of the GWAS identified genes, MEIS1, has also been explored. The role of Btbd9 in iron regulation and RLS-like behaviors has been further evaluated in mice carrying a null mutation of the gene and in fruit flies when the BTBD9 protein is degraded. The BTBD9 and MEIS1 stories originate from human GWAS research, supported by work in a genetic reference population of mice (forward genetics) and further verified in mice, fish flies, and worms. Finally, the role of genetics is further supported by an inbred mouse strain that displays many of the phenotypic characteristics of RLS. The role of animal models of RLS phenotypes is also extended to include periodic limb movements.
Collapse
|
107
|
Mitchelle A, Watson C. The organization of spinal motor neurons in a monotreme is consistent with a six-region schema of the mammalian spinal cord. J Anat 2016; 229:394-405. [PMID: 27173752 PMCID: PMC4974545 DOI: 10.1111/joa.12492] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2016] [Indexed: 01/13/2023] Open
Abstract
The motor neurons in the spinal cord of an echidna (Tachyglossus aculeatus) have been mapped in Nissl-stained sections from spinal cord segments defined by spinal nerve anatomy. A medial motor column of motor neurons is found at all spinal cord levels, and a hypaxial column is found at most levels. The organization of the motor neuron clusters in the lateral motor column of the brachial (C5 to T3) and crural (L2 to S3) limb enlargements is very similar to the pattern previously revealed by retrograde tracing in placental mammals, and the motor neuron clusters have been tentatively identified according to the muscle groups they are likely to supply. The region separating the two limb enlargements (T4 to L1) contains preganglionic motor neurons that appear to represent the spinal sympathetic outflow. Immediately caudal to the crural limb enlargement is a short column of preganglionic motor neurons (S3 to S4), which it is believed represents the pelvic parasympathetic outflow. The rostral and caudal ends of the spinal cord contain neither a lateral motor column nor a preganglionic column. Branchial motor neurons (which are believed to supply the sternomastoid and trapezius muscles) are present at the lateral margin of the ventral horn in rostral cervical segments (C2-C4). These same segments contain the phrenic nucleus, which belongs to the hypaxial column. The presence or absence of the main spinal motor neuron columns in the different regions echidna spinal cord (and also in that of other amniote vertebrates) provides a basis for dividing the spinal cord into six main regions - prebrachial, brachial, postbrachial, crural, postcrural and caudal. The considerable biological and functional significance of this subdivision pattern is supported by recent studies on spinal cord hox gene expression in chicks and mice. On the other hand, the familiar 'segments' of the spinal cord are defined only by the anatomy of adjacent vertebrae, and are not demarcated by intrinsic gene expression. The recognition of segments defined by vertebrae (somites) is obviously of great value in defining topography, but the emphasis on such segments obscures the underlying evolutionary reality of a spinal cord comprised of six genetically defined regions. The six-region system can be usefully applied to the spinal cord of any amniote (and probably most anurans), independent of the number of vertebral segments in each part of the spinal column.
Collapse
Affiliation(s)
- Amer Mitchelle
- Faculty of MedicineNotre Dame UniversityPerthWAAustralia
| | - Charles Watson
- Faculty of Health SciencesCurtin UniversityPerthWAAustralia
| |
Collapse
|
108
|
Ciau-Uitz A, Patient R. The embryonic origins and genetic programming of emerging haematopoietic stem cells. FEBS Lett 2016; 590:4002-4015. [PMID: 27531714 DOI: 10.1002/1873-3468.12363] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 07/26/2016] [Accepted: 08/12/2016] [Indexed: 11/10/2022]
Abstract
Haematopoietic stem cells (HSCs) emerge from the haemogenic endothelium (HE) localised in the ventral wall of the embryonic dorsal aorta (DA). The HE generates HSCs through a process known as the endothelial to haematopoietic transition (EHT), which has been visualised in live embryos and is currently under intense study. However, EHT is the culmination of multiple programming events, which are as yet poorly understood, that take place before the specification of HE. A number of haematopoietic precursor cells have been described before the emergence of definitive HSCs, but only one haematovascular progenitor, the definitive haemangioblast (DH), gives rise to the DA, HE and HSCs. DHs emerge in the lateral plate mesoderm (LPM) and have a distinct origin and genetic programme compared to other, previously described haematovascular progenitors. Although DHs have so far only been established in Xenopus embryos, evidence for their existence in the LPM of mouse and chicken embryos is discussed here. We also review the current knowledge of the origins, lineage relationships, genetic programming and differentiation of the DHs that leads to the generation of HSCs. Importantly, we discuss the significance of the gene regulatory network (GRN) that controls the programming of DHs, a better understanding of which may aid in the establishment of protocols for the de novo generation of HSCs in vitro.
Collapse
Affiliation(s)
- Aldo Ciau-Uitz
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, UK
| | - Roger Patient
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, UK
| |
Collapse
|
109
|
Hanley O, Zewdu R, Cohen LJ, Jung H, Lacombe J, Philippidou P, Lee DH, Selleri L, Dasen JS. Parallel Pbx-Dependent Pathways Govern the Coalescence and Fate of Motor Columns. Neuron 2016; 91:1005-1020. [PMID: 27568519 DOI: 10.1016/j.neuron.2016.07.043] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 06/20/2016] [Accepted: 07/14/2016] [Indexed: 01/08/2023]
Abstract
The clustering of neurons sharing similar functional properties and connectivity is a common organizational feature of vertebrate nervous systems. Within motor networks, spinal motor neurons (MNs) segregate into longitudinally arrayed subtypes, establishing a central somatotopic map of peripheral target innervation. MN organization and connectivity relies on Hox transcription factors expressed along the rostrocaudal axis; however, the developmental mechanisms governing the orderly arrangement of MNs are largely unknown. We show that Pbx genes, which encode Hox cofactors, are essential for the segregation and clustering of neurons within motor columns. In the absence of Pbx1 and Pbx3 function, Hox-dependent programs are lost and the remaining MN subtypes are unclustered and disordered. Identification of Pbx gene targets revealed an unexpected and apparently Hox-independent role in defining molecular features of dorsally projecting medial motor column (MMC) neurons. These results indicate Pbx genes act in parallel genetic pathways to orchestrate neuronal subtype differentiation, connectivity, and organization.
Collapse
Affiliation(s)
- Olivia Hanley
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Rediet Zewdu
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Lisa J Cohen
- Genome Technology Center, NYU Langone Medical Center, 550 First Avenue, New York, NY 10016, USA
| | - Heekyung Jung
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Julie Lacombe
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Polyxeni Philippidou
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - David H Lee
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Licia Selleri
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Jeremy S Dasen
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
110
|
Modeling ALS with motor neurons derived from human induced pluripotent stem cells. Nat Neurosci 2016; 19:542-53. [PMID: 27021939 DOI: 10.1038/nn.4273] [Citation(s) in RCA: 185] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 02/22/2016] [Indexed: 02/08/2023]
Abstract
Directing the differentiation of induced pluripotent stem cells into motor neurons has allowed investigators to develop new models of amyotrophic lateral sclerosis (ALS). However, techniques vary between laboratories and the cells do not appear to mature into fully functional adult motor neurons. Here we discuss common developmental principles of both lower and upper motor neuron development that have led to specific derivation techniques. We then suggest how these motor neurons may be matured further either through direct expression or administration of specific factors or coculture approaches with other tissues. Ultimately, through a greater understanding of motor neuron biology, it will be possible to establish more reliable models of ALS. These in turn will have a greater chance of validating new drugs that may be effective for the disease.
Collapse
|
111
|
Laser capture microscopy coupled with Smart-seq2 for precise spatial transcriptomic profiling. Nat Commun 2016; 7:12139. [PMID: 27387371 PMCID: PMC4941116 DOI: 10.1038/ncomms12139] [Citation(s) in RCA: 195] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 06/05/2016] [Indexed: 01/05/2023] Open
Abstract
Laser capture microscopy (LCM) coupled with global transcriptome profiling could enable precise analyses of cell populations without the need for tissue dissociation, but has so far required relatively large numbers of cells. Here we report a robust and highly efficient strategy for LCM coupled with full-length mRNA-sequencing (LCM-seq) developed for single-cell transcriptomics. Fixed cells are subjected to direct lysis without RNA extraction, which both simplifies the experimental procedures as well as lowers technical noise. We apply LCM-seq on neurons isolated from mouse tissues, human post-mortem tissues, and illustrate its utility down to single captured cells. Importantly, we demonstrate that LCM-seq can provide biological insight on highly similar neuronal populations, including motor neurons isolated from different levels of the mouse spinal cord, as well as human midbrain dopamine neurons of the substantia nigra compacta and the ventral tegmental area. Laser capture microscopy (LCM) coupled with global transcriptome profiling requires relatively large numbers of cells. Here, the authors show that LCM coupled with full-length mRNA-sequencing (LCM-seq) can sequence single cells, and that LCM-seq can provide biological insight on highly similar neuronal populations.
Collapse
|
112
|
Partridge EC, Watkins TA, Mendenhall EM. Every transcription factor deserves its map: Scaling up epitope tagging of proteins to bypass antibody problems. Bioessays 2016; 38:801-11. [PMID: 27311628 DOI: 10.1002/bies.201600028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Genome-wide identification of transcription factor binding sites with the ChIP-seq method is an extremely important scientific endeavor - one that should ideally be performed for every transcription factor in as many cell types as possible. A major hurdle on the way to this goal is the necessity for a specific, ChIP-grade antibody for each transcription factor of interest, which is often not available. Here, we describe CETCh-seq, a recently published method utilizing genome engineering with the CRISPR/Cas9 system to circumvent the need for a specific antibody. Using the CETCh-seq method, targeted genomic editing results in an epitope-tagged transcription factor, which is recognized by a well-characterized, standard antibody, efficacious for ChIP-seq. We have used CETCh-seq in human cancer cell lines as well as mouse embryonic stem cells. We find that roughly 60% of transcription factors tagged using CETCh-seq produce a high quality ChIP-seq map, a significant improvement over traditional antibody-based methods.
Collapse
Affiliation(s)
| | | | - Eric M Mendenhall
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA.,University of Alabama in Huntsville, AL, USA
| |
Collapse
|
113
|
Poliak S, Norovich AL, Yamagata M, Sanes JR, Jessell TM. Muscle-type Identity of Proprioceptors Specified by Spatially Restricted Signals from Limb Mesenchyme. Cell 2016; 164:512-25. [PMID: 26824659 DOI: 10.1016/j.cell.2015.12.049] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Revised: 11/18/2015] [Accepted: 12/22/2015] [Indexed: 11/20/2022]
Abstract
The selectivity with which proprioceptive sensory neurons innervate their central and peripheral targets implies that they exhibit distinctions in muscle-type identity. The molecular correlates of proprioceptor identity and its origins remain largely unknown, however. In screens to define muscle-type proprioceptor character, we find all-or-none differences in gene expression for proprioceptors that control antagonistic muscles at a single hindlimb joint. Analysis of three of these genes, cadherin13 (cdh13), semaphorin5a (sema5a), and cartilage-acidic protein-1 (crtac1), reveals expression in proprioceptor subsets that supply muscle groups located at restricted dorsoventral and proximodistal domains of the limb. Genetically altering the dorsoventral character of the limb mesenchyme elicits a change in the profile of proprioceptor cdh13, sema5a, and crtac1 expression. These findings indicate that proprioceptors acquire aspects of their muscle-type identity in response to mesenchymal signals expressed in restricted proximodistal and dorsoventral domains of the developing limb.
Collapse
Affiliation(s)
- Sebastian Poliak
- Department of Neuroscience, Biochemistry, and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Amy L Norovich
- Department of Biological Sciences, Columbia University, New York, NY 10032, USA
| | - Masahito Yamagata
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Thomas M Jessell
- Department of Neuroscience, Biochemistry, and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA.
| |
Collapse
|
114
|
Leijnse JN, D'Herde K. Revisiting the segmental organization of the human spinal cord. J Anat 2016; 229:384-93. [PMID: 27173936 DOI: 10.1111/joa.12493] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2016] [Indexed: 11/30/2022] Open
Abstract
In classic anatomic atlases, the spinal cord is standardly represented in its anatomical form with symmetrically emerging anterior and posterior roots, which at the level of the intervertebral foramen combine into the spinal nerves. The parts of the cord delimited by the boundaries of the roots are called segments or myelomeres. Associated with their regular repetitive appearance is the notion that the cord is segmentally organized. This segmental view is reinforced by clinical practice. Spinal cord roots innervate specific body parts. The level of cord trauma is diagnosed by the de-innervation symptoms of these parts. However, systemically, the case for a segmentally organized cord is not so clear. To date, developmental and genetic research points to a regionally rather than a segmentally organized cord. In the present study, to what degree the fila radicularia are segmentally implanted along the cord was investigated. The research hypothesis was that if the fila radicularia were non-segmentally implanted at the cord surface, it would be unlikely that the internal neuron stratum would be segmented. The visual segmented aspect of the myelomeres would then be the consequence of the necessary bundling of axons towards the vertebral foramen as the only exits of the vertebral canal, rather than of an underlying segment organization of the cord itself. To investigate the research hypothesis, the fila radicularia in the cervical-upper thoracic part of five spinal cords were detached from their spinal nerves and dissected in detail. The principal research question was if the fila radicularia are separated from their spinal nerves and dissected from their connective tissues up to the cord, would it be possible to reconstruct the original spinal segments from the morphology and interspaces of the fila? The dissections revealed that the anterior fila radicularia emerge from the cord at regular regionally modulated interspaces without systematic segmental delineations. The posterior fila radicularia are somewhat more segmentally implanted, but the pattern is individually inconsistent. The posterior and anterior roots have notable morphological differences, and hypotheses are presented to help explain these. The macroscopic observations are consistent with a regionally but not a segmentally organized cord. This conclusion was visually summarized in photographs of spinal cords with ipsilateral intact roots and contralateral individually dissected fila radicularia. It was suggested that this dual view of the spinal cord be added to the standard anatomic textbooks to counterbalance the current possibly biased view of a segmented cord.
Collapse
Affiliation(s)
- J N Leijnse
- Department of Anatomy and Embryology, University of Ghent, Ghent, Belgium
| | - K D'Herde
- Department of Anatomy and Embryology, University of Ghent, Ghent, Belgium
| |
Collapse
|
115
|
Tung YT, Lu YL, Peng KC, Yen YP, Chang M, Li J, Jung H, Thams S, Huang YP, Hung JH, Chen JA. Mir-17∼92 Governs Motor Neuron Subtype Survival by Mediating Nuclear PTEN. Cell Rep 2016; 11:1305-18. [PMID: 26004179 DOI: 10.1016/j.celrep.2015.04.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 03/17/2015] [Accepted: 04/22/2015] [Indexed: 01/07/2023] Open
Abstract
Motor neurons (MNs) are unique because they project their axons outside of the CNS to innervate the peripheral muscles. Limb-innervating lateral motor column MNs (LMC-MNs) travel substantially to innervate distal limb mesenchyme. How LMC-MNs fine-tune the balance between survival and apoptosis while wiring the sensorimotor circuit en route remains unclear. Here, we show that the mir-17∼92 cluster is enriched in embryonic stem cell (ESC)-derived LMC-MNs and that conditional mir-17∼92 deletion in MNs results in the death of LMC-MNs in vitro and in vivo. mir-17∼92 overexpression rescues MNs from apoptosis, which occurs spontaneously during embryonic development. PTEN is a primary target of mir-17∼92 responsible for LMC-MN degeneration. Additionally, mir-17∼92 directly targets components of E3 ubiquitin ligases, affecting PTEN subcellular localization through monoubiquitination. This miRNA-mediated regulation modulates both target expression and target subcellular localization, providing LMC-MNs with an intricate defensive mechanism that controls their survival.
Collapse
|
116
|
Gabitto MI, Pakman A, Bikoff JB, Abbott LF, Jessell TM, Paninski L. Bayesian Sparse Regression Analysis Documents the Diversity of Spinal Inhibitory Interneurons. Cell 2016; 165:220-233. [PMID: 26949187 DOI: 10.1016/j.cell.2016.01.026] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/30/2015] [Accepted: 01/15/2016] [Indexed: 12/14/2022]
Abstract
Documenting the extent of cellular diversity is a critical step in defining the functional organization of tissues and organs. To infer cell-type diversity from partial or incomplete transcription factor expression data, we devised a sparse Bayesian framework that is able to handle estimation uncertainty and can incorporate diverse cellular characteristics to optimize experimental design. Focusing on spinal V1 inhibitory interneurons, for which the spatial expression of 19 transcription factors has been mapped, we infer the existence of ~50 candidate V1 neuronal types, many of which localize in compact spatial domains in the ventral spinal cord. We have validated the existence of inferred cell types by direct experimental measurement, establishing this Bayesian framework as an effective platform for cell-type characterization in the nervous system and elsewhere.
Collapse
Affiliation(s)
- Mariano I Gabitto
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA.
| | - Ari Pakman
- Department of Statistics and Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA
| | - Jay B Bikoff
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - L F Abbott
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Thomas M Jessell
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Liam Paninski
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Statistics and Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
117
|
Catela C, Shin MM, Lee DH, Liu JP, Dasen JS. Hox Proteins Coordinate Motor Neuron Differentiation and Connectivity Programs through Ret/Gfrα Genes. Cell Rep 2016; 14:1901-15. [PMID: 26904955 DOI: 10.1016/j.celrep.2016.01.067] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 12/07/2015] [Accepted: 01/21/2016] [Indexed: 11/25/2022] Open
Abstract
The accuracy of neural circuit assembly relies on the precise spatial and temporal control of synaptic specificity determinants during development. Hox transcription factors govern key aspects of motor neuron (MN) differentiation; however, the terminal effectors of their actions are largely unknown. We show that Hox/Hox cofactor interactions coordinate MN subtype diversification and connectivity through Ret/Gfrα receptor genes. Hox and Meis proteins determine the levels of Ret in MNs and define the intrasegmental profiles of Gfrα1 and Gfrα3 expression. Loss of Ret or Gfrα3 leads to MN specification and innervation defects similar to those observed in Hox mutants, while expression of Ret and Gfrα1 can bypass the requirement for Hox genes during MN pool differentiation. These studies indicate that Hox proteins contribute to neuronal fate and muscle connectivity through controlling the levels and pattern of cell surface receptor expression, consequently gating the ability of MNs to respond to limb-derived instructive cues.
Collapse
Affiliation(s)
- Catarina Catela
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Maggie M Shin
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - David H Lee
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Jeh-Ping Liu
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Jeremy S Dasen
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
118
|
Zheng C, Diaz-Cuadros M, Chalfie M. Hox Genes Promote Neuronal Subtype Diversification through Posterior Induction in Caenorhabditis elegans. Neuron 2016; 88:514-27. [PMID: 26539892 DOI: 10.1016/j.neuron.2015.09.049] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 08/05/2015] [Accepted: 09/19/2015] [Indexed: 10/22/2022]
Abstract
Although Hox genes specify the differentiation of neuronal subtypes along the anterior-posterior axis, their mode of action is not entirely understood. Using two subtypes of the touch receptor neurons (TRNs) in C. elegans, we found that a "posterior induction" mechanism underlies the Hox control of terminal neuronal differentiation. The anterior subtype maintains a default TRN state, whereas the posterior subtype undergoes further morphological and transcriptional specification induced by the posterior Hox proteins, mainly EGL-5/Abd-B. Misexpression of the posterior Hox proteins transformed the anterior TRN subtype toward a posterior identity both morphologically and genetically. The specification of the posterior subtype requires EGL-5-induced repression of TALE cofactors, which antagonize EGL-5 functions, and the activation of rfip-1, a component of recycling endosomes, which mediates Hox activities by promoting subtype-specific neurite outgrowth. Finally, EGL-5 is required for subtype-specific circuit formation by acting in both the sensory neuron and downstream interneuron to promote functional connectivity.
Collapse
Affiliation(s)
- Chaogu Zheng
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | | - Martin Chalfie
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
119
|
Abstract
Transcription factors control neuronal differentiation by acting as "terminal selectors" that determine the specific cell fates of different types of neurons. The specification of cell fate, however, requires high fidelity, which relies on stable and robust expression of the terminal selectors. Our recent studies in C. elegans suggest that a second set of transcription factors function as reinforcing or protecting factors to stabilize the expression and activity of terminal selectors. Some serve as "guarantors" to ensure the activation and continuous expression of the selectors by reducing stochastic fluctuations in gene expression; others safeguard the protein function of selectors by repressing inhibitors that would block their activity. These transcription factors, unlike the terminal selectors, do not induce specification but secure neuronal cell fate and provide reliability in differentiation.
Collapse
|
120
|
|
121
|
Generating Diverse Spinal Motor Neuron Subtypes from Human Pluripotent Stem Cells. Stem Cells Int 2015; 2016:1036974. [PMID: 26823667 PMCID: PMC4707335 DOI: 10.1155/2016/1036974] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 09/14/2015] [Indexed: 12/18/2022] Open
Abstract
Resolving the mechanisms underlying human neuronal diversification remains a major challenge in developmental and applied neurobiology. Motor neurons (MNs) represent a diverse pool of neuronal subtypes exhibiting differential vulnerability in different human neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). The ability to predictably manipulate MN subtype lineage restriction from human pluripotent stem cells (PSCs) will form the essential basis to establishing accurate, clinically relevant in vitro disease models. I first overview motor neuron developmental biology to provide some context for reviewing recent studies interrogating pathways that influence the generation of MN diversity. I conclude that motor neurogenesis from PSCs provides a powerful reductionist model system to gain insight into the developmental logic of MN subtype diversification and serves more broadly as a leading exemplar of potential strategies to resolve the molecular basis of neuronal subclass differentiation within the nervous system. These studies will in turn permit greater mechanistic understanding of differential MN subtype vulnerability using in vitro human disease models.
Collapse
|
122
|
Transcriptional regulation of mouse hypoglossal motor neuron somatotopic map formation. Brain Struct Funct 2015; 221:4187-4202. [DOI: 10.1007/s00429-015-1160-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 11/24/2015] [Indexed: 11/25/2022]
|
123
|
Retinoic Acid-Mediated Regulation of GLI3 Enables Efficient Motoneuron Derivation from Human ESCs in the Absence of Extrinsic SHH Activation. J Neurosci 2015; 35:11462-81. [PMID: 26290227 DOI: 10.1523/jneurosci.3046-14.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED The derivation of somatic motoneurons (MNs) from ES cells (ESCs) after exposure to sonic hedgehog (SHH) and retinoic acid (RA) is one of the best defined, directed differentiation strategies to specify fate in pluripotent lineages. In mouse ESCs, MN yield is particularly high after RA + SHH treatment, whereas human ESC (hESC) protocols have been generally less efficient. In an effort to optimize yield, we observe that functional MNs can be derived from hESCs at high efficiencies if treated with patterning molecules at very early differentiation steps before neural induction. Remarkably, under these conditions, equal numbers of human MNs were obtained in the presence or absence of SHH exposure. Using pharmacological and genetic strategies, we demonstrate that early RA treatment directs MN differentiation independently of extrinsic SHH activation by suppressing the induction of GLI3. We further demonstrate that neural induction triggers a switch from a poised to an active chromatin state at GLI3. Early RA treatment prevents this switch by direct binding of the RA receptor at the GLI3 promoter. Furthermore, GLI3 knock-out hESCs can bypass the requirement for early RA patterning to yield MNs efficiently. Our data demonstrate that RA-mediated suppression of GLI3 is sufficient to generate MNs in an SHH-independent manner and that temporal changes in exposure to patterning factors such as RA affect chromatin state and competency of hESC-derived lineages to adopt specific neuronal fates. Finally, our work presents a streamlined platform for the highly efficient derivation of human MNs from ESCs and induced pluripotent stem cells. SIGNIFICANCE STATEMENT Our study presents a rapid and efficient protocol to generate human motoneurons from embryonic and induced pluripotent stem cells. Surprisingly, and in contrast to previous work, motoneurons are generated in the presence of retinoic acid but in the absence of factors that activate sonic hedgehog signaling. We show that early exposure to retinoic acid modulates the chromatin state of cells to be permissive for motoneuron generation and directly suppresses the induction of GLI3, a negative regulator of SHH signaling. Therefore, our data point to a novel mechanism by which retinoic acid exposure can bypass the requirement for extrinsic SHH treatment during motoneuron induction.
Collapse
|
124
|
Zheng C, Jin FQ, Chalfie M. Hox Proteins Act as Transcriptional Guarantors to Ensure Terminal Differentiation. Cell Rep 2015; 13:1343-1352. [PMID: 26547238 DOI: 10.1016/j.celrep.2015.10.044] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 09/29/2015] [Accepted: 10/19/2015] [Indexed: 11/18/2022] Open
Abstract
Cell differentiation usually occurs with high fidelity, but the expression of many transcription factors is variable. Using the touch receptor neurons (TRNs) in C. elegans, we found that the Hox proteins CEH-13/lab and EGL-5/Abd-B overcome this variability by facilitating the activation of the common TRN fate determinant mec-3 in the anterior and posterior TRNs, respectively. CEH-13 and EGL-5 increase the probability of mec-3 transcriptional activation by the POU-homeodomain transcription factor UNC-86 using the same Hox/Pbx binding site. Mutation of ceh-13 and egl-5 resulted in an incomplete (∼40%) loss of the TRN fate in respective TRNs, which correlates with quantitative mRNA measurements showing two distinct modes (all or none) of mec-3 transcription. Therefore, Hox proteins act as transcriptional "guarantors" in order to ensure reliable and robust gene expression during terminal neuronal differentiation. Guarantors do not activate gene expression by themselves but promote full activation of target genes regulated by other transcription factors.
Collapse
Affiliation(s)
- Chaogu Zheng
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Felix Qiaochu Jin
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Martin Chalfie
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
125
|
Abstract
Control of movement is a fundamental and complex task of the vertebrate nervous system, which relies on communication between circuits distributed throughout the brain and spinal cord. Many of the networks essential for the execution of basic locomotor behaviors are composed of discrete neuronal populations residing within the spinal cord. The organization and connectivity of these circuits is established through programs that generate functionally diverse neuronal subtypes, each contributing to a specific facet of motor output. Significant progress has been made in deciphering how neuronal subtypes are specified and in delineating the guidance and synaptic specificity determinants at the core of motor circuit assembly. Recent studies have shed light on the basic principles linking locomotor circuit connectivity with function, and they are beginning to reveal how more sophisticated motor behaviors are encoded. In this review, we discuss the impact of developmental programs in specifying motor behaviors governed by spinal circuits.
Collapse
Affiliation(s)
- Catarina Catela
- Neuroscience Institute and Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016;
| | - Maggie M Shin
- Neuroscience Institute and Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016;
| | - Jeremy S Dasen
- Neuroscience Institute and Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016;
| |
Collapse
|
126
|
Geyer A, Koltsaki I, Hessinger C, Renner S, Rogulja-Ortmann A. Impact of Ultrabithorax alternative splicing on Drosophila embryonic nervous system development. Mech Dev 2015; 138 Pt 2:177-189. [PMID: 26299253 DOI: 10.1016/j.mod.2015.08.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 08/13/2015] [Accepted: 08/17/2015] [Indexed: 11/17/2022]
Abstract
Hox genes control divergent segment identities along the anteroposterior body axis of bilateral animals by regulating a large number of processes in a cell context-specific manner. How Hox proteins achieve this functional diversity is a long-standing question in developmental biology. In this study we investigate the role of alternative splicing in functional specificity of the Drosophila Hox gene Ultrabithorax (Ubx). We focus specifically on the embryonic central nervous system (CNS) and provide a description of temporal expression patterns of three major Ubx isoforms during development of this tissue. These analyses imply distinct functions for individual isoforms in different stages of neural development. We also examine the set of Ubx isoforms expressed in two isoform-specific Ubx mutant strains and analyze for the first time the effects of splicing defects on regional neural stem cell (neuroblast) identity. Our findings support the notion of specific isoforms having different effects in providing individual neuroblasts with positional identity along the anteroposterior body axis, as well as being involved in regulation of progeny cell fate.
Collapse
Affiliation(s)
- Aenne Geyer
- Institute of Genetics, University of Mainz, Mainz, Germany
| | | | | | - Simone Renner
- Institute of Genetics, University of Mainz, Mainz, Germany
| | | |
Collapse
|
127
|
Burbach JPH, Hellemons AJCGM, Grant P, Pant HC. The homeodomain transcription factor Phox2 in the stellate ganglion of the squid Loligo pealei. Biol Open 2015; 4:954-60. [PMID: 26116657 PMCID: PMC4542286 DOI: 10.1242/bio.012476] [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] [Indexed: 12/04/2022] Open
Abstract
Homeodomain transcription factors regulate development of embryos and cellular physiology in adult systems. Paired-type homeodomain genes constitute a subclass that has been particularly implicated in establishment of neuronal identity in the mammalian nervous system. We isolated fragments of eight homeodomain genes of this subclass expressed in the stellate ganglion of the North Atlantic long finned squid Loligo pealei (lp) [Note: Loligo pealei has been officially renamed Doryteuthis pealei. For reasons of uniformity and clarity Loligo pealei (lp) is used here]. Of the most abundant ones, we cloned a full length cDNA which encoded the squid ortholog of the paired-type homeodomain proteins Phox2a/b. The homology of lpPhox2 to invertebrate and mammalian Phox2 was limited to the homeodomain. In contrast to mouse Phox2b, lpPhox2 was unable to transactivate the dopamine beta-hydroxylase (DBH) promoter in a heterologous mammalian transfection system. In vivo, lpPhox2 was expressed in the developing stellate ganglion of stage 27 squid embryos and continued to be expressed in the adult stellate neurons where expression was confined to the giant fiber lobe containing the neurons that form the giant axons. The expression of lpPhox was similarly timed and distributed as the Fmrf gene. Furthermore, the Fmrf upstream region contained putative Phox2a/b binding sites. These results suggest a role of lpPhox2 in the developmental specification of neuronal identity and regulation of neurons of the squid giant axon.
Collapse
Affiliation(s)
- J. Peter H. Burbach
- Brain Center Rudolf Magnus, Department of Translational Neuroscience, University Medical Center Utrecht, Utrecht University, Utrecht 3584CG, The Netherlands
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Anita J. C. G. M. Hellemons
- Brain Center Rudolf Magnus, Department of Translational Neuroscience, University Medical Center Utrecht, Utrecht University, Utrecht 3584CG, The Netherlands
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Philip Grant
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Harish C. Pant
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| |
Collapse
|
128
|
Albersheim-Carter J, Blubaum A, Ballagh IH, Missaghi K, Siuda ER, McMurray G, Bass AH, Dubuc R, Kelley DB, Schmidt MF, Wilson RJA, Gray PA. Testing the evolutionary conservation of vocal motoneurons in vertebrates. Respir Physiol Neurobiol 2015; 224:2-10. [PMID: 26160673 DOI: 10.1016/j.resp.2015.06.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 06/23/2015] [Accepted: 06/29/2015] [Indexed: 11/15/2022]
Abstract
Medullary motoneurons drive vocalization in many vertebrate lineages including fish, amphibians, birds, and mammals. The developmental history of vocal motoneuron populations in each of these lineages remains largely unknown. The highly conserved transcription factor Paired-like Homeobox 2b (Phox2b) is presumed to be expressed in all vertebrate hindbrain branchial motoneurons, including laryngeal motoneurons essential for vocalization in humans. We used immunohistochemistry and in situ hybridization to examine Phox2b protein and mRNA expression in caudal hindbrain and rostral spinal cord motoneuron populations in seven species across five chordate classes. Phox2b was present in motoneurons dedicated to sound production in mice and frogs (bullfrog, African clawed frog), but not those in bird (zebra finch) or bony fish (midshipman, channel catfish). Overall, the pattern of caudal medullary motoneuron Phox2b expression was conserved across vertebrates and similar to expression in sea lamprey. These observations suggest that motoneurons dedicated to sound production in vertebrates are not derived from a single developmentally or evolutionarily conserved progenitor pool.
Collapse
Affiliation(s)
- Jacob Albersheim-Carter
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Aleksandar Blubaum
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Irene H Ballagh
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA; Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Kianoush Missaghi
- Department of Exercise Science, Faculté des Sciences, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada; Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Edward R Siuda
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - George McMurray
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Andrew H Bass
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Réjean Dubuc
- Department of Exercise Science, Faculté des Sciences, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada; Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Darcy B Kelley
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Marc F Schmidt
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Richard J A Wilson
- Hotchkiss Brain Institute and ACH Research Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N4N1, Canada
| | - Paul A Gray
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| |
Collapse
|
129
|
Lu DC, Niu T, Alaynick WA. Molecular and cellular development of spinal cord locomotor circuitry. Front Mol Neurosci 2015; 8:25. [PMID: 26136656 PMCID: PMC4468382 DOI: 10.3389/fnmol.2015.00025] [Citation(s) in RCA: 131] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/30/2015] [Indexed: 01/20/2023] Open
Abstract
The spinal cord of vertebrate animals is comprised of intrinsic circuits that are capable of sensing the environment and generating complex motor behaviors. There are two major perspectives for understanding the biology of this complicated structure. The first approaches the spinal cord from the point of view of function and is based on classic and ongoing research in electrophysiology, adult behavior, and spinal cord injury. The second view considers the spinal cord from a developmental perspective and is founded mostly on gene expression and gain-of-function and loss-of-function genetic experiments. Together these studies have uncovered functional classes of neurons and their lineage relationships. In this review, we summarize our knowledge of developmental classes, with an eye toward understanding the functional roles of each group.
Collapse
Affiliation(s)
- Daniel C Lu
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA USA
| | - Tianyi Niu
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA USA
| | - William A Alaynick
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA USA
| |
Collapse
|
130
|
Identification of the Avulsion-Injured Spinal Motoneurons. J Mol Neurosci 2015; 57:142-51. [PMID: 26025326 PMCID: PMC4543425 DOI: 10.1007/s12031-015-0588-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 05/21/2015] [Indexed: 12/31/2022]
Abstract
In laboratory studies, counting the spinal motoneurons that survived axonal injury is a major method to estimate the severity and regenerative capacity of the injured motoneurons after the axonal injury and rehabilitation surgery. However, the typical motoneuron marker, the choline acetyltransferase (ChAT), could not be detected in the injured motoneurons within the first 3–4 weeks postinjury. It is necessary to explore the useful and reliable specific phenotypic markers to assess the fate of injured motoneurons in axonal injury. Here, we used the fluorogold to retrograde trace the injured motoneurons in the spinal cord and studied the expression patterns of the alpha-motoneuron marker, the neuronal nuclei DNA-binding protein (NeuN) and the peripheral nerve injury marker, the activating transcriptional factor (ATF-3), and the oxidative stress marker, the neuronal nitric oxide synthase (nNOS) within the first 4 weeks of the root avulsion of the right brachial plexus (BPRA) in the adult male Sprague-Dawley rats. Our results showed that ATF-3 was rapidly induced and sustained to express only in the nuclei of the fluorogold-labeled injured motoneurons but none in the unaffected motoneurons from the 24 h of the injury; meanwhile, the NeuN almost disappeared in the avulsion-affected motoneurons within the first 4 weeks. The nNOS was not detected in the motoneurons until the second week of the injury. On the basis of the present data, we suggest that ATF-3 labels avulsion-injured motoneurons while NeuN and nNOS are poor markers within the first 4 weeks of BPRA.
Collapse
|
131
|
Abstract
Evolutionary modifications in nervous systems enabled organisms to adapt to their specific environments and underlie the remarkable diversity of behaviors expressed by animals. Resolving the pathways that shaped and modified neural circuits during evolution remains a significant challenge. Comparative studies have revealed a surprising conservation in the intrinsic signaling systems involved in early patterning of bilaterian nervous systems but also raise the question of how neural circuit compositions and architectures evolved within specific animal lineages. In this review, we discuss the mechanisms that contributed to the emergence and diversity of animal nervous systems, focusing on the circuits governing vertebrate locomotion.
Collapse
Affiliation(s)
- Heekyung Jung
- Howard Hughes Medical Institute (HHMI), NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA
| | - Jeremy S Dasen
- Howard Hughes Medical Institute (HHMI), NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
132
|
Foxp1-mediated programming of limb-innervating motor neurons from mouse and human embryonic stem cells. Nat Commun 2015; 6:6778. [PMID: 25868900 PMCID: PMC4397664 DOI: 10.1038/ncomms7778] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Accepted: 02/26/2015] [Indexed: 01/11/2023] Open
Abstract
Spinal motor neurons (MNs) control diverse motor tasks including respiration, posture and locomotion that are disrupted by neurodegenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. Methods directing MN differentiation from stem cells have been developed to enable disease modelling in vitro. However, most protocols produce only a limited subset of endogenous MN subtypes. Here we demonstrate that limb-innervating lateral motor column (LMC) MNs can be efficiently generated from mouse and human embryonic stem cells through manipulation of the transcription factor Foxp1. Foxp1-programmed MNs exhibit features of medial and lateral LMC MNs including expression of specific motor pool markers and axon guidance receptors. Importantly, they preferentially project axons towards limb muscle explants in vitro and distal limb muscles in vivo upon transplantation-hallmarks of bona fide LMC MNs. These results present an effective approach for generating specific MN populations from stem cells for studying MN development and disease.
Collapse
|
133
|
Allan DW, Thor S. Transcriptional selectors, masters, and combinatorial codes: regulatory principles of neural subtype specification. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:505-28. [PMID: 25855098 PMCID: PMC4672696 DOI: 10.1002/wdev.191] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 03/04/2015] [Accepted: 03/04/2015] [Indexed: 01/08/2023]
Abstract
The broad range of tissue and cellular diversity of animals is generated to a large extent by the hierarchical deployment of sequence-specific transcription factors and co-factors (collectively referred to as TF's herein) during development. Our understanding of these developmental processes has been facilitated by the recognition that the activities of many TF's can be meaningfully described by a few functional categories that usefully convey a sense for how the TF's function, and also provides a sense for the regulatory organization of the developmental processes in which they participate. Here, we draw on examples from studies in Caenorhabditis elegans, Drosophila melanogaster, and vertebrates to discuss how the terms spatial selector, temporal selector, tissue/cell type selector, terminal selector and combinatorial code may be usefully applied to categorize the activities of TF's at critical steps of nervous system construction. While we believe that these functional categories are useful for understanding the organizational principles by which TF's direct nervous system construction, we however caution against the assumption that a TF's function can be solely or fully defined by any single functional category. Indeed, most TF's play diverse roles within different functional categories, and their roles can blur the lines we draw between these categories. Regardless, it is our belief that the concepts discussed here are helpful in clarifying the regulatory complexities of nervous system development, and hope they prove useful when interpreting mutant phenotypes, designing future experiments, and programming specific neuronal cell types for use in therapies. WIREs Dev Biol 2015, 4:505–528. doi: 10.1002/wdev.191 For further resources related to this article, please visit the WIREs website.
Collapse
Affiliation(s)
- Douglas W Allan
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden
| |
Collapse
|
134
|
Deterministic HOX patterning in human pluripotent stem cell-derived neuroectoderm. Stem Cell Reports 2015; 4:632-44. [PMID: 25843047 PMCID: PMC4400649 DOI: 10.1016/j.stemcr.2015.02.018] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 11/25/2022] Open
Abstract
Colinear HOX expression during hindbrain and spinal cord development diversifies and assigns regional neural phenotypes to discrete rhombomeric and vertebral domains. Despite the precision of HOX patterning in vivo, in vitro approaches for differentiating human pluripotent stem cells (hPSCs) to posterior neural fates coarsely pattern HOX expression thereby generating cultures broadly specified to hindbrain or spinal cord regions. Here, we demonstrate that successive activation of fibroblast growth factor, Wnt/β-catenin, and growth differentiation factor signaling during hPSC differentiation generates stable, homogenous SOX2+/Brachyury+ neuromesoderm that exhibits progressive, full colinear HOX activation over 7 days. Switching to retinoic acid treatment at any point during this process halts colinear HOX activation and transitions the neuromesoderm into SOX2+/PAX6+ neuroectoderm with predictable, discrete HOX gene/protein profiles that can be further differentiated into region-specific cells, e.g., motor neurons. This fully defined approach significantly expands capabilities to derive regional neural phenotypes from diverse hindbrain and spinal cord domains. Deterministic HOX expression in hPSC-derived neuromesoderm progenitors (NMPs) Wnt/β-catenin, FGF, and GDF signaling regulate HOX activation in NMPs Retinoic acid (RA) transitions NMPs to neuroectoderm and halts HOX activation Neural cells can be patterned to any rostrocaudal hindbrain or spinal cord domain
Collapse
|
135
|
Narendra V, Rocha PP, An D, Raviram R, Skok JA, Mazzoni EO, Reinberg D. CTCF establishes discrete functional chromatin domains at the Hox clusters during differentiation. Science 2015; 347:1017-21. [PMID: 25722416 DOI: 10.1126/science.1262088] [Citation(s) in RCA: 383] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Polycomb and Trithorax group proteins encode the epigenetic memory of cellular positional identity by establishing inheritable domains of repressive and active chromatin within the Hox clusters. Here we demonstrate that the CCCTC-binding factor (CTCF) functions to insulate these adjacent yet antagonistic chromatin domains during embryonic stem cell differentiation into cervical motor neurons. Deletion of CTCF binding sites within the Hox clusters results in the expansion of active chromatin into the repressive domain. CTCF functions as an insulator by organizing Hox clusters into spatially disjoint domains. Ablation of CTCF binding disrupts topological boundaries such that caudal Hox genes leave the repressed domain and become subject to transcriptional activation. Hence, CTCF is required to insulate facultative heterochromatin from impinging euchromatin to produce discrete positional identities.
Collapse
Affiliation(s)
- Varun Narendra
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Pedro P Rocha
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA
| | - Disi An
- Department of Biology, New York University, New York, NY 10003, USA
| | - Ramya Raviram
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA
| | - Jane A Skok
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA
| | - Esteban O Mazzoni
- Department of Biology, New York University, New York, NY 10003, USA.
| | - Danny Reinberg
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
136
|
Yoshikawa M, Hirabayashi M, Ito R, Ozaki S, Aizawa S, Masuda T, Senzaki K, Shiga T. Contribution of the Runx1 transcription factor to axonal pathfinding and muscle innervation by hypoglossal motoneurons. Dev Neurobiol 2015; 75:1295-314. [PMID: 25762373 DOI: 10.1002/dneu.22285] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 02/18/2015] [Accepted: 03/01/2015] [Indexed: 11/12/2022]
Abstract
The runt-related transcription factor Runx1 contributes to cell type specification and axonal targeting projections of the nociceptive dorsal root ganglion neurons. Runx1 is also expressed in the central nervous system, but little is known of its functions in brain development. At mouse embryonic day (E) 17.5, Runx1-positive neurons were detected in the ventrocaudal subdivision of the hypoglossal nucleus. Runx1-positive neurons lacked calcitonin gene-related peptide (CGRP) expression, whereas Runx1-negative neurons expressed CGRP. Expression of CGRP was not changed in Runx1-deficient mice at E17.5, suggesting that Runx1 alone does not suppress CGRP expression. Hypoglossal axon projections to the intrinsic vertical (V) and transverse (T) tongue muscles were sparser in Runx1-deficient mice at E17.5 compared to age-matched wild-type littermates. Concomitantly, vesicular acetylcholine transporter-positive axon terminals and acetylcholine receptor clusters were less dense in the V and T tongue muscles of Runx1-deficient mice. These abnormalities in axonal projection were not caused by a reduction in the total number hypoglossal neurons, failed synaptogenesis, or tongue muscles deficits. Our results implicate Runx1 in the targeting of ventrocaudal hypoglossal axons to specific tongue muscles. However, Runx1 deficiency did not alter neuronal survival or the expression of multiple motoneuron markers as in other neuronal populations. Thus, Runx1 appears to have distinct developmental functions in different brain regions.
Collapse
Affiliation(s)
- Masaaki Yoshikawa
- Division of Anatomical Science, Department of Functional Morphology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi, Tokyo, 173-8610, Japan.,Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Mizuki Hirabayashi
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Ryota Ito
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Shigeru Ozaki
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Shin Aizawa
- Division of Anatomical Science, Department of Functional Morphology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi, Tokyo, 173-8610, Japan
| | - Tomoyuki Masuda
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Kouji Senzaki
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Takashi Shiga
- Doctoral Program in Kansei, Behavioral and Brain Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| |
Collapse
|
137
|
The spinal cord of the common marmoset (Callithrix jacchus). Neurosci Res 2015; 93:164-75. [PMID: 25575643 DOI: 10.1016/j.neures.2014.12.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 12/22/2014] [Accepted: 12/24/2014] [Indexed: 11/24/2022]
Abstract
The marmoset spinal cord possesses all the characteristic features of a typical mammalian spinal cord, but with some interesting variation in the levels of origin of the limb nerves. In our study Nissl and ChAT sections of the each segment of the spinal cord in two marmosets (Ma5 and Ma8), we found that the spinal cord can be functionally and anatomically divided into six regions: the prebrachial region (C1 to C3); the brachial region (C4 to C8) - segments supplying the upper limb; the post-brachial region (T1 to L1) - containing the sympathetic outflow, and supplying the hypaxial muscles of the body wall; the crural region (L2 to L5) - segments supplying the lower limb; the postcrural region (L6) - containing the parasympathetic outflow; and the caudal region (L7 to Co4) - supplying the tail. In the rat, mouse, and rhesus monkey, the prebrachial region consists of segments C1 to C4 (with the phrenic nucleus located at the C4 segment), and the brachial region extends from C5 to T1 inclusive. The prefixing of the upper limb outflow in these two marmosets mirrors the finding in the literature that a large C4 contribution to the brachial plexus is common in humans.
Collapse
|
138
|
Schulte EC, Winkelmann J. Clinical Phenotype and Genetics of Restless Legs Syndrome. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00076-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
|
139
|
Goetz C, Pivetta C, Arber S. Distinct limb and trunk premotor circuits establish laterality in the spinal cord. Neuron 2014; 85:131-144. [PMID: 25543457 DOI: 10.1016/j.neuron.2014.11.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2014] [Indexed: 12/31/2022]
Abstract
Movement coordination between opposite body sides relies on neuronal circuits capable of controlling muscle contractions according to motor commands. Trunk and limb muscles engage in distinctly lateralized behaviors, yet how regulatory spinal circuitry differs is less clear. Here, we intersect virus technology and mouse genetics to unravel striking distribution differences of interneurons connected to functionally distinct motor neurons. We find that premotor interneurons conveying information to axial motor neurons reside in symmetrically balanced locations while mostly ipsilateral premotor interneurons synapse with limb-innervating motor neurons, especially those innervating more distal muscles. We show that observed distribution differences reflect specific premotor interneuron subpopulations defined by genetic and neurotransmitter identity. Synaptic input across the midline reaches axial motor neurons preferentially through commissural axon arborization, and to a lesser extent, through midline-crossing dendrites capturing contralateral synaptic input. Together, our findings provide insight into principles of circuit organization underlying weighted lateralization of movement.
Collapse
Affiliation(s)
- Cyrill Goetz
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Chiara Pivetta
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Silvia Arber
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland.
| |
Collapse
|
140
|
Hutlet B, Theys N, Coste C, Ahn MT, Doshishti-Agolli K, Lizen B, Gofflot F. Systematic expression analysis of Hox genes at adulthood reveals novel patterns in the central nervous system. Brain Struct Funct 2014; 221:1223-43. [PMID: 25527350 DOI: 10.1007/s00429-014-0965-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 12/10/2014] [Indexed: 12/30/2022]
Abstract
Hox proteins are key regulators of animal development, providing positional identity and patterning information to cells along the rostrocaudal axis of the embryo. Although their embryonic expression and function are well characterized, their presence and biological importance in adulthood remains poorly investigated. We provide here the first detailed quantitative and neuroanatomical characterization of the expression of the 39 Hox genes in the adult mouse brain. Using RT-qPCR we determined the expression of 24 Hox genes mainly in the brainstem of the adult brain, with low expression of a few genes in the cerebellum and the forebrain. Using in situ hybridization (ISH) we have demonstrated that expression of Hox genes is maintained in territories derived from the early segmental Hox expression domains in the hindbrain. Indeed, we show that expression of genes belonging to paralogy groups PG2-8 is maintained in the hindbrain derivatives at adulthood. The spatial colinearity, which characterizes the early embryonic expression of Hox genes, is still observed in sequential antero-posterior boundaries of expression. Moreover, the main mossy and climbing fibres precerebellar nuclei express PG2-8 Hox genes according to their migration origins. Second, ISH confirms the presence of Hox gene transcripts in territories where they are not detected during development, suggesting neo-expression in these territories in adulthood. Within the forebrain, we have mapped Hoxb1, Hoxb3, Hoxb4, Hoxd3 and Hoxa5 expression in restricted areas of the sensory cerebral cortices as well as in specific thalamic relay nuclei. Our data thus suggest a requirement of Hox genes beyond their role of patterning genes, providing a new dimension to their functional relevance in the central nervous system.
Collapse
Affiliation(s)
- Bertrand Hutlet
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium
| | - Nicolas Theys
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium
| | - Cécile Coste
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium.,Laboratory of Developmental Neurobiology, GIGA-Neurosciences Research Center, University of Liège, 4000, Liège, Belgium
| | - Marie-Thérèse Ahn
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium
| | | | - Benoît Lizen
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium
| | - Françoise Gofflot
- Institut des Sciences de la Vie, Université catholique de Louvain, 1348, Louvain-La-Neuve, Belgium.
| |
Collapse
|
141
|
Lyons DB, Magklara A, Goh T, Sampath SC, Schaefer A, Schotta G, Lomvardas S. Heterochromatin-mediated gene silencing facilitates the diversification of olfactory neurons. Cell Rep 2014; 9:884-92. [PMID: 25437545 PMCID: PMC4251488 DOI: 10.1016/j.celrep.2014.10.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 08/29/2014] [Accepted: 09/27/2014] [Indexed: 01/26/2023] Open
Abstract
An astounding property of the nervous system is its cellular diversity. This diversity, which was initially realized by morphological and electrophysiological differences, is ultimately produced by variations in gene-expression programs. In most cases, these variations are determined by external cues. However, a growing number of neuronal types have been identified in which inductive signals cannot explain the few but decisive transcriptional differences that cause cell diversification. Here, we show that heterochromatic silencing, which we find is governed by histone methyltransferases G9a (KMT1C) and GLP (KMT1D), is essential for stochastic and singular olfactory receptor (OR) expression. Deletion of G9a and GLP dramatically reduces the complexity of the OR transcriptome, resulting in transcriptional domination by a few ORs and loss of singularity in OR expression. Thus, our data suggest that, in addition to its previously known functions, heterochromatin creates an epigenetic platform that affords stochastic, mutually exclusive gene choices and promotes cellular diversity.
Collapse
Affiliation(s)
- David B Lyons
- Tetrad Program, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Angeliki Magklara
- Division of Biomedical Research, Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 45110 Ioannina, Greece
| | - Tracie Goh
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94920, USA
| | - Srihari C Sampath
- Laboratory of Immune Cell Epigenetics and Signaling, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Anne Schaefer
- Laboratory of Immune Cell Epigenetics and Signaling, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Gunnar Schotta
- Munich Center for Integrated Protein Science, Adolf-Butenandt-Institute, Ludwig Maximilian University, Schillerstrasse 44, 80336 Munich, Germany
| | - Stavros Lomvardas
- Tetrad Program, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Anatomy, University of California, San Francisco, San Francisco, CA 94920, USA.
| |
Collapse
|
142
|
Stifani N. Motor neurons and the generation of spinal motor neuron diversity. Front Cell Neurosci 2014; 8:293. [PMID: 25346659 PMCID: PMC4191298 DOI: 10.3389/fncel.2014.00293] [Citation(s) in RCA: 178] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Accepted: 09/02/2014] [Indexed: 11/13/2022] Open
Abstract
Motor neurons (MNs) are neuronal cells located in the central nervous system (CNS) controlling a variety of downstream targets. This function infers the existence of MN subtypes matching the identity of the targets they innervate. To illustrate the mechanism involved in the generation of cellular diversity and the acquisition of specific identity, this review will focus on spinal MNs (SpMNs) that have been the core of significant work and discoveries during the last decades. SpMNs are responsible for the contraction of effector muscles in the periphery. Humans possess more than 500 different skeletal muscles capable to work in a precise time and space coordination to generate complex movements such as walking or grasping. To ensure such refined coordination, SpMNs must retain the identity of the muscle they innervate. Within the last two decades, scientists around the world have produced considerable efforts to elucidate several critical steps of SpMNs differentiation. During development, SpMNs emerge from dividing progenitor cells located in the medial portion of the ventral neural tube. MN identities are established by patterning cues working in cooperation with intrinsic sets of transcription factors. As the embryo develop, MNs further differentiate in a stepwise manner to form compact anatomical groups termed pools connecting to a unique muscle target. MN pools are not homogeneous and comprise subtypes according to the muscle fibers they innervate. This article aims to provide a global view of MN classification as well as an up-to-date review of the molecular mechanisms involved in the generation of SpMN diversity. Remaining conundrums will be discussed since a complete understanding of those mechanisms constitutes the foundation required for the elaboration of prospective MN regeneration therapies.
Collapse
Affiliation(s)
- Nicolas Stifani
- Medical Neuroscience, Dalhousie University Halifax, NS, Canada
| |
Collapse
|
143
|
Modeling motor neuron disease: the matter of time. Trends Neurosci 2014; 37:642-52. [PMID: 25156326 DOI: 10.1016/j.tins.2014.07.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 07/11/2014] [Accepted: 07/25/2014] [Indexed: 12/12/2022]
Abstract
Stem cell technologies have created new opportunities to generate unlimited numbers of human neurons in the lab and study neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Although some disease hallmarks have been reported in patient-derived stem cell models, it is proving more difficult to recapitulate the full phenotypic extent of these disorders. The problem with these stem cell models lies in the disparity between the advanced age of onset of neurodegenerative disorders and the embryonic nature of the in vitro derived cell types. In this review we discuss experimental methods of in vitro aging of neural cell types as a means to elicit late-onset symptoms in induced pluripotent stem cell (iPSC) models of neurodegenerative disease.
Collapse
|
144
|
Schulte EC, Kousi M, Tan PL, Tilch E, Knauf F, Lichtner P, Trenkwalder C, Högl B, Frauscher B, Berger K, Fietze I, Hornyak M, Oertel WH, Bachmann CG, Zimprich A, Peters A, Gieger C, Meitinger T, Müller-Myhsok B, Katsanis N, Winkelmann J. Targeted resequencing and systematic in vivo functional testing identifies rare variants in MEIS1 as significant contributors to restless legs syndrome. Am J Hum Genet 2014; 95:85-95. [PMID: 24995868 DOI: 10.1016/j.ajhg.2014.06.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 06/10/2014] [Indexed: 11/19/2022] Open
Abstract
Restless legs syndrome (RLS) is a common neurologic condition characterized by nocturnal dysesthesias and an urge to move, affecting the legs. RLS is a complex trait, for which genome-wide association studies (GWASs) have identified common susceptibility alleles of modest (OR 1.2-1.7) risk at six genomic loci. Among these, variants in MEIS1 have emerged as the largest risk factors for RLS, suggesting that perturbations in this transcription factor might be causally related to RLS susceptibility. To establish this causality, direction of effect, and total genetic burden of MEIS1, we interrogated 188 case subjects and 182 control subjects for rare alleles not captured by previous GWASs, followed by genotyping of ∼3,000 case subjects and 3,000 control subjects, and concluded with systematic functionalization of all discovered variants using a previously established in vivo model of neurogenesis. We observed a significant excess of rare MEIS1 variants in individuals with RLS. Subsequent assessment of all nonsynonymous variants by in vivo complementation revealed an excess of loss-of-function alleles in individuals with RLS. Strikingly, these alleles compromised the function of the canonical MEIS1 splice isoform but were irrelevant to an isoform known to utilize an alternative 3' sequence. Our data link MEIS1 loss of function to the etiopathology of RLS, highlight how combined sequencing and systematic functional annotation of rare variation at GWAS loci can detect risk burden, and offer a plausible explanation for the specificity of phenotypic expressivity of loss-of-function alleles at a locus broadly necessary for neurogenesis and neurodevelopment.
Collapse
Affiliation(s)
- Eva C Schulte
- Neurologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany; Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Maria Kousi
- Center for Human Disease Modeling, Department of Cell Biology, Duke University, Durham, NC 27710, USA
| | - Perciliz L Tan
- Center for Human Disease Modeling, Department of Cell Biology, Duke University, Durham, NC 27710, USA
| | - Erik Tilch
- Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany; Institut für Humangenetik, Technische Universität München, 81675 Munich, Germany
| | - Franziska Knauf
- Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Peter Lichtner
- Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany; Institut für Humangenetik, Technische Universität München, 81675 Munich, Germany
| | - Claudia Trenkwalder
- Paracelsus Elena Klinik, 34128 Kassel, Germany; Klinik für Neurochirurgie, Georg August Universität, 37075 Göttingen, Germany
| | - Birgit Högl
- Department of Neurology, Medizinische Universität Innsbruck, 6020 Innsbruck, Austria
| | - Birgit Frauscher
- Department of Neurology, Medizinische Universität Innsbruck, 6020 Innsbruck, Austria
| | - Klaus Berger
- Institut für Epidemiologie und Sozialmedizin, Westfälische Wilhelms Universität Münster, 48149 Münster, Germany
| | - Ingo Fietze
- Zentrum für Schlafmedizin, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Magdolna Hornyak
- Neurologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany; Interdisziplinäres Schmerzzentrum, Albert-Ludwigs Universität Freiburg, 79106 Freiburg, Germany; Diakoniewerk München-Maxvorstadt, 80799 Munich, Germany
| | - Wolfgang H Oertel
- Klinik für Neurologie, Philipps Universität Marburg, 35039 Marburg, Germany
| | - Cornelius G Bachmann
- Abteilung für Neurologie, Paracelsus Klinikum Osnabrück, 49076 Osnabrück, Germany; Klinische Neurophysiologie, Georg August Universität, 37075 Göttingen, Germany
| | - Alexander Zimprich
- Department of Neurology, Medizinische Universität Wien, 1090 Vienna, Austria
| | - Annette Peters
- Institute of Epidemiology II, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Christian Gieger
- Institute of Genetic Epidemiology, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Thomas Meitinger
- Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany; Institut für Humangenetik, Technische Universität München, 81675 Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Bertram Müller-Myhsok
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany; Max-Planck Institut für Psychiatrie München, 80804 Munich, Germany; Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, UK
| | - Nicholas Katsanis
- Center for Human Disease Modeling, Department of Cell Biology, Duke University, Durham, NC 27710, USA
| | - Juliane Winkelmann
- Neurologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany; Institut für Humangenetik, Helmholtz Zentrum München, 85764 Munich, Germany; Institut für Humangenetik, Technische Universität München, 81675 Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany; Department of Neurology and Neurosciences, Center for Sleep Sciences and Medicine, Stanford University, Palo Alto, CA 94304, USA.
| |
Collapse
|
145
|
Abstract
Limb innervation is established by opposing Hox-dependent activities. In this issue of Developmental Cell, Jung et al. (2014) show that Hoxc9 restriction of Foxp1, high levels of which specify limb-innervating motor neurons, first appeared in vertebrates concomitantly with paired appendages. Spatial control of this activity shapes neural networks controlling locomotion patterns.
Collapse
Affiliation(s)
- Moisés Mallo
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal.
| |
Collapse
|
146
|
Allodi I, Hedlund E. Directed midbrain and spinal cord neurogenesis from pluripotent stem cells to model development and disease in a dish. Front Neurosci 2014; 8:109. [PMID: 24904255 PMCID: PMC4033221 DOI: 10.3389/fnins.2014.00109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 04/28/2014] [Indexed: 12/29/2022] Open
Abstract
Induction of specific neuronal fates is restricted in time and space in the developing CNS through integration of extrinsic morphogen signals and intrinsic determinants. Morphogens impose regional characteristics on neural progenitors and establish distinct progenitor domains. Such domains are defined by unique expression patterns of fate determining transcription factors. These processes of neuronal fate specification can be recapitulated in vitro using pluripotent stem cells. In this review, we focus on the generation of dopamine neurons and motor neurons, which are induced at ventral positions of the neural tube through Sonic hedgehog (Shh) signaling, and defined at anteroposterior positions by fibroblast growth factor (Fgf) 8, Wnt1, and retinoic acid (RA). In vitro utilization of these morphogenic signals typically results in the generation of multiple neuronal cell types, which are defined at the intersection of these signals. If the purpose of in vitro neurogenesis is to generate one cell type only, further lineage restriction can be accomplished by forced expression of specific transcription factors in a permissive environment. Alternatively, cell-sorting strategies allow for selection of neuronal progenitors or mature neurons. However, modeling development, disease and prospective therapies in a dish could benefit from structured heterogeneity, where desired neurons are appropriately synaptically connected and thus better reflect the three-dimensional structure of that region. By modulating the extrinsic environment to direct sequential generation of neural progenitors within a domain, followed by self-organization and synaptic establishment, a reductionist model of that brain region could be created. Here we review recent advances in neuronal fate induction in vitro, with a focus on the interplay between cell intrinsic and extrinsic factors, and discuss the implications for studying development and disease in a dish.
Collapse
Affiliation(s)
- Ilary Allodi
- Department of Neuroscience, Karolinska Institutet Stockholm, Sweden
| | - Eva Hedlund
- Department of Neuroscience, Karolinska Institutet Stockholm, Sweden
| |
Collapse
|
147
|
Jung H, Mazzoni EO, Soshnikova N, Hanley O, Venkatesh B, Duboule D, Dasen JS. Evolving Hox activity profiles govern diversity in locomotor systems. Dev Cell 2014; 29:171-87. [PMID: 24746670 DOI: 10.1016/j.devcel.2014.03.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/07/2014] [Accepted: 03/13/2014] [Indexed: 11/28/2022]
Abstract
The emergence of limb-driven locomotor behaviors was a key event in the evolution of vertebrates and fostered the transition from aquatic to terrestrial life. We show that the generation of limb-projecting lateral motor column (LMC) neurons in mice relies on a transcriptional autoregulatory module initiated via transient activity of multiple genes within the HoxA and HoxC clusters. Repression of this module at thoracic levels restricts expression of LMC determinants, thus dictating LMC position relative to the limbs. This suppression is mediated by a key regulatory domain that is specifically found in the Hoxc9 proteins of appendage-bearing vertebrates. The profile of Hoxc9 expression inversely correlates with LMC position in land vertebrates and likely accounts for the absence of LMC neurons in limbless species such as snakes. Thus, modulation of both Hoxc9 protein function and Hoxc9 gene expression likely contributed to evolutionary transitions between undulatory and ambulatory motor circuit connectivity programs.
Collapse
Affiliation(s)
- Heekyung Jung
- Howard Hughes Medical Institute, NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA
| | | | - Natalia Soshnikova
- Department of Genetics and Evolution, University of Geneva, Sciences III, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland; Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany
| | - Olivia Hanley
- Howard Hughes Medical Institute, NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA
| | - Byrappa Venkatesh
- Comparative Genomics Laboratory, Institute of Molecular and Cell Biology, A(∗)STAR, Biopolis, Singapore 138673, Singapore; Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore
| | - Denis Duboule
- Department of Genetics and Evolution, University of Geneva, Sciences III, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland; School of Life Sciences, Ecole Polytechnique Fédérale, 1015 Lausanne, Switzerland
| | - Jeremy S Dasen
- Howard Hughes Medical Institute, NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
148
|
Machado CB, Kanning KC, Kreis P, Stevenson D, Crossley M, Nowak M, Iacovino M, Kyba M, Chambers D, Blanc E, Lieberam I. Reconstruction of phrenic neuron identity in embryonic stem cell-derived motor neurons. Development 2014; 141:784-94. [PMID: 24496616 PMCID: PMC3912827 DOI: 10.1242/dev.097188] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Air breathing is an essential motor function for vertebrates living on land. The rhythm that drives breathing is generated within the central nervous system and relayed via specialised subsets of spinal motor neurons to muscles that regulate lung volume. In mammals, a key respiratory muscle is the diaphragm, which is innervated by motor neurons in the phrenic nucleus. Remarkably, relatively little is known about how this crucial subtype of motor neuron is generated during embryogenesis. Here, we used direct differentiation of motor neurons from mouse embryonic stem cells as a tool to identify genes that direct phrenic neuron identity. We find that three determinants, Pou3f1, Hoxa5 and Notch, act in combination to promote a phrenic neuron molecular identity. We show that Notch signalling induces Pou3f1 in developing motor neurons in vitro and in vivo. This suggests that the phrenic neuron lineage is established through a local source of Notch ligand at mid-cervical levels. Furthermore, we find that the cadherins Pcdh10, which is regulated by Pou3f1 and Hoxa5, and Cdh10, which is controlled by Pou3f1, are both mediators of like-like clustering of motor neuron cell bodies. This specific Pcdh10/Cdh10 activity might provide the means by which phrenic neurons are assembled into a distinct nucleus. Our study provides a framework for understanding how phrenic neuron identity is conferred and will help to generate this rare and inaccessible yet vital neuronal subtype directly from pluripotent stem cells, thus facilitating subsequent functional investigations.
Collapse
|
149
|
Abstract
Expression of appropriate ion channels is essential to allow developing neurons to form functional networks. Our previous studies have identified LIM-homeodomain (HD) transcription factors (TFs), expressed by developing neurons, that are specifically able to regulate ion channel gene expression. In this study, we use the technique of DNA adenine methyltransferase identification (DamID) to identify putative gene targets of four such TFs that are differentially expressed in Drosophila motoneurons. Analysis of targets for Islet (Isl), Lim3, Hb9, and Even-skipped (Eve) identifies both ion channel genes and genes predicted to regulate aspects of dendritic and axonal morphology. Significantly, some ion channel genes are bound by more than one TF, consistent with the possibility of combinatorial regulation. One such gene is Shaker (Sh), which encodes a voltage-dependent fast K(+) channel (Kv1.1). DamID reveals that Sh is bound by both Isl and Lim3. We used body wall muscle as a test tissue because in conditions of low Ca(2+), the fast K(+) current is carried solely by Sh channels (unlike neurons in which a second fast K(+) current, Shal, also contributes). Ectopic expression of isl, but not Lim3, is sufficient to reduce both Sh transcript and Sh current level. By contrast, coexpression of both TFs is additive, resulting in a significantly greater reduction in both Sh transcript and current compared with isl expression alone. These observations provide evidence for combinatorial activity of Isl and Lim3 in regulating ion channel gene expression.
Collapse
|
150
|
Prin F, Serpente P, Itasaki N, Gould AP. Hox proteins drive cell segregation and non-autonomous apical remodelling during hindbrain segmentation. Development 2014; 141:1492-502. [PMID: 24574009 PMCID: PMC3957373 DOI: 10.1242/dev.098954] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 01/22/2014] [Indexed: 01/26/2023]
Abstract
Hox genes encode a conserved family of homeodomain transcription factors regulating development along the major body axis. During embryogenesis, Hox proteins are expressed in segment-specific patterns and control numerous different segment-specific cell fates. It has been unclear, however, whether Hox proteins drive the epithelial cell segregation mechanism that is thought to initiate the segmentation process. Here, we investigate the role of vertebrate Hox proteins during the partitioning of the developing hindbrain into lineage-restricted units called rhombomeres. Loss-of-function mutants and ectopic expression assays reveal that Hoxb4 and its paralogue Hoxd4 are necessary and sufficient for cell segregation, and for the most caudal rhombomere boundary (r6/r7). Hox4 proteins regulate Eph/ephrins and other cell-surface proteins, and can function in a non-cell-autonomous manner to induce apical cell enlargement on both sides of their expression border. Similarly, other Hox proteins expressed at more rostral rhombomere interfaces can also regulate Eph/ephrins, induce apical remodelling and drive cell segregation in ectopic expression assays. However, Krox20, a key segmentation factor expressed in odd rhombomeres (r3 and r5), can largely override Hox proteins at the level of regulation of a cell surface target, Epha4. This study suggests that most, if not all, Hox proteins share a common potential to induce cell segregation but in some contexts this is masked or modulated by other transcription factors.
Collapse
Affiliation(s)
- Fabrice Prin
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Patricia Serpente
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Nobue Itasaki
- Division of Developmental Neurobiology, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Alex P. Gould
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| |
Collapse
|