51
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Abstract
Previous studies in the chick embryo have shown that sensory neurons fail to innervate muscle in the absence of motor neurons. Instead, motor neuron deletion causes more sensory axons to project to the skin. We used this experimental paradigm to determine when sensory neurons are specified to become proprioceptive afferents. Experimental embryos were treated with either saline or exogenous neurotrophin-3 (NT-3) to promote the survival of proprioceptive afferents. In saline-treated embryos, motor neuron deletion caused an increase in sensory neuron apoptosis on the deleted side, an effect reversed by NT3. Motor neuron deletion also eliminated the sartorious muscle nerve, as previously reported. In NT3-treated embryos, this altered nerve pattern was accompanied by the enlargement of the adjacent cutaneous nerve. These embryos were further analyzed by using immunohistochemistry for trkC (a receptor for NT3) retrograde and transganglionic labeling. Our results show that, following motor neuron deletion, more trkC+ afferents project in cutaneous nerves on the deleted side of NT3-treated embryos. Transganglionic labeling demonstrated that at least some of these neurons made spinal projections that are typical of proprioceptive afferents. These results therefore indicate that the proprioceptive phenotype is specified prior to target innervation and that these neurons can retain their identity despite projecting to inappropriate (cutaneous) targets.
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Affiliation(s)
- Robert A Oakley
- Department of Anatomy and Cell Biology, The George Washington University Medical Center, Washington, DC 20037, USA.
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52
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Zirlinger M, Lo L, McMahon J, McMahon AP, Anderson DJ. Transient expression of the bHLH factor neurogenin-2 marks a subpopulation of neural crest cells biased for a sensory but not a neuronal fate. Proc Natl Acad Sci U S A 2002; 99:8084-9. [PMID: 12060754 PMCID: PMC123024 DOI: 10.1073/pnas.122231199] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lineage-tracing experiments have indicated that some premigratory neural crest cells (NCCs) are pleuripotent, generating sensory and sympathetic neurons and their associated glia. Using an inducible Cre recombinase-based fate mapping system, we have permanently marked a subpopulation of NCCs that expresses Ngn2, a bHLH transcription factor required for sensory neurogenesis, and compared its fate to the bulk NCC population marked by expression of Wnt1. Ngn2(+) progenitors were four times more likely than Wnt1(+) NCCs to contribute to sensory rather than sympathetic ganglia. Within dorsal root ganglia, however, both Ngn2- and Wnt1-expressing cells were equally likely to generate neurons or glia. These data suggest that Ngn2 marks an NCC subpopulation with a predictable fate bias, early in migration. Taken together with previous work, these data suggest that NCCs become restricted to sensory or autonomic sublineages before becoming committed to neuronal or glial fates.
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Affiliation(s)
- Mariela Zirlinger
- Division of Biology 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
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53
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Kubu CJ, Orimoto K, Morrison SJ, Weinmaster G, Anderson DJ, Verdi JM. Developmental changes in Notch1 and numb expression mediated by local cell-cell interactions underlie progressively increasing delta sensitivity in neural crest stem cells. Dev Biol 2002; 244:199-214. [PMID: 11900468 DOI: 10.1006/dbio.2002.0568] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neural stem cells become progressively less neurogenic and more gliogenic with development. Here, we show that between E10.5 and E14.5, neural crest stem cells (NCSCs) become increasingly sensitive to the Notch ligand Delta-Fc, a progliogenic and anti-neurogenic signal. This transition is correlated with a 20- to 30-fold increase in the relative ratio of expression of Notch and Numb (a putative inhibitor of Notch signaling). Misexpression experiments suggest that these changes contribute causally to increased Delta sensitivity. Moreover, such changes can occur in NCSCs cultured at clonal density in the absence of other cell types. However, they require local cell-cell interactions within developing clones. Delta-Fc mimics the effect of such cell-cell interactions to increase Notch and decrease Numb expression in isolated NCSCs. Thus, Delta-mediated feedback interactions between NCSCs, coupled with positive feedback control of Notch sensitivity within individual cells, may underlie developmental changes in the ligand-sensitivity of these cells.
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Affiliation(s)
- Chris J Kubu
- Laboratory of Neural Stem Cell Biology, John P. Robarts Research Institute, 100 Perth Drive, London Ontario, N6A5K8, Canada
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54
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Abstract
Schwann cells are the major glial population of the vertebrate peripheral nervous system. In the adult, they build a protecting sheath around neuronal processes and myelinate large-caliber axons. Already early in development, Schwann cells and neurons establish close contacts. Later development and the maintenance of peripheral nerves are crucially dependent on the controlled bi-directional dialogue between these two cell types. Several major phases can be distinguished in the life of a Schwann cell: determination, differentiation, and potentially myelination. The aim of this review is to summarize the molecular and cellular characteristics of the first steps in the life of a Schwann cell, the development from a multipotent neural crest cell to a differentiated Schwann cell.
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Affiliation(s)
- Christian S Lobsiger
- Institute of Cell Biology, Department of Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, Zurich
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55
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Namaka MP, Sawchuk M, MacDonald SC, Jordan LM, Hochman S. Neurogenesis in postnatal mouse dorsal root ganglia. Exp Neurol 2001; 172:60-9. [PMID: 11681840 DOI: 10.1006/exnr.2001.7761] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Neurogenesis continues in various regions of the central nervous system (CNS) throughout life. As the mitogen basic fibroblast growth factor (bFGF) can proliferate neuronal precursors of CNS neurons in culture, and is also upregulated within adult dorsal root ganglia following axotomy, it is possible that the postnatal dorsal root ganglia contain bFGF-responsive neuronal precursors. We undertook cell culture of postnatal mouse dorsal root ganglia to demonstrate neurogenesis. Basic FGF induced a cellular proliferative response in dorsal root ganglia cell culture. After 2 weeks in serum-free medium containing bFGF, neurons were rarely observed. However, following removal of bFGF and addition of trophic factors, many cells were observed that morphologically resembled dorsal root ganglia neurons, stained for neuronal markers, and generated action potentials. Furthermore, bromodeoxyuridine, used as a marker of cytogenesis, was detected in neurofilament-160(+) and/or microtubule-associated protein-2(+) cells that morphologically resembled neurons. In addition to bFGF, epidermal growth factor, nerve growth factor, and sonic hedgehog were also capable of generating spherical cell clusters that contained cells that stained for neuronal markers following the addition of trophic factors. These results suggest that early postnatal dorsal root ganglia contain neural precursors that appear to proliferate in response to various factors and can then be induced to differentiate into neurons. In conclusion, the existence of neural precursors and the possibility of neurogenesis in postnatal dorsal root ganglia may provide a greater range of plasticity available to somatosensory systems during growth or following injury, perhaps to replace ineffectual or dying neurons.
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Affiliation(s)
- M P Namaka
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0W3
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56
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Abstract
Cranial placodes are focal regions of thickened ectoderm in the head of vertebrate embryos that give rise to a wide variety of cell types, including elements of the paired sense organs and neurons in cranial sensory ganglia. They are essential for the formation of much of the cranial sensory nervous system. Although relatively neglected today, interest in placodes has recently been reawakened with the isolation of molecular markers for different stages in their development. This has enabled a more finely tuned approach to the understanding of placode induction and development and in some cases has resulted in the isolation of inducing molecules for particular placodes. Both morphological and molecular data support the existence of a preplacodal domain within the cranial neural plate border region. Nonetheless, multiple tissues and molecules (where known) are involved in placode induction, and each individual placode is induced at different times by a different combination of these tissues, consistent with their diverse fates. Spatiotemporal changes in competence are also important in placode induction. Here, we have tried to provide a comprehensive review that synthesises the highlights of a century of classical experimental research, together with more modern evidence for the tissues and molecules involved in the induction of each placode.
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Affiliation(s)
- C V Baker
- Division of Biology 139-74, California Institute of Technology, Pasadena, California, 91125, USA.
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57
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Affiliation(s)
- D J Anderson
- Division of Biology 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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58
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Young HM, Newgreen D. Enteric neural crest-derived cells: origin, identification, migration, and differentiation. THE ANATOMICAL RECORD 2001; 262:1-15. [PMID: 11146424 DOI: 10.1002/1097-0185(20010101)262:1<1::aid-ar1006>3.0.co;2-2] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- H M Young
- Department of Anatomy and Cell Biology, University of Melbourne, 3010, VIC, Australia.
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59
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White PM, Morrison SJ, Orimoto K, Kubu CJ, Verdi JM, Anderson DJ. Neural crest stem cells undergo cell-intrinsic developmental changes in sensitivity to instructive differentiation signals. Neuron 2001; 29:57-71. [PMID: 11182081 DOI: 10.1016/s0896-6273(01)00180-5] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Rat neural crest stem cells (NCSCs) prospectively isolated from uncultured E14.5 sciatic nerve and transplanted into chick embryos generate fewer neurons than do NCSCs isolated from E10.5 neural tube explants. In addition, they differentiate primarily to cholinergic parasympathetic neurons, although in culture they can also generate noradrenergic sympathetic neurons. This in vivo behavior can be explained, at least in part, by a reduced sensitivity of sciatic nerve-derived NCSCs to the neurogenic signal BMP2 and by the observation that cholinergic neurons differentiate at a lower BMP2 concentration than do noradrenergic neurons in vitro. These results demonstrate that neural stem cells can undergo cell-intrinsic changes in their sensitivity to instructive signals, while maintaining multipotency and self-renewal capacity. They also suggest that the choice between sympathetic and parasympathetic fates may be determined by the local concentration of BMP2.
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Affiliation(s)
- P M White
- Division of Biology 216-76, California Institute of Technology, Pasadena, CA 91125, USA
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60
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Abstract
The transcription factor Pax6 is expressed in discrete domains in the developing brain, generally limited to progenitor populations. However, in the embryonic mouse diencephalon, Pax6 is not only expressed in neuroepithelial progenitors, but also at high levels in a specific set of initial neurons. These neurons first appeared on embryonic day 9.5 (E9.5) in the presumptive ventral thalamus and were fated to become A13 dopaminergic neurons of the medial zona incerta. To further characterize the initial differentiation of these neurons, and the function of Pax6 in their formation, the expression patterns of a number of transcription factors were described. The progenitor population was defined by reciprocal overlapping expression gradients of Pax6 and Nkx2.2, and a subset of proliferating progenitors were labeled with an antibody against DLX transcription factors. The initial neurons expressed combinations of transcription factors, including Pax6, DLX, and the LIM-domain proteins islet-1, Lhx1 (Lim1), and Lhx5 (Lim-2). Bromo-deoxyuridine (BrdU) labeling was used to follow the fate of a cohort of proliferating cells, defining a step-wise sequence of gene activation during differentiation. Pax6 up-regulation occurred only several hours postdifferentiation. The loss of Pax6 altered progenitor specification, and the Lhx1 neuronal marker was lost, indicating a role for Pax6 in the specification of forebrain neuron identity.
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Affiliation(s)
- G S Mastick
- Department of Biology, University of Nevada, Reno, Nevada 89557, USA.
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61
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Christiansen JH, Coles EG, Wilkinson DG. Molecular control of neural crest formation, migration and differentiation. Curr Opin Cell Biol 2000; 12:719-24. [PMID: 11063938 DOI: 10.1016/s0955-0674(00)00158-7] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Induction, migration and differentiation of the neural crest are crucial for the development of the vertebrate embryo, and elucidation of the underlying mechanisms remains an important challenge. In the past year, a novel signal regulating the formation of neural crest cells has been identified, and advances have been made in uncovering roles for bone morphogenetic protein signals and for a transcription factor in the onset of neural crest migration. There have been new insights into the migration and plasticity of branchial neural crest cells. Important progress has been made in dissecting the roles of bone morphogenetic protein, Wnt and Notch signalling systems and their associated downstream transcription factors in the control of neural crest cell differentiation.
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Affiliation(s)
- J H Christiansen
- Division of Developmental Neurobiology, National Institute for Medical Research, The Ridgeway, Mill Hill, NW7 1AA, London, UK
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62
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Abstract
Neural crest cells are multipotent progenitors, capable of producing diverse cell types upon differentiation. Recent studies have identified significant heterogeneity in both the fates produced and genes expressed by different premigratory crest cells. While these cells may be specified toward particular fates prior to migration, transplant studies show that some may still be capable of respecification at this time. Here we summarize evidence that extracellular signals in the local environment may act to specify premigratory crest and thus generate diversity in the population. Three main classes of signals-Wnts, BMP2/BMP4 and TGFbeta1,2,3-have been shown to directly influence the production of particular neural crest cell fates, and all are expressed near the premigratory crest. This system may therefore provide a good model for integration of multiple signaling pathways during embryonic cell fate specification.
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Affiliation(s)
- R I Dorsky
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, WA, USA.
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63
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Anderson DJ. Genes, lineages and the neural crest: a speculative review. Philos Trans R Soc Lond B Biol Sci 2000; 355:953-64. [PMID: 11128989 PMCID: PMC1692804 DOI: 10.1098/rstb.2000.0631] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sensory and sympathetic neurons are generated from the trunk neural crest. The prevailing view has been that these two classes of neurons are derived from a common neural crest-derived progenitor that chooses between neuronal fates only after migrating to sites of peripheral ganglion formation. Here I reconsider this view in the light of new molecular and genetic data on the differentiation of sensory and autonomic neurons. These data raise several paradoxes when taken in the context of classical studies of the timing and spatial patterning of sensory and autonomic ganglion formation. These paradoxes can be most easily resolved by assuming that the restriction of neural crest cells to either sensory or autonomic lineages occurs at a very early stage, either before and/or shortly after they exit the neural tube.
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Affiliation(s)
- D J Anderson
- Division of Biology, Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA.
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64
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López-Coviella I, Berse B, Krauss R, Thies RS, Blusztajn JK. Induction and maintenance of the neuronal cholinergic phenotype in the central nervous system by BMP-9. Science 2000; 289:313-6. [PMID: 10894782 DOI: 10.1126/science.289.5477.313] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Bone morphogenetic proteins (BMPs) have multiple functions in the developing nervous system. A member of this family, BMP-9, was found to be highly expressed in the embryonic mouse septum and spinal cord, indicating a possible role in regulating the cholinergic phenotype. In cultured neurons, BMP-9 directly induced the expression of the cholinergic gene locus encoding choline acetyltransferase and the vesicular acetylcholine transporter and up-regulated acetylcholine synthesis. The effect was reversed upon withdrawal of BMP-9. Intracerebroventricular injection of BMP-9 increased acetylcholine levels in vivo. Although certain other BMPs also up-regulated the cholinergic phenotype in vitro, they were less effective than BMP-9. These data indicate that BMP-9 is a differentiating factor for cholinergic central nervous system neurons.
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Affiliation(s)
- I López-Coviella
- Department of Psychiatry and Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA 02118, USA
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65
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Dupin E, Glavieux C, Vaigot P, Le Douarin NM. Endothelin 3 induces the reversion of melanocytes to glia through a neural crest-derived glial-melanocytic progenitor. Proc Natl Acad Sci U S A 2000; 97:7882-7. [PMID: 10884419 PMCID: PMC16639 DOI: 10.1073/pnas.97.14.7882] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2000] [Indexed: 12/24/2022] Open
Abstract
Functional signaling of endothelin 3 (ET3) and its receptor B (ETRB) has been shown to be required for the development of neural crest (NC)-derived pigment cells in mouse, but the precise role of ET3 is not completely understood. Using the avian embryo as a model, we previously reported that ET3 promotes the survival and proliferation of unipotent melanocyte and bipotent glia-melanocyte precursors in trunk NC cultures. Here we investigated whether, at later stages, embryonic pigment cells respond to ET3. Such a possibility is supported by the previous finding that, in vivo, avian melanocytes express endothelin receptor B2 (ETRB2) during migration and after their differentiation in the skin. We found that in vitro ET3 exerts a dose-dependent stimulation of proliferation and melanogenesis in NC cells that had homed to the epidermis of embryonic quail dorsal skin. Moreover, in clonal cultures of skin-derived pigment cells, ET3 induces rapid cell divisions of clonogenic melanocytes that generate a mixed progeny of melanocytes and cells devoid of pigment granules and expressing glial markers in more than 40% of the colonies. It can therefore be concluded that ET3 is strongly mitogenic to embryonic pigment cells and able to alter their differentiation program, leading them to recapitulate the glial-melanocyte bipotentiality of their NC ancestors.
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Affiliation(s)
- E Dupin
- Institut d'Embryologie Cellulaire et Moléculaire, Centre National de la Recherche Scientifique (FRE 2160), 49 bis Avenue Belle Gabrielle, 94736 Nogent-sur-Marne Cedex, France
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66
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Desai AR, McConnell SK. Progressive restriction in fate potential by neural progenitors during cerebral cortical development. Development 2000; 127:2863-72. [PMID: 10851131 DOI: 10.1242/dev.127.13.2863] [Citation(s) in RCA: 231] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During early stages of cerebral cortical development, progenitor cells in the ventricular zone are multipotent, producing neurons of many layers over successive cell divisions. The laminar fate of their progeny depends on environmental cues to which the cells respond prior to mitosis. By the end of neurogenesis, however, progenitors are lineally committed to producing upper-layer neurons. Here we assess the laminar fate potential of progenitors at a middle stage of cortical development. The progenitors of layer 4 neurons were first transplanted into older brains in which layer 2/3 was being generated. The transplanted neurons adopted a laminar fate appropriate for the new environment (layer 2/3), revealing that layer 4 progenitors are multipotent. Mid-stage progenitors were then transplanted into a younger environment, in which layer 6 neurons were being generated. The transplanted neurons bypassed layer 6, revealing that layer 4 progenitors have a restricted fate potential and are incompetent to respond to environmental cues that trigger layer 6 production. Instead, the transplanted cells migrated to layer 4, the position typical of their origin, and also to layer 5, a position appropriate for neither the host nor the donor environment. Because layer 5 neurogenesis is complete by the stage that progenitors were removed for transplantation, restrictions in laminar fate potential must lag behind the final production of a cortical layer. These results suggest that a combination of intrinsic and environmental cues controls the competence of cortical progenitor cells to produce neurons of different layers.
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Affiliation(s)
- A R Desai
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA.
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67
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Anderson DJ. Lineages and transcription factors in the specification of vertebrate primary sensory neurons. Curr Opin Neurobiol 1999; 9:517-24. [PMID: 10508743 DOI: 10.1016/s0959-4388(99)00015-x] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Recent advances have indentified some of the key transcriptional regulators of mammalian genes, the neurogenins. Neurogenins 1 and 2 appear to control distinct sublineages for different classes of sensory neurons, including a 'pioneer' lineage for proprioceptors specified early in neural crest migration. Neurogenins act via a cascade of downstream transcriptional regulators, some of which have been identified.
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Affiliation(s)
- D J Anderson
- Howard Hughes Medical Institute Division of Biology 216-76 California Institute of Technology Pasadena, California 91125, USA.
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