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Abstract
The RNA-binding protein LIN28 is known to regulate cell fate, tissue growth, and pluripotency; however, a unified understanding of its role at the cellular level has not been achieved. Here, we address its developmental activity in mammalian postnatal neurogenesis. Constitutive expression of LIN28 in progenitor cells of the mouse subventricular zone (SVZ) caused several distinct effects: 1) the number of differentiated neurons in the olfactory bulb was dramatically reduced, whereas the relative abundance of 2 neuronal subtypes was significantly altered, 2) the population of proliferating neural progenitors in the SVZ was reduced, whereas the proportion of neuroblasts was increased, and 3) the number of astrocytes was reduced, occasionally causing them to appear early. Thus, LIN28 acts at a poststem cell/predifferentiation step, and its continuous expression caused a precocious phenotype unlike in other experimental systems. Furthermore, for the first time in a vertebrate system, we separate the majority of the biologic role of LIN28 from its known activity of blocking the microRNA let-7 by using a circular RNA sponge. We find that although LIN28 has a multifaceted role in the number and types of cells produced during postnatal neurogenesis, it appears that its action through let-7 is responsible for only a fraction of these effects.—Romer-Seibert, J. S., Hartman, N. W., Moss, E. G. The RNA-binding protein LIN28 controls progenitor and neuronal cell fate during postnatal neurogenesis.
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Affiliation(s)
- Jennifer S Romer-Seibert
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University, Stratford, New Jersey, USA; and
| | - Nathaniel W Hartman
- School of Natural Sciences and Mathematics, Stockton University, Galloway, New Jersey, USA
| | - Eric G Moss
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University, Stratford, New Jersey, USA; and
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Mahoney C, Feliciano DM, Bordey A, Hartman NW. Switching on mTORC1 induces neurogenesis but not proliferation in neural stem cells of young mice. Neurosci Lett 2016; 614:112-8. [PMID: 26812181 DOI: 10.1016/j.neulet.2015.12.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/04/2015] [Accepted: 12/18/2015] [Indexed: 01/28/2023]
Abstract
Recent evidence reported that activation of the mechanistic target of rapamycin complex 1 (mTORC1) induces terminal differentiation of neural stem cells (NSCs) in the neonatal subventricular zone (SVZ), but did not affect their proliferation. Here, we investigated whether such an effect of hyperactive mTORC1 would be recapitulated in young adults following removal of the negative mTORC1 regulator TSC1as seen in the neurological disorder tuberous sclerosis complex, TSC. Conditional mTORC1 activation in NSCs of 3-4 weeks old mice resulted in the generation of proliferative (Ki67+) cells and newborn neuroblasts. However, hyperactive mTORC1 did not induce NSCs to proliferate, consistent with the findings that mTORC1 induces symmetric division and differentiation of slow-cycling NSCs into proliferative daughter cells. Taken together these data suggest that hyperactivity of mTORC1 could lead to the progressive loss of NSCs over time.
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Affiliation(s)
- Colleen Mahoney
- School of Natural Sciences and Mathematics, Stockton University, Galloway, NJ, USA.
| | - David M Feliciano
- Department of Biological Sciences, Clemson University, Clemson, SC, USA.
| | - Angélique Bordey
- Departments of Neurosurgery, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA.
| | - Nathaniel W Hartman
- School of Natural Sciences and Mathematics, Stockton University, Galloway, NJ, USA.
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Hartman NW, Lin TV, Zhang L, Paquelet GE, Feliciano DM, Bordey A. mTORC1 targets the translational repressor 4E-BP2, but not S6 kinase 1/2, to regulate neural stem cell self-renewal in vivo. Cell Rep 2013; 5:433-44. [PMID: 24139800 DOI: 10.1016/j.celrep.2013.09.017] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 08/14/2013] [Accepted: 09/11/2013] [Indexed: 12/21/2022] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) integrates signals important for cell growth, and its dysregulation in neural stem cells (NSCs) is implicated in several neurological disorders associated with abnormal neurogenesis and brain size. However, the function of mTORC1 on NSC self-renewal and the downstream regulatory mechanisms are ill defined. Here, we found that genetically decreasing mTORC1 activity in neonatal NSCs prevented their differentiation, resulting in reduced lineage expansion and aborted neuron production. Constitutive activation of the translational repressor 4E-BP1, which blocked cap-dependent translation, had similar effects and prevented hyperactive mTORC1 induction of NSC differentiation and promoted self-renewal. Although 4E-BP2 knockdown promoted NSC differentiation, p70 S6 kinase 1 and 2 (S6K1/S6K2) knockdown did not affect NSC differentiation but reduced NSC soma size and prevented hyperactive mTORC1-induced increase in soma size. These data demonstrate a crucial role of mTORC1 and 4E-BP for switching on and off cap-dependent translation in NSC differentiation.
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Affiliation(s)
- Nathaniel W Hartman
- Departments of Neurosurgery, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8082, USA
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Feliciano DM, Lin TV, Hartman NW, Bartley CM, Kubera C, Hsieh L, Lafourcade C, O'Keefe RA, Bordey A. A circuitry and biochemical basis for tuberous sclerosis symptoms: from epilepsy to neurocognitive deficits. Int J Dev Neurosci 2013; 31:667-78. [PMID: 23485365 DOI: 10.1016/j.ijdevneu.2013.02.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/15/2013] [Accepted: 02/18/2013] [Indexed: 01/17/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is an autosomal dominant monogenetic disorder that is characterized by the formation of benign tumors in several organs as well as brain malformations and neuronal defects. TSC is caused by inactivating mutations in one of two genes, TSC1 and TSC2, resulting in increased activity of the mammalian Target of Rapamycin (mTOR). Here, we explore the cytoarchitectural and functional CNS aberrations that may account for the neurological presentations of TSC, notably seizures, hydrocephalus, and cognitive and psychological impairments. In particular, recent mouse models of brain lesions are presented with an emphasis on using electroporation to allow the generation of discrete lesions resulting from loss of heterozygosity during perinatal development. Cortical lesions are thought to contribute to epileptogenesis and worsening of cognitive defects. However, it has recently been suggested that being born with a mutant allele without loss of heterozygosity and associated cortical lesions is sufficient to generate cognitive and neuropsychiatric problems. We will thus discuss the function of mTOR hyperactivity on neuronal circuit formation and the potential consequences of being born heterozygous on neuronal function and the biochemistry of synaptic plasticity, the cellular substrate of learning and memory. Ultimately, a major goal of TSC research is to identify the cellular and molecular mechanisms downstream of mTOR underlying the neurological manifestations observed in TSC patients and identify novel therapeutic targets to prevent the formation of brain lesions and restore neuronal function.
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Affiliation(s)
- David M Feliciano
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, USA; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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Germain ND, Hartman NW, Cai C, Becker S, Naegele JR, Grabel LB. Teratocarcinoma Formation in Embryonic Stem Cell-Derived Neural Progenitor Hippocampal Transplants. Cell Transplant 2012; 21:1603-11. [DOI: 10.3727/096368912x647243] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Embryonic stem cells (ESCs) hold great therapeutic potential due to their ability to differentiate into cells of the three primary germ layers, which can be used to repopulate disease-damaged tissues. In fact, two cell therapies using ESC derivatives are currently in phase I clinical trials. A main concern in using ESCs and their derivatives for cell transplantation is the ability of undifferentiated ESCs to generate tumors in the host. Positive selection steps are often included in protocols designed to generate particular cell types from ESCs; however, the transition from ESC to progenitor cell or terminally differentiated cell is not synchronous, and residual undifferentiated cells often remain. In our transplants of ESC-derived neural progenitors (ESNPs) into the adult mouse hippocampus, we have observed the formation of teratocarcinomas. We set out to reduce teratocarcinoma formation by enrichment of ESNPs using fluorescence-activated cell sorting (FACS) and have found that, although enrichment prior to transplant reduces the overall rate of teratocarcinoma formation, the tumorigenicity of cell batches can vary widely, even after FACS enrichment to as much as 95% ESNPs. Our data suggest that this variability may be due to the percentage of residual ESCs remaining in the transplant cell population and to the presence of pluripotent epiblast-like cells, not previously identified in transplant batches. Our data emphasize the need for stringent characterization of transplant cell populations that will be used for cell replacement therapies in order to reduce the risk of tumor formation.
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Affiliation(s)
| | | | - Chunyu Cai
- Department of Biology, Wesleyan University, Middletown, CT, USA
| | - Sandy Becker
- Department of Biology, Wesleyan University, Middletown, CT, USA
| | - Janice R. Naegele
- Department of Biology, Wesleyan University, Middletown, CT, USA
- Program in Neuroscience and Behavior, Wesleyan University, Middletown, CT, USA
| | - Laura B. Grabel
- Department of Biology, Wesleyan University, Middletown, CT, USA
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Lacar B, Herman P, Hartman NW, Hyder F, Bordey A. S phase entry of neural progenitor cells correlates with increased blood flow in the young subventricular zone. PLoS One 2012; 7:e31960. [PMID: 22359646 PMCID: PMC3281100 DOI: 10.1371/journal.pone.0031960] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Accepted: 01/16/2012] [Indexed: 01/09/2023] Open
Abstract
The postnatal subventricular zone (SVZ) contains proliferating neural progenitor cells in close proximity to blood vessels. Insults and drug treatments acutely stimulate cell proliferation in the SVZ, which was assessed by labeling cells entering S phase. Although G1-to-S progression is metabolically demanding on a minute-to-hour time scale, it remains unknown whether increased SVZ cell proliferation is accompanied by a local hemodynamic response. This neurovascular coupling provides energy substrates to active neuronal assemblies. Transcardial dye perfusion revealed the presence of capillaries throughout the SVZ that constrict upon applications of the thromboxane A2 receptor agonist U-46119 in acute brain slice preparations. We then monitored in vivo blood flow using laser Doppler flowmetry via a microprobe located either in the SVZ or a mature network. U-46119 injections into the lateral ventricle decreased blood flow in the SVZ and the striatum, which are near the ventricle. A 1-hour ventricular injection of epidermal and basic fibroblast growth factor (EGF and bFGF) significantly increased the percentage of Sox2 transcription factor-positive cells in S phase 1.5 hours post-injection. This increase was accompanied by a sustained rise in blood flow in the SVZ but not in the striatum. Direct growth factor injections into the cortex did not alter local blood flow, ruling out direct effects on capillaries. These findings suggest that an acute increase in the number of G1-to-S cycling SVZ cells is accompanied by neurometabolic-vascular coupling, which may provide energy and nutrient for cell cycle progression.
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Affiliation(s)
- Benjamin Lacar
- Department of Neurosurgery and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Peter Herman
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Core Center for Quantitative Neuroscience with Magnetic Resonance, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Nathaniel W. Hartman
- Department of Neurosurgery and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Fahmeed Hyder
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Core Center for Quantitative Neuroscience with Magnetic Resonance, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Angelique Bordey
- Department of Neurosurgery and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Hartman NW, Carpentino JE, LaMonica K, Mor DE, Naegele JR, Grabel L. CXCL12-mediated guidance of migrating embryonic stem cell-derived neural progenitors transplanted into the hippocampus. PLoS One 2010; 5:e15856. [PMID: 21209827 PMCID: PMC3013129 DOI: 10.1371/journal.pone.0015856] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 11/26/2010] [Indexed: 01/19/2023] Open
Abstract
Stem cell therapies for neurodegenerative disorders require accurate delivery of the transplanted cells to the sites of damage. Numerous studies have established that fluid injections to the hippocampus can induce lesions in the dentate gyrus (DG) that lead to cell death within the upper blade. Using a mouse model of temporal lobe epilepsy, we previously observed that embryonic stem cell-derived neural progenitors (ESNPs) survive and differentiate within the granule cell layer after stereotaxic delivery to the DG, replacing the endogenous cells of the upper blade. To investigate the mechanisms for ESNP migration and repair in the DG, we examined the role of the chemokine CXCL12 in mice subjected to kainic acid-induced seizures. We now show that ESNPs transplanted into the DG show extensive migration through the upper blade, along the septotemporal axis of the hippocampus. Seizures upregulate CXCL12 and infusion of the CXCR4 antagonist AMD3100 by osmotic minipump attenuated ESNP migration. We also demonstrate that seizures promote the differentiation of transplanted ESNPs toward neuronal rather than astrocyte fates. These findings suggest that ESNPs transplanted into the adult rodent hippocampus migrate in response to cytokine-mediated signals.
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Affiliation(s)
- Nathaniel W Hartman
- Department of Biology, Wesleyan University, Middletown, Connecticut, United States of America.
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Carpentino JE, Hartman NW, Grabel LB, Naegele JR. Region-specific differentiation of embryonic stem cell-derived neural progenitor transplants into the adult mouse hippocampus following seizures. J Neurosci Res 2008; 86:512-24. [DOI: 10.1002/jnr.21514] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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