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Abstract
This review by Jain and Epstein discusses the developmental processes that influence cardiac lineage decisions and cellular competence and advances our understanding of cardiac cell specification, gene regulation, and chromatin organization and how they impact cardiac development. The mature heart is composed primarily of four different cell types: cardiac myocytes, endothelium, smooth muscle, and fibroblasts. These cell types derive from pluripotent progenitors that become progressively restricted with regard to lineage potential, giving rise to multipotent cardiac progenitor cells and, ultimately, the differentiated cell types of the heart. Recent studies have begun to shed light on the defining characteristics of the intermediary cell types that exist transiently during this developmental process and the extrinsic and cell-autonomous factors that influence cardiac lineage decisions and cellular competence. This information will shape our understanding of congenital and adult cardiac disease and guide regenerative therapeutic approaches. In addition, cardiac progenitor specification can serve as a model for understanding basic mechanisms regulating the acquisition of cellular identity. In this review, we present the concept of “chromatin competence” that describes the potential for three-dimensional chromatin organization to function as the molecular underpinning of the ability of a progenitor cell to respond to inductive lineage cues and summarize recent studies advancing our understanding of cardiac cell specification, gene regulation, and chromatin organization and how they impact cardiac development.
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Affiliation(s)
- Rajan Jain
- Department of Medicine, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Penn Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Jonathan A Epstein
- Department of Medicine, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Penn Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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2
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Poleshko A, Shah PP, Gupta M, Babu A, Morley MP, Manderfield LJ, Ifkovits JL, Calderon D, Aghajanian H, Sierra-Pagán JE, Sun Z, Wang Q, Li L, Dubois NC, Morrisey EE, Lazar MA, Smith CL, Epstein JA, Jain R. Genome-Nuclear Lamina Interactions Regulate Cardiac Stem Cell Lineage Restriction. Cell 2017; 171:573-587.e14. [PMID: 29033129 DOI: 10.1016/j.cell.2017.09.018] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [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: 04/14/2017] [Revised: 08/25/2017] [Accepted: 09/12/2017] [Indexed: 01/15/2023]
Abstract
Progenitor cells differentiate into specialized cell types through coordinated expression of lineage-specific genes and modification of complex chromatin configurations. We demonstrate that a histone deacetylase (Hdac3) organizes heterochromatin at the nuclear lamina during cardiac progenitor lineage restriction. Specification of cardiomyocytes is associated with reorganization of peripheral heterochromatin, and independent of deacetylase activity, Hdac3 tethers peripheral heterochromatin containing lineage-relevant genes to the nuclear lamina. Deletion of Hdac3 in cardiac progenitor cells releases genomic regions from the nuclear periphery, leading to precocious cardiac gene expression and differentiation into cardiomyocytes; in contrast, restricting Hdac3 to the nuclear periphery rescues myogenesis in progenitors otherwise lacking Hdac3. Our results suggest that availability of genomic regions for activation by lineage-specific factors is regulated in part through dynamic chromatin-nuclear lamina interactions and that competence of a progenitor cell to respond to differentiation signals may depend upon coordinated movement of responding gene loci away from the nuclear periphery.
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Affiliation(s)
- Andrey Poleshko
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Parisha P Shah
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mudit Gupta
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Apoorva Babu
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael P Morley
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lauren J Manderfield
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jamie L Ifkovits
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Damelys Calderon
- Department of Cell, Developmental, and Regenerative Biology, Mindich Child Health and Development Institute, and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Haig Aghajanian
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Javier E Sierra-Pagán
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zheng Sun
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine and the Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Qiaohong Wang
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Li Li
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nicole C Dubois
- Department of Cell, Developmental, and Regenerative Biology, Mindich Child Health and Development Institute, and Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Edward E Morrisey
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mitchell A Lazar
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine and the Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Cheryl L Smith
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jonathan A Epstein
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Rajan Jain
- Departments of Medicine and Cell and Developmental Biology, Institute for Regenerative Medicine, and the Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
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Jobe EM, Gao Y, Eisinger BE, Mladucky JK, Giuliani CC, Kelnhofer LE, Zhao X. Methyl-CpG-Binding Protein MBD1 Regulates Neuronal Lineage Commitment through Maintaining Adult Neural Stem Cell Identity. J Neurosci 2017; 37:523-36. [PMID: 28100736 DOI: 10.1523/JNEUROSCI.1075-16.2016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 10/31/2016] [Accepted: 11/22/2016] [Indexed: 01/09/2023] Open
Abstract
Methyl-CpG-binding domain 1 (MBD1) belongs to a family of methyl-CpG-binding proteins that are epigenetic "readers" linking DNA methylation to transcriptional regulation. MBD1 is expressed in neural stem cells residing in the dentate gyrus of the adult hippocampus (aNSCs) and MBD1 deficiency leads to reduced neuronal differentiation, impaired neurogenesis, learning deficits, and autism-like behaviors in mice; however, the precise function of MBD1 in aNSCs remains unexplored. Here, we show that MBD1 is important for maintaining the integrity and stemness of NSCs, which is critical for their ability to generate neurons. MBD1 deficiency leads to the accumulation of undifferentiated NSCs and impaired transition into the neuronal lineage. Transcriptome analysis of neural stem and progenitor cells isolated directly from the dentate gyrus of MBD1 mutant (KO) and WT mice showed that gene sets related to cell differentiation, particularly astrocyte lineage genes, were upregulated in KO cells. We further demonstrated that, in NSCs, MBD1 binds and represses directly specific genes associated with differentiation. Our results suggest that MBD1 maintains the multipotency of NSCs by restraining the onset of differentiation genes and that untimely expression of these genes in MBD1-deficient stem cells may interfere with normal cell lineage commitment and cause the accumulation of undifferentiated cells. Our data reveal a novel role for MBD1 in stem cell maintenance and provide insight into how epigenetic regulation contributes to adult neurogenesis and the potential impact of its dysregulation. SIGNIFICANCE STATEMENT Adult neural stem cells (aNSCs) in the hippocampus self-renew and generate neurons throughout life. We show that methyl-CpG-binding domain 1 (MBD1), a DNA methylation "reader," is important for maintaining the integrity of NSCs, which is critical for their neurogenic potency. Our data reveal a novel role for MBD1 in stem cell maintenance and provide insight into how epigenetic regulation preserves the multipotency of stem cells for subsequent differentiation.
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Watson C, Leanage G, Makki N, Tvrdik P. Escapees from Rhombomeric Lineage Restriction: Extensive Migration Rostral to the r4/r5 Border of Hox-a3 Expression. Anat Rec (Hoboken) 2017; 300:1838-1846. [PMID: 28667681 DOI: 10.1002/ar.23628] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [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: 08/17/2016] [Revised: 10/15/2016] [Accepted: 10/19/2016] [Indexed: 12/20/2022]
Abstract
The rhombomeric compartments of the hindbrain are characterized by lineage restriction; cells born in one compartment generally remain there and do not migrate to neighboring rhombomeres. Two well-known exceptions are the substantial migrations of the pontine nuclei and the mammalian facial nucleus. In this study we used Hoxa3-Cre lineage to permanently mark cells that originate in rhombomeres caudal to r4. We found that cells born caudal to the r4/r5 border migrate forwards to a number of different locations in rhombomeres 1-4; the final locations include the interfascicular trigeminal nucleus, the principal trigeminal nucleus, the pontine nuclei, the reticulotegmental nucleus, the ventral nucleus of the lateral lemniscus, and the lateral and medial vestibular nuclei. We suggest that there are numerous exceptions to the principle of rhombomeric lineage restriction that have previously gone unnoticed. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1838-1846, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Charles Watson
- Faculty of Health Sciences, Curtin University, Perth, Australia.,Neurosciences Research Australia, Sydney, Australia
| | - Gayeshika Leanage
- Faculty of Medicine, University of Western Australia, Perth, Australia
| | - Nadja Makki
- Department of Bioengineering and Therapeutic Science, University of California San Francisco, San Francisco, California
| | - Petr Tvrdik
- Department of Neurosurgery, University of Utah, Salt Lake City, Utah
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Wang Y, Yao H, Cui C, Wauthier E, Barbier C, Costello MJ, Moss N, Yamauchi M, Sricholpech M, Gerber D, Loboa EG, Reid LM. Paracrine signals from mesenchymal cell populations govern the expansion and differentiation of human hepatic stem cells to adult liver fates. Hepatology 2010; 52:1443-54. [PMID: 20721882 PMCID: PMC2947554 DOI: 10.1002/hep.23829] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
UNLABELLED The differentiation of embryonic or determined stem cell populations into adult liver fates under known conditions yields cells with some adult-specific genes but not others, aberrant regulation of one or more genes, and variations in the results from experiment to experiment. We tested the hypothesis that sets of signals produced by freshly isolated, lineage-dependent mesenchymal cell populations would yield greater efficiency and reproducibility in driving the differentiation of human hepatic stem cells (hHpSCs) into adult liver fates. The subpopulations of liver-derived mesenchymal cells, purified by immunoselection technologies, included (1) angioblasts, (2) mature endothelia, (3) hepatic stellate cell precursors, (4) mature stellate cells (pericytes), and (5) myofibroblasts. Freshly immunoselected cells of each of these subpopulations were established in primary cultures under wholly defined (serum-free) conditions that we developed for short-term cultures and were used as feeders with hHpSCs. Feeders of angioblasts yielded self-replication, stellate cell precursors caused lineage restriction to hepatoblasts, mature endothelia produced differentiation into hepatocytes, and mature stellate cells and/or myofibroblasts resulted in differentiation into cholangiocytes. Paracrine signals produced by the different feeders were identified by biochemical, immunohistochemical, and quantitative reverse-transcription polymerase chain reaction analyses, and then those signals were used to replace the feeders in monolayer and three-dimensional cultures to elicit the desired biological responses from hHpSCs. The defined paracrine signals were proved to be able to yield reproducible responses from hHpSCs and to permit differentiation into fully mature and functional parenchymal cells. CONCLUSION Paracrine signals from defined mesenchymal cell populations are important for the regulation of stem cell populations into specific adult fates; this finding is important for basic and clinical research as well as industrial investigations.
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Affiliation(s)
- Y. Wang
- Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - H. Yao
- Department of Biomedical Engineering, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - C. Cui
- Department of Surgery, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - E. Wauthier
- Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - C. Barbier
- Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - M. J. Costello
- Department of Cell and Developmental Biology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - N. Moss
- Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - M. Yamauchi
- Department of Periodontology, School of Dentistry, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - M. Sricholpech
- Department of Periodontology, School of Dentistry, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - D. Gerber
- Department of Surgery, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - E. G. Loboa
- Department of Biomedical Engineering, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
| | - L. M. Reid
- Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
- Department of Biomedical Engineering, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
- Program in Molecular Biology and Biotechnology, School of Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599 USA
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Monier B, Pélissier-Monier A, Brand AH, Sanson B. An actomyosin-based barrier inhibits cell mixing at compartmental boundaries in Drosophila embryos. Nat Cell Biol 2010; 12:60-9. [PMID: 19966783 PMCID: PMC4016768 DOI: 10.1038/ncb2005] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Accepted: 11/12/2009] [Indexed: 12/30/2022]
Abstract
Partitioning tissues into compartments that do not intermix is essential for the correct morphogenesis of animal embryos and organs. Several hypotheses have been proposed to explain compartmental cell sorting, mainly differential adhesion, but also regulation of the cytoskeleton or of cell proliferation. Nevertheless, the molecular and cellular mechanisms that keep cells apart at boundaries remain unclear. Here we demonstrate, in early Drosophila melanogaster embryos, that actomyosin-based barriers stop cells from invading neighbouring compartments. Our analysis shows that cells can transiently invade neighbouring compartments, especially when they divide, but are then pushed back into their compartment of origin. Actomyosin cytoskeletal components are enriched at compartmental boundaries, forming cable-like structures when the epidermis is mitotically active. When MyoII (non-muscle myosin II) function is inhibited, including locally at the cable by chromophore-assisted laser inactivation (CALI), in live embryos, dividing cells are no longer pushed back, leading to compartmental cell mixing. We propose that local regulation of actomyosin contractibility, rather than differential adhesion, is the primary mechanism sorting cells at compartmental boundaries.
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Affiliation(s)
- Bruno Monier
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Anne Pélissier-Monier
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Andrea H. Brand
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Bénédicte Sanson
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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Erickson T, Scholpp S, Brand M, Moens CB, Waskiewicz AJ. Pbx proteins cooperate with Engrailed to pattern the midbrain-hindbrain and diencephalic-mesencephalic boundaries. Dev Biol 2007; 301:504-17. [PMID: 16959235 PMCID: PMC1850147 DOI: 10.1016/j.ydbio.2006.08.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 07/26/2006] [Accepted: 08/07/2006] [Indexed: 11/27/2022]
Abstract
Pbx proteins are a family of TALE-class transcription factors that are well characterized as Hox co-factors acting to impart segmental identity to the hindbrain rhombomeres. However, no role for Pbx in establishing more anterior neural compartments has been demonstrated. Studies done in Drosophila show that Engrailed requires Exd (Pbx orthologue) for its biological activity. Here, we present evidence that zebrafish Pbx proteins cooperate with Engrailed to compartmentalize the midbrain by regulating the maintenance of the midbrain-hindbrain boundary (MHB) and the diencephalic-mesencephalic boundary (DMB). Embryos lacking Pbx function correctly initiate midbrain patterning, but fail to maintain eng2a, pax2a, fgf8, gbx2, and wnt1 expression at the MHB. Formation of the DMB is also defective as shown by a caudal expansion of diencephalic epha4a and pax6a expression into midbrain territory. These phenotypes are similar to the phenotype of an Engrailed loss-of-function embryo, supporting the hypothesis that Pbx and Engrailed act together on a common genetic pathway. Consistent with this model, we demonstrate that zebrafish Engrailed and Pbx interact in vitro and that this interaction is required for both the eng2a overexpression phenotype and Engrailed's role in patterning the MHB. Our data support a novel model of midbrain development in which Pbx and Engrailed proteins cooperatively pattern the mesencephalic region of the neural tube.
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Affiliation(s)
- Timothy Erickson
- Department of Biological Sciences, CW405, Biological Sciences Building, University of Alberta, Edmonton AB, Canada T6G2E9
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Vallières L, Sawchenko PE. Bone marrow-derived cells that populate the adult mouse brain preserve their hematopoietic identity. J Neurosci 2003; 23:5197-207. [PMID: 12832544 PMCID: PMC6741180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
Cytogenesis in the adult brain can result from the recruitment of circulating precursors, but the proposal that some such cells transdifferentiate into neural elements is controversial. We have reinvestigated this issue by following the phenotypic fate of bone marrow cells expressing the green fluorescent protein transplanted into the systemic circulation of irradiated mice. Thousands of donor-derived cells were detected throughout brains of recipients killed 1-12 months after transplantation, but none displayed neuronal, macroglial, or endothelial characteristics, even after injury. Among those that crossed the endothelium of the cerebral cortex, >99.7% were identified as perivascular macrophages. Newly formed parenchymal microglia were found in significant numbers only in the cerebellum and at injury sites. Therefore, bone marrow does supply the mature brain with new specialized cells; however, mesenchymal precursors neither adopt neural phenotypes nor contribute to cerebral vascular remodeling. This continuous traffic of macrophages across the blood-brain barrier provides a vehicle to introduce therapeutic genes into the nervous system.
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Affiliation(s)
- Luc Vallières
- Laboratoire d'Endocrinologie Moléculaire, Centre de Recherche du Centre Hospitalier de l'Université Laval, Université Laval, Québec, Québec, G1V 4G2, Canada.
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Abstract
About 130 years ago, Giulio Bizozzero, then in Pavia, made a seminal observation [1]. He divided the tissues of the vertebrate body into three categories: those that divide constantly (labile), such as blood and skin, those that never divide, such as striated muscle and brain (perennial), and those that normally do not divide but can do so if injured (stable). As a consequence, diseases that perturb cell division, such as cancer, affect labile tissues, while degenerative diseases affect perennial tissues where repair is inefficient. Epithelia and blood possess a reservoir of cells that divide and maintain a progenitor pool throughout life (the stem cells) whereas striated muscle and brain were supposed not to contain stem cells. Furthermore, stem cells were supposed to generate only the cells of the tissue where they belong.
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Affiliation(s)
- G Cossu
- Stem Cell Research Institute, H.S. Raffaele Milan and Dept. of Histology and Medical Embryology, II Medical School, University of Rome, La Sapienza, Italy
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Abstract
Lineage commitment in B lymphopoiesis remains poorly understood due to the inability to clearly define newly committed B lineage progenitors and their multipotential descendants. We examined the potential of three recently described progenitor populations in adult mouse bone marrow to differentiate into each hematopoietic lineage. The earliest of these, termed fraction (Fr.) A0, exhibited myeloid, erythroid, and B and T lymphoid progenitor activity and included individual cells with myeloid/B lymphoid potential. In sharp contrast, two later populations, termed Frs. A1 and A2 and characterized by surface B220 expression and transcription of the germline immunoglobulin heavy chain (IgH) locus, lacked progenitor activity for all hematopoietic lineages except B lymphocytes. These observations, together with single cell polymerase chain reaction analysis showing a lack of DHJH rearrangements in each population and experiments showing identical precursor potentials when these populations were derived from recombination activating gene (Rag)-1(-/-) and JH-/- mice, demonstrate that commitment to the B lymphoid lineage occurs before and independently of VHDHJH recombination.
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Affiliation(s)
- D Allman
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
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