2501
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Choi N, Zhang B, Zhang L, Ittmann M, Xin L. Adult murine prostate basal and luminal cells are self-sustained lineages that can both serve as targets for prostate cancer initiation. Cancer Cell 2012; 21:253-65. [PMID: 22340597 PMCID: PMC3285423 DOI: 10.1016/j.ccr.2012.01.005] [Citation(s) in RCA: 253] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 01/02/2012] [Accepted: 01/06/2012] [Indexed: 12/21/2022]
Abstract
The prostate epithelial lineage hierarchy and the cellular origin for prostate cancer remain inadequately defined. Using a lineage-tracing approach, we show that adult rodent prostate basal and luminal cells are independently self-sustained in vivo. Disrupting the tumor suppressor Pten in either lineage led to prostate cancer initiation. However, the cellular composition and onset dynamics of the resulting tumors are distinctive. Prostate luminal cells are more responsive to Pten null-induced mitogenic signaling. In contrast, basal cells are resistant to direct transformation. Instead, loss of Pten activity induces the capability of basal cells to differentiate into transformation-competent luminal cells. Our study suggests that deregulation of epithelial differentiation is a critical step for the initiation of prostate cancers of basal cell origin.
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Affiliation(s)
- Nahyun Choi
- Department of Molecular and Cellular Biology
| | - Boyu Zhang
- Department of Molecular and Cellular Biology
| | - Li Zhang
- Department of Molecular and Cellular Biology
| | - Michael Ittmann
- Department of Pathology and Immunology
- Dan L. Duncan Cancer Center
| | - Li Xin
- Department of Molecular and Cellular Biology
- Department of Pathology and Immunology
- Dan L. Duncan Cancer Center
- Corresponding author: Li Xin, Ph.D., Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, Phone: 713-798-1650, FAX: 713-798-3017,
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2502
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N-cadherin in osteolineage cells is not required for maintenance of hematopoietic stem cells. Blood 2012; 120:295-302. [PMID: 22323481 DOI: 10.1182/blood-2011-09-377457] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
There is evidence suggesting that N-cadherin expression on osteoblast lineage cells regulates hematopoietic stem cell (HSC) function and quiescence. To test this hypothesis, we conditionally deleted N-cadherin (Cdh2) in osteoblasts using Cdh2(flox/flox) Osx-Cre mice. N-cadherin expression was efficiently ablated in osteoblast lineage cells as assessed by mRNA expression and immunostaining of bone sections. Basal hematopoiesis is normal in these mice. In particular, HSC number, cell cycle status, long-term repopulating activity, and self-renewal capacity were normal. Moreover, engraftment of wild-type cells into N-cadherin-deleted recipients was normal. Finally, these mice responded normally to G-CSF, a stimulus that mobilizes HSCs by inducing alterations to the stromal micro-environment. In conclusion, N-cadherin expression in osteoblast lineage cells is dispensable for HSC maintenance in mice.
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2503
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Lange SS, Wittschieben JP, Wood RD. DNA polymerase zeta is required for proliferation of normal mammalian cells. Nucleic Acids Res 2012; 40:4473-82. [PMID: 22319213 PMCID: PMC3378892 DOI: 10.1093/nar/gks054] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Unique among translesion synthesis (TLS) DNA polymerases, pol ζ is essential during embryogenesis. To determine whether pol ζ is necessary for proliferation of normal cells, primary mouse fibroblasts were established in which Rev3L could be conditionally inactivated by Cre recombinase. Cells were grown in 2% O2 to prevent oxidative stress-induced senescence. Cells rapidly became senescent or apoptotic and ceased growth within 3–4 population doublings. Within one population doubling following Rev3L deletion, DNA double-strand breaks and chromatid aberrations were found in 30–50% of cells. These breaks were replication dependent, and found in G1 and G2 phase cells. Double-strand breaks were reduced when cells were treated with the reactive oxygen species scavenger N-acetyl-cysteine, but this did not rescue the cell proliferation defect, indicating that several classes of endogenously formed DNA lesions require Rev3L for tolerance or repair. T-antigen immortalization of cells allowed cell growth. In summary, even in the absence of external challenges to DNA, pol ζ is essential for preventing replication-dependent DNA breaks in every division of normal mammalian cells. Loss of pol ζ in slowly proliferating mouse cells in vivo may allow accumulation of chromosomal aberrations that could lead to tumorigenesis. Pol ζ is unique amongst TLS polymerases for its essential role in cell proliferation.
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Affiliation(s)
- Sabine S Lange
- Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center Science Park, and the Graduate School of Biomedical Sciences at Houston, Smithville Texas, P.O. Box 389, Smithville, TX 78957, USA
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2504
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Kurihara T, Westenskow PD, Krohne TU, Aguilar E, Johnson RS, Friedlander M. Astrocyte pVHL and HIF-α isoforms are required for embryonic-to-adult vascular transition in the eye. ACTA ACUST UNITED AC 2012; 195:689-701. [PMID: 22084310 PMCID: PMC3257537 DOI: 10.1083/jcb.201107029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The von Hippel–Lindau tumor suppressor and the hypoxia-inducible factor-αs are essential for the transition from embryonic hyaloidal vascular system to adult retinal vasculature in the mouse eye. Successful transition from embryonic to adult circulation is critical for survival of mammalian organisms. This shift occurs in the central cardiovascular circulation and in the eye as oxygen tension increases. However, its regulation is not well understood. We have used combinatorial gene deletion and overexpression assays to assess the effect of astrocyte-targeted deletion of von Hippel–Lindau tumor suppressor (Vhl), hypoxia-inducible factor-αs (Hif-αs), and Vegf on the normal regression of the hyaloidal vessels, the fetal ocular circulation system. Astrocytic Vhl deletion induced accelerated hyaloidal regression and subsequent massive secondary outgrowth. Combinatorial gene deletion involving Vhl, Hif-αs, and Vegf genes revealed that HIF-2α/vascular endothelial growth factor signaling induces secondary outgrowth in Vhl mutants. Conversely, HIF-1α regulated macrophage migration inhibitory factor and promoted macrophage infiltration that accelerates hyaloidal vessel regression. The phenotype observed in Vhl mutants strongly resembles human persistent hyperplastic primary vitreous cases and may provide insights into vascular remodeling mechanisms in other systems.
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Affiliation(s)
- Toshihide Kurihara
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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2505
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Jefferis GSXE, Livet J. Sparse and combinatorial neuron labelling. Curr Opin Neurobiol 2012; 22:101-10. [PMID: 22030345 DOI: 10.1016/j.conb.2011.09.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 09/27/2011] [Indexed: 11/16/2022]
Abstract
Sparse, random labelling of individual cells is a key approach to study brain circuit organisation and development. An array of methods based on genetic engineering now complements older methods such as Golgi staining, facilitating analysis while providing higher information content. Increasingly refined expression strategies based on transcriptional modulators and site-specific recombinases are used to distribute markers or combinations of markers within specific neuronal subsets. Several trends are emerging: first, increasing labelling density with multiplexed markers to allow more cells to be reliably distinguished; second, using labels to report lineage relationships among defined cells in addition to anatomy; third, coupling cell labelling with genetic manipulations that reveal or perturb cell function. These strategies offer new opportunities for characterizing the fine scale architecture of neuronal circuits, and understanding lineage and functional relations among their cellular components in normal or experimental situations.
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Affiliation(s)
- Gregory S X E Jefferis
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
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2506
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Masedunskas A, Porat-Shliom N, Weigert R. Regulated exocytosis: novel insights from intravital microscopy. Traffic 2012; 13:627-34. [PMID: 22243493 DOI: 10.1111/j.1600-0854.2012.01328.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/11/2012] [Accepted: 01/13/2012] [Indexed: 12/20/2022]
Abstract
Regulated exocytosis is a fundamental process that every secretory cell uses to deliver molecules to the cell surface and the extracellular space by virtue of membranous carriers. This process has been extensively studied using various approaches such as biochemistry, electrophysiology and electron microscopy. However, recent developments in time-lapse light microscopy have made possible imaging individual exocytic events, hence, advancing our understanding of this process at a molecular level. In this review, we focus on intravital microscopy (IVM), a light microscopy-based approach that enables imaging subcellular structures in live animals, and discuss its recent application to study regulated exocytosis. IVM has revealed differences in regulation and modality of regulated exocytosis between in vitro and in vivo model systems, unraveled novel aspects of this process that can be appreciated only in in vivo settings and provided valuable and novel information on its molecular machinery. In conclusion, we make the case for IVM being a mature technique that can be used to investigate the molecular machinery of several intracellular events under physiological conditions.
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Affiliation(s)
- Andrius Masedunskas
- Intracellular Membrane Trafficking Unit, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, 30 Convent Dr. 303A, Bethesda, MD 20892-4340, USA
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2507
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YAP1, the nuclear target of Hippo signaling, stimulates heart growth through cardiomyocyte proliferation but not hypertrophy. Proc Natl Acad Sci U S A 2012; 109:2394-9. [PMID: 22308401 DOI: 10.1073/pnas.1116136109] [Citation(s) in RCA: 417] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Heart growth is tightly controlled so that the heart reaches a predetermined size. Fetal heart growth occurs through cardiomyocyte proliferation, whereas postnatal heart growth involves primarily physiological cardiomyocyte hypertrophy. The Hippo kinase cascade is an important regulator of organ growth. A major target of this kinase cascade is YAP1, a transcriptional coactivator that is inactivated by Hippo kinase activity. Here, we used both genetic gain and loss of Yap1 function to investigate its role in regulating proliferative and physiologic hypertrophic heart growth. Fetal Yap1 inactivation caused marked, lethal myocardial hypoplasia and decreased cardiomyocyte proliferation, whereas fetal activation of YAP1 stimulated cardiomyocyte proliferation. Enhanced proliferation was particularly dramatic in trabecular cardiomyocytes that normally exit from the cell cycle. Remarkably, YAP1 activation was sufficient to stimulate proliferation of postnatal cardiomyocytes, both in culture and in the intact heart. A dominant negative peptide that blocked YAP1 binding to TEAD transcription factors inhibited YAP1 proliferative activity, indicating that this activity requires YAP1-TEAD interaction. Although Yap1 was a critical regulator of cardiomyocyte proliferation, it did not influence physiological hypertrophic growth of cardiomyocytes, because postnatal Yap1 gain or loss of function did not significantly alter cardiomyocyte size. These studies demonstrate that Yap1 is a crucial regulator of cardiomyocyte proliferation, cardiac morphogenesis, and myocardial trabeculation. Activation of Yap1 in postnatal cardiomyocytes may be a useful strategy to stimulate cardiomyocyte expansion in therapeutic myocardial regeneration.
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2508
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Yablonka-Reuveni Z. The skeletal muscle satellite cell: still young and fascinating at 50. J Histochem Cytochem 2012; 59:1041-59. [PMID: 22147605 DOI: 10.1369/0022155411426780] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The skeletal muscle satellite cell was first described and named based on its anatomic location between the myofiber plasma and basement membranes. In 1961, two independent studies by Alexander Mauro and Bernard Katz provided the first electron microscopic descriptions of satellite cells in frog and rat muscles. These cells were soon detected in other vertebrates and acquired candidacy as the source of myogenic cells needed for myofiber growth and repair throughout life. Cultures of isolated myofibers and, subsequently, transplantation of single myofibers demonstrated that satellite cells were myogenic progenitors. More recently, satellite cells were redefined as myogenic stem cells given their ability to self-renew in addition to producing differentiated progeny. Identification of distinctively expressed molecular markers, in particular Pax7, has facilitated detection of satellite cells using light microscopy. Notwithstanding the remarkable progress made since the discovery of satellite cells, researchers have looked for alternative cells with myogenic capacity that can potentially be used for whole body cell-based therapy of skeletal muscle. Yet, new studies show that inducible ablation of satellite cells in adult muscle impairs myofiber regeneration. Thus, on the 50th anniversary since its discovery, the satellite cell's indispensable role in muscle repair has been reaffirmed.
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Affiliation(s)
- Zipora Yablonka-Reuveni
- Department of Biological Structure, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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2509
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Murphy PA, Kim TN, Lu G, Bollen AW, Schaffer CB, Wang RA. Notch4 normalization reduces blood vessel size in arteriovenous malformations. Sci Transl Med 2012; 4:117ra8. [PMID: 22261032 PMCID: PMC3320799 DOI: 10.1126/scitranslmed.3002670] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Abnormally enlarged blood vessels underlie many life-threatening disorders including arteriovenous (AV) malformations (AVMs). The core defect in AVMs is high-flow AV shunts, which connect arteries directly to veins, "stealing" blood from capillaries. Here, we studied mouse brain AV shunts caused by up-regulation of Notch signaling in endothelial cells (ECs) through transgenic expression of constitutively active Notch4 (Notch4*). Using four-dimensional two-photon imaging through a cranial window, we found that normalizing Notch signaling by repressing Notch4* expression converted large-caliber, high-flow AV shunts to capillary-like vessels. The structural regression of the high-flow AV shunts returned blood to capillaries, thus reversing tissue hypoxia. This regression was initiated by vessel narrowing without the loss of ECs and required restoration of EphB4 receptor expression by venous ECs. Normalization of Notch signaling resulting in regression of high-flow AV shunts, and a return to normal blood flow suggests that targeting the Notch pathway may be useful therapeutically for treating diseases such as AVMs.
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Affiliation(s)
- Patrick A Murphy
- Laboratory for Accelerated Vascular Research, Division of Vascular Surgery, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
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2510
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Boyer SW, Schroeder AV, Smith-Berdan S, Forsberg EC. All hematopoietic cells develop from hematopoietic stem cells through Flk2/Flt3-positive progenitor cells. Cell Stem Cell 2012; 9:64-73. [PMID: 21726834 DOI: 10.1016/j.stem.2011.04.021] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 03/18/2011] [Accepted: 04/22/2011] [Indexed: 01/09/2023]
Abstract
While it is clear that a single hematopoietic stem cell (HSC) is capable of giving rise to all other hematopoietic cell types, the differentiation paths beyond HSC remain controversial. Contradictory reports on the lineage potential of progenitor populations have questioned their physiological contribution of progenitor populations to multilineage differentiation. Here, we established a lineage tracing mouse model that enabled direct assessment of differentiation pathways in vivo. We provide definitive evidence that differentiation into all hematopoietic lineages, including megakaryocyte/erythroid cell types, involves Flk2-expressing non-self-renewing progenitors. A Flk2+ stage was used during steady-state hematopoiesis, after irradiation-induced stress and upon HSC transplantation. In contrast, HSC origin and maintenance do not include a Flk2+ stage. These data demonstrate that HSC specification and maintenance are Flk2 independent, and that hematopoietic lineage separation occurs downstream of Flk2 upregulation.
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Affiliation(s)
- Scott W Boyer
- Program in Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064, USA
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2511
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Fuerst PG, Bruce F, Rounds RP, Erskine L, Burgess RW. Cell autonomy of DSCAM function in retinal development. Dev Biol 2012; 361:326-37. [PMID: 22063212 PMCID: PMC3246579 DOI: 10.1016/j.ydbio.2011.10.028] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2011] [Revised: 10/19/2011] [Accepted: 10/21/2011] [Indexed: 01/19/2023]
Abstract
Cell adhesion molecules (CAMs) provide identifying cues by which neural architecture is sculpted. The Down Syndrome Cell Adhesion Molecule (DSCAM) is required for many neurodevelopmental processes in different species and also has several potential mechanisms of activity, including homophilic adhesion, homophilic repulsion and heterophilic interactions. In the mouse retina, Dscam is expressed in many, but not all neuronal subtypes. Mutations in Dscam cause the fasciculation of dendrites of neighboring homotypic neurons, indicating a role in self-avoidance among cells of a given type, a disruption of the non-random patterning of their cell bodies, and a decrease in developmental cell death in affected cell populations. In order to address how DSCAM facilitates retinal pattering, we developed a conditional allele of Dscam to use alongside existing Dscam mutant mouse strains. Conditional deletion of Dscam reproduces cell spacing, cell number and dendrite arborization defects. Inducible deletion of Dscam and retinal ganglion cell depletion in Brn3b mutant retinas both indicate that these DSCAM-mediated phenotypes can occur independently. In chimeric retinas, in which wild type and Dscam mutant cells are comingled, Dscam mutant cells entangle adjacent wild type cells of the same type, as if both cells were lacking Dscam, consistent with DSCAM-dependent cell spacing and neurite arborization being mediated through homophilic binding cell-to-cell. Deletion of Dscam in specific cell types causes cell-type-autonomous cell body spacing defects, indicating that DSCAM mediates arborization and spacing by acting within given cell types. We also examine the cell autonomy of DSCAM in laminar stratification and find that laminar disorganization can be caused in a non-cell autonomous fashion. Finally, we find Dscam dosage-dependent defects in developmental cell death and amacrine cell spacing, relevant to the increased cell death and other disorders observed in Down syndrome mouse models and human patients, in which Dscam is present in three copies.
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Affiliation(s)
- Peter G Fuerst
- Department of Biological Sciences and WWAMI Medical Education Program, University of Idaho, Moscow, ID 83844, USA.
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2512
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Gautron L, Sakata I, Udit S, Zigman JM, Wood JN, Elmquist JK. Genetic tracing of Nav1.8-expressing vagal afferents in the mouse. J Comp Neurol 2012; 519:3085-101. [PMID: 21618224 DOI: 10.1002/cne.22667] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nav1.8 is a tetrodotoxin-resistant sodium channel present in large subsets of peripheral sensory neurons, including both spinal and vagal afferents. In spinal afferents, Nav1.8 plays a key role in signaling different types of pain. Little is known, however, about the exact identity and role of Nav1.8-expressing vagal neurons. Here we generated mice with restricted expression of tdTomato fluorescent protein in all Nav1.8-expressing afferent neurons. As a result, intense fluorescence was visible in the cell bodies, central relays, and sensory endings of these neurons, revealing the full extent of their innervation sites in thoracic and abdominal viscera. For instance, vagal and spinal Nav1.8-expressing endings were seen clearly within the gastrointestinal mucosa and myenteric plexus, respectively. In the gastrointestinal muscle wall, labeled endings included a small subset of vagal tension receptors but not any stretch receptors. We also examined the detailed innervation of key metabolic tissues such as liver and pancreas and evaluated the anatomical relationship of Nav1.8-expressing vagal afferents with select enteroendocrine cells (i.e., ghrelin, glucagon, GLP-1). Specifically, our data revealed the presence of Nav1.8-expressing vagal afferents in several metabolic tissues and varying degrees of proximity between Nav1.8-expressing mucosal afferents and enteroendocrine cells, including apparent neuroendocrine apposition. In summary, this study demonstrates the power and versatility of the Cre-LoxP technology to trace identified visceral afferents, and our data suggest a previously unrecognized role for Nav1.8-expressing vagal neurons in gastrointestinal functions.
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Affiliation(s)
- Laurent Gautron
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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2513
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Li JL, Goh CC, Keeble JL, Qin JS, Roediger B, Jain R, Wang Y, Chew WK, Weninger W, Ng LG. Intravital multiphoton imaging of immune responses in the mouse ear skin. Nat Protoc 2012; 7:221-34. [PMID: 22240584 DOI: 10.1038/nprot.2011.438] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Multiphoton (MP) microscopy enables the direct in vivo visualization, with high spatial and temporal resolution, of fluorescently tagged immune cells, extracellular matrix and vasculature in tissues. This approach, therefore, represents a powerful alternative to traditional methods of assessing immune cell function in the skin, which are mainly based on flow cytometry and histology. Here we provide a step-by-step protocol describing experimental procedures for intravital MP imaging of the mouse ear skin, which can be easily adapted to address many specific skin-related biological questions. We demonstrate the use of this procedure by characterizing the response of neutrophils during cutaneous inflammation, which can be used to perform in-depth analysis of neutrophil behavior in the context of the skin microanatomy, including the epidermis, dermis and blood vessels. Such experiments are typically completed within 1 d, but as the procedures are minimally invasive, it is possible to perform longitudinal studies through repeated imaging.
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Affiliation(s)
- Jackson LiangYao Li
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore
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2514
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Scotti M, Kmita M. Recruitment of 5' Hoxa genes in the allantois is essential for proper extra-embryonic function in placental mammals. Development 2012; 139:731-9. [PMID: 22219351 DOI: 10.1242/dev.075408] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Hox gene family is well known for its functions in establishing morphological diversity along the anterior-posterior axis of developing embryos. In mammals, one of these genes, Hoxa13, is crucial for embryonic survival, as its function is required for the proper expansion of the fetal vasculature in the placenta. Thus, it appears that the developmental strategy specific to placental mammals is linked, at least in part, to the recruitment of Hoxa13 function in developing extra-embryonic tissues. Yet, the mechanism underlying this extra-embryonic recruitment is unknown. Here, we provide evidence that this functional novelty is not exclusive to Hoxa13 but is shared with its neighboring Hoxa11 and Hoxa10 genes. We show that the extra-embryonic function of these three Hoxa genes stems from their specific expression in the allantois, an extra-embryonic hallmark of amniote vertebrates. Interestingly, Hoxa10-13 expression in the allantois is conserved in chick embryos, which are non-placental amniotes, suggesting that the extra-embryonic recruitment of Hoxa10, Hoxa11 and Hoxa13 most likely arose in amniotes, i.e. prior to the emergence of placental mammals. Finally, using a series of targeted recombination and transgenic assays, we provide evidence that the regulatory mechanism underlying Hoxa expression in the allantois is extremely complex and relies on several cis-regulatory sequences.
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Affiliation(s)
- Martina Scotti
- Laboratory of Genetics and Development, Institut de Recherches Cliniques de Montréal, Université de Montréal, 110 avenue des Pins Ouest, Montréal, Québec, Canada
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2515
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Zhou B, Pu WT. Isolation and characterization of embryonic and adult epicardium and epicardium-derived cells. Methods Mol Biol 2012; 843:155-68. [PMID: 22222530 DOI: 10.1007/978-1-61779-523-7_15] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Epicardium is the outer cell layer of the heart. Its integrity and function are essential for normal heart development. To study the role of epicardium in both fetal and adult hearts, it is desirable to isolate and culture pure populations of these cells. Here we describe methods with Cre-loxP technology to lineage tag epicardial cells (EpiCs) and epicardium-derived cells (EPDCs), dissociate and isolate them by flow-activated cytometry sorting (FACS), and characterize them by quantitative PCR and immunostaining. This platform allows further characterization and manipulation of EpiCs and EPDCs for expression studies and functional assays.
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Affiliation(s)
- Bin Zhou
- Department of Cardiology, Children's Hospital Boston, Boston, MA, USA.
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2516
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Xenopoulos P, Nowotschin S, Hadjantonakis AK. Live imaging fluorescent proteins in early mouse embryos. Methods Enzymol 2012; 506:361-89. [PMID: 22341233 DOI: 10.1016/b978-0-12-391856-7.00042-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mouse embryonic development comprises highly dynamic and coordinated events that drive key cell lineage specification and morphogenetic events. These processes involve cellular behaviors including proliferation, migration, apoptosis, and differentiation, each of which is regulated both spatially and temporally. Live imaging of developing embryos provides an essential tool to investigate these coordinated processes in three-dimensional space over time. For this purpose, the development and application of genetically encoded fluorescent protein (FP) reporters has accelerated over the past decade allowing for the high-resolution visualization of developmental progression. Ongoing efforts are aimed at generating improved reporters, where spectrally distinct as well as novel FPs whose optical properties can be photomodulated, are exploited for live imaging of mouse embryos. Moreover, subcellular tags in combination with using FPs allow for the visualization of multiple subcellular characteristics, such as cell position and cell morphology, in living embryos. Here, we review recent advances in the application of FPs for live imaging in the early mouse embryo, as well as some of the methods used for ex utero embryo development that facilitate on-stage time-lapse specimen visualization.
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2517
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Liu W, Liu Y, Lai X, Kuang S. Intramuscular adipose is derived from a non-Pax3 lineage and required for efficient regeneration of skeletal muscles. Dev Biol 2012; 361:27-38. [PMID: 22037676 PMCID: PMC3321350 DOI: 10.1016/j.ydbio.2011.10.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 10/02/2011] [Accepted: 10/03/2011] [Indexed: 12/22/2022]
Abstract
Ectopic accumulation of adipose in the skeletal muscle is associated with muscle wasting, insulin resistance and diabetes. However, the developmental origin of postnatal intramuscular adipose and its interaction with muscle tissue are unclear. We report here that compared to the fast EDL muscles, slow SOL muscles are more enriched with adipogenic progenitors and have higher propensity to form adipose. Using Cre/LoxP mediated lineage tracing in mice, we show that intramuscular adipose in both EDL and SOL muscles is exclusively derived from a Pax3(-) non-myogenic lineage. In contrast, inter-scapular brown adipose is derived from the Pax3(+) lineage. To dissect the interaction between adipose and skeletal muscle tissues, we used Myf5-Cre and aP2-Cre mice in combination with ROSA26-iDTR mice to genetically ablate myogenic and adipogenic cell lineages, respectively. Whereas ablation of the myogenic cell lineage facilitated adipogenic differentiation, ablation of the adipogenic cell lineage surprisingly impaired the regeneration of acutely injured skeletal muscles. These results reveal striking heterogeneity of tissue-specific adipose and a previously unappreciated role of intramuscular adipose in skeletal muscle regeneration.
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Affiliation(s)
- Weiyi Liu
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Yaqin Liu
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Xinsheng Lai
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Shihuan Kuang
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
- Purdue University Center for Cancer Research, West Lafayette, IN 47907, USA
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2518
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Abstract
A major challenge in neuroscience is to understand how universal behaviors, such as sensation, movement, cognition, and emotion, arise from the interactions of specific cells that are present within intricate neural networks in the brain. Dissection of such complex networks has typically relied on disturbing the activity of individual gene products, perturbing neuronal activities pharmacologically, or lesioning specific brain regions, to investigate the network's response in a behavioral output. Though informative for many kinds of studies, these approaches are not sufficiently fine-tuned for examining the functionality of specific cells or cell classes in a spatially or temporally restricted context. Recent advances in the field of optogenetics now enable researchers to monitor and manipulate the activity of genetically defined cell populations with the speed and precision uniquely afforded by light. Transgenic mice engineered to express optogenetic tools in a cell type-specific manner offer a powerful approach for examining the role of particular cells in discrete circuits in a defined and reproducible way. Not surprisingly then, recent years have seen substantial efforts directed toward generating transgenic mouse lines that express functionally relevant levels of optogenetic tools. In this chapter, we review the state of these efforts and consider aspects of the current technology that would benefit from additional improvement.
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Affiliation(s)
- Hongkui Zeng
- Allen Institute for Brain Science, Seattle, WA, USA.
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2519
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Rawlins EL, Perl AK. The a"MAZE"ing world of lung-specific transgenic mice. Am J Respir Cell Mol Biol 2011; 46:269-82. [PMID: 22180870 DOI: 10.1165/rcmb.2011-0372ps] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The purpose of this review is to give a comprehensive overview of transgenic mouse lines suitable for studying gene function and cellular lineage relationships in lung development, homeostasis, injury, and repair. Many of the mouse strains reviewed in this Perspective have been widely shared within the lung research community, and new strains are continuously being developed. There are many transgenic lines that target subsets of lung cells, but it remains a challenge for investigators to select the correct transgenic modules for their experiment. This review covers the tetracycline- and tamoxifen-inducible systems and focuses on conditional lines that target the epithelial cells. We point out the limitations of each strain so investigators can choose the system that will work best for their scientific question. Current mesenchymal and endothelial lines are limited by the fact that they are not lung specific. These lines are summarized in a brief overview. In addition, useful transgenic reporter mice for studying lineage relationships, promoter activity, and signaling pathways will complete our lung-specific conditional transgenic mouse shopping list.
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Affiliation(s)
- Emma L Rawlins
- Children's Hospital Medical Center, Divisions of Neonatology and Pulmonary Biology, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
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2520
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Lethal arrhythmias in Tbx3-deficient mice reveal extreme dosage sensitivity of cardiac conduction system function and homeostasis. Proc Natl Acad Sci U S A 2011; 109:E154-63. [PMID: 22203979 DOI: 10.1073/pnas.1115165109] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
TBX3 is critical for human development: mutations in TBX3 cause congenital anomalies in patients with ulnar-mammary syndrome. Data from mice and humans suggest multiple roles for Tbx3 in development and function of the cardiac conduction system. The mechanisms underlying the functional development, maturation, and maintenance of the conduction system are not well understood. We tested the requirements for Tbx3 in these processes. We generated a unique series of Tbx3 hypomorphic and conditional mouse mutants with varying levels and locations of Tbx3 activity within the heart, and developed techniques for evaluating in vivo embryonic conduction system function. Disruption of Tbx3 function in different regions of the developing heart causes discrete phenotypes and lethal arrhythmias: sinus pauses and bradycardia indicate sinoatrial node dysfunction, whereas preexcitation and atrioventricular block reveal abnormalities in the atrioventricular junction. Surviving Tbx3 mutants are at increased risk for sudden death. Arrhythmias induced by knockdown of Tbx3 in adults reveal its requirement for conduction system homeostasis. Arrhythmias in Tbx3-deficient embryos are accompanied by disrupted expression of multiple ion channels despite preserved expression of previously described conduction system markers. These findings indicate that Tbx3 is required for the conduction system to establish and maintain its correct molecular identity and functional properties. In conclusion, Tbx3 is required for the functional development, maturation, and homeostasis of the conduction system in a highly dosage-sensitive manner. TBX3 and its regulatory targets merit investigation as candidates for human arrhythmias.
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2521
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Sachs N, Claessen N, Aten J, Kreft M, Teske GJD, Koeman A, Zuurbier CJ, Janssen H, Sonnenberg A. Blood pressure influences end-stage renal disease of Cd151 knockout mice. J Clin Invest 2011; 122:348-58. [PMID: 22201679 DOI: 10.1172/jci58878] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 10/12/2011] [Indexed: 11/17/2022] Open
Abstract
Podocytes of the kidney adhere tightly to the underlying glomerular basement membrane (GBM) in order to maintain a functional filtration barrier. The clinical importance of podocyte binding to the GBM via an integrin-laminin-actin axis has been illustrated in models with altered function of α3β1 integrin, integrin-linked kinase, laminin-521, and α-actinin 4. Here we expanded on the podocyte-GBM binding model by showing that the main podocyte adhesion receptor, integrin α3β1, interacts with the tetraspanin CD151 in situ in humans. Deletion of Cd151 in mouse glomerular epithelial cells led to reduced adhesive strength to laminin by redistributing α3β1 at the cell-matrix interface. Moreover, in vivo podocyte-specific deletion of Cd151 led to glomerular nephropathy. Although global Cd151-null B6 mice were not susceptible to renal disease, as has been shown previously, increasing blood and transcapillary filtration pressure induced nephropathy in these mice. Importantly, blocking the angiotensin-converting enzyme in renal disease-susceptible global Cd151-null FVB mice prolonged their median life span. Together, these results establish CD151 as a crucial modifier of integrin-mediated adhesion of podocytes to the GBM and show that blood pressure is an important factor in the initiation and progression of Cd151 knockout-induced nephropathy.
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Affiliation(s)
- Norman Sachs
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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2522
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Williams M, Burdsal C, Periasamy A, Lewandoski M, Sutherland A. Mouse primitive streak forms in situ by initiation of epithelial to mesenchymal transition without migration of a cell population. Dev Dyn 2011; 241:270-83. [PMID: 22170865 DOI: 10.1002/dvdy.23711] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2011] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND During gastrulation, an embryo acquires the three primordial germ layers that will give rise to all of the tissues in the body. In amniote embryos, this process occurs via an epithelial to mesenchymal transition (EMT) of epiblast cells at the primitive streak. Although the primitive streak is vital to development, many aspects of how it forms and functions remain poorly understood. RESULTS Using live, 4 dimensional imaging and immunohistochemistry, we have shown that the posterior epiblast of the pre-streak murine embryo does not display convergence and extension behavior or large scale migration or rearrangement of a cell population. Instead, the primitive streak develops in situ and elongates by progressive initiation EMT in the posterior epiblast. Loss of basal lamina (BL) is the first step of this EMT, and is strictly correlated with ingression of nascent mesoderm. Once the BL is lost in a given region, cells leave the epiblast by apical constriction in order to enter the primitive streak. CONCLUSIONS This is the first description of dynamic cell behavior during primitive streak formation in the mouse embryo, and reveals mechanisms that are quite distinct from those observed in other amniote model systems. Unlike chick and rabbit, the murine primitive streak arises in situ by progressive initiation of EMT beginning in the posterior epiblast, without large-scale movement or convergence and extension of epiblast cells.
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Affiliation(s)
- Margot Williams
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA
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2523
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DeMaio L, Buckley ST, Krishnaveni MS, Flodby P, Dubourd M, Banfalvi A, Xing Y, Ehrhardt C, Minoo P, Zhou B, Crandall ED, Borok Z. Ligand-independent transforming growth factor-β type I receptor signalling mediates type I collagen-induced epithelial-mesenchymal transition. J Pathol 2011; 226:633-44. [PMID: 21984393 DOI: 10.1002/path.3016] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 08/26/2011] [Accepted: 09/23/2011] [Indexed: 12/21/2022]
Abstract
Evidence suggests epithelial-mesenchymal transition (EMT) as one potential source of fibroblasts in idiopathic pulmonary fibrosis. To assess the contribution of alveolar epithelial cell (AEC) EMT to fibroblast accumulation in vivo following lung injury and the influence of extracellular matrix on AEC phenotype in vitro, Nkx2.1-Cre;mT/mG mice were generated in which AECs permanently express green fluorescent protein (GFP). On days 17-21 following intratracheal bleomycin administration, ~4% of GFP-positive epithelial-derived cells expressed vimentin or α-smooth muscle actin (α-SMA). Primary AECs from Nkx2.1-Cre;mT/mG mice cultured on laminin-5 or fibronectin maintained an epithelial phenotype. In contrast, on type I collagen, cells of epithelial origin displayed nuclear localization of Smad3, acquired spindle-shaped morphology, expressed α-SMA and phospho-Smad3, consistent with activation of the transforming growth factor-β (TGFβ) signalling pathway and EMT. α-SMA induction and Smad3 nuclear localization were blocked by the TGFβ type I receptor (TβRI, otherwise known as Alk5) inhibitor SB431542, while AEC derived from Nkx2.1-Cre;Alk5(flox/KO) mice did not undergo EMT on collagen, consistent with a requirement for signalling via Alk5 in collagen-induced EMT. Inability of a pan-specific TGFβ neutralizing antibody to inhibit effects of collagen together with absence of active TGFβ in culture supernatants is consistent with TGFβ ligand-independent activation of Smad signalling. These results support the notion that AECs can acquire a mesenchymal phenotype following injury in vivo and implicate type I collagen as a key regulator of EMT in AECs through signalling via Alk5, likely in a TGFβ ligand-independent manner.
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Affiliation(s)
- Lucas DeMaio
- Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Southern California, CA 90033, USA
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2524
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Takeda N, Jain R, LeBoeuf MR, Wang Q, Lu MM, Epstein JA. Interconversion between intestinal stem cell populations in distinct niches. Science 2011; 334:1420-4. [PMID: 22075725 PMCID: PMC3705713 DOI: 10.1126/science.1213214] [Citation(s) in RCA: 576] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Intestinal epithelial stem cell identity and location have been the subject of substantial research. Cells in the +4 niche are slow-cycling and label-retaining, whereas a different stem cell niche located at the crypt base is occupied by crypt base columnar (CBC) cells. CBCs are distinct from +4 cells, and the relationship between them is unknown, though both give rise to all intestinal epithelial lineages. We demonstrate that Hopx, an atypical homeobox protein, is a specific marker of +4 cells. Hopx-expressing cells give rise to CBCs and all mature intestinal epithelial lineages. Conversely, CBCs can give rise to +4 Hopx-positive cells. These findings demonstrate a bidirectional lineage relationship between active and quiescent stem cells in their niches.
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Affiliation(s)
- Norifumi Takeda
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Institute of Regenerative Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Rajan Jain
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Institute of Regenerative Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew R. LeBoeuf
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Dermatology Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Qiaohong Wang
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Institute of Regenerative Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Min Min Lu
- Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jonathan A. Epstein
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Penn Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Institute of Regenerative Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
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2525
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Sun M, Chen S, Adams SM, Florer JB, Liu H, Kao WWY, Wenstrup RJ, Birk DE. Collagen V is a dominant regulator of collagen fibrillogenesis: dysfunctional regulation of structure and function in a corneal-stroma-specific Col5a1-null mouse model. J Cell Sci 2011; 124:4096-105. [PMID: 22159420 DOI: 10.1242/jcs.091363] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Collagen V is a regulatory fibril-forming collagen that forms heterotypic fibrils with collagen I. Deletion of collagen V in the mouse is associated with a lack of fibril assembly in the embryonic mesenchyme, with a resultant lethal phenotype. The current work elucidates the regulatory roles of collagen V during development and growth of tissues. A conditional mouse model with a mutation in Col5a1 was developed using a Cre-loxP approach. Col5a1 was ablated in Col5a1(flox/flox) mice using a cornea stroma-specific Kera-Cre driver mouse to produce a bitransgenic Col5a1(Δst/Δst) line that is null for collagen V. This permits analyses of the corneal stroma, a widely used model for studies of collagen V. The collagen-V-knockout stroma demonstrated severe dysfunctional regulation of fibrillogenesis. Fibril diameters were significantly increased, with an abnormal, heterogeneous distribution; fibril structure was abnormal, fibril number was decreased and lamellae were disorganized with decreased stroma thickness. The phenotype was more severe in the anterior versus posterior stroma. Opacity was demonstrated throughout the Col5a1(Δst/Δst) stroma, with significantly increased haze intensity compared with control mice. These data indicate central regulatory roles for collagen V in fibril and matrix assembly during tissue development, with dysfunctional regulation resulting in a functional loss of transparency.
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Affiliation(s)
- Mei Sun
- Department of Pathology and Cell Biology, University of South Florida College of Medicine, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
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2526
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Powell KA, Wilson D. 3-dimensional imaging modalities for phenotyping genetically engineered mice. Vet Pathol 2011; 49:106-15. [PMID: 22146851 DOI: 10.1177/0300985811429814] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A variety of 3-dimensional (3D) digital imaging modalities are available for whole-body assessment of genetically engineered mice: magnetic resonance microscopy (MRM), X-ray microcomputed tomography (microCT), optical projection tomography (OPT), episcopic and cryoimaging, and ultrasound biomicroscopy (UBM). Embryo and adult mouse phenotyping can be accomplished at microscopy or near microscopy spatial resolutions using these modalities. MRM and microCT are particularly well-suited for evaluating structural information at the organ level, whereas episcopic and OPT imaging provide structural and functional information from molecular fluorescence imaging at the cellular level. UBM can be used to monitor embryonic development longitudinally in utero. Specimens are not significantly altered during preparation, and structures can be viewed in their native orientations. Technologies for rapid automated data acquisition and high-throughput phenotyping have been developed and continually improve as this exciting field evolves.
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Affiliation(s)
- K A Powell
- Small Animal Imaging Shared Resource, The James Comprehensive Cancer Center Department of Biomedical Informatics, Ohio State University, Columbus, Ohio, USA.
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2527
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Alvarez JI, Dodelet-Devillers A, Kebir H, Ifergan I, Fabre PJ, Terouz S, Sabbagh M, Wosik K, Bourbonnière L, Bernard M, van Horssen J, de Vries HE, Charron F, Prat A. The Hedgehog pathway promotes blood-brain barrier integrity and CNS immune quiescence. Science 2011; 334:1727-31. [PMID: 22144466 DOI: 10.1126/science.1206936] [Citation(s) in RCA: 566] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The blood-brain barrier (BBB) is composed of tightly bound endothelial cells (ECs) and perivascular astrocytes that regulate central nervous system (CNS) homeostasis. We showed that astrocytes secrete Sonic hedgehog and that BBB ECs express Hedgehog (Hh) receptors, which together promote BBB formation and integrity during embryonic development and adulthood. Using pharmacological inhibition and genetic inactivation of the Hh signaling pathway in ECs, we also demonstrated a critical role of the Hh pathway in promoting the immune quiescence of BBB ECs by decreasing the expression of proinflammatory mediators and the adhesion and migration of leukocytes, in vivo and in vitro. Overall, the Hh pathway provides a barrier-promoting effect and an endogenous anti-inflammatory balance to CNS-directed immune attacks, as occurs in multiple sclerosis.
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Affiliation(s)
- Jorge Ivan Alvarez
- Neuroimmunology Unit, Center of Excellence in Neuromics, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Faculty of Medicine, Université de Montréal, Montréal, Quebec, Canada
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2528
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Srinivasan RS, Oliver G. Prox1 dosage controls the number of lymphatic endothelial cell progenitors and the formation of the lymphovenous valves. Genes Dev 2011; 25:2187-97. [PMID: 22012621 DOI: 10.1101/gad.16974811] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Arteries, veins, and lymphatic vessels are functionally linked, and their physical interaction is tightly regulated. The lymphatic vessels communicate with the blood vessels only at the junction of the jugular and subclavian veins. Here, we characterize the embryonic lymphovenous valves controlling this vital communication and show that they are formed by the intercalation of lymphatic endothelial cells (LECs) with a subpopulation of venous endothelial cells (ECs) at the junction of the jugular and subclavian veins. We found that unlike LEC progenitors, which move out from the veins and differentiate into mature LECs, these Prox1-expressing ECs remain in the veins and do not acquire LEC features. We demonstrate that the development of this Prox1-expressing venous EC population, and therefore of lymphovenous valves, requires two functional copies of Prox1, as the valves are absent in Prox1 heterozygous mice. We show that this is due to a defect in the maintenance of Prox1 expression in venous ECs and LEC progenitors promoted by a reduction in Coup-TFII/Prox1 complex formation. This is the first report describing the molecular mechanism controlling lymphovenous communication.
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Affiliation(s)
- R Sathish Srinivasan
- Department of Genetics, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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2529
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Abstract
Reconstructing the lineage of cells is central to understanding development and is now also an important issue in stem cell research. Technological advances in genetically engineered permanent cell labeling, together with a multiplicity of fluorescent markers and sophisticated imaging, open new possibilities for prospective and retrospective clonal analysis.
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Affiliation(s)
- Margaret E Buckingham
- Molecular Genetics of Development Unit, CNRS URA 2578, Department of Developmental Biology, Institut Pasteur, Paris, France.
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2530
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Berlin I, Luciani F, Gallagher SJ, Rambow F, Conde-Perez A, Colombo S, Champeval D, Delmas V, Larue L. General strategy to analyse coat colour phenotypes in mice. Pigment Cell Melanoma Res 2011; 25:117-9. [PMID: 22085368 DOI: 10.1111/j.1755-148x.2011.00912.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Irina Berlin
- Institut Curie, Developmental Genetics of Melanocytes, Orsay, France
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2531
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Le Bouffant R, Souquet B, Duval N, Duquenne C, Hervé R, Frydman N, Robert B, Habert R, Livera G. Msx1 and Msx2 promote meiosis initiation. Development 2011; 138:5393-402. [PMID: 22071108 DOI: 10.1242/dev.068452] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanisms regulating germ line sex determination and meiosis initiation are poorly understood. Here, we provide evidence for the involvement of homeobox Msx transcription factors in foetal meiosis initiation in mammalian germ cells. Upon meiosis initiation, Msx1 and Msx2 genes are strongly expressed in the foetal ovary, possibly stimulated by soluble factors found there: bone morphogenetic proteins Bmp2 and Bmp4, and retinoic acid. Analysis of Msx1/Msx2 double mutant embryos revealed a majority of undifferentiated germ cells remaining in the ovary and, importantly, a decrease in the number of meiotic cells. In vivo, the Msx1/Msx2 double-null mutation prevented full activation of Stra8, a gene required for meiosis. In F9 cells, Msx1 can bind to Stra8 regulatory sequences and Msx1 overexpression stimulates Stra8 transcription. Collectively, our data demonstrate for the first time that some homeobox genes are required for meiosis initiation in the female germ line.
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Affiliation(s)
- Ronan Le Bouffant
- CEA, DSV/iRCM/SCSR/LDG, Laboratoire de Développement des Gonades, Unité Cellules Souches et Radiation, F-92265 Fontenay aux Roses, France
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2532
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Ramadas RA, Roche MI, Moon JJ, Ludwig T, Xavier RJ, Medoff BD. CARMA1 is necessary for optimal T cell responses in a murine model of allergic asthma. THE JOURNAL OF IMMUNOLOGY 2011; 187:6197-207. [PMID: 22075698 DOI: 10.4049/jimmunol.1101348] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
CARMA1 is a lymphocyte-specific scaffold protein necessary for T cell activation. Deletion of CARMA1 prevents the development of allergic airway inflammation in a mouse model of asthma due to a defect in naive T cell activation. However, it is unknown if CARMA1 is important for effector and memory T cell responses after the initial establishment of inflammation, findings that would be more relevant to asthma therapies targeted to CARMA1. In the current study, we sought to elucidate the role of CARMA1 in T cells that have been previously activated. Using mice in which floxed CARMA1 exons can be selectively deleted in T cells by OX40-driven Cre recombinase (OX40(+/Cre)CARMA1(F/F)), we report that CD4(+) T cells from these mice have impaired T cell reactivation responses and NF-κB signaling in vitro. Furthermore, in an in vivo recall model of allergic airway inflammation that is dependent on memory T cell function, OX40(+/Cre)CARMA1(F/F) mice have attenuated eosinophilic airway inflammation, T cell activation, and Th2 cytokine production. Using MHC class II tetramers, we demonstrate that the development and maintenance of Ag-specific memory T cells is not affected in OX40(+/Cre)CARMA1(F/F) mice. In addition, adoptive transfer of Th2-polarized OX40(+/Cre)CARMA1(F/F) Ag-specific CD4(+) T cells into wild-type mice induces markedly less airway inflammation in response to Ag challenge than transfer of wild-type Th2 cells. These data demonstrate a novel role for CARMA1 in effector and memory T cell responses and suggest that therapeutic strategies targeting CARMA1 could help treat chronic inflammatory disorders such as asthma.
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Affiliation(s)
- Ravisankar A Ramadas
- Pulmonary and Critical Care Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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2533
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Stegbauer J, Gurley SB, Sparks MA, Woznowski M, Kohan DE, Yan M, Lehrich RW, Coffman TM. AT1 receptors in the collecting duct directly modulate the concentration of urine. J Am Soc Nephrol 2011; 22:2237-46. [PMID: 22052052 DOI: 10.1681/asn.2010101095] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Mice lacking AT(1) angiotensin receptors have an impaired capacity to concentrate the urine, but the underlying mechanism is unknown. To determine whether direct actions of AT(1) receptors in epithelial cells of the collecting duct regulate water reabsorption, we used Cre-Loxp technology to specifically eliminate AT(1A) receptors from the collecting duct in mice (CD-KOs). Although levels of AT(1A) receptor mRNA in the inner medulla of CD-KO mice were significantly reduced, their kidneys appeared structurally normal. Under basal conditions, plasma and urine osmolalities and urine volumes were similar between CD-KO mice and controls. The increase in urine osmolality in response to water deprivation or vasopressin administration, however, was consistently attenuated in CD-KO mice. Similarly, levels of aquaporin-2 protein in inner and outer medulla after water deprivation were significantly lower in CD-KO mice compared with controls, despite its normal localization to the apical membrane. In summary, these results demonstrate that AT(1A) receptors in epithelial cells of the collecting duct directly modulate aquaporin-2 levels and contribute to the concentration of urine.
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Affiliation(s)
- Johannes Stegbauer
- Department of Medicine, Division of Nephrology, Duke University Medical Center, MSRBII Room 2018, 106 Research Drive, Durham, NC 27710, USA
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2534
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Abstract
It has been reported that the intracellular antiapoptotic factor myeloid cell leukemia sequence 1 (Mcl-1) is required for mast cell survival in vitro, and that genetic manipulation of Mcl-1 can be used to delete individual hematopoietic cell populations in vivo. In the present study, we report the generation of C57BL/6 mice in which Cre recombinase is expressed under the control of a segment of the carboxypeptidase A3 (Cpa3) promoter. C57BL/6-Cpa3-Cre; Mcl-1(fl/fl) mice are severely deficient in mast cells (92%-100% reduced in various tissues analyzed) and also have a marked deficiency in basophils (58%-78% reduced in the compartments analyzed), whereas the numbers of other hematopoietic cell populations exhibit little or no changes. Moreover, Cpa3-Cre; Mcl-1(fl/fl) mice exhibited marked reductions in the tissue swelling and leukocyte infiltration that are associated with both mast cell- and IgE-dependent passive cutaneous anaphylaxis (except at sites engrafted with in vitro-derived mast cells) and a basophil- and IgE-dependent model of chronic allergic inflammation, and do not develop IgE-dependent passive systemic anaphylaxis. Our findings support the conclusion that Mcl-1 is required for normal mast cell and basophil development/survival in vivo in mice, and also suggest that Cpa3-Cre; Mcl-1(fl/fl) mice may be useful in analyzing the roles of mast cells and basophils in health and disease.
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2535
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Murphy MM, Lawson JA, Mathew SJ, Hutcheson DA, Kardon G. Satellite cells, connective tissue fibroblasts and their interactions are crucial for muscle regeneration. Development 2011; 138:3625-37. [PMID: 21828091 DOI: 10.1242/dev.064162] [Citation(s) in RCA: 838] [Impact Index Per Article: 64.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Muscle regeneration requires the coordinated interaction of multiple cell types. Satellite cells have been implicated as the primary stem cell responsible for regenerating muscle, yet the necessity of these cells for regeneration has not been tested. Connective tissue fibroblasts also are likely to play a role in regeneration, as connective tissue fibrosis is a hallmark of regenerating muscle. However, the lack of molecular markers for these fibroblasts has precluded an investigation of their role. Using Tcf4, a newly identified fibroblast marker, and Pax7, a satellite cell marker, we found that after injury satellite cells and fibroblasts rapidly proliferate in close proximity to one another. To test the role of satellite cells and fibroblasts in muscle regeneration in vivo, we created Pax7(CreERT2) and Tcf4(CreERT2) mice and crossed these to R26R(DTA) mice to genetically ablate satellite cells and fibroblasts. Ablation of satellite cells resulted in a complete loss of regenerated muscle, as well as misregulation of fibroblasts and a dramatic increase in connective tissue. Ablation of fibroblasts altered the dynamics of satellite cells, leading to premature satellite cell differentiation, depletion of the early pool of satellite cells, and smaller regenerated myofibers. Thus, we provide direct, genetic evidence that satellite cells are required for muscle regeneration and also identify resident fibroblasts as a novel and vital component of the niche regulating satellite cell expansion during regeneration. Furthermore, we demonstrate that reciprocal interactions between fibroblasts and satellite cells contribute significantly to efficient, effective muscle regeneration.
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Affiliation(s)
- Malea M Murphy
- Department of Human Genetics, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA
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2536
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Ghosh S, Lau H, Simons BW, Powell JD, Meyers DJ, De Marzo AM, Berman DM, Lotan TL. PI3K/mTOR signaling regulates prostatic branching morphogenesis. Dev Biol 2011; 360:329-42. [PMID: 22015718 DOI: 10.1016/j.ydbio.2011.09.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 08/24/2011] [Accepted: 09/26/2011] [Indexed: 11/26/2022]
Abstract
Prostatic branching morphogenesis is an intricate event requiring precise temporal and spatial integration of numerous hormonal and growth factor-regulated inputs, yet relatively little is known about the downstream signaling pathways that orchestrate this process. In this study, we use a novel mesenchyme-free embryonic prostate culture system, newly available mTOR inhibitors and a conditional PTEN loss-of-function model to investigate the role of the interconnected PI3K and mTOR signaling pathways in prostatic organogenesis. We demonstrate that PI3K levels and PI3K/mTOR activity are robustly induced by androgen during murine prostatic development and that PI3K/mTOR signaling is necessary for prostatic epithelial bud invasion of surrounding mesenchyme. To elucidate the cellular mechanism by which PI3K/mTOR signaling regulates prostatic branching, we show that PI3K/mTOR inhibition does not significantly alter epithelial proliferation or apoptosis, but rather decreases the efficiency and speed with which the developing prostatic epithelial cells migrate. Using mTOR kinase inhibitors to tease out the independent effects of mTOR signaling downstream of PI3K, we find that simultaneous inhibition of mTORC1 and mTORC2 activity attenuates prostatic branching and is sufficient to phenocopy combined PI3K/mTOR inhibition. Surprisingly, however, mTORC1 inhibition alone has the reverse effect, increasing the number and length of prostatic branches. Finally, simultaneous activation of PI3K and downstream mTORC1/C2 via epithelial PTEN loss-of-function also results in decreased budding reversible by mTORC1 inhibition, suggesting that the effect of mTORC1 on branching is not primarily mediated by negative feedback on PI3K/mTORC2 signaling. Taken together, our data point to an important role for PI3K/mTOR signaling in prostatic epithelial invasion and migration and implicates the balance of PI3K and downstream mTORC1/C2 activity as a critical regulator of prostatic epithelial morphogenesis.
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Affiliation(s)
- Susmita Ghosh
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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2537
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Nikitas G, Deschamps C, Disson O, Niault T, Cossart P, Lecuit M. Transcytosis of Listeria monocytogenes across the intestinal barrier upon specific targeting of goblet cell accessible E-cadherin. ACTA ACUST UNITED AC 2011; 208:2263-77. [PMID: 21967767 PMCID: PMC3201198 DOI: 10.1084/jem.20110560] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Listeria monocytogenes targets accessible E-cadherin expressed on mucus-producing goblet cells to invade the intestinal tissue. Listeria monocytogenes (Lm) is a foodborne pathogen that crosses the intestinal barrier upon interaction between its surface protein InlA and its species-specific host receptor E-cadherin (Ecad). Ecad, the key constituent of adherens junctions, is typically situated below tight junctions and therefore considered inaccessible from the intestinal lumen. In this study, we investigated how Lm specifically targets its receptor on intestinal villi and crosses the intestinal epithelium to disseminate systemically. We demonstrate that Ecad is luminally accessible around mucus-expelling goblet cells (GCs), around extruding enterocytes at the tip and lateral sides of villi, and in villus epithelial folds. We show that upon preferential adherence to accessible Ecad on GCs, Lm is internalized, rapidly transcytosed across the intestinal epithelium, and released in the lamina propria by exocytosis from where it disseminates systemically. Together, these results show that Lm exploits intrinsic tissue heterogeneity to access its receptor and reveal transcytosis as a novel and unanticipated pathway that is hijacked by Lm to breach the intestinal epithelium and cause systemic infection.
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Affiliation(s)
- Georgios Nikitas
- Microbes and Host Barriers Group, French National Reference Center and World Health Organization Collaborating Center on Listeria, Institut Pasteur, Paris, France
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2538
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Notch lineages and activity in intestinal stem cells determined by a new set of knock-in mice. PLoS One 2011; 6:e25785. [PMID: 21991352 PMCID: PMC3185035 DOI: 10.1371/journal.pone.0025785] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 09/09/2011] [Indexed: 12/21/2022] Open
Abstract
The conserved role of Notch signaling in controlling intestinal cell fate specification and homeostasis has been extensively studied. Nevertheless, the precise identity of the cells in which Notch signaling is active and the role of different Notch receptor paralogues in the intestine remain ambiguous, due to the lack of reliable tools to investigate Notch expression and function in vivo. We generated a new series of transgenic mice that allowed us, by lineage analysis, to formally prove that Notch1 and Notch2 are specifically expressed in crypt stem cells. In addition, a novel Notch reporter mouse, Hes1-EmGFPSAT, demonstrated exclusive Notch activity in crypt stem cells and absorptive progenitors. This roster of knock-in and reporter mice represents a valuable resource to functionally explore the Notch pathway in vivo in virtually all tissues.
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2539
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Qiang L, Fujita R, Yamashita T, Angulo S, Rhinn H, Rhee D, Doege C, Chau L, Aubry L, Vanti WB, Moreno H, Abeliovich A. Directed conversion of Alzheimer's disease patient skin fibroblasts into functional neurons. Cell 2011; 146:359-71. [PMID: 21816272 DOI: 10.1016/j.cell.2011.07.007] [Citation(s) in RCA: 198] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 06/01/2011] [Accepted: 07/08/2011] [Indexed: 11/16/2022]
Abstract
Directed conversion of mature human cells, as from fibroblasts to neurons, is of potential clinical utility for neurological disease modeling as well as cell therapeutics. Here, we describe the efficient generation of human-induced neuronal (hiN) cells from adult skin fibroblasts of unaffected individuals and Alzheimer's patients, using virally transduced transcription regulators and extrinsic support factors. hiN cells from unaffected individuals display morphological, electrophysiological, and gene expression profiles that typify glutamatergic forebrain neurons and are competent to integrate functionally into the rodent CNS. hiN cells from familial Alzheimer disease (FAD) patients with presenilin-1 or -2 mutations exhibit altered processing and localization of amyloid precursor protein (APP) and increased production of Aβ, relative to the source patient fibroblasts or hiN cells from unaffected individuals. Together, our findings demonstrate directed conversion of human fibroblasts to a neuronal phenotype and reveal cell type-selective pathology in hiN cells derived from FAD patients.
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Affiliation(s)
- Liang Qiang
- Departments of Pathology, Cell Biology, and Neurology and Taub Institute, Columbia University, New York, NY 10032, USA
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2540
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Liu J, Pascal LE, Isharwal S, Metzger D, Ramos Garcia R, Pilch J, Kasper S, Williams K, Basse PH, Nelson JB, Chambon P, Wang Z. Regenerated luminal epithelial cells are derived from preexisting luminal epithelial cells in adult mouse prostate. Mol Endocrinol 2011; 25:1849-57. [PMID: 21940754 DOI: 10.1210/me.2011-1081] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Determining the source of regenerated luminal epithelial cells in the adult prostate during androgen deprivation and replacement will provide insights into the origin of prostate cancer cells and their fate during androgen deprivation therapy. Prostate stem cells in the epithelial layer have been suggested to give rise to luminal epithelium. However, the extent of stem cell participation to prostate regrowth is not clear. In this report, using prostate-specific antigen-CreER(T2)-based genetic lineage marking/tracing in mice, preexisting luminal epithelial cells were shown to be a source of regenerated luminal epithelial cells in the adult prostate. Prostatic luminal epithelial cells could survive androgen deprivation and were capable of proliferating upon androgen replacement. Prostate cancer cells, typically exhibiting a luminal epithelial phenotype, may retain this intrinsic capability to survive and regenerate in response to changes in androgen signaling, providing part of the mechanism for the ultimate failure of androgen deprivation therapy in prostate cancer.
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Affiliation(s)
- June Liu
- Department of Urology, University of Pittsburgh School of Medicine, Pennsylvania 15232, USA.
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2541
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Impaired stria vascularis integrity upon loss of E-cadherin in basal cells. Dev Biol 2011; 359:95-107. [PMID: 21925491 DOI: 10.1016/j.ydbio.2011.08.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 08/11/2011] [Accepted: 08/31/2011] [Indexed: 12/28/2022]
Abstract
In the cochlea, sensory transduction depends on the endocochlear potential (EP) and the unique composition of the endolymph, both of which are maintained by a highly specialized epithelium at the cochlear lateral wall, the stria vascularis. The generation of the EP by the stria vascularis, in turn, relies on the insulation of an intrastrial extracellular compartment by epithelial basal cells. Despite the physiological importance of basal cells, their cellular origin and the molecular pathways that lead to their differentiation are unclear. Here, we show by genetic lineage tracing in the mouse that basal cells exclusively derive from the otic mesenchyme. Conditional deletion of E-cadherin in the otic mesenchyme and its descendants does not abrogate the transition from mesenchymal precursors to epithelial basal cells. Rather, dedifferentiation of intermediate cells, altered morphology of basal and marginal cells and hearing impairment due to decreased EP in E-cadherin mutant mice demonstrate an essential role of E-cadherin in terminal basal cell differentiation and their interaction with other strial cell types to establish and maintain the functional architecture of the stria vascularis.
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2542
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Lopes M, Goupille O, Saint Cloment C, Lallemand Y, Cumano A, Robert B. Msx genes define a population of mural cell precursors required for head blood vessel maturation. Development 2011; 138:3055-66. [PMID: 21693521 DOI: 10.1242/dev.063214] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Vessels are primarily formed from an inner endothelial layer that is secondarily covered by mural cells, namely vascular smooth muscle cells (VSMCs) in arteries and veins and pericytes in capillaries and veinules. We previously showed that, in the mouse embryo, Msx1(lacZ) and Msx2(lacZ) are expressed in mural cells and in a few endothelial cells. To unravel the role of Msx genes in vascular development, we have inactivated the two Msx genes specifically in mural cells by combining the Msx1(lacZ), Msx2(lox) and Sm22α-Cre alleles. Optical projection tomography demonstrated abnormal branching of the cephalic vessels in E11.5 mutant embryos. The carotid and vertebral arteries showed an increase in caliber that was related to reduced vascular smooth muscle coverage. Taking advantage of a newly constructed Msx1(CreERT2) allele, we demonstrated by lineage tracing that the primary defect lies in a population of VSMC precursors. The abnormal phenotype that ensues is a consequence of impaired BMP signaling in the VSMC precursors that leads to downregulation of the metalloprotease 2 (Mmp2) and Mmp9 genes, which are essential for cell migration and integration into the mural layer. Improper coverage by VSMCs secondarily leads to incomplete maturation of the endothelial layer. Our results demonstrate that both Msx1 and Msx2 are required for the recruitment of a population of neural crest-derived VSMCs.
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Affiliation(s)
- Miguel Lopes
- Institut Pasteur, Génétique Moléculaire de la Morphogenèse, CNRS URA 2578, Paris, France
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2543
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Niesner RA, Hauser AE. Recent advances in dynamic intravital multi-photon microscopy. Cytometry A 2011; 79:789-98. [DOI: 10.1002/cyto.a.21140] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 08/11/2011] [Accepted: 08/13/2011] [Indexed: 01/09/2023]
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2544
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Grosse AS, Pressprich MF, Curley LB, Hamilton KL, Margolis B, Hildebrand JD, Gumucio DL. Cell dynamics in fetal intestinal epithelium: implications for intestinal growth and morphogenesis. Development 2011; 138:4423-32. [PMID: 21880782 DOI: 10.1242/dev.065789] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The cellular mechanisms that drive growth and remodeling of the early intestinal epithelium are poorly understood. Current dogma suggests that the murine fetal intestinal epithelium is stratified, that villi are formed by an epithelial remodeling process involving the de novo formation of apical surface at secondary lumina, and that radial intercalation of the stratified cells constitutes a major intestinal lengthening mechanism. Here, we investigate cell polarity, cell cycle dynamics and cell shape in the fetal murine intestine between E12.5 and E14.5. We show that, contrary to previous assumptions, this epithelium is pseudostratified. Furthermore, epithelial nuclei exhibit interkinetic nuclear migration, a process wherein nuclei move in concert with the cell cycle, from the basal side (where DNA is synthesized) to the apical surface (where mitosis takes place); such nuclear movements were previously misinterpreted as the radial intercalation of cells. We further demonstrate that growth of epithelial girth between E12.5 and E14.5 is driven by microtubule- and actinomyosin-dependent apicobasal elongation, rather than by progressive epithelial stratification as was previously thought. Finally, we show that the actin-binding protein Shroom3 is crucial for the maintenance of the single-layered pseudostratified epithelium. In mice lacking Shroom3, the epithelium is disorganized and temporarily stratified during villus emergence. These results favor an alternative model of intestinal morphogenesis in which the epithelium remains single layered and apicobasally polarized throughout early intestinal development.
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Affiliation(s)
- Ann S Grosse
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
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2545
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Agarwal A, Dibaj P, Kassmann CM, Goebbels S, Nave KA, Schwab MH. In vivo imaging and noninvasive ablation of pyramidal neurons in adult NEX-CreERT2 mice. ACTA ACUST UNITED AC 2011; 22:1473-86. [PMID: 21880656 DOI: 10.1093/cercor/bhr214] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To study the function of individual neurons that are embedded in a complex neural network is difficult in mice. Conditional mutagenesis permits the spatiotemporal control of gene expression including the ablation of cells by toxins. To direct expression of a tamoxifen-inducible variant of Cre recombinase (CreERT2) selectively to cortical neurons, we replaced the coding region of the murine Nex1 gene by CreERT2 cDNA via homologous recombination in embryonic stem cells. When injected with tamoxifen, adult NEX-CreERT2 mice induced reporter gene expression exclusively in projection neurons of the neocortex and hippocampus. By titrating the tamoxifen dosage, we achieved recombination in single cells, which allowed multiphoton imaging of neocortical neurons in live mice. When hippocampal projection neurons were genetically ablated by induced expression of diphteria toxin, within 20 days the inflammatory response included the infiltration of CD3+ T cells. This marks a striking difference from similar studies, in which dying oligodendrocytes failed to recruit cells of the adaptive immune system.
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Affiliation(s)
- Amit Agarwal
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Goettingen, Germany
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2546
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NF-kappaB activation within macrophages leads to an anti-tumor phenotype in a mammary tumor lung metastasis model. Breast Cancer Res 2011; 13:R83. [PMID: 21884585 PMCID: PMC3236346 DOI: 10.1186/bcr2935] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 07/05/2011] [Accepted: 08/31/2011] [Indexed: 01/30/2023] Open
Abstract
Introduction Metastasis from primary tumor to the lungs is a major cause of the mortality associated with breast cancer. Both immune and inflammatory responses impact whether circulating mammary tumor cells successfully colonize the lungs leading to established metastases. Nuclear factor -kappaB (NF-κB) transcription factors regulate both immune and inflammatory responses mediated in part by the activities of macrophages. Therefore, NF-κB activity specifically within macrophages may be a critical determinant of whether circulating tumor cells successfully colonize the lungs. Methods To investigate NF-κB signaling within macrophages during metastasis, we developed novel inducible transgenic models which target expression of the reverse tetracycline transactivator (rtTA) to macrophages using the cfms promoter in combination with inducible transgenics that express either an activator (cIKK2) or an inhibitor (IκBα-DN). Doxycyline treatment led to activation or inhibition of NF-κB within macrophages. We used a tail vein metastasis model with mammary tumor cell lines established from MMTV-Polyoma Middle T-Antigen-derived tumors to investigate the effects of modulating NF-κB in macrophages during different temporal windows of the metastatic process. Results We found that activation of NF-κB in macrophages during seeding leads to a reduction in lung metastases. The mechanism involved expression of inflammatory cytokines and reactive oxygen species, leading to apoptosis of tumor cells and preventing seeding in the lung. Activation of NF-κB within macrophages after the seeding phase has no significant impact on establishment of metastases. Conclusions Our results have identified a brief, defined window in which activation of NF-κB has significant anti-metastatic effects and inhibition of NF-κB results in a worse outcome.
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2547
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Carson RP, Van Nielen DL, Winzenburger PA, Ess KC. Neuronal and glia abnormalities in Tsc1-deficient forebrain and partial rescue by rapamycin. Neurobiol Dis 2011; 45:369-80. [PMID: 21907282 DOI: 10.1016/j.nbd.2011.08.024] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 08/02/2011] [Accepted: 08/18/2011] [Indexed: 12/20/2022] Open
Abstract
Tuberous Sclerosis Complex (TSC) is a multiorgan genetic disease that prominently features brain malformations (tubers) with many patients suffering from epilepsy and autism. These malformations typically exhibit neuronal as well as glial cell abnormalities and likely underlie much of the neurological morbidity seen in TSC. Tuber pathogenesis remains poorly understood though upregulation of the mTORC1 signaling pathway in TSC has been consistently demonstrated. Here we address abnormal brain development in TSC by inactivating the mouse Tsc1 gene in embryonic neural progenitor cells. This strategy permits evaluation of the role of the Tsc1 gene in both neuronal as well as glial cell lineages. Tsc1(Emx1-Cre) conditional knockout (CKO) animals die by 25 days of life. Their brains have increased size and contain prominent large cells within the cerebral cortex that have greatly increased mTORC1 signaling and decreased mTORC2 signaling. Severe defects of cortical lamination, enlarged dysmorphic astrocytes and decreased myelination were also found. Tsc1(Emx1-Cre) CKO mice were then treated with rapamycin to see if the premature death and brain abnormalities can be rescued. Postnatal rapamycin treatment completely prevented premature death and largely reversed the glia pathology but not abnormal neuronal lamination. These findings support a model that loss of function of the TSC genes in embryonic neural progenitor cells causes cortical malformations in patients with TSC. The dramatic effect of rapamycin suggests that even with extensive multi-lineage abnormalities, a postnatal therapeutic window may exist for patients with TSC.
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Affiliation(s)
- Robert P Carson
- Department of Neurology and Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37232, USA
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2548
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Rinkevich Y, Lindau P, Ueno H, Longaker MT, Weissman IL. Germ-layer and lineage-restricted stem/progenitors regenerate the mouse digit tip. Nature 2011; 476:409-13. [PMID: 21866153 DOI: 10.1038/nature10346] [Citation(s) in RCA: 300] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 06/30/2011] [Indexed: 01/06/2023]
Abstract
The regrowth of amputated limbs and the distal tips of digits represent models of tissue regeneration in amphibians, fish and mice. For decades it had been assumed that limb regeneration derived from the blastema, an undifferentiated pluripotent cell population thought to be derived from mature cells via dedifferentiation. Here we show that a wide range of tissue stem/progenitor cells contribute towards the restoration of the mouse distal digit. Genetic fate mapping and clonal analysis of individual cells revealed that these stem cells are lineage restricted, mimicking digit growth during development. Transplantation of cyan-fluorescent-protein-expressing haematopoietic stem cells, and parabiosis between genetically marked mice, confirmed that the stem/progenitor cells are tissue resident, including the cells involved in angiogenesis. These results, combined with those from appendage regeneration in other vertebrate subphyla, collectively demonstrate that tissue stem cells rather than pluripotent blastema cells are an evolutionarily conserved cellular mode for limb regeneration after amputation.
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Affiliation(s)
- Yuval Rinkevich
- Stanford Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California 94305-5323, USA.
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2549
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Defining the anatomical localisation of subsets of the murine mononuclear phagocyte system using integrin alpha X (Itgax, CD11c) and colony stimulating factor 1 receptor (Csf1r, CD115) expression fails to discriminate dendritic cells from macrophages. Immunobiology 2011; 216:1228-37. [PMID: 21885153 DOI: 10.1016/j.imbio.2011.08.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 08/12/2011] [Indexed: 01/22/2023]
Abstract
The murine mononuclear phagocyte (MNP) system comprises a diverse population of cells, including monocytes, dendritic cells (DC) and macrophages. Derived from the myeloid haematopoietic lineage, this group of cells express a variety of well characterized surface markers. Expression of the integrin alpha X (Itgax, CD11c) is commonly used to identify classical DC, and similarly expression of colony stimulating factor 1 receptor (Csf1r, CD115) to identify macrophages. We have characterized the expression of these markers using a variety of transgenic mouse models. We confirmed previous observations of Itgax expression in anatomically defined subsets of MNPs in secondary lymphoid organs, including all MNPs identified within the germinal centres. The majority of MNPs in the intestinal lamina propria and lung express Itgax. All mucosal Itgax expressing cells also express Csf1r suggesting Csf1-dependent haematopoietic derivation. This double-positive population included germinal centre MNPs. These data reveal that Itgax expression alone does not specifically define classical DC. These results suggest more cautious interpretation of Itgax-dependent experimentation and direct equation with uniquely DC-mediated activities, particularly in the functioning of non-lymphoid MNPs within the intestinal lamina propria.
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2550
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Iverson SV, Comstock KM, Kundert JA, Schmidt EE. Contributions of new hepatocyte lineages to liver growth, maintenance, and regeneration in mice. Hepatology 2011; 54:655-63. [PMID: 21538442 PMCID: PMC3145049 DOI: 10.1002/hep.24398] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 04/19/2011] [Indexed: 01/01/2023]
Abstract
UNLABELLED The contributions that de novo differentiation of new hepatocyte lineages makes to normal liver physiology are unknown. In this study, a system that uniquely marks cells during a finite period following primary activation of a serum albumin gene promoter/enhancer-driven Cre recombinase (albCre) transgene was used to investigate birthrates of new hepatocyte lineages from albumin (Alb)-naive precursors in mice. Elapsed time was measured with a two-color fluorescent marker gene that converts from expressing tandem dimer Tomato (tdT; a red fluorescent protein) to expressing green fluorescent protein (GFP) following primary exposure to Cre. The accumulation of GFP and the decay of tdT each contributed to a regular fluorescence transition, which was calibrated in vivo. In normal adults, this system revealed that a steady-state level of 0.076% of all hepatocytes had differentiated within the previous 4 days from albCre-naive cell lineages. In comparison with resting adult livers, the relative abundance of these newborn hepatocytes was elevated 3.7-fold in the growing livers of juveniles and 8.6-fold during liver regeneration after partial hepatectomy in adults. CONCLUSION Newborn hepatocyte lineages arising from Alb-naive cells contribute to liver maintenance under normal conditions. Hepatocyte lineage birthrates can vary in response to the liver's physiological status.
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Affiliation(s)
- Sonya V. Iverson
- Department of Immunology and Disease, Montana State University, Bozeman, MT 59718, USA
| | | | - Jean A. Kundert
- Animal Resources Center, Montana State University, Bozeman, MT 59718, USA
| | - Edward E. Schmidt
- Department of Immunology and Disease, Montana State University, Bozeman, MT 59718, USA
,Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
,To whom correspondences should be addressed
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