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Soheilmoghaddam F, Hezaveh H, Rumble M, Cooper-White JJ. Driving Osteocytogenesis from Mesenchymal Stem Cells in Osteon-like Biomimetic Nanofibrous Scaffolds. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 39044386 DOI: 10.1021/acsami.3c14785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
The treatment of critical-sized bone defects caused by tumor removal, skeletal injuries, or infections continues to pose a major clinical challenge. A popular potential alternative solution to autologous bone grafts is a tissue-engineered approach that utilizes the combination of mesenchymal stromal/stem cells (MSCs) with synthetic biomaterial scaffolds. This approach aims to support new bone formation by mimicking many of the biochemical and biophysical cues present within native bone. Regrettably, osteocyte cells, crucial for bone maturation and homeostasis, are rarely produced within MSC-seeded scaffolds, thereby restricting the development of fully mature cortical bone from these synthetic implants. In this work, we have constructed a multimodal scaffold by combining electrospun poly(lactic-co-glycolic acid) (PLGA) fibrous scaffolds with poly(ethylene glycol) (PEG)-based hydrogels that mimic the functional unit of cortical bone, osteon (osteon-mimetic) scaffolds. These scaffolds were decorated with a novel bone morphogenic protein-6 (BMP6) peptide (BMP6p) after our findings revealed that the BMP6p drives higher levels of Smad signaling than the full-length protein counterpart, soluble or when bound to the PEG hydrogel backbone. We show that our osteon-mimetic scaffolds, in presenting concentric layers of BMP6p-PEG hydrogel overlaid on MSC-seeded PLGA nanofibers, promoted the rapid formation of osteocyte-like cells with a phenotypic dendritic morphology, producing early osteocyte markers, including E11/gp38 (E11). Maturation of these osteocyte-like cells was further confirmed by the observation of significant dentin matrix protein 1 (DMP1) throughout our bilayered scaffolds after 3 weeks, even when cultured in a medium without dexamethasone (DEX) or any other osteogenic supplements. These results demonstrate that these osteon-mimetic scaffolds, in presenting biochemical and topographical cues reminiscent of the forming osteon, can drive the formation of osteocyte-like cells in vitro from hBMSCs without the need for any osteogenic factor media supplementation.
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Affiliation(s)
- Farhad Soheilmoghaddam
- Tissue Engineering and Microfluidics Laboratory, The Australian Institute for Bioengineering and Nanotechnology (AIBN), University of Queensland, St. Lucia, QLD 4072, Australia
- School of Chemical Engineering, University of Queensland, St. Lucia, QLD 4072, Australia
| | - Hadi Hezaveh
- Tissue Engineering and Microfluidics Laboratory, The Australian Institute for Bioengineering and Nanotechnology (AIBN), University of Queensland, St. Lucia, QLD 4072, Australia
| | - Madeleine Rumble
- School of Chemical Engineering, University of Queensland, St. Lucia, QLD 4072, Australia
| | - Justin J Cooper-White
- Tissue Engineering and Microfluidics Laboratory, The Australian Institute for Bioengineering and Nanotechnology (AIBN), University of Queensland, St. Lucia, QLD 4072, Australia
- School of Chemical Engineering, University of Queensland, St. Lucia, QLD 4072, Australia
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Reich S, Kayastha P, Teegala S, Weinstein DC. Tbx2 mediates dorsal patterning and germ layer suppression through inhibition of BMP/GDF and Activin/Nodal signaling. BMC Mol Cell Biol 2020; 21:39. [PMID: 32466750 PMCID: PMC7257154 DOI: 10.1186/s12860-020-00282-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 05/11/2020] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Members of the T-box family of DNA-binding proteins play a prominent role in the differentiation of the three primary germ layers. VegT, Brachyury, and Eomesodermin function as transcriptional activators and, in addition to directly activating the transcription of endoderm- and mesoderm-specific genes, serve as regulators of growth factor signaling during induction of these germ layers. In contrast, the T-box gene, tbx2, is expressed in the embryonic ectoderm, where Tbx2 functions as a transcriptional repressor and inhibits mesendodermal differentiation by the TGFβ ligand Activin. Tbx2 misexpression also promotes dorsal ectodermal fate via inhibition of the BMP branch of the TGFβ signaling network. RESULTS Here, we report a physical association between Tbx2 and both Smad1 and Smad2, mediators of BMP and Activin/Nodal signaling, respectively. We perform structure/function analysis of Tbx2 to elucidate the roles of both Tbx2-Smad interaction and Tbx2 DNA-binding in germ layer suppression. CONCLUSION Our studies demonstrate that Tbx2 associates with intracellular mediators of the Activin/Nodal and BMP/GDF pathways. We identify a novel repressor domain within Tbx2, and have determined that Tbx2 DNA-binding activity is required for repression of TGFβ signaling. Finally, our data also point to overlapping yet distinct mechanisms for Tbx2-mediated repression of Activin/Nodal and BMP/GDF signaling.
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Affiliation(s)
- Shoshana Reich
- The Graduate Center, The City University of New York, New York, NY, 10016, USA
| | - Peter Kayastha
- Department of Biology, Queens College, The City University of New York, Queens, NY, 11367, USA
| | - Sushma Teegala
- Department of Biology, Queens College, The City University of New York, Queens, NY, 11367, USA
| | - Daniel C Weinstein
- The Graduate Center, The City University of New York, New York, NY, 10016, USA. .,Department of Biology, Queens College, The City University of New York, Queens, NY, 11367, USA.
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Hox Gene Collinearity May Be Related to Noether Theory on Symmetry and Its Linked Conserved Quantity. J 2020. [DOI: 10.3390/j3020013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hox Gene Collinearity (HGC) is a fundamental property that controls the development of many animal species, including vertebrates. In the Hox gene clusters, the genes are located in a sequential order Hox1, Hox2, Hox3, etc., along the 3’ to 5’ direction of the cluster in the chromosome. During Hox cluster activation, the Hox genes are expressed sequentially in the ontogenetic units D1, D2, D3, etc., along the anterior–posterior axis (A-P) of the early embryo. This collinearity, first observed by E.B. Lewis, is surprising because the spatial collinearity of these structures (Hox clusters and embryos) correlates entities that differ by about four orders of magnitude. Biomolecular mechanisms alone cannot explain such correlations. Long-range physical interactions, such as diffusion or electric attractions, should be involved. A biophysical model (BM) was formulated, which, in alignment with the biomolecular processes, successfully describes the existing vertebrate genetic engineering data. One hundred years ago, Emmy Noether made a fundamental discovery in mathematics and physics. She proved, rigorously, that a physical system obeying a symmetry law (e.g., rotations or self-similarity) is followed by a conserved physical quantity. It is argued here that HGC obeys a ‘primitive’ self-similarity symmetry. In this case, the associated primitive conserved quantity is the irreversibly increasing ‘ratchet’-like Hoxgene ordering where some genes may be missing. The genes of a vertebrate Hox clusterare located along a finite straight line. The same order follows the ontogenetic unitsof the vertebrate embryo. Therefore, HGC is a manifestation of a primitive Noether Theory (NT). NT may be applied to other than the vertebrate case, for instance, to animals with a circular topological symmetry. For example, the observed abnormal Hox gene ordering of the echinoderm Hox clusters may be reproduced by a double-strand break of the circular Hox gene ordering and its subsequent incorporation in the flanking chromosome.
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Papageorgiou S. Abnormal Elongations of HOX Gene Clusters May Cause Cancer. Front Cell Dev Biol 2018; 6:25. [PMID: 29662879 PMCID: PMC5890142 DOI: 10.3389/fcell.2018.00025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 02/27/2018] [Indexed: 12/21/2022] Open
Affiliation(s)
- Spyros Papageorgiou
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", Athens, Greece
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Leibovich A, Kot-Leibovich H, Ben-Zvi D, Fainsod A. ADMP controls the size of Spemann's organizer through a network of self-regulating expansion-restriction signals. BMC Biol 2018; 16:13. [PMID: 29357852 PMCID: PMC5778663 DOI: 10.1186/s12915-018-0483-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 01/08/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The bone morphogenetic protein (BMP) signaling gradient is central for dorsoventral patterning in amphibian embryos. This gradient is established through the interaction of several BMPs and BMP antagonists and modulators, some secreted by Spemann's organizer, a cluster of cells coordinating embryonic development. Anti-dorsalizing morphogenetic protein (ADMP), a BMP-like transforming growth factor beta ligand, negatively affects the formation of the organizer, although it is robustly expressed within the organizer itself. Previously, we proposed that this apparent discrepancy may be important for the ability of ADMP to scale the BMP gradient with embryo size, but how this is achieved is unclear. RESULTS Here we report that ADMP acts in the establishment of the organizer via temporally and mechanistically distinct signals. At the onset of gastrulation, ADMP is required to establish normal organizer-specific gene expression domains, thus displaying a dorsal, organizer-promoting function. The organizer-restricting, BMP-like function of ADMP becomes apparent slightly later, from mid-gastrula. The organizer-promoting signal of ADMP is mediated by the activin A type I receptor, ACVR1 (also known as activin receptor-like kinase-2, ALK2). ALK2 is expressed in the organizer and is required for organizer establishment. The anti-organizer function of ADMP is mediated by ACVRL1 (ALK1), a putative ADMP receptor expressed in the lateral regions flanking the organizer that blocks expansion of the organizer. Truncated ALK1 prevents the organizer-restricting effects of ADMP overexpression, suggesting a ligand-receptor interaction. We also present a mathematical model of the regulatory network controlling the size of the organizer. CONCLUSIONS We show that the opposed, organizer-promoting and organizer-restricting roles of ADMP are mediated by different receptors. A self-regulating network is proposed in which ADMP functions early through ALK2 to expand its own expression domain, the organizer, and later functions through ALK1 to restrict this domain. These effects are dependent on ADMP concentration, timing, and the spatial localization of the two receptors. This self-regulating temporal switch may control the size of the organizer and the genes expressed within in response to genetic and external stimuli during gastrulation.
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Affiliation(s)
- Avi Leibovich
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel
| | - Hadas Kot-Leibovich
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel
| | - Danny Ben-Zvi
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel
| | - Abraham Fainsod
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel.
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Abstract
Hox gene collinearity was discovered be Edward B. Lewis in 1978. It consists of the Hox1, Hox2, Hox3 ordering of the Hox genes in the chromosome from the telomeric to the centromeric side of the chromosome. Surprisingly, the spatial activation of the Hox genes in the ontogenetic units of the embryo follows the same ordering along the anterior-posterior embryonic axis. The chromosome microscale differs from the embryo macroscale by 3 to 4 orders of magnitude. The traditional biomolecular mechanisms are not adequate to comprise phenomena at so divergent spatial domains. A Biophysical Model of physical forces was proposed which can bridge the intermediate space and explain the results of genetic engineering experiments. Recent progress in constructing instruments and achieving high resolution imaging (e.g., 3D DNA FISH, STORM etc.) enable the assessment of the geometric structure of the chromatin during the different phases of Hox gene activation. It is found that the mouse HoxD gene cluster is elongated up to 5-6 times during Hox gene transcription. These unexpected findings agree with the BM predictions. It is now possible to measure several physical quantities inside the nucleus during Hox gene activation. New experiments are proposed to test further this model.
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Houston DW. Vertebrate Axial Patterning: From Egg to Asymmetry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:209-306. [PMID: 27975274 PMCID: PMC6550305 DOI: 10.1007/978-3-319-46095-6_6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The emergence of the bilateral embryonic body axis from a symmetrical egg has been a long-standing question in developmental biology. Historical and modern experiments point to an initial symmetry-breaking event leading to localized Wnt and Nodal growth factor signaling and subsequent induction and formation of a self-regulating dorsal "organizer." This organizer forms at the site of notochord cell internalization and expresses primarily Bone Morphogenetic Protein (BMP) growth factor antagonists that establish a spatiotemporal gradient of BMP signaling across the embryo, directing initial cell differentiation and morphogenesis. Although the basics of this model have been known for some time, many of the molecular and cellular details have only recently been elucidated and the extent that these events remain conserved throughout vertebrate evolution remains unclear. This chapter summarizes historical perspectives as well as recent molecular and genetic advances regarding: (1) the mechanisms that regulate symmetry-breaking in the vertebrate egg and early embryo, (2) the pathways that are activated by these events, in particular the Wnt pathway, and the role of these pathways in the formation and function of the organizer, and (3) how these pathways also mediate anteroposterior patterning and axial morphogenesis. Emphasis is placed on comparative aspects of the egg-to-embryo transition across vertebrates and their evolution. The future prospects for work regarding self-organization and gene regulatory networks in the context of early axis formation are also discussed.
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Affiliation(s)
- Douglas W Houston
- Department of Biology, The University of Iowa, 257 BB, Iowa City, IA, 52242, USA.
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Berezhkovskii AM, Shvartsman SY. Kinetics of receptor occupancy during morphogen gradient formation. J Chem Phys 2014; 138:244105. [PMID: 23822225 DOI: 10.1063/1.4811654] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
During embryogenesis, sheets of cells are patterned by concentration profiles of morphogens, molecules that act as dose-dependent regulators of gene expression and cell differentiation. Concentration profiles of morphogens can be formed by a source-sink mechanism, whereby an extracellular protein is secreted from a localized source, diffuses through the tissue and binds to cell surface receptors. A morphogen molecule bound to its receptor can either dissociate or be internalized by the cell. The effects of morphogens on cells depend on the occupancy of surface receptors, which in turn depends on morphogen concentration. In the simplest case, the local concentrations of the morphogen and morphogen-receptor complexes monotonically increase with time from zero to their steady-state values. Here, we derive analytical expressions for the time scales which characterize the formation of the steady-state concentrations of both the diffusible morphogen molecules and morphogen-receptor complexes at a given point in the patterned tissue.
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Affiliation(s)
- Alexander M Berezhkovskii
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, USA
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Almirantis Y, Provata A, Papageorgiou S. Evolutionary constraints favor a biophysical model explaining hox gene collinearity. Curr Genomics 2013; 14:279-88. [PMID: 24294108 PMCID: PMC3731818 DOI: 10.2174/13892029113149990003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/27/2013] [Accepted: 05/28/2013] [Indexed: 11/23/2022] Open
Abstract
The Hox gene collinearity enigma has often been approached using models based on biomolecular mechanisms. The biophysical model is an alternative approach based on the hypothesis that collinearity is caused by physical forces pulling the Hox genes from a territory where they are inactive to a distinct spatial domain where they are activated in a step by step manner. Such Hox gene translocations have recently been observed in support of the biophysical model. Genetic engineering experiments, performed on embryonic mice, gave rise to several unexpected mutant expressions that the biomolecular models cannot predict. On the contrary, the biophysical model offers convincing explanation. Evolutionary constraints consolidate the Hox clusters and as a result, denser and well organized clusters may create more efficient physical forces and a more emphatic manifestation of gene collinearity. This is demonstrated by stochastic modeling with white noise perturbing the expression of Hox genes. As study cases the genomes of mouse and amphioxus are used. The results support the working hypothesis that vertebrates have adopted their comparably more compact Hox clustering as a tool needed to develop more complex body structures. Several experiments are proposed in order to test further the physical forces hypothesis.
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Affiliation(s)
- Yannis Almirantis
- National Center for Scientific Research "Demokritos", Institute of Biosciences and Applications, 153 10 Athens, Greece
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Dynamics of TGF-β signaling reveal adaptive and pulsatile behaviors reflected in the nuclear localization of transcription factor Smad4. Proc Natl Acad Sci U S A 2012; 109:E1947-56. [PMID: 22689943 DOI: 10.1073/pnas.1207607109] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The TGF-β pathway plays a vital role in development and disease and regulates transcription through a complex composed of receptor-regulated Smads (R-Smads) and Smad4. Extensive biochemical and genetic studies argue that the pathway is activated through R-Smad phosphorylation; however, the dynamics of signaling remain largely unexplored. We monitored signaling and transcriptional dynamics and found that although R-Smads stably translocate to the nucleus under continuous pathway stimulation, transcription of direct targets is transient. Surprisingly, Smad4 nuclear localization is confined to short pulses that coincide with transcriptional activity. Upon perturbation, the dynamics of transcription correlate with Smad4 nuclear localization rather than with R-Smad activity. In Xenopus embryos, Smad4 shows stereotyped, uncorrelated bursts of nuclear localization, but activated R-Smads are uniform. Thus, R-Smads relay graded information about ligand levels that is integrated with intrinsic temporal control reflected in Smad4 into the active signaling complex.
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Abstract
Some aspects of pattern formation in developing embryos can be described by nonlinear reaction-diffusion equations. An important class of these models accounts for diffusion and degradation of a locally produced single chemical species. At long times, solutions of such models approach a steady state in which the concentration decays with distance from the source of production. We present analytical results that characterize the dynamics of this process and are in quantitative agreement with numerical solutions of the underlying nonlinear equations. The derived results provide an explicit connection between the parameters of the problem and the time needed to reach a steady state value at a given position. Our approach can be used for the quantitative analysis of tissue patterning by morphogen gradients, a subject of active research in biophysics and developmental biology.
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Daughters RS, Chen Y, Slack JMW. Origin of muscle satellite cells in the Xenopus embryo. Development 2011; 138:821-30. [PMID: 21270051 DOI: 10.1242/dev.056481] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have studied the origin of muscle satellite cells in embryos of Xenopus laevis. Fate mapping at the open neural plate stage was carried out using orthotopic grafts from transgenic embryos expressing GFP. This shows that most satellite cells originate from the dorsolateral plate rather than from the paraxial mesoderm. Specification studies were made by isolation of explants from the paraxial and dorsolateral regions of neurulae and these also indicated that the satellite cell progenitors arise from the dorsolateral plate. Muscle satellite cells express Pax7, but overexpression of Pax7 in blastomeres of whole embryos that populate the myogenic areas does not induce the formation of additional satellite cells. Moreover, a dominant-negative construct, Pax7EnR, does not reduce satellite cell formation. Neither Pax7 nor other myogenic transcription factor genes will induce satellite cell formation in animal caps treated with FGF. However, BMP RNA or protein will do so, both for FGF-treated animal caps and for paraxial neurula explants. Conversely, the induction of Noggin in dorsolateral explants from HGEM-Noggin transgenic neurulae will block formation of satellite cells, showing that BMP signaling is required in vivo for satellite cell formation. We conclude that satellite cell progenitors are initially specified in the dorsal part of the lateral plate mesoderm and later become incorporated into the myotomes. The initial specification occurs at the neurula stage and depends on the ventral-to-dorsal BMP gradient in the early embryo.
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Affiliation(s)
- Randall S Daughters
- Stem Cell Institute, University of Minnesota, MTRF, 2001 6th Street SE, Minneapolis, MN 55455, USA
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Christiaen L, Stolfi A, Levine M. BMP signaling coordinates gene expression and cell migration during precardiac mesoderm development. Dev Biol 2010; 340:179-87. [DOI: 10.1016/j.ydbio.2009.11.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 01/09/2023]
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Gerhart J, Pfautz J, Neely C, Elder J, DuPrey K, Menko AS, Knudsen K, George-Weinstein M. Noggin producing, MyoD-positive cells are crucial for eye development. Dev Biol 2009; 336:30-41. [PMID: 19778533 DOI: 10.1016/j.ydbio.2009.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 09/15/2009] [Accepted: 09/15/2009] [Indexed: 11/15/2022]
Abstract
A subpopulation of cells expresses MyoD mRNA and the cell surface G8 antigen in the epiblast prior to the onset of gastrulation. When an antibody to the G8 antigen was applied to the epiblast, labeled cells were later found in the ocular primordia and muscle and non-muscle forming tissues of the eyes. In the lens, retina and periocular mesenchyme, G8-positive cells synthesized MyoD mRNA and the bone morphogenetic protein inhibitor Noggin. MyoD expressing cells were ablated in the epiblast by labeling them with the G8 MAb and lysing them with complement. Their ablation in the epiblast resulted in eye defects, including anopthalmia, micropthalmia, altered pigmentation and malformations of the lens and/or retina. The right eye was more severely affected than the left eye. The asymmetry of the eye defects in ablated embryos correlated with differences in the number of residual Noggin producing, MyoD-positive cells in ocular tissues. Exogenously supplied Noggin compensated for the ablated epiblast cells. This study demonstrates that MyoD expressing cells serve as a Noggin delivery system to regulate the morphogenesis of the lens and optic cup.
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Affiliation(s)
- Jacquelyn Gerhart
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA
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15
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Transforming growth factor beta depletion is the primary determinant of Smad signaling kinetics. Mol Cell Biol 2009; 29:2443-55. [PMID: 19223462 DOI: 10.1128/mcb.01443-08] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A cell's decision to growth arrest, apoptose, or differentiate in response to transforming growth factor beta (TGF-beta) superfamily ligands depends on the ligand concentration. How cells sense the concentration of extracellular bioavailable TGF-beta remains poorly understood. We therefore undertook a systematic quantitative analysis of how TGF-beta ligand concentration is transduced into downstream phospho-Smad2 kinetics, and we found that the rate of TGF-beta ligand depletion is the principal determinant of Smad signal duration. TGF-beta depletion is caused by two mechanisms: (i) cellular uptake of TGF-beta by a TGF-beta type II receptor-dependent mechanism and (ii) reversible binding of TGF-beta to the cell surface. Our results indicate that cells sense TGF-beta dose by depleting TGF-beta via constitutive TGF-beta type II receptor trafficking processes. Our results also have implications for the role of the TGF-beta type II receptor in disease, as tumor cells harboring TGF-beta type II receptor mutations exhibit impaired TGF-beta depletion, which may contribute to the overproduction of TGF-beta and a consequently poor prognosis in cancer.
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Wagner T, Kraeussling M, Fedorov L, Reiss C, Kneitz B, Schartl M. STAT3 and SMAD1 Signaling in Medaka Embryonic Stem-Like Cells and Blastula Embryos. Stem Cells Dev 2009; 18:151-60. [DOI: 10.1089/scd.2007.0262] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- T.U. Wagner
- University of Wurzburg, Physiological Chemistry I, Wurzburg, Germany
| | - M. Kraeussling
- University of Wurzburg, Physiological Chemistry I, Wurzburg, Germany
| | - L.M. Fedorov
- University of Wurzburg, Physiological Chemistry I, Wurzburg, Germany
| | - C. Reiss
- University of Wurzburg, Physiological Chemistry I, Wurzburg, Germany
| | - B. Kneitz
- Department of Urology and Paediatric Urology, Bavarian Julius Maximilians University Medical School, Wurzburg, Germany
| | - M. Schartl
- University of Wurzburg, Physiological Chemistry I, Wurzburg, Germany
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Ibañes M, Belmonte JCI. Theoretical and experimental approaches to understand morphogen gradients. Mol Syst Biol 2008; 4:176. [PMID: 18364710 PMCID: PMC2290935 DOI: 10.1038/msb.2008.14] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Accepted: 02/06/2008] [Indexed: 12/31/2022] Open
Abstract
Morphogen gradients, which specify different fates for cells in a direct concentration-dependent manner, are a highly influential framework in which pattern formation processes in developmental biology can be characterized. A common analysis approach is combining experimental and theoretical strategies, thereby fostering relevant data on the dynamics and transduction of gradients. The mechanisms of morphogen transport and conversion from graded information to binary responses are some of the topics on which these combined strategies have shed light. Herein, we review these data, emphasizing, on the one hand, how theoretical approaches have been helpful and, on the other hand, how these have been combined with experimental strategies. In addition, we discuss those cases in which gradient formation and gradient interpretation at the molecular and/or cellular level may influence each other within a mutual feedback loop. To understand this interplay and the features it yields, it becomes essential to take system-level approaches that combine experimental and theoretical strategies.
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Affiliation(s)
- Marta Ibañes
- Department of Estructura i Constituents de la Matèria, University of Barcelona, Barcelona, Spain
| | - Juan Carlos Izpisúa Belmonte
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
- Centre of Regenerative Medicine in Barcelona, Barcelona, Spain
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Müller F, Rohrer H, Vogel-Höpker A. Bone morphogenetic proteins specify the retinal pigment epithelium in the chick embryo. Development 2007; 134:3483-93. [PMID: 17728349 DOI: 10.1242/dev.02884] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In vertebrates, the neuroepithelium of the optic vesicle is initially multipotential, co-expressing a number of transcription factors that are involved in retinal pigment epithelium (RPE) and neural retina (NR)development. Subsequently, extrinsic signals emanating from the surrounding tissues induce the separation of the optic vesicle into three domains: the optic stalk/nerve, the NR and the RPE. Here, we show that bone morphogenetic proteins (BMPs) are sufficient and essential for RPE development in vivo. Bmp4 and Bmp7 are expressed in the surface ectoderm overlying the optic vesicle, the surrounding mesenchyme and/or presumptive RPE during the initial stages of eye development. During the initial stages of chick eye development the microphthalmia-associated transcription factor(Mitf), important for RPE development, is expressed in the optic primordium that is covered by the BMP-expressing surface ectoderm. Following BMP application, the optic neuroepithelium, including the presumptive optic stalk/nerve and NR domain, develop into RPE as assessed by the expression of Otx2, Mitf, Wnt2b and the pigmented cell marker MMP115. By contrast, interfering with BMP signalling prevents RPE development in the outer layer of the optic cup and induces NR-specific gene expression (e.g. Chx10). Our results show that BMPs are sufficient and essential for RPE development during optic vesicle stages. We propose a model in which the BMP-expressing surface ectoderm initiates RPE specification by inducing Mitf expression in the underlying neuroepithelium of the optic vesicle.
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Affiliation(s)
- Frank Müller
- Max-Planck-Institute for Brain Research, Department of Neurochemistry, Deutschordenstr. 46, 60528 Frankfurt/M., Germany
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