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Abstract
Hedgehog (Hh) proteins constitute one family of a small number of secreted signaling proteins that together regulate multiple aspects of animal development, tissue homeostasis and regeneration. Originally uncovered through genetic analyses in Drosophila, their subsequent discovery in vertebrates has provided a paradigm for the role of morphogens in positional specification. Most strikingly, the Sonic hedgehog protein was shown to mediate the activity of two classic embryonic organizing centers in vertebrates and subsequent studies have implicated it and its paralogs in a myriad of processes. Moreover, dysfunction of the signaling pathway has been shown to underlie numerous human congenital abnormalities and diseases, especially certain types of cancer. This review focusses on the genetic studies that uncovered the key components of the Hh signaling system and the subsequent, biochemical, cell and structural biology analyses of their functions. These studies have revealed several novel processes and principles, shedding new light on the cellular and molecular mechanisms underlying cell-cell communication. Notable amongst these are the involvement of cholesterol both in modifying the Hh proteins and in activating its transduction pathway, the role of cytonemes, filipodia-like extensions, in conveying Hh signals between cells; and the central importance of the Primary Cilium as a cellular compartment within which the components of the signaling pathway are sequestered and interact.
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Affiliation(s)
- Philip William Ingham
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.
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2
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Young M, Selleri L, Capellini TD. Genetics of scapula and pelvis development: An evolutionary perspective. Curr Top Dev Biol 2019; 132:311-349. [PMID: 30797513 PMCID: PMC6430119 DOI: 10.1016/bs.ctdb.2018.12.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
In tetrapods, the scapular and pelvic girdles perform the important function of anchoring the limbs to the trunk of the body and facilitating the movement of each appendage. This shared function, however, is one of relatively few similarities between the scapula and pelvis, which have significantly different morphologies, evolutionary histories, embryonic origins, and underlying genetic pathways. The scapula evolved in jawless fish prior to the pelvis, and its embryonic development is unique among bones in that it is derived from multiple progenitor cell populations, including the dermomyotome, somatopleure, and neural crest. Conversely, the pelvis evolved several million years later in jawed fish, and it develops from an embryonic somatopleuric cell population. The genetic networks controlling the formation of the pelvis and scapula also share similarities and differences, with a number of genes shaping only one or the other, while other gene products such as PBX transcription factors act as hierarchical developmental regulators of both girdle structures. Here, we provide a detailed review of the cellular processes and genetic networks underlying pelvis and scapula formation in tetrapods, while also highlighting unanswered questions about girdle evolution and development.
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Affiliation(s)
- Mariel Young
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, United States
| | - Licia Selleri
- Program in Craniofacial Biology, Department of Orofacial Sciences, Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research, University of California, Institute of Human Genetics, San Francisco, CA, United States; Program in Craniofacial Biology, Department of Anatomy, Eli and Edythe Broad Center of Regeneration Medicine & Stem Cell Research, University of California, Institute of Human Genetics, San Francisco, CA, United States.
| | - Terence D Capellini
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, United States; Broad Institute of Harvard and MIT, Cambridge, MA, United States.
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3
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Chang CN, Kioussi C. Location, Location, Location: Signals in Muscle Specification. J Dev Biol 2018; 6:E11. [PMID: 29783715 PMCID: PMC6027348 DOI: 10.3390/jdb6020011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/11/2018] [Accepted: 05/15/2018] [Indexed: 12/15/2022] Open
Abstract
Muscles control body movement and locomotion, posture and body position and soft tissue support. Mesoderm derived cells gives rise to 700 unique muscles in humans as a result of well-orchestrated signaling and transcriptional networks in specific time and space. Although the anatomical structure of skeletal muscles is similar, their functions and locations are specialized. This is the result of specific signaling as the embryo grows and cells migrate to form different structures and organs. As cells progress to their next state, they suppress current sequence specific transcription factors (SSTF) and construct new networks to establish new myogenic features. In this review, we provide an overview of signaling pathways and gene regulatory networks during formation of the craniofacial, cardiac, vascular, trunk, and limb skeletal muscles.
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Affiliation(s)
- Chih-Ning Chang
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, OR 97331, USA.
- Molecular Cell Biology Graduate Program, Oregon State University, Corvallis, OR 97331, USA.
| | - Chrissa Kioussi
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, OR 97331, USA.
- Molecular Cell Biology Graduate Program, Oregon State University, Corvallis, OR 97331, USA.
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4
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Chal J, Al Tanoury Z, Hestin M, Gobert B, Aivio S, Hick A, Cherrier T, Nesmith AP, Parker KK, Pourquié O. Generation of human muscle fibers and satellite-like cells from human pluripotent stem cells in vitro. Nat Protoc 2016; 11:1833-50. [PMID: 27583644 DOI: 10.1038/nprot.2016.110] [Citation(s) in RCA: 173] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Progress toward finding a cure for muscle diseases has been slow because of the absence of relevant cellular models and the lack of a reliable source of muscle progenitors for biomedical investigation. Here we report an optimized serum-free differentiation protocol to efficiently produce striated, millimeter-long muscle fibers together with satellite-like cells from human pluripotent stem cells (hPSCs) in vitro. By mimicking key signaling events leading to muscle formation in the embryo, in particular the dual modulation of Wnt and bone morphogenetic protein (BMP) pathway signaling, this directed differentiation protocol avoids the requirement for genetic modifications or cell sorting. Robust myogenesis can be achieved in vitro within 1 month by personnel experienced in hPSC culture. The differentiating culture can be subcultured to produce large amounts of myogenic progenitors amenable to numerous downstream applications. Beyond the study of myogenesis, this differentiation method offers an attractive platform for the development of relevant in vitro models of muscle dystrophies and drug screening strategies, as well as providing a source of cells for tissue engineering and cell therapy approaches.
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Affiliation(s)
- Jérome Chal
- Institut de Génétique et de Biologie Moléculaireet Cellulaire (IGBMC), CNRS (UMR 7104), Inserm U964, Université de Strasbourg, Illkirch-Graffenstaden, France
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
- Harvard Stem Cell Institute, Boston, Massachusetts, USA
| | - Ziad Al Tanoury
- Institut de Génétique et de Biologie Moléculaireet Cellulaire (IGBMC), CNRS (UMR 7104), Inserm U964, Université de Strasbourg, Illkirch-Graffenstaden, France
| | - Marie Hestin
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
- Harvard Stem Cell Institute, Boston, Massachusetts, USA
| | - Bénédicte Gobert
- Institut de Génétique et de Biologie Moléculaireet Cellulaire (IGBMC), CNRS (UMR 7104), Inserm U964, Université de Strasbourg, Illkirch-Graffenstaden, France
| | - Suvi Aivio
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
- Harvard Stem Cell Institute, Boston, Massachusetts, USA
| | - Aurore Hick
- Anagenesis Biotechnologies, Parc d'innovation, Illkirch-Graffenstaden, France
| | - Thomas Cherrier
- Institut de Génétique et de Biologie Moléculaireet Cellulaire (IGBMC), CNRS (UMR 7104), Inserm U964, Université de Strasbourg, Illkirch-Graffenstaden, France
| | - Alexander P Nesmith
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - Kevin K Parker
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - Olivier Pourquié
- Institut de Génétique et de Biologie Moléculaireet Cellulaire (IGBMC), CNRS (UMR 7104), Inserm U964, Université de Strasbourg, Illkirch-Graffenstaden, France
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
- Harvard Stem Cell Institute, Boston, Massachusetts, USA
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5
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Genome-wide association study identifies new susceptibility loci for adolescent idiopathic scoliosis in Chinese girls. Nat Commun 2015; 6:8355. [PMID: 26394188 PMCID: PMC4595747 DOI: 10.1038/ncomms9355] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 08/13/2015] [Indexed: 02/05/2023] Open
Abstract
Adolescent idiopathic scoliosis (AIS) is a structural deformity of the spine affecting millions of children. As a complex disease, the genetic aetiology of AIS remains obscure. Here we report the results of a four-stage genome-wide association study (GWAS) conducted in a sample of 4,317 AIS patients and 6,016 controls. Overall, we identify three new susceptibility loci at 1p36.32 near AJAP1 (rs241215, Pcombined=2.95 × 10−9), 2q36.1 between PAX3 and EPHA4 (rs13398147, Pcombined=7.59 × 10−13) and 18q21.33 near BCL-2 (rs4940576, Pcombined=2.22 × 10−12). In addition, we refine a previously reported region associated with AIS at 10q24.32 (rs678741, Pcombined=9.68 × 10−37), which suggests LBX1AS1, encoding an antisense transcript of LBX1, might be a functional variant of AIS. This is the first GWAS investigating genetic variants associated with AIS in Chinese population, and the findings provide new insight into the multiple aetiological mechanisms of AIS. The authors perform a genome-wide association study of adolescent idiopathic scoliosis patients of Han Chinese descent, and identify 3 new loci for disease susceptibility.
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6
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Abstract
This review will focus on the use of the chicken and quail as model systems to analyze myogenesis and as such will emphasize the experimental approaches that are strongest in these systems-the amenability of the avian embryo to manipulation and in ovo observation. During somite differentiation, a wide spectrum of developmental processes occur such as cellular differentiation, migration, and fusion. Cell lineage studies combined with recent advancements in cell imaging allow these biological phenomena to be readily observed and hypotheses tested extremely rapidly-a strength that is restricted to the avian system. A clear weakness of the chicken in the past has been genetic approaches to modulate gene function. Recent advances in the electroporation of expression vectors, siRNA constructs, and use of tissue specific reporters have opened the door to increasingly sophisticated experiments that address questions of interest not only to the somite/muscle field in particular but also fundamental to biology in general. Importantly, an ever-growing body of evidence indicates that somite differentiation in birds is indistinguishable to that of mammals; therefore, these avian studies complement the complex genetic models of the mouse.
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Affiliation(s)
- Claire E Hirst
- EMBL Australia, Australian Regenerative Medicine Institute (ARMI), Monash University, Clayton, VIC, 3800, Australia,
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7
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Fan CM, Li L, Rozo ME, Lepper C. Making skeletal muscle from progenitor and stem cells: development versus regeneration. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2014; 1:315-27. [PMID: 22737183 DOI: 10.1002/wdev.30] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
For locomotion, vertebrate animals use the force generated by contractile skeletal muscles. These muscles form an actin/myosin-based biomachinery that is attached to skeletal elements to affect body movement and maintain posture. The mechanics, physiology, and homeostasis of skeletal muscles in normal and disease states are of significant clinical interest. How muscles originate from progenitors during embryogenesis has attracted considerable attention from developmental biologists. How skeletal muscles regenerate and repair themselves after injury by the use of stem cells is an important process to maintain muscle homeostasis throughout lifetime. In recent years, much progress has been made toward uncovering the origins of myogenic progenitors and stem cells as well as the regulation of these cells during development and regeneration.
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Affiliation(s)
- Chen-Ming Fan
- Department of Embryology, Carnegie Institution of Washington, Baltimore, MD, USA.
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8
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Abstract
Body axis elongation and segmentation are major morphogenetic events that take place concomitantly during vertebrate embryonic development. Establishment of the final body plan requires tight coordination between these two key processes. In this review, we detail the cellular and molecular as well as the physical processes underlying body axis formation and patterning. We discuss how formation of the anterior region of the body axis differs from that of the posterior region. We describe the developmental mechanism of segmentation and the regulation of body length and segment numbers. We focus mainly on the chicken embryo as a model system. Its accessibility and relatively flat structure allow high-quality time-lapse imaging experiments, which makes it one of the reference models used to study morphogenesis. Additionally, we illustrate conservation and divergence of specific developmental mechanisms by discussing findings in other major embryonic model systems, such as mice, frogs, and zebrafish.
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Affiliation(s)
- Bertrand Bénazéraf
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS (UMR 7104), Université de Strasbourg, Illkirch F-67400, France;
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9
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Sato K, Aoki M, Kondo R, Matsushita K, Akiba Y, Kamada T. Administration of insulin to newly hatched chicks improves growth performance via impairment of MyoD gene expression and enhancement of cell proliferation in chicken myoblasts. Gen Comp Endocrinol 2012; 175:457-63. [PMID: 22172340 DOI: 10.1016/j.ygcen.2011.11.043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 11/03/2011] [Accepted: 11/29/2011] [Indexed: 11/19/2022]
Abstract
The insulin/PI3K/Akt signaling pathway is strongly involved in the differentiation of C2C12 cells, as has been demonstrated by the addition of IGFs and insulin to culture media. In this study, we have characterized the role of insulin in chick myoblast proliferation and differentiation in vitro and in vivo, and have revealed novel details of how this exogenous hormone influences myogenic genes during differentiation. Chick myoblast cells cultured in differentiation medium (DMEM containing 2% FBS) supplemented with insulin exhibited a significant decrease in MyoD and myogenin mRNA expression after 12h of culture compared to cells cultured in differentiation media alone. MyoD and myogenin immunoreactive proteins in cells cultured in differentiation medium supplemented with insulin were quite low compared to those in control culture. Supplementation of the differentiation media containing insulin with LY294002 (a PI3K inhibitor) induced myoblast differentiation. A significant increase in MyoD and myogenin mRNA expression was observed in these cells after incubation for 12h, and the level of expression was similar to that of control cells incubated with differentiation media alone. The DNA content and the phosphor-Erk1/2 protein level were increased by the addition of insulin to the differentiation medium. These results suggest that insulin and its signaling pathway play an inhibitory role in chick myoblast differentiation. A high level of Pax7 mRNA was observed in the skeletal muscle of 3-day-old chicks administered insulin or tolbutamide at 1-day-of-age. In addition, body weight at 21 and 50 days-of-age was significantly greater for chickens administered insulin or tolbutamide at 1-day-of-age than for control chickens. These results detail not only species-specific differences in insulin action for myoblasts but also provide novel information that may be used for the improvement of chicken meat production.
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Affiliation(s)
- Kan Sato
- Animal Science, Department of Biological Production, Tokyo University of Agriculture and Technology, Fuchu-shi, Tokyo 183-8509, Japan.
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10
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Halperin-Barlev O, Kalcheim C. Sclerotome-derived Slit1 drives directional migration and differentiation of Robo2-expressing pioneer myoblasts. Development 2011; 138:2935-45. [PMID: 21653616 DOI: 10.1242/dev.065714] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Pioneer myoblasts generate the first myotomal fibers and act as a scaffold to pattern further myotome development. From their origin in the medial epithelial somite, they dissociate and migrate towards the rostral edge of each somite, from which differentiation proceeds in both rostral-to-caudal and medial-to-lateral directions. The mechanisms underlying formation of this unique wave of pioneer myofibers remain unknown. We show that rostrocaudal or mediolateral somite inversions in avian embryos do not alter the original directions of pioneer myoblast migration and differentiation into fibers, demonstrating that regulation of pioneer patterning is somite-intrinsic. Furthermore, pioneer myoblasts express Robo2 downstream of MyoD and Myf5, whereas the dermomyotome and caudal sclerotome express Slit1. Loss of Robo2 or of sclerotome-derived Slit1 function perturbed both directional cell migration and fiber formation, and their effects were mediated through RhoA. Although myoblast specification was not affected, expression of the intermediate filament desmin was reduced. Hence, Slit1 and Robo2, via RhoA, act to pattern formation of the pioneer myotome through the regulation of cytoskeletal assembly.
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Affiliation(s)
- Osnat Halperin-Barlev
- Department of Medical Neurobiology, IMRIC and ELSC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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11
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Abstract
Vertebrate embryo somite formation is temporally controlled by the cyclic expression of somitogenesis clock genes in the presomitic mesoderm (PSM). The somitogenesis clock is believed to be an intrinsic property of this tissue, operating independently of embryonic midline structures and the signaling molecules produced therein, namely Sonic hedgehog (Shh). This work revisits the notochord signaling contribution to temporal control of PSM segmentation by assessing the rate and number of somites formed and somitogenesis molecular clock gene expression oscillations upon notochord ablation. The absence of the notochord causes a delay in somite formation, accompanied by an increase in the period of molecular clock oscillations. Shh is the notochord-derived signal responsible for this effect, as these alterations are recapitulated by Shh signaling inhibitors and rescued by an external Shh supply. We have characterized chick smoothened expression pattern and have found that the PSM expresses both patched1 and smoothened Shh signal transducers. Upon notochord ablation, patched1, gli1, and fgf8 are down-regulated, whereas gli2 and gli3 are overexpressed. Strikingly, notochord-deprived PSM segmentation rate recovers over time, concomitant with raldh2 overexpression. Accordingly, exogenous RA supplement rescues notochord ablation effects on somite formation. A model is presented in which Shh and RA pathways converge to inhibit PSM Gli activity, ensuring timely somite formation. Altogether, our data provide evidence that a balance between different pathways ensures the robustness of timely somite formation and that notochord-derived Shh is a component of the molecular network regulating the pace of the somitogenesis clock.
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12
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Zhao X, Sirbu IO, Mic FA, Molotkova N, Molotkov A, Kumar S, Duester G. Retinoic acid promotes limb induction through effects on body axis extension but is unnecessary for limb patterning. Curr Biol 2009; 19:1050-7. [PMID: 19464179 DOI: 10.1016/j.cub.2009.04.059] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Revised: 04/09/2009] [Accepted: 04/28/2009] [Indexed: 12/11/2022]
Abstract
Retinoic acid (RA) is thought to be a key signaling molecule involved in limb bud patterning along the proximodistal or anteroposterior axes functioning through induction of Meis2 and Shh, respectively. Here, we utilize Raldh2-/- and Raldh3-/- mouse embryos lacking RA synthesis to demonstrate that RA signaling is not required for limb expression of Shh and Meis2. We demonstrate that RA action is required outside of the limb field in the body axis during forelimb induction but that RA is unnecessary at later stages when hindlimb budding and patterning occur. We provide evidence for a model of trunk mesodermal RA action in which forelimb induction requires RA repression of Fgf8 in the developing trunk similar to how RA controls somitogenesis and heart development. We demonstrate that pectoral fin development in RA-deficient zebrafish embryos can be rescued by an FGF receptor antagonist SU5402. In addition, embryo ChIP assays demonstrate that RA receptors bind the Fgf8 promoter in vivo. Our findings suggest that RA signaling is not required for limb proximodistal or anteroposterior patterning but that RA inhibition of FGF8 signaling during the early stages of body axis extension provides an environment permissive for induction of forelimb buds.
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Affiliation(s)
- Xianling Zhao
- Development and Aging Program, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
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13
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Formation and Differentiation of Avian Somite Derivatives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 638:1-41. [DOI: 10.1007/978-0-387-09606-3_1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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14
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Abstract
Retinoic acid, a derivative of vitamin A, is an essential component of cell-cell signaling during vertebrate organogenesis. In early development, retinoic acid organizes the trunk by providing an instructive signal for posterior neuroectoderm and foregut endoderm and a permissive signal for trunk mesoderm differentiation. At later stages, retinoic acid contributes to the development of the eye and other organs. Recent studies suggest that retinoic acid may act primarily in a paracrine manner and provide insight into the cell-cell signaling networks that control differentiation of pluripotent cells.
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Affiliation(s)
- Gregg Duester
- Burnham Institute for Medical Research, Development and Aging Program, La Jolla, CA 92037, USA.
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15
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Geetha-Loganathan P, Nimmagadda S, Scaal M, Huang R, Christ B. Wnt signaling in somite development. Ann Anat 2008; 190:208-22. [DOI: 10.1016/j.aanat.2007.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 12/10/2007] [Indexed: 01/30/2023]
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16
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Pryce BA, Brent AE, Murchison ND, Tabin CJ, Schweitzer R. Generation of transgenic tendon reporters, ScxGFP and ScxAP, using regulatory elements of the scleraxis gene. Dev Dyn 2007; 236:1677-82. [PMID: 17497702 DOI: 10.1002/dvdy.21179] [Citation(s) in RCA: 207] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Defects in tendon patterning and differentiation are seldom assessed in mouse mutants due to the difficulty in visualizing connective tissue structures. To facilitate tendon analysis, we have generated mouse lines harboring two different transgene reporters, alkaline phosphatase (AP) and green fluorescent protein (GFP), each expressed using regulatory elements derived from the endogenous Scleraxis (Scx) locus. Scx encodes a transcription factor expressed in all developing tendons and ligaments as well as in their progenitors. Both the ScxGFP and ScxAP transgenes are expressed in patterns recapitulating almost entirely the endogenous developmental expression of Scx including very robust expression in the tendons and ligaments. These reporter lines will facilitate isolation of tendon cells and phenotypic analysis of these tissues in a variety of genetic backgrounds.
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Affiliation(s)
- Brian A Pryce
- Shriners Hospital for Children, Research Division, Portland, Oregon 97239, USA
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17
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Abstract
Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of data on the complex molecular interactions leading to the formation of various somitic derivatives. In this review, we focus on the crucial role of the somites in building the body wall and limbs of amniote embryos. We give an overview on the current knowledge on the specification and differentiation of somitic cell lineages leading to the development of the vertebral column, skeletal muscle, connective tissue, meninges, and vessel endothelium, and highlight the importance of the somites in establishing the metameric pattern of the vertebrate body.
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Affiliation(s)
- Bodo Christ
- Institute of Anatomy und Cell Biology, Department of Molecular Embryology, University of Freiburg, Albertstr. 17, 79104 Freiburg, Germany.
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18
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Otto A, Schmidt C, Patel K. Pax3 and Pax7 expression and regulation in the avian embryo. ACTA ACUST UNITED AC 2006; 211:293-310. [PMID: 16506066 DOI: 10.1007/s00429-006-0083-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2006] [Indexed: 10/25/2022]
Abstract
Satellite cells are essential for postnatal growth and repair of skeletal muscle. The paired-box transcription factors Pax3 and Pax7 are expressed in emerging muscle precursors. Recent studies have traced the origin of satellite cells to the embryonic dermomyotome, however, their developmental regulation throughout embryogenesis remains unclear. We show the overlying surface ectoderm and lateral plate are essential for Pax3 expression, and that the overlying surface ectoderm and neural tube are necessary for Pax7 expression within the dorsal somite. Furthermore we show that the notochord acts to down regulate the expression of both genes. Moreover, we identify diffusible factors within these tissues that act to maintain expression of Pax3 ( + ) and Pax7 (+) muscle precursors. We show that Wnt1, 3a, 4 and 6 proteins are able to up regulate and expand the expression of Pax3 and Pax7 within the dorsal somite. Finally, we show that Wnt6 can mimic the effect of the dorsal ectoderm to maintain Pax3 and Pax7 expression.
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Affiliation(s)
- Anthony Otto
- Department Veterinary Basic Sciences, Royal Veterinary College, Royal College Street, NW1 OUT, London, UK
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Seo KW, Wang Y, Kokubo H, Kettlewell JR, Zarkower DA, Johnson RL. Targeted disruption of the DM domain containing transcription factor Dmrt2 reveals an essential role in somite patterning. Dev Biol 2006; 290:200-10. [PMID: 16387292 DOI: 10.1016/j.ydbio.2005.11.027] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 10/18/2005] [Accepted: 11/14/2005] [Indexed: 11/21/2022]
Abstract
Dmrt2 is expressed in the dermomyotome of developing vertebrate somites. To determine the role of Dmrt2 during mouse embryonic development, we generated a null mutation of Dmrt2 via homologous recombination in embryonic stem cells. Dmrt2 heterozygous mice derived from these cells are phenotypically normal. However, Dmrt2 homozygotes die soon after birth. The cause of death is likely due to abnormal rib and sternal development, leading to an inability to breathe. Loss of Dmrt2 leads to embryonic somite patterning defects, first evidenced at embryonic day (E) 10.5 and more pronounced by E11.5. Notably, both the dermomyotome and myotome fail to adopt a normal epithelial morphology in the absence of Dmrt2. Accompanying these morphological defects are alterations in the expression patterns of dermomyotomal and myotomal transcription factors including Pax3, Paraxis, Myf5, myogenin, Mrf4 and MyoD. Despite these defects, embryos harvested from E13.5 onwards exhibited relatively normal muscle pattern and mass, suggesting that early myotomal defects are corrected by a Dmrt2-independent mechanism. Taken together, our results define an essential function for Dmrt2 in somite development and provide evidence that DM domain genes have been co-opted into other critical developmental pathways distinct from that of sex determination or differentiation.
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Affiliation(s)
- Kwang Won Seo
- Department of Biochemistry and Molecular Biology, University of Texas, MD Anderson Cancer Center, Houston, 77030, USA
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20
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Geetha-Loganathan P, Nimmagadda S, Pröls F, Patel K, Scaal M, Huang R, Christ B. Ectodermal Wnt-6 promotes Myf5-dependent avian limb myogenesis. Dev Biol 2005; 288:221-33. [PMID: 16271265 DOI: 10.1016/j.ydbio.2005.09.035] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 09/12/2005] [Accepted: 09/19/2005] [Indexed: 01/31/2023]
Abstract
Limb muscles of vertebrates are derived from precursor cells that migrate from the lateral edge of the dermomyotome into the limb bud. Although several signaling molecules have been reported to be involved in the process of limb myogenesis, none of their activities has led to a consolidate idea about the limb myogenic pathway. Particularly, the role of ectodermal signals in limb myogenesis is still obscure. Here, we investigated the role of the ectoderm and ectodermal Wnt-6 during limb muscle development. We found that ectopic expression of Wnt-6 in the limb bud specifically extends the expression domains of Pax3, Paraxis, Myf5, Myogenin, Desmin and Myosin heavy chain (MyHC) but inhibits MyoD expression. Ectoderm removal results in a loss of expression of all of these myogenic markers. We show that Wnt-6 can compensate the absence of the ectoderm by rescuing the expression of Pax3, Paraxis, Myf5, Myogenin, Desmin and MyHC but not MyoD. These results show that, in chick, at least two signals from the limb ectoderm are necessary for muscle development. One of the signals is Wnt-6, which plays a unique role in promoting limb myogenesis via Pax3/Paraxis-Myf5, whereas the other putative signaling pathway involving MyoD expression is negatively regulated by Wnt-6 signaling.
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Affiliation(s)
- Poongodi Geetha-Loganathan
- Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Albertstrasse 17, D-79104 Freiburg, Germany
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21
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Nimmagadda S, Geetha Loganathan P, Huang R, Scaal M, Schmidt C, Christ B. BMP4 and noggin control embryonic blood vessel formation by antagonistic regulation of VEGFR-2 (Quek1) expression. Dev Biol 2005; 280:100-10. [PMID: 15766751 DOI: 10.1016/j.ydbio.2005.01.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2004] [Revised: 12/06/2004] [Accepted: 01/05/2005] [Indexed: 11/19/2022]
Abstract
Regulation of VEGFR-2 (Quek1) is an important mechanism during blood vessel formation. In the paraxial mesoderm, Quek1 expression is restricted to the lateral portion of the somite and later to sclerotomal cells surrounding the neural tube. By grafting of either intermediate mesoderm or BMP4 beads into the paraxial mesoderm, we show that BMP4 is a positive regulator of VEGFR-2 (Quek1) expression in the quail embryo. Separation of somites from intermediate mesoderm leads to down-regulation of Quek1 expression. The expression of Quek1 in the medial somite half is normally repressed by the notochord and becomes up-regulated and lateromedially expanded after separation of the notochord. Our results show that up-regulation of BMP4 leads to an increase of the number of blood vessels, whereas inhibition of BMP4 by noggin results in a reduction of blood vessels.
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Affiliation(s)
- Suresh Nimmagadda
- Institute of Anatomy and Cell Biology II, University of Freiburg, Albertstrasse 17, D-79104 Freiburg, Germany
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22
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Lee CT, Li L, Takamoto N, Martin JF, Demayo FJ, Tsai MJ, Tsai SY. The nuclear orphan receptor COUP-TFII is required for limb and skeletal muscle development. Mol Cell Biol 2004; 24:10835-43. [PMID: 15572686 PMCID: PMC533959 DOI: 10.1128/mcb.24.24.10835-10843.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nuclear orphan receptor COUP-TFII is widely expressed in multiple tissues and organs throughout embryonic development, suggesting that COUP-TFII is involved in multiple aspects of embryogenesis. Because of the early embryonic lethality of COUP-TFII knockout mice, the role of COUP-TFII during limb development has not been determined. COUP-TFII is expressed in lateral plate mesoderm of the early embryo prior to limb bud formation. In addition, COUP-TFII is also expressed in the somites and skeletal muscle precursors of the limbs. Therefore, in order to study the potential role of COUP-TFII in limb and skeletal muscle development, we bypassed the early embryonic lethality of the COUP-TFII mutant by using two methods. First, embryonic chimera analysis has revealed an obligatory role for COUP-TFII in limb bud outgrowth since mutant cells are unable to contribute to the distally growing limb mesenchyme. Second, we used a conditional-knockout approach to ablate COUP-TFII specifically in the limbs. Loss of COUP-TFII in the limbs leads to hypoplastic skeletal muscle development, as well as shorter limbs. Taken together, our results demonstrate that COUP-TFII plays an early role in limb bud outgrowth but not limb bud initiation. Also, COUP-TFII is required for appropriate development of the skeletal musculature of developing limbs.
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Affiliation(s)
- Christopher T Lee
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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23
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Schmidt C, Stoeckelhuber M, McKinnell I, Putz R, Christ B, Patel K. Wnt 6 regulates the epithelialisation process of the segmental plate mesoderm leading to somite formation. Dev Biol 2004; 271:198-209. [PMID: 15196961 DOI: 10.1016/j.ydbio.2004.03.016] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2003] [Revised: 02/09/2004] [Accepted: 03/01/2004] [Indexed: 11/29/2022]
Abstract
In higher vertebrates, the paraxial mesoderm undergoes a mesenchymal to epithelial transformation to form segmentally organised structures called somites. Experiments have shown that signals originating from the ectoderm overlying the somites or from midline structures are required for the formation of the somites, but their identity has yet to be determined. Wnt6 is a good candidate as a somite epithelialisation factor from the ectoderm since it is expressed in this tissue. In this study, we show that injection of Wnt6-producing cells beneath the ectoderm at the level of the segmental plate or lateral to the segmental plate leads to the formation of numerous small epithelial somites. Ectopic expression of Wnt6 leads to sustained expression of markers associated with the epithelial somites and reduced or delayed expression of markers associated with mesenchymally organised somitic tissue. More importantly, we show that Wnt6-producing cells are able to rescue somite formation after ectoderm ablation. Furthermore, injection of Wnt6-producing cells following the isolation of the neural tube/notochord from the segmental plate was able to rescue somite formation at both the structural (epithelialisation) and molecular level, as determined by the expression of marker genes like Paraxis or Pax-3. We show that Wnts are indeed responsible for the epithelialisation of somites by applying Wnt antagonists, which result in the segmental plate being unable to form somites. These results show that Wnt6, the only known member of this family to be localised to the chick paraxial ectoderm, is able to regulate the development of epithelial somites and that cellular organisation is pivotal in the execution of the differentiation programmes. We propose a model in which the localisation of Wnt6 and its antagonists regulates the process of epithelialisation in the paraxial mesoderm.
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Affiliation(s)
- Corina Schmidt
- Institute of Anatomy, Ludwigs-Maximilians-University of Munich, D-80336, Germany
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24
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Galli LM, Willert K, Nusse R, Yablonka-Reuveni Z, Nohno T, Denetclaw W, Burrus LW. A proliferative role for Wnt-3a in chick somites. Dev Biol 2004; 269:489-504. [PMID: 15110715 DOI: 10.1016/j.ydbio.2004.01.041] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Revised: 01/23/2004] [Accepted: 01/30/2004] [Indexed: 11/30/2022]
Abstract
The proper patterning of somites to give rise to sclerotome, dermomyotome, and myotome involves the coordination of many different cellular processes, including lineage specification, cell proliferation, cell death, and differentiation, by intercellular signals. One such family of secreted signaling proteins known to influence somite patterning is the Wnt family. Although the participation of Wnt-3a in the patterning of dorsal structures in the somite is well established, no clear consensus has emerged about the cellular processes that are governed by Wnt-3a in the somite. The recent demonstration that Wnt-3a has a proliferative role in the neural tube [Development 129 (2002) 2087] suggested that Wnt-3a might also act to regulate proliferation in somites. To test this hypothesis, we first analyzed the effects of Wnt-3a on segmental plate and somite explants (from Hamburger and Hamilton stage 10 chick embryos) grown in culture. These studies indicate that Wnt-3a is capable of maintaining and/or inducing expression of both Pax-3 and Pax-7, transcription factors that have been implicated in proliferation. To directly test for a role in proliferation, explants were immunostained with antibodies against phospho-histone H3. Explants treated with Wnt-3a show an increase in the percentage of cells expressing phospho-histone H3 as compared to controls. To test the proliferative effect of Wnt-3a in vivo, we ectopically expressed Wnt-3a in chick neural tubes via electroporation. Consistent with previous studies, ectopic expression of Wnt-3a in vivo results in a mediolateral expansion of the dermomyotome and myotome. We now show that proliferation of dorsal/dermomyotomal cells is significantly enhanced by ectopic Wnt-3a. Collectively, our explant and in vivo studies indicate that an increase in proliferation plays an important role in the expansion of the dermomyotome and myotome in Wnt-3a-treated embryos. Furthermore, our results demonstrate that small changes in proliferation can dramatically influence patterning and morphogenesis.
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Affiliation(s)
- Lisa M Galli
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
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25
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Venters SJ, Argent RE, Deegan FM, Perez-Baron G, Wong TS, Tidyman WE, Denetclaw WF, Marcelle C, Bronner-Fraser M, Ordahl CP. Precocious terminal differentiation of premigratory limb muscle precursor cells requires positive signalling. Dev Dyn 2004; 229:591-9. [PMID: 14991714 DOI: 10.1002/dvdy.20016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The timing of myogenic differentiation of hypaxial muscle precursor cells in the somite lags behind that of epaxial precursors. Two hypotheses have been proposed to explain this delay. One attributes the delay to the presence of negative-acting signals from the lateral plate mesoderm adjacent to the hypaxial muscle precursor cells located in the ventrolateral lip of the somitic dermomyotome (Pourquié et al. [1995] Proc. Natl. Acad. Sci. USA 92:3219-3223). The second attributes the delay to an absence of positive-acting inductive signals, similar to those from the axial structures that induce epaxial myotome development (Pownall et al. [1996] Development 122:1475-1488). Because both studies relied principally upon changes in the expression pattern of mRNAs specific to early muscle precursor cell markers, we revisited these experiments using two methods to assess muscle terminal differentiation. First, injection of fluorescent dyes before surgery was used to determine whether ventrolateral lip cells transform from epithelial cells to elongated myocytes. Second, an antibody to a terminal differentiation marker and a new monoclonal antibody that recognises avian and mammalian Pax3 were used for immunohistochemistry to assess the transition from precursor cell to myocyte. The results support both hypotheses and show further that placing axial structures adjacent to the somite ventrolateral lip induces an axial pattern of myocyte terminal differentiation and elongation.
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Affiliation(s)
- Sara J Venters
- Department of Anatomy, University of California, San Francisco, California 94143, USA
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26
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Tonegawa A, Kasai T, Takahashi Y. Systematic screening for signaling molecules expressed during somitogenesis by the signal sequence trap method. Dev Biol 2003; 262:32-50. [PMID: 14512016 DOI: 10.1016/s0012-1606(03)00327-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We describe a systematic screening to search for molecules that act as an extracellular signal during somitogenesis in vertebrates. Somitogenesis, which gives rise to segmented structures of axial bones and muscles, is a consequence of cooperative morphogenetic movements caused by precisely regulated cell and tissue interactions. We employed a strategy that combined subtractive hybridization to enrich paraxial mesoderm/somite-specific cDNAs and the signal sequence trap method, which selects signal sequence-containing molecules. Ninety-two independent cDNAs found to possess a putative signal sequence or a transmembrane domain are presented with a data base accession number for each. These clones include cDNAs which were previously identified with a function characterized, cDNAs previously identified with an undetermined function, and also cDNAs with no similarity to known sequences. Among them, 16 clones exhibited peculiar patterns of expression in the presomitic mesoderm/somites revealed by whole-mount and section in situ hybridization techniques, with some clones also being expressed in the forming neural tube. This is the first report in which an elaborate strategy combining three different screening steps was employed to identify signaling molecules relevant to a particular morphogenetic process.
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Affiliation(s)
- Akane Tonegawa
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara, 630-0101, Japan
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27
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Abstract
Cell signaling plays a key role in the development of all multicellular organisms. Numerous studies have established the importance of Hedgehog signaling in a wide variety of regulatory functions during the development of vertebrate and invertebrate organisms. Several reviews have discussed the signaling components in this pathway, their various interactions, and some of the general principles that govern Hedgehog signaling mechanisms. This review focuses on the developing systems themselves, providing a comprehensive survey of the role of Hedgehog signaling in each of these. We also discuss the increasing significance of Hedgehog signaling in the clinical setting.
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Affiliation(s)
- Andrew P McMahon
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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28
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Pownall ME, Gustafsson MK, Emerson CP. Myogenic regulatory factors and the specification of muscle progenitors in vertebrate embryos. Annu Rev Cell Dev Biol 2003; 18:747-83. [PMID: 12142270 DOI: 10.1146/annurev.cellbio.18.012502.105758] [Citation(s) in RCA: 415] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Embryological and genetic studies of mouse, bird, zebrafish, and frog embryos are providing new insights into the regulatory functions of the myogenic regulatory factors, MyoD, Myf5, Myogenin, and MRF4, and the transcriptional and signaling mechanisms that control their expression during the specification and differentiation of muscle progenitors. Myf5 and MyoD genes have genetically redundant, but developmentally distinct regulatory functions in the specification and the differentiation of somite and head muscle progenitor lineages. Myogenin and MRF4 have later functions in muscle differentiation, and Pax and Hox genes coordinate the migration and specification of somite progenitors at sites of hypaxial and limb muscle formation in the embryo body. Transcription enhancers that control Myf5 and MyoD activation in muscle progenitors and maintain their expression during muscle differentiation have been identified by transgenic analysis. In epaxial, hypaxial, limb, and head muscle progenitors, Myf5 is controlled by lineage-specific transcription enhancers, providing evidence that multiple mechanisms control progenitor specification at different sites of myogenesis in the embryo. Developmental signaling ligands and their signal transduction effectors function both interactively and independently to control Myf5 and MyoD activation in muscle progenitor lineages, likely through direct regulation of their transcription enhancers. Future investigations of the signaling and transcriptional mechanisms that control Myf5 and MyoD in the muscle progenitor lineages of different vertebrate embryos can be expected to provide a detailed understanding of the developmental and evolutionary mechanisms for anatomical muscles formation in vertebrates. This knowledge will be a foundation for development of stem cell therapies to repair diseased and damaged muscles.
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29
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Huang R, Stolte D, Kurz H, Ehehalt F, Cann GM, Stockdale FE, Patel K, Christ B. Ventral axial organs regulate expression of myotomal Fgf-8 that influences rib development. Dev Biol 2003; 255:30-47. [PMID: 12618132 DOI: 10.1016/s0012-1606(02)00051-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Fgf-8 encodes a secreted signaling molecule mediating key roles in embryonic patterning. This study analyzes the expression pattern, regulation, and function of this growth factor in the paraxial mesoderm of the avian embryo. In the mature somite, expression of Fgf-8 is restricted to a subpopulation of myotome cells, comprising most, but not all, epaxial and hypaxial muscle precursors. Following ablation of the notochord and floor plate, Fgf-8 expression is not activated in the somites, in either the epaxial or the hypaxial domain, while ablation of the dorsal neural tube does not affect Fgf-8 expression in paraxial mesoderm. Contrary to the view that hypaxial muscle precursors are independent of regulatory influences from axial structures, these findings provide the first evidence for a regulatory influence of ventral, but not dorsal axial structures on the hypaxial muscle domain. Sonic hedgehog can substitute for the ventral neural tube and notochord in the initiation of Fgf-8 expression in the myotome. It is also shown that Fgf-8 protein leads to an increase in sclerotomal cell proliferation and enhances rib cartilage development in mature somites, whereas inhibition of Fgf signaling by SU 5402 causes deletions in developing ribs. These observations demonstrate: (1) a regulatory influence of the ventral axial organs on the hypaxial muscle compartment; (2) regulation of epaxial and hypaxial expression of Fgf-8 by Sonic hedgehog; and (3) independent regulation of Fgf-8 and MyoD in the hypaxial myotome by ventral axial organs. It is postulated that the notochord and ventral neural tube influence hypaxial expression of Fgf-8 in the myotome and that, in turn, Fgf-8 has a functional role in rib formation.
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Affiliation(s)
- Ruijin Huang
- Institute of Anatomy, University of Freiburg, Germany
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30
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Parkyn G, Mootoosamy RC, Cheng L, Thorpe C, Dietrich S. Hypaxial muscle development. Results Probl Cell Differ 2003; 38:127-41. [PMID: 12132392 DOI: 10.1007/978-3-540-45686-5_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Affiliation(s)
- Gary Parkyn
- King's College London, Department of Craniofacial Development, Floor 27 Guy's Tower, Guy's Hospital, London SE1 9RT, UK
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31
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Marcelle C, Lesbros C, Linker C. Somite patterning: a few more pieces of the puzzle. Results Probl Cell Differ 2003; 38:81-108. [PMID: 12132400 DOI: 10.1007/978-3-540-45686-5_4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Christophe Marcelle
- University Aix-Marseille II, LGPD, CNRS UMR 6545, Developmental Biology Institute of Marseille, Campus de Luminy, Case 907, 13288 Marseille, France
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32
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Wigmore PM, Evans DJR. Molecular and cellular mechanisms involved in the generation of fiber diversity during myogenesis. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 216:175-232. [PMID: 12049208 DOI: 10.1016/s0074-7696(02)16006-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Skeletal muscles have a characteristic proportion and distribution of fiber types, a pattern which is set up early in development. It is becoming clear that different mechanisms produce this pattern during early and late stages of myogenesis. In addition, there are significant differences between the formation of muscles in head and those found in rest of the body. Early fiber type differentiation is dependent upon an interplay between patterning systems which include the Wnt and Hox gene families and different myoblast populations. During later stages, innervation, hormones, and functional demand increasingly act to determine fiber type, but individual muscles still retain an intrinsic commitment to form particular fiber types. Head muscle is the only muscle not derived from the somites and follows a different development pathway which leads to the formation of particular fiber types not found elsewhere. This review discusses the formation of fiber types in both head and other muscles using results from both chick and mammalian systems.
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Affiliation(s)
- Peter M Wigmore
- School of Biomedical Sciences, Queen's Medical Centre, Nottingham, United Kingdom
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33
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Amthor H, Huang R, McKinnell I, Christ B, Kambadur R, Sharma M, Patel K. The regulation and action of myostatin as a negative regulator of muscle development during avian embryogenesis. Dev Biol 2002; 251:241-57. [PMID: 12435355 DOI: 10.1006/dbio.2002.0812] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myostatin is a potent inhibitor of muscle growth. Genetic deletion of Myostatin leads to massive hyperplasia and hypertrophy of skeletal muscle. However, the overall muscle pattern is preserved. We show that, during chick embryonic development, Myostatin is expressed at stages and positions unlikely to influence qualitative muscle development. In the somites, Myostatin is predominantly expressed in a central domain of the dermomyotome but not at the dorsomedial and ventrolateral lips, where most cells for myotomal elongation are recruited. During limb bud development, Myostatin is transiently expressed at early stages in both myogenic and nonmyogenic regions. Myostatin is reexpressed during limb bud development at a time when splitting of muscle is underway. Heterotopically developed wing buds that fail to form muscle still express Myostatin. This demonstrates that, in the limb, not all Myostatin-expressing cells are of myogenic origin. Ectoderm and Sonic hedgehog have different effects on the expression of Myostatin dependent on stages at which the operation was performed and the length of the postoperative period. Finally, we show that application of Myostatin protein into the developing limb bud results in a down-regulation of Pax-3 and Myf-5, both genes associated with proliferation of myogenic cells; and, furthermore, Myostatin also prevents the expression of MyoD, a gene associated with muscle differentiation. The long-term effect of Myostatin treatment leads to a deficiency of limb muscle. Therefore, Myostatin negatively affects gene expression of transcription factors, which are necessary for establishing myogenic cell identity.
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Affiliation(s)
- Helge Amthor
- Department of Veterinary Basic Sciences, Royal Veterinary College, Royal College Street, London, NW1 OTU, England
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34
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Edom-Vovard F, Schuler B, Bonnin MA, Teillet MA, Duprez D. Fgf4 positively regulates scleraxis and tenascin expression in chick limb tendons. Dev Biol 2002; 247:351-66. [PMID: 12086472 DOI: 10.1006/dbio.2002.0707] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In vertebrates, tendons connect muscles to skeletal elements. Surgical experiments in the chick have underlined developmental interactions between tendons and muscles. Initial formation of tendons occurs autonomously with respect to muscle. However, further tendon development requires the presence of muscle. The molecular signals involved in these interactions remain unknown. In the chick limb, Fgf4 transcripts are located at the extremities of muscles, where the future tendons will attach. In this paper, we analyse the putative role of muscle-Fgf4 on tendon development. We have used three general tendon markers, scleraxis, tenascin, and Fgf8 to analyse the regulation of these tendon-associated molecules by Fgf4 under different experimental conditions. In the absence of Fgf4, in muscleless and aneural limbs, the expression of the three tendon-associated molecules, scleraxis, tenascin, and Fgf8, is down-regulated. Exogenous implantation of Fgf4 in normal, aneural, and muscleless limbs induces scleraxis and tenascin expression but not that of Fgf8. These results indicate that Fgf4 expressed in muscle is required for the maintenance of scleraxis and tenascin but not Fgf8 expression in tendons.
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Affiliation(s)
- Frédérique Edom-Vovard
- Institut d'Embryologie Cellulaire et Moléculaire du CNRS et du Collège de France (UMR 7128), 49 bis, avenue de la Belle Gabrielle, Nogent-sur-Marne, 94736, France
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35
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Chen JC, Love CM, Goldhamer DJ. Two upstream enhancers collaborate to regulate the spatial patterning and timing of MyoD transcription during mouse development. Dev Dyn 2001; 221:274-88. [PMID: 11458388 DOI: 10.1002/dvdy.1138] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
MyoD is a member of the basic-helix-loop-helix (bHLH) transcription factor family, which regulates muscle determination and differentiation in vertebrates. While it is now well established that the MyoD gene is regulated by Sonic hedgehog, Wnts, and other signals, it is not known how MyoD transcription is initiated and maintained in response to these signals. We have investigated the cis control of MyoD expression to identify and characterize the DNA targets that mediate MyoD transcription in embryos. By monitoring lacZ reporter gene expression in transgenic mice, we show that regulatory information contained in 24 kb of human MyoD 5' flanking sequence is sufficient to accurately control MyoD expression in embryos. Previous studies have identified two muscle-specific regulatory regions upstream of MyoD, a 4-kb region centered at -20 kb (designated fragment 3) that contains a highly conserved 258-bp core enhancer sequence, and a more proximal enhancer at -5 kb, termed the distal regulatory region (DRR), that heretofore has been identified only in mice. Here, we identify DRR-related sequences in humans and show that DRR function is conserved in humans and mice. In addition, transcriptional activity of MyoD 5' flanking sequences in somites and limb buds is largely a composite of the individual specificities of the two enhancers. Deletion of fragment 3 resulted in dramatic but temporary expression defects in the hypaxial myotome and limb buds, suggesting that this regulatory region is essential for proper temporal and spatial patterning of MyoD expression. These data indicate that regulatory sequences in fragment 3 are important targets of embryonic signaling required for the initiation of MyoD expression.
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Affiliation(s)
- J C Chen
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6058, USA
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36
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Borycki AG, Emerson CP. Multiple tissue interactions and signal transduction pathways control somite myogenesis. Curr Top Dev Biol 2001; 48:165-224. [PMID: 10635460 DOI: 10.1016/s0070-2153(08)60757-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- A G Borycki
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia 19104-6058, USA
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37
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Krüger M, Mennerich D, Fees S, Schäfer R, Mundlos S, Braun T. Sonic hedgehog is a survival factor for hypaxial muscles during mouse development. Development 2001; 128:743-52. [PMID: 11171399 DOI: 10.1242/dev.128.5.743] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sonic hedgehog (Shh) has been proposed to function as an inductive and trophic signal that controls development of epaxial musculature in vertebrate embryos. In contrast, development of hypaxial muscles was assumed to occur independently of Shh. We here show that formation of limb muscles was severely affected in two different mouse strains with inactivating mutations of the Shh gene. The limb muscle defect became apparent relatively late and initial stages of hypaxial muscle development were unaffected or only slightly delayed. Micromass cultures and cultures of tissue fragments derived from limbs under different conditions with or without the overlaying ectoderm indicated that Shh is required for the maintenance of the expression of myogenic regulatory factors (MRFs) and, consecutively, for the formation of differentiated limb muscle myotubes. We propose that Shh acts as a survival and proliferation factor for myogenic precursor cells during hypaxial muscle development. Detection of a reduced but significant level of Myf5 expression in the epaxial compartment of somites of Shh homozygous mutant embryos at E9.5 indicated that Shh might be dispensable for the initiation of myogenesis both in hypaxial and epaxial muscles. Our data suggest that Shh acts similarly in both somitic compartments as a survival and proliferation factor and not as a primary inducer of myogenesis.
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Affiliation(s)
- M Krüger
- Institute of Physiological Chemistry, University of Halle-Wittenberg, Hollystr. 1, Germany
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38
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Olivera-Martinez I, Thélu J, Teillet MA, Dhouailly D. Dorsal dermis development depends on a signal from the dorsal neural tube, which can be substituted by Wnt-1. Mech Dev 2001; 100:233-44. [PMID: 11165480 DOI: 10.1016/s0925-4773(00)00540-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To investigate the origin and nature of the signals responsible for specification of the dermatomal lineage, excised axial organs in 2-day-old chick embryos were replaced by grafts of the dorsal neural tube, or the ventral neural tube plus the notochord, or aggregates of cells engineered to produce Sonic hedgehog (Shh), Noggin, BMP-2, Wnt-1, or Wnt-3a. By E10, grafts of the ventral neural tube plus notochord or of cells producing Shh led to differentiation of cartilage and muscles, and an impaired dermis derived from already segmented somites. In contrast, grafts of the dorsal neural tube, or of cells producing Wnt-1, triggered the formation of a feather-inducing dermis. These results show that the dermatome inducer is produced by the dorsal neural tube. The signal can be Wnt-1 itself, or can be mediated, or at least mimicked by Wnt-1.
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Affiliation(s)
- I Olivera-Martinez
- Equipe Biologie de la Différenciation Epithéliale, UMR Centre National de la Recherche Scientifique (CNRS) 5538, LEDAC, Institut Albert Bonniot, Université Joseph Fourier, Grenoble, France
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39
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Cotrina ML, González-Hoyuela M, Barbas JA, Rodríguez-Tébar A. Programmed cell death in the developing somites is promoted by nerve growth factor via its p75(NTR) receptor. Dev Biol 2000; 228:326-36. [PMID: 11112333 DOI: 10.1006/dbio.2000.9948] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurotrophins control neuron number during development by promoting the generation and survival of neurons and by regulating programmed neuronal death. In the latter case, the cell death induced by nerve growth factor (NGF) in the developing chick retina is mediated by p75(NTR), the common neurotrophin receptor (J. M. Frade, A. Rodriguez-Tebar, and Y.-A. Barde, 1996, Nature 383, 166-168). Here we show that NGF also induces the programmed death of paraxial mesoderm cells in the developing somites. Both NGF and p75(NTR) are expressed in the somites of chick embryos at the time and the place of programmed cell death. Moreover, neutralizing the activity of endogenous NGF with a specific blocking antibody, or antagonizing NGF binding to p75(NTR) by the application of human NT-4/5, reduces the levels of apoptotic cell death in both the sclerotome and the dermamyotome by about 50 and 70%, respectively. Previous data have shown that Sonic hedgehog is necessary for the survival of differentiated somite cells. Consistent with this, Sonic hedgehog induces a decrease of NGF mRNA in somite explant cultures, thus showing the antagonistic effect of NGF and Sonic hedgehog with respect to somite cell survival. The regulation of programmed cell death by NGF/p75(NTR) in a mesoderm-derived tissue demonstrates the capacity of neurotrophins and their receptors to influence critical developmental processes both within and outside of the nervous system.
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Affiliation(s)
- M L Cotrina
- Instituto Cajal de Neurobiología, CSIC, Avenida Doctor Arce, 37, E-28002 Madrid, Spain
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40
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Olivera-Martinez I, Coltey M, Dhouailly D, Pourquié O. Mediolateral somitic origin of ribs and dermis determined by quail-chick chimeras. Development 2000; 127:4611-7. [PMID: 11023864 DOI: 10.1242/dev.127.21.4611] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Somites are transient mesodermal structures giving rise to all skeletal muscles of the body, the axial skeleton and the dermis of the back. Somites arise from successive segmentation of the presomitic mesoderm (PSM). They appear first as epithelial spheres that rapidly differentiate into a ventral mesenchyme, the sclerotome, and a dorsal epithelial dermomyotome. The sclerotome gives rise to vertebrae and ribs while the dermomyotome is the source of all skeletal muscles and the dorsal dermis. Quail-chick fate mapping and diI-labeling experiments have demonstrated that the epithelial somite can be further subdivided into a medial and a lateral moiety. These two subdomains are derived from different regions of the primitive streak and give rise to different sets of muscles. The lateral somitic cells migrate to form the musculature of the limbs and body wall, known as the hypaxial muscles, while the medial somite gives rise to the vertebrae and the associated epaxial muscles. The respective contribution of the medial and lateral somitic compartments to the other somitic derivatives, namely the dermis and the ribs has not been addressed and therefore remains unknown. We have created quail-chick chimeras of either the medial or lateral part of the PSM to examine the origin of the dorsal dermis and the ribs. We demonstrate that the whole dorsal dermis and the proximal ribs exclusively originates from the medial somitic compartment, whereas the distal ribs derive from the lateral compartment.
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Affiliation(s)
- I Olivera-Martinez
- Equipe Biologie de la Différenciation Epithéliale, UMR CNRS 5538, LEDAC, Institut Albert Bonniot, Université Joseph Fourier, Grenoble, France
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41
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Summerbell D, Ashby PR, Coutelle O, Cox D, Yee S, Rigby PW. The expression of Myf5 in the developing mouse embryo is controlled by discrete and dispersed enhancers specific for particular populations of skeletal muscle precursors. Development 2000; 127:3745-57. [PMID: 10934019 DOI: 10.1242/dev.127.17.3745] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development of skeletal muscle in vertebrate embryos is controlled by a transcriptional cascade that includes the four myogenic regulatory factors Myf5, Myogenin, MRF4 and MyoD. In the mouse embryo, Myf5 is the first of these factors to be expressed and mutational analyses suggest that this protein acts early in the process of commitment to the skeletal muscle fate. We have therefore analysed the regulation of Myf5 gene expression using transgenic technology and find that its control is markedly different from that of the other two myogenic regulatory factor genes previously analysed, Myogenin and MyoD. We show that Myf5 is regulated through a number of distinct and discrete enhancers, dispersed throughout 14 kb spanning the MRF4/Myf5 locus, each of which drives reporter gene expression in a particular subset of skeletal muscle precursors. This region includes four separate enhancers controlling expression in the epaxial muscle precursors of the body, some hypaxial precursors of the body, some facial muscles and the central nervous system. These elements separately or together are unable to drive expression in the cells that migrate to the limb buds and in some other muscle subsets and to correctly maintain expression at late times. We suggest that this complex mechanism of control has evolved because different inductive signals operate in each population of muscle precursors and thus distinct enhancers, and cognate transcription factors, are required to interpret them.
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Affiliation(s)
- D Summerbell
- Division of Eukaryotic Molecular Genetics, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
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42
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Pirskanen A, Kiefer JC, Hauschka SD. IGFs, insulin, Shh, bFGF, and TGF-beta1 interact synergistically to promote somite myogenesis in vitro. Dev Biol 2000; 224:189-203. [PMID: 10926759 DOI: 10.1006/dbio.2000.9784] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies from our group and others have shown that in vitro somite myogenesis is regulated by neural tube and notochord factors including Wnt, Sonic hedgehog (Shh), and basic fibroblast growth factor (bFGF) together with transforming growth factor-beta1 (TGF-beta1). In this study we report that insulin and insulin-like growth factors I and II (IGF-I and -II) also promote myogenesis in explant cultures containing single somites or somite-sized pieces of segmental plate mesoderm from 2-day (stage 10-14) chicken embryos and that the combination of insulin/IGFs with bFGF plus TGF-beta1 promotes even higher levels of myogenesis. We also found that Shh promotes myogenesis in this in vitro system and that Shh interacts synergistically with insulin/IGFs to promote high levels of myogenesis. RT-PCR analysis detected insulin, IGF-II, insulin receptor, and IGF receptor mRNAs in both the neural tube and the somites, whereas IGF-I transcripts were detected in entire embryos but not in the neural tube or somites. Treatment of somite-neural tube cocultures with anti-insulin, anti-IGF-II, anti-insulin receptor, or anti-IGF receptor blocking antibodies caused a significant decrease in myogenesis. These results are consistent with the hypothesis that systemic IGF-I as well as insulin and IGF-II secreted by the neural tube act as additional early myogenic signals during embryogenesis. Further studies indicate that insulin, IGFs, bFGF, and Shh also stimulate somite cell proliferation and influence apoptosis.
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Affiliation(s)
- A Pirskanen
- Department of Biochemistry, University of Washington, Seattle 98195, USA
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43
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Hirsinger E, Jouve C, Dubrulle J, Pourquié O. Somite formation and patterning. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 198:1-65. [PMID: 10804460 DOI: 10.1016/s0074-7696(00)98002-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
As a consequence of their segmented arrangement and the diversity of their tissue derivatives, somites are key elements in the establishment of the metameric body plan in vertebrates. This article aims to largely review what is known about somite development, from the initial stages of somite formation through the process of somite regionalization along the three major body axes. The role of both cell intrinsic mechanisms and environmental cues are evaluated. The periodic and bilaterally synchronous nature of somite formation is proposed to rely on the existence of a developmental clock. Molecular mechanisms underlying these events are reported. The importance of an antero-posterior somitic polarity with respect to somite formation on one hand and body segmentation on the other hand is discussed. Finally, the mechanisms leading to the regionalization of somites along the dorso-ventral and medio-lateral axes are reviewed. This somitic compartmentalization is believed to underlie the segregation of dermis, skeleton, and dorsal and appendicular musculature.
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Affiliation(s)
- E Hirsinger
- Laboratoire de Génétique et de Physiologie du Développement (LGPD), Université de la Méditerranée-AP de Marseille, France
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Williams BA, Ordahl CP. Fate restriction in limb muscle precursor cells precedes high-level expression of MyoD family member genes. Development 2000; 127:2523-36. [PMID: 10821752 DOI: 10.1242/dev.127.12.2523] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mechanisms by which pluripotent embryonic cells generate unipotent tissue progenitor cells during development are unknown. Molecular/genetic experiments in cultured cells have led to the hypothesis that the product of a single member of the MyoD gene family (MDF) is necessary and sufficient to establish the positive aspects of the determined state of myogenic precursor cells: i.e., the ability to initiate and maintain the differentiated state (Weintraub, H., Davis, R., Tapscott, S., Thayer, M., Krause, M., Benezra, R., Blackwell, T. K., Turner, D., Rupp, R., Hollenberg, S. et al. (1991) Science 251, 761–766). Embryonic cell type determination also involves negative regulation, such as the restriction of developmental potential for alternative cell types, that is not directly addressed by the MDF model. In the experiments reported here, phenotypic restriction in myogenic precursor cells is assayed by an in vivo ‘notochord challenge’ to evaluate their potential to ‘choose’ between two alternative cell fate endpoints: cartilage and muscle (Williams, B. A. and Ordahl, C. P. (1997) Development 124, 4983–4997). Two separate myogenic precursor cell populations were found to be phenotypically restricted while expressing the Pax3 gene and prior to MDF gene activation. Therefore, while MDF family members act positively during myogenic differentiation, phenotypic restriction, the negative aspect of cell specification, requires cellular and molecular events and interactions that precede MDF expression in myogenic precursor cells. The qualities of muscle formed by the determined myogenic precursor cells in these experiments further indicate that their developmental potential is intermediate between that of myoblastic stem cells taken from fetal or adult tissue (which lack mitotic and morphogenetic potential when tested in vivo) and embryonic stem cells (which are multipotent). We hypothesize that such embryonic myogenic progenitor cells represent a distinct class of determined embryonic cell, one that is responsible for both tissue growth and tissue morphogenesis.
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Affiliation(s)
- B A Williams
- Department of Anatomy and Cardiovascular Research Institute, University of California, San Francisco, CA 94143-0452, USA
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45
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Constantin B, Cronier L. Involvement of gap junctional communication in myogenesis. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 196:1-65. [PMID: 10730212 DOI: 10.1016/s0074-7696(00)96001-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell-to-cell communication plays important roles in development and in tissue morphogenesis. Gap junctional intercellular communication (GJIC) has been implicated in embryonic development of various tissues and provides a pathway to exchange ions, secondary messengers, and metabolites through the intercellular gap junction channels. Although GJIC is absent in adult skeletal muscles, the formation of skeletal muscles involves a sequence of complex events including cell-cell interaction processes where myogenic cells closely adhere to each other. Much experimental evidence has shown that myogenic precursors and developing muscle fibers can directly communicate through junctional channels. This review summarizes current knowledge on the GJIC and developmental events involved in the formation of skeletal muscle fibers and describes recent progress in the investigation of the role of GJIC in myogenesis: evidence of gap junctions in somitic and myotomal tissue as well as in developing muscle fibers in situ, GJIC between perfusion myoblasts in culture, and involvement of GJIC in cytodifferentiation of skeletal muscle cells and in myoblast fusion. A model of intercellular signaling is proposed where GJIC participates to coordinate a multicellular population of interacting myogenic precursors to allow commitment to the skeletal muscle fate.
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Affiliation(s)
- B Constantin
- Laboratoire de Physiologie Générale, CNRS UMR 6558, University of Poitiers, France.
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46
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Lopes ML, Schmidt GS, Coutinho LL. Identification of proliferating cells in chicken embryos using 5-bromo- 2'-deoxyuridine immunohistochemical detection. Genet Mol Biol 2000. [DOI: 10.1590/s1415-47572000000100028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chicken embryos were incubated with BrdU, embedded in plastic resin, sectioned and screened immunohistochemically to identify proliferating cells in the neural tube and somites. Fixation in 4% paraformaldehyde for 1 h was essential for detecting specific colorimetric signals of BrdU incorporation into cells during the S phase of the cell cycle. Transverse sections of the neural tube showed that the nuclei of proliferating cells (BrdU positive) had a uniform and centralized distribution, whereas unstained nuclei were found only along the extremities of the neural tube. Transverse sections of differentiated somites showed proliferating cells in the scleratome and dermatome. However, no incorporation of BrdU was observed in myotomic cells, which give rise to axial skeletal muscle. In spite of their proximity, the dermatome and myotome showed marked differences in cell proliferation. The excellent preservation of morphological characteristics in the embryonic tissues facilitated identification of variations in BrdU incorporation.
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47
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Abstract
The paraxial mesoderm of the neck and trunk of mouse embryos undergoes extensive morphogenesis in forming somites. Paraxial mesoderm is divided into segments, it elongates along its anterior posterior axis, and its cells organize into epithelia. Experiments were performed to determine if these processes are autonomous to the mesoderm that gives rise to the somites. Presomitic mesoderm at the tailbud stage was cultured in the presence and absence of its adjacent tissues. Somite segmentation occurred in the absence of neural tube, notochord, gut and surface ectoderm, and occurred in posterior fragments in the absence of anterior presomitic mesoderm. Mesodermal expression of Dll1 and Notch1, genes with roles in segmentation, was largely independent of other tissues, consistent with autonomous segmentation. However, surface ectoderm was found to be necessary for elongation of the mesoderm along the anterior-posterior axis and for somite epithelialization. To determine if there is specificity in the interaction between ectoderm and mesoderm, ectoderm from different sources was recombined with presomitic mesoderm. Surface ectoderm from only certain parts of the embryo supported somite epithelialization and elongation. Somite epithelialization induced by ectoderm was correlated with expression of the basic-helix-loop-helix gene Paraxis in the mesoderm. This is consistent with the genetically defined requirement for Paraxis in somite epithelialization. However, trunk ectoderm was able to induce somite epithelialization in the absence of strong Paraxis expression. We conclude that somitogenesis consists of autonomous segmentation patterned by Notch signaling and nonautonomous induction of elongation and epithelialization by surface ectoderm.
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Affiliation(s)
- K M Correia
- Department of Genetics, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, OH 44106-4955, USA
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48
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Cleaver O, Seufert DW, Krieg PA. Endoderm patterning by the notochord: development of the hypochord in Xenopus. Development 2000; 127:869-79. [PMID: 10648245 DOI: 10.1242/dev.127.4.869] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The patterning and differentiation of the vertebrate endoderm requires signaling from adjacent tissues. In this report, we demonstrate that signals from the notochord are critical for the development of the hypochord, which is a transient, endodermally derived structure that lies immediately ventral to the notochord in the amphibian and fish embryo. It appears likely that the hypochord is required for the formation of the dorsal aorta in these organisms. We show that removal of the notochord during early neurulation leads to the complete failure of hypochord development and to the elimination of expression of the hypochord marker, VEGF. Removal of the notochord during late neurulation, however, does not interfere with hypochord formation. These results suggest that signals arising in the notochord instruct cells in the underlying endoderm to take on a hypochord fate during early neural stages, and that the hypochord does not depend on further notochord signals for maintenance. In reciprocal experiments, when the endoderm receives excess notochord signaling, a significantly enlarged hypochord develops. Overall, these results demonstrate that, in addition to patterning neural and mesodermal tissues, the notochord plays an important role in patterning of the endoderm.
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Affiliation(s)
- O Cleaver
- Division of Molecular Cell and Developmental Biology, School of Biological Sciences, University of Texas at Austin, Austin, TX 78712, USA
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49
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Abstract
Inductive events in the development of the sclerotome and their possible underlying mechanisms were reviewed from the primary literature. A brief review of morphological and anatomical aspects of sclerotome development was given. The importance of the notochord and neural tube in sclerotome induction and somite chondrogenesis in vivo and in vitro was established. The functions and patterns of expression of different sclerotome markers were discussed. Shh and Noggin were discussed as two molecules produced by the neural tube and notochord that appear to maintain and initiate the sclerotome, respectively. While the abilities of the axial organs and Shh and Noggin to induce sclerotome marker expression in the somite was not disputed, the exact nature of these inductions was discussed with regard to possible effects on gene expression, effects on cell survival, and physical effects on the cells and it was argued that the fundamental nature of inductive events in the sclerotome is still unknown.
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Affiliation(s)
- J L Dockter
- Department of Anatomy, University of California, San Francisco 94143, USA
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50
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Monsoro-Burq AH, Le Douarin N. Duality of molecular signaling involved in vertebral chondrogenesis. Curr Top Dev Biol 2000; 48:43-75. [PMID: 10635457 DOI: 10.1016/s0070-2153(08)60754-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- A H Monsoro-Burq
- Institut d'Embryologie Cellulaire et Moléculaire du CNRS et du Collège de France, Nogent-sur-Marne, France
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