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Kahane N, Dahan-Barda Y, Kalcheim C. A Spatio-Temporal-Dependent Requirement of Sonic Hedgehog in the Early Development of Sclerotome-Derived Vertebrae and Ribs. Int J Mol Sci 2024; 25:5602. [PMID: 38891790 PMCID: PMC11171667 DOI: 10.3390/ijms25115602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 05/13/2024] [Accepted: 05/19/2024] [Indexed: 06/21/2024] Open
Abstract
Derived from axial structures, Sonic Hedgehog (Shh) is secreted into the paraxial mesoderm, where it plays crucial roles in sclerotome induction and myotome differentiation. Through conditional loss-of-function in quail embryos, we investigate the timing and impact of Shh activity during early formation of sclerotome-derived vertebrae and ribs, and of lateral mesoderm-derived sternum. To this end, Hedgehog interacting protein (Hhip) was electroporated at various times between days 2 and 5. While the vertebral body and rib primordium showed consistent size reduction, rib expansion into the somatopleura remained unaffected, and the sternal bud developed normally. Additionally, we compared these effects with those of locally inhibiting BMP activity. Transfection of Noggin in the lateral mesoderm hindered sternal bud formation. Unlike Hhip, BMP inhibition via Noggin or Smad6 induced myogenic differentiation of the lateral dermomyotome lip, while impeding the growth of the myotome/rib complex into the somatic mesoderm, thus affirming the role of the lateral dermomyotome epithelium in rib guidance. Overall, these findings underscore the continuous requirement for opposing gradients of Shh and BMP activity in the morphogenesis of proximal and distal flank skeletal structures, respectively. Future research should address the implications of these early interactions to the later morphogenesis and function of the musculo-skeletal system and of possible associated malformations.
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Affiliation(s)
| | | | - Chaya Kalcheim
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem-Hadassah Medical School, P.O. Box 12272, Jerusalem 9112102, Israel; (N.K.); (Y.D.-B.)
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2
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Peng H, Qiao J, Wang G, Shi W, Xia F, Qiao R, Dong B. A collagen-rich arch in the urochordate notochord coordinates cell shaping and multi-tissue elongation. Curr Biol 2023; 33:5390-5403.e3. [PMID: 37995694 DOI: 10.1016/j.cub.2023.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 10/26/2023] [Accepted: 11/01/2023] [Indexed: 11/25/2023]
Abstract
Cell and tissue reshaping is crucial for coordinating three-dimensional pattern formation, in which the size and shape of the cells must be accurately regulated via signal transport and communication among tissues. However, the identity of signaling and transportation mechanisms in this process remains elusive. In our study, we identified an extracellular matrix (ECM) structure with a vertebra-like shape surrounding the central notochord tissue in the larval tail of the urochordate Ciona. Additionally, we verified that the ECM structure was formed de novo, mainly from collagens secreted by notochord cells. Fluorescence recovery after photobleaching and simulation results revealed that this structure was formed via diffusional collagen flow from a notochord that was restricted and molded in the spaces among tail tissues. We revealed that the collagen structure was essential for notochord cell arrangement and elongation. Furthermore, we observed that the central notochord connects with the epidermis through this ECM structure. The disruption of this structure by collagen knockdown and loss-of-collagen function caused the failure of notochord elongation. More importantly, the epidermis could not elongate proportionally with notochord, indicating that the collagen-rich structure serves as a scaffold to coordinate the concurrent elongation of the tail tissues. These findings provide insights into how the central tissue forms and molds its surrounding ECM structure, by not only regulating its own morphogenesis but also functioning as a scaffold for signal transmission to orchestrate the coordinated morphologic reshaping of the surrounding tissues.
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Affiliation(s)
- Hongzhe Peng
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Jinghan Qiao
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Guilin Wang
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Wenjie Shi
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Fan Xia
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Runyu Qiao
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Bo Dong
- Fang Zongxi Center, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China; Laoshan Laboratory, Qingdao 266237, China; MoE Key Laboratory of Evolution & Marine Biodiversity, Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.
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3
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Crump KB, Alminnawi A, Bermudez‐Lekerika P, Compte R, Gualdi F, McSweeney T, Muñoz‐Moya E, Nüesch A, Geris L, Dudli S, Karppinen J, Noailly J, Le Maitre C, Gantenbein B. Cartilaginous endplates: A comprehensive review on a neglected structure in intervertebral disc research. JOR Spine 2023; 6:e1294. [PMID: 38156054 PMCID: PMC10751983 DOI: 10.1002/jsp2.1294] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 09/15/2023] [Accepted: 09/26/2023] [Indexed: 12/30/2023] Open
Abstract
The cartilaginous endplates (CEP) are key components of the intervertebral disc (IVD) necessary for sustaining the nutrition of the disc while distributing mechanical loads and preventing the disc from bulging into the adjacent vertebral body. The size, shape, and composition of the CEP are essential in maintaining its function, and degeneration of the CEP is considered a contributor to early IVD degeneration. In addition, the CEP is implicated in Modic changes, which are often associated with low back pain. This review aims to tackle the current knowledge of the CEP regarding its structure, composition, permeability, and mechanical role in a healthy disc, how they change with degeneration, and how they connect to IVD degeneration and low back pain. Additionally, the authors suggest a standardized naming convention regarding the CEP and bony endplate and suggest avoiding the term vertebral endplate. Currently, there is limited data on the CEP itself as reported data is often a combination of CEP and bony endplate, or the CEP is considered as articular cartilage. However, it is clear the CEP is a unique tissue type that differs from articular cartilage, bony endplate, and other IVD tissues. Thus, future research should investigate the CEP separately to fully understand its role in healthy and degenerated IVDs. Further, most IVD regeneration therapies in development failed to address, or even considered the CEP, despite its key role in nutrition and mechanical stability within the IVD. Thus, the CEP should be considered and potentially targeted for future sustainable treatments.
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Affiliation(s)
- Katherine B. Crump
- Tissue Engineering for Orthopaedics & Mechanobiology, Bone & Joint Program, Department for BioMedical Research (DBMR), Medical FacultyUniversity of BernBernSwitzerland
- Department of Orthopaedic Surgery and Traumatology, InselspitalBern University Hospital, Medical Faculty, University of BernBernSwitzerland
- Graduate School for Cellular and Biomedical Sciences (GCB)University of BernBernSwitzerland
| | - Ahmad Alminnawi
- GIGA In Silico MedicineUniversity of LiègeLiègeBelgium
- Skeletal Biology and Engineering Research Center, KU LeuvenLeuvenBelgium
- Biomechanics Research Unit, KU LeuvenLeuvenBelgium
| | - Paola Bermudez‐Lekerika
- Tissue Engineering for Orthopaedics & Mechanobiology, Bone & Joint Program, Department for BioMedical Research (DBMR), Medical FacultyUniversity of BernBernSwitzerland
- Department of Orthopaedic Surgery and Traumatology, InselspitalBern University Hospital, Medical Faculty, University of BernBernSwitzerland
- Graduate School for Cellular and Biomedical Sciences (GCB)University of BernBernSwitzerland
| | - Roger Compte
- Twin Research & Genetic EpidemiologySt. Thomas' Hospital, King's College LondonLondonUK
| | - Francesco Gualdi
- Institut Hospital del Mar d'Investigacions Mèdiques (IMIM)BarcelonaSpain
| | - Terence McSweeney
- Research Unit of Health Sciences and TechnologyUniversity of OuluOuluFinland
| | - Estefano Muñoz‐Moya
- BCN MedTech, Department of Information and Communication TechnologiesUniversitat Pompeu FabraBarcelonaSpain
| | - Andrea Nüesch
- Division of Clinical Medicine, School of Medicine and Population HealthUniversity of SheffieldSheffieldUK
| | - Liesbet Geris
- GIGA In Silico MedicineUniversity of LiègeLiègeBelgium
- Skeletal Biology and Engineering Research Center, KU LeuvenLeuvenBelgium
- Biomechanics Research Unit, KU LeuvenLeuvenBelgium
| | - Stefan Dudli
- Center of Experimental RheumatologyDepartment of Rheumatology, University Hospital Zurich, University of ZurichZurichSwitzerland
- Department of Physical Medicine and RheumatologyBalgrist University Hospital, Balgrist Campus, University of ZurichZurichSwitzerland
| | - Jaro Karppinen
- Research Unit of Health Sciences and TechnologyUniversity of OuluOuluFinland
- Finnish Institute of Occupational HealthOuluFinland
- Rehabilitation Services of South Karelia Social and Health Care DistrictLappeenrantaFinland
| | - Jérôme Noailly
- BCN MedTech, Department of Information and Communication TechnologiesUniversitat Pompeu FabraBarcelonaSpain
| | - Christine Le Maitre
- Division of Clinical Medicine, School of Medicine and Population HealthUniversity of SheffieldSheffieldUK
| | - Benjamin Gantenbein
- Tissue Engineering for Orthopaedics & Mechanobiology, Bone & Joint Program, Department for BioMedical Research (DBMR), Medical FacultyUniversity of BernBernSwitzerland
- Department of Orthopaedic Surgery and Traumatology, InselspitalBern University Hospital, Medical Faculty, University of BernBernSwitzerland
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4
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From Bipotent Neuromesodermal Progenitors to Neural-Mesodermal Interactions during Embryonic Development. Int J Mol Sci 2021; 22:ijms22179141. [PMID: 34502050 PMCID: PMC8431582 DOI: 10.3390/ijms22179141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 08/22/2021] [Accepted: 08/23/2021] [Indexed: 11/17/2022] Open
Abstract
To ensure the formation of a properly patterned embryo, multiple processes must operate harmoniously at sequential phases of development. This is implemented by mutual interactions between cells and tissues that together regulate the segregation and specification of cells, their growth and morphogenesis. The formation of the spinal cord and paraxial mesoderm derivatives exquisitely illustrate these processes. Following early gastrulation, while the vertebrate body elongates, a population of bipotent neuromesodermal progenitors resident in the posterior region of the embryo generate both neural and mesodermal lineages. At later stages, the somitic mesoderm regulates aspects of neural patterning and differentiation of both central and peripheral neural progenitors. Reciprocally, neural precursors influence the paraxial mesoderm to regulate somite-derived myogenesis and additional processes by distinct mechanisms. Central to this crosstalk is the activity of the axial notochord, which, via sonic hedgehog signaling, plays pivotal roles in neural, skeletal muscle and cartilage ontogeny. Here, we discuss the cellular and molecular basis underlying this complex developmental plan, with a focus on the logic of sonic hedgehog activities in the coordination of the neural-mesodermal axis.
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5
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Kaji DA, Montero AM, Patel R, Huang AH. Transcriptional profiling of mESC-derived tendon and fibrocartilage cell fate switch. Nat Commun 2021; 12:4208. [PMID: 34244516 PMCID: PMC8270956 DOI: 10.1038/s41467-021-24535-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 06/24/2021] [Indexed: 12/13/2022] Open
Abstract
The transcriptional regulators underlying induction and differentiation of dense connective tissues such as tendon and related fibrocartilaginous tissues (meniscus and annulus fibrosus) remain largely unknown. Using an iterative approach informed by developmental cues and single cell RNA sequencing (scRNA-seq), we establish directed differentiation models to generate tendon and fibrocartilage cells from mouse embryonic stem cells (mESCs) by activation of TGFβ and hedgehog pathways, achieving 90% induction efficiency. Transcriptional signatures of the mESC-derived cells recapitulate embryonic tendon and fibrocartilage signatures from the mouse tail. scRNA-seq further identify retinoic acid signaling as a critical regulator of cell fate switch between TGFβ-induced tendon and fibrocartilage lineages. Trajectory analysis by RNA sequencing define transcriptional modules underlying tendon and fibrocartilage fate induction and identify molecules associated with lineage-specific differentiation. Finally, we successfully generate 3-dimensional engineered tissues using these differentiation protocols and show activation of mechanotransduction markers with dynamic tensile loading. These findings provide a serum-free approach to generate tendon and fibrocartilage cells and tissues at high efficiency for modeling development and disease.
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Affiliation(s)
- Deepak A Kaji
- Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Angela M Montero
- Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Roosheel Patel
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Alice H Huang
- Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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6
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Kahane N, Kalcheim C. Neural tube development depends on notochord-derived sonic hedgehog released into the sclerotome. Development 2020; 147:dev183996. [PMID: 32345743 PMCID: PMC7272346 DOI: 10.1242/dev.183996] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 04/06/2020] [Indexed: 12/18/2022]
Abstract
Sonic hedgehog (Shh), produced in the notochord and floor plate, is necessary for both neural and mesodermal development. To reach the myotome, Shh has to traverse the sclerotome and a reduction of sclerotomal Shh affects myotome differentiation. By investigating loss and gain of Shh function, and floor-plate deletions, we report that sclerotomal Shh is also necessary for neural tube development. Reducing the amount of Shh in the sclerotome using a membrane-tethered hedgehog-interacting protein or Patched1, but not dominant active Patched, decreased the number of Olig2+ motoneuron progenitors and Hb9+ motoneurons without a significant effect on cell survival or proliferation. These effects were a specific and direct consequence of Shh reduction in the mesoderm. In addition, grafting notochords in a basal but not apical location, vis-à-vis the tube, profoundly affected motoneuron development, suggesting that initial ligand presentation occurs at the basal side of epithelia corresponding to the sclerotome-neural tube interface. Collectively, our results reveal that the sclerotome is a potential site of a Shh gradient that coordinates the development of mesodermal and neural progenitors.
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Affiliation(s)
- Nitza Kahane
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem-Hadassah Medical School, Jerusalem 9112102, P.O. Box 12272, Israel
| | - Chaya Kalcheim
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem-Hadassah Medical School, Jerusalem 9112102, P.O. Box 12272, Israel
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7
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Regulation of Hedgehog signaling Offers A Novel Perspective for Bone Homeostasis Disorder Treatment. Int J Mol Sci 2019; 20:ijms20163981. [PMID: 31426273 PMCID: PMC6719140 DOI: 10.3390/ijms20163981] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 08/10/2019] [Accepted: 08/14/2019] [Indexed: 02/07/2023] Open
Abstract
The hedgehog (HH) signaling pathway is central to the regulation of bone development and homeostasis. HH signaling is not only involved in osteoblast differentiation from bone marrow mesenchymal stem cells (BM-MSCs), but also acts upstream within osteoblasts via the OPG/RANK/RANKL axis to control the expression of RANKL. HH signaling has been found to up-regulate parathyroid hormone related protein (PTHrP) expression in osteoblasts, which in turn activates its downstream targets nuclear factor of activated T cells (NFAT) and cAMP responsive element binding protein (CREB), and as a result CREB and NFAT cooperatively increase RANKL expression and osteoclastogenesis. Osteoblasts must remain in balance with osteoclasts in order to avoid excessive bone formation or resorption, thereby maintaining bone homeostasis. This review systemically summarizes the mechanisms whereby HH signaling induces osteoblast development and controls RANKL expression through PTHrP in osteoblasts. Proper targeting of HH signaling may offer a therapeutic option for treating bone homeostasis disorders.
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8
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Mohanty S, Dahia CL. Defects in intervertebral disc and spine during development, degeneration, and pain: New research directions for disc regeneration and therapy. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2019; 8:e343. [PMID: 30977275 DOI: 10.1002/wdev.343] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 03/11/2019] [Accepted: 03/25/2019] [Indexed: 12/12/2022]
Abstract
Intervertebral discs are cartilaginous joints present between vertebrae. The centers of the intervertebral discs consist of a gelatinous nucleus pulposus derived from the embryonic notochord. With age or injury, intervertebral discs may degenerate, causing neurological symptoms including back pain, which affects millions of people worldwide. Back pain is a multifactorial disorder, and disc degeneration is one of the primary contributing factors. Recent studies in mice have identified the key molecules involved in the formation of intervertebral discs. Several of these key molecules including sonic hedgehog and Brachyury are not only expressed by notochord during development, but are also expressed by neonatal mouse nucleus pulposus cells, and are crucial for postnatal disc maintenance. These findings suggest that intrinsic signals in each disc may maintain the nucleus pulposus microenvironment. However, since expression of these developmental signals declines with age and degeneration, disc degeneration may be related to the loss of these intrinsic signals. In addition, findings from mouse and other mammalian models have identified similarities between the patterning capabilities of the embryonic notochord and young nucleus pulposus cells, suggesting that mouse is a suitable model system to understand disc development and aging. Future research aimed at understanding the upstream regulators of these developmental signals and the modes by which they regulate disc growth and maintenance will likely provide mechanistic insights into disc growth and aging. Further, such findings will likely provide insights relevant to the development of effective therapies for treatment of back pain and reversing the disc degenerative process. This article is categorized under: Birth Defects > Organ Anomalies Vertebrate Organogenesis > Musculoskeletal and Vascular Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Adult Stem Cells, Tissue Renewal, and Regeneration > Stem Cells and Aging.
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Affiliation(s)
- Sarthak Mohanty
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York
| | - Chitra L Dahia
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York.,Department of Cell and Developmental Biology, Weill Cornell Medicine, Graduate School of Medical Science, New York, New York
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9
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Abstract
Development of the axial skeleton is a complex, stepwise process that relies on intricate signaling and coordinated cellular differentiation. Disruptions to this process can result in a myriad of skeletal malformations that range in severity. The notochord and the sclerotome are embryonic tissues that give rise to the major components of the intervertebral discs and the vertebral bodies of the spinal column. Through a number of mouse models and characterization of congenital abnormalities in human patients, various growth factors, transcription factors, and other signaling proteins have been demonstrated to have critical roles in the development of the axial skeleton. Balance between opposing growth factors as well as other environmental cues allows for cell fate specification and divergence of tissue types during development. Furthermore, characterization of progenitor cells for specific cell lineages has furthered the understanding of specific spatiotemporal cues that cells need in order to initiate and complete development of distinct tissues. Identifying specific marker genes that can distinguish between the various embryonic and mature cell types is also of importance. Clinically, understanding developmental clues can aid in the generation of therapeutics for musculoskeletal disease through the process of developmental engineering. Studies into potential stem cell therapies are based on knowledge of the normal processes that occur in the embryo, which can then be applied to stepwise tissue engineering strategies.
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Affiliation(s)
| | | | - Rosa Serra
- Department of Cell Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States.
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10
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Sonic Hedgehog signaling and Gli-1 during embryonic chick myogenesis. Biochem Biophys Res Commun 2018; 507:496-502. [PMID: 30449599 DOI: 10.1016/j.bbrc.2018.11.071] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 11/12/2018] [Indexed: 12/27/2022]
Abstract
The Sonic Hedgehog signaling (Shh) pathway has been implicated in both proliferation of myoblast cells and terminal differentiation of muscle fibers, and contradictory results of these effects have been described. To clarify the role of Shh during myogenesis, we decided to study the effects of recombinant Shh and the distribution of Gli-1 during in vitro and in situ embryonic chick skeletal muscle differentiation at later stages of development. Gli-1 was found in small aggregates near the nucleus in mononucleated myoblasts and in multinucleated myotubes both in vitro and in situ chick muscle cells. Some Gli-1 aggregates colocalized with gamma-tubulin positive-centrosomes. Gli-1 was also found in striations and at the subsarcolemmal membrane in muscle fibers in situ. Recombinant Shh added to in vitro grown muscle cells induced the nuclear translocation of Gli-1, as well as an increase in the number of myoblasts and in the number of nuclei within myotubes. We suggest that Gli-1 aggregates observed in chick muscle cells near the nuclei of myoblasts and myotubes could be a storage site for the rapid cellular redistribution of Gli-1 upon specific signals during muscle differentiation.
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Alkhatib B, Ban GI, Williams S, Serra R. IVD Development: Nucleus pulposus development and sclerotome specification. CURRENT MOLECULAR BIOLOGY REPORTS 2018; 4:132-141. [PMID: 30505649 PMCID: PMC6261384 DOI: 10.1007/s40610-018-0100-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
PURPOSE OF REVIEW Intervertebral discs (IVD) are derived from embryonic notochord and sclerotome. The nucleus pulposus is derived from notochord while other connective tissues of the spine are derived from sclerotome. This manuscript will review the past 5 years of research into IVD development. RECENT FINDINGS Over the past several years, advances in understanding the step-wise process that govern development of the nucleus pulposus and the annulus fibrosus have been made. Generation of tissues from induced or embryonic stem cells into nucleus pulposus and paraxial mesoderm derived tissues has been accomplished in vitro using pathways identified in normal development. A balance between BMP and TGF-β signaling as well as transcription factors including Pax1/Pax9, Mkx and Nkx3.2 appear to be very important for cell fate decisions generating tissues of the IVD. SUMMARY Understanding how the IVD develops will provide the foundation for future repair, regeneration, and tissue engineering strategies for IVD disease.
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Affiliation(s)
| | - Ga I Ban
- University of Alabama at Birmingham
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12
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Séguin CA, Chan D, Dahia CL, Gazit Z. Latest advances in intervertebral disc development and progenitor cells. JOR Spine 2018; 1:e1030. [PMID: 30687811 PMCID: PMC6338208 DOI: 10.1002/jsp2.1030] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 07/23/2018] [Accepted: 07/26/2018] [Indexed: 12/12/2022] Open
Abstract
This paper is a concise review aiming to assemble the most relevant topics presented by the authors at ORS-Philadelphia Spine Research Society Fourth International Spine Research Symposium. It centers on the latest advances in disc development, its main structural entities, and the populating cells, with emphasis on the advances in pivotal molecular pathways responsible for forming the intervertebral discs (IVD). The objective of finding and emphasizing pathways and mechanisms that function to control tissue formation is to identify and to explore modifications occurring during normal aging, disease, and tissue repair. Thus, to comprehend that the cellular and molecular basis of tissue degeneration are crucial in the study of the dynamic interplay that includes cell-cell communication, gene regulation, and growth factors required to form a healthy and functional tissue during normal development.
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Affiliation(s)
- Cheryle A Séguin
- Schulich School of Medicine and Dentistry Bone and Joint Institute, The University of Western Ontario London ON Canada
| | - Danny Chan
- School of Biomedical Sciences LKS Faculty of Medicine, The University of Hong Kong Hong Kong China
| | - Chitra L Dahia
- Hospital for Special Surgery Weill Cornell Medical College New York New York
| | - Zulma Gazit
- Department of Surgery Regenerative Medicine Institute, Cedars-Sinai Medical Center Los Angeles California
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13
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Mok GF, Lozano-Velasco E, Maniou E, Viaut C, Moxon S, Wheeler G, Münsterberg A. miR-133-mediated regulation of the Hedgehog pathway orchestrates embryo myogenesis. Development 2018; 145:dev.159657. [PMID: 29802149 PMCID: PMC6031409 DOI: 10.1242/dev.159657] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 05/10/2018] [Indexed: 12/23/2022]
Abstract
Skeletal myogenesis serves as a paradigm to investigate the molecular mechanisms underlying exquisitely regulated cell fate decisions in developing embryos. The evolutionarily conserved miR-133 family of microRNAs is expressed in the myogenic lineage, but how it acts remains incompletely understood. Here, we performed genome-wide differential transcriptomics of miR-133 knockdown (KD) embryonic somites, the source of vertebrate skeletal muscle. These analyses, performed in chick embryos, revealed extensive downregulation of Sonic hedgehog (Shh) pathway components: patched receptors, Hedgehog interacting protein and the transcriptional activator Gli1. By contrast, Gli3, a transcriptional repressor, was de-repressed and confirmed as a direct miR-133 target. Phenotypically, miR-133 KD impaired myotome formation and growth by disrupting proliferation, extracellular matrix deposition and epithelialization. Together, these observations suggest that miR-133-mediated Gli3 silencing is crucial for embryonic myogenesis. Consistent with this idea, we found that activation of Shh signalling by either purmorphamine, or KD of Gli3 by antisense morpholino, rescued the miR-133 KD phenotype. Thus, we identify a novel Shh/myogenic regulatory factor/miR-133/Gli3 axis that connects epithelial morphogenesis with myogenic fate specification. Summary: Here, using chick embryos, we showed that post-transcriptional silencing of the Gli3 repressor by miR-133 is required to stably establish the myogenic programme in early somites.
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Affiliation(s)
- Gi Fay Mok
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Estefania Lozano-Velasco
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Eirini Maniou
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Camille Viaut
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Simon Moxon
- The Earlham Institute, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Grant Wheeler
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Andrea Münsterberg
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
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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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15
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Current Progress and Challenges for Skeletal Muscle Differentiation from Human Pluripotent Stem Cells Using Transgene-Free Approaches. Stem Cells Int 2018; 2018:6241681. [PMID: 29760730 PMCID: PMC5924987 DOI: 10.1155/2018/6241681] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 02/11/2018] [Accepted: 02/18/2018] [Indexed: 12/13/2022] Open
Abstract
Neuromuscular diseases are caused by functional defects of skeletal muscles, directly via muscle pathology or indirectly via disruption of the nervous system. Extensive studies have been performed to improve the outcomes of therapies; however, effective treatment strategies have not been fully established for any major neuromuscular disease. Human pluripotent stem cells have a great capacity to differentiate into myogenic progenitors and skeletal myocytes for use in treating and modeling neuromuscular diseases. Recent advances have allowed the creation of patient-derived stem cells, which can be used as a unique platform for comprehensive study of disease mechanisms, in vitro drug screening, and potential new cell-based therapies. In the last decade, a number of methods have been developed to derive skeletal muscle cells from human pluripotent stem cells. By controlling the process of myogenesis using transcription factors and signaling molecules, human pluripotent stem cells can be directed to differentiate into cell types observed during muscle development. In this review, we highlight signaling pathways relevant to the formation of muscle tissue during embryonic development. We then summarize current methods to differentiate human pluripotent stem cells toward the myogenic lineage, specifically focusing on transgene-free approaches. Lastly, we discuss existing challenges for deriving skeletal myocytes and myogenic progenitors from human pluripotent stem cells.
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16
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Fogel JL, Lakeland DL, Mah IK, Mariani FV. A minimally sufficient model for rib proximal-distal patterning based on genetic analysis and agent-based simulations. eLife 2017; 6:e29144. [PMID: 29068314 PMCID: PMC5693115 DOI: 10.7554/elife.29144] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 10/24/2017] [Indexed: 12/19/2022] Open
Abstract
For decades, the mechanism of skeletal patterning along a proximal-distal axis has been an area of intense inquiry. Here, we examine the development of the ribs, simple structures that in most terrestrial vertebrates consist of two skeletal elements-a proximal bone and a distal cartilage portion. While the ribs have been shown to arise from the somites, little is known about how the two segments are specified. During our examination of genetically modified mice, we discovered a series of progressively worsening phenotypes that could not be easily explained. Here, we combine genetic analysis of rib development with agent-based simulations to conclude that proximal-distal patterning and outgrowth could occur based on simple rules. In our model, specification occurs during somite stages due to varying Hedgehog protein levels, while later expansion refines the pattern. This framework is broadly applicable for understanding the mechanisms of skeletal patterning along a proximal-distal axis.
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Affiliation(s)
- Jennifer L Fogel
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell ResearchUniversity of Southern CaliforniaLos AngelesUnited States
| | | | - In Kyoung Mah
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell ResearchUniversity of Southern CaliforniaLos AngelesUnited States
| | - Francesca V Mariani
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell ResearchUniversity of Southern CaliforniaLos AngelesUnited States
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17
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Bhattacharyya S, Rainey MA, Arya P, Mohapatra BC, Mushtaq I, Dutta S, George M, Storck MD, McComb RD, Muirhead D, Todd GL, Gould K, Datta K, Gelineau-van Waes J, Band V, Band H. Endocytic recycling protein EHD1 regulates primary cilia morphogenesis and SHH signaling during neural tube development. Sci Rep 2016; 6:20727. [PMID: 26884322 PMCID: PMC4756679 DOI: 10.1038/srep20727] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 01/11/2016] [Indexed: 12/20/2022] Open
Abstract
Members of the four-member C-terminal EPS15-Homology Domain-containing (EHD) protein family play crucial roles in endocytic recycling of cell surface receptors from endosomes to the plasma membrane. In this study, we show that Ehd1 gene knockout in mice on a predominantly B6 background is embryonic lethal. Ehd1-null embryos die at mid-gestation with a failure to complete key developmental processes including neural tube closure, axial turning and patterning of the neural tube. We found that Ehd1-null embryos display short and stubby cilia on the developing neuroepithelium at embryonic day 9.5 (E9.5). Loss of EHD1 also deregulates the ciliary SHH signaling with Ehd1-null embryos displaying features indicative of increased SHH signaling, including a significant downregulation in the formation of the GLI3 repressor and increase in the ventral neuronal markers specified by SHH. Using Ehd1-null MEFS we found that EHD1 protein co-localizes with the SHH receptor Smoothened in the primary cilia upon ligand stimulation. Under the same conditions, EHD1 was shown to co-traffic with Smoothened into the developing primary cilia and we identify EHD1 as a direct binding partner of Smoothened. Overall, our studies identify the endocytic recycling regulator EHD1 as a novel regulator of the primary cilium-associated trafficking of Smoothened and Hedgehog signaling.
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Affiliation(s)
- Sohinee Bhattacharyya
- The Department of Pathology &Microbiology, University of Nebraska Medical Center, Omaha, NE, USA.,Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA
| | - Mark A Rainey
- Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA
| | - Priyanka Arya
- The Department of Genetics, Cell Biology &Anatomy, University of Nebraska Medical Center, Omaha, NE, USA.,Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA
| | | | | | - Samikshan Dutta
- The Department of Biochemistry &Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Manju George
- Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA
| | - Matthew D Storck
- Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA
| | - Rodney D McComb
- The Department of Pathology &Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - David Muirhead
- The Department of Pathology &Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Gordon L Todd
- The Department of Genetics, Cell Biology &Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
| | - Karen Gould
- The Department of Genetics, Cell Biology &Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
| | - Kaustubh Datta
- The Department of Biochemistry &Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | | | - Vimla Band
- The Department of Genetics, Cell Biology &Anatomy, University of Nebraska Medical Center, Omaha, NE, USA.,Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA.,Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Hamid Band
- The Department of Pathology &Microbiology, University of Nebraska Medical Center, Omaha, NE, USA.,The Department of Genetics, Cell Biology &Anatomy, University of Nebraska Medical Center, Omaha, NE, USA.,Eppley Institute for Research in Cancer and Allied Diseases,University of Nebraska Medical Center, Omaha, NE, USA.,Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
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18
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Corallo D, Trapani V, Bonaldo P. The notochord: structure and functions. Cell Mol Life Sci 2015; 72:2989-3008. [PMID: 25833128 PMCID: PMC11114051 DOI: 10.1007/s00018-015-1897-z] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 03/23/2015] [Accepted: 03/26/2015] [Indexed: 01/08/2023]
Abstract
The notochord is an embryonic midline structure common to all members of the phylum Chordata, providing both mechanical and signaling cues to the developing embryo. In vertebrates, the notochord arises from the dorsal organizer and it is critical for proper vertebrate development. This evolutionary conserved structure located at the developing midline defines the primitive axis of embryos and represents the structural element essential for locomotion. Besides its primary structural function, the notochord is also a source of developmental signals that patterns surrounding tissues. Among the signals secreted by the notochord, Hedgehog proteins play key roles during embryogenesis. The Hedgehog signaling pathway is a central regulator of embryonic development, controlling the patterning and proliferation of a wide variety of organs. In this review, we summarize the current knowledge on notochord structure and functions, with a particular emphasis on the key developmental events that take place in vertebrates. Moreover, we discuss some genetic studies highlighting the phenotypic consequences of impaired notochord development, which enabled to understand the molecular basis of different human congenital defects and diseases.
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Affiliation(s)
- Diana Corallo
- Department of Molecular Medicine, University of Padova, Viale G. Colombo 3, 35131 Padua, Italy
| | - Valeria Trapani
- Department of Molecular Medicine, University of Padova, Viale G. Colombo 3, 35131 Padua, Italy
| | - Paolo Bonaldo
- Department of Molecular Medicine, University of Padova, Viale G. Colombo 3, 35131 Padua, Italy
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19
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Mok GF, Mohammed RH, Sweetman D. Expression of myogenic regulatory factors in chicken embryos during somite and limb development. J Anat 2015; 227:352-60. [PMID: 26183709 PMCID: PMC4560569 DOI: 10.1111/joa.12340] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2015] [Indexed: 01/24/2023] Open
Abstract
The expression of the myogenic regulatory factors (MRFs), Myf5, MyoD, myogenin (Mgn) and MRF4 have been analysed during the development of chicken embryo somites and limbs. In somites, Myf5 is expressed first in somites and paraxial mesoderm at HH stage 9 followed by MyoD at HH stage 12, and Mgn and MRF4 at HH stage 14. In older somites, Myf5 and MyoD are also expressed in the ventrally extending myotome prior to Mgn and MRF4 expression. In limb muscles a similar temporal sequence is observed with Myf5 expression detected first in forelimbs at HH stage 22, MyoD at HH stage 23, Mgn at HH stage 24 and MRF4 at HH stage 30. This report describes the precise time of onset of expression of each MRF in somites and limbs during chicken embryo development, and provides a detailed comparative timeline of MRF expression in different embryonic muscle groups.
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Affiliation(s)
- Gi Fay Mok
- School of Biosciences, University of Nottingham, Sutton Bonington, UK
| | | | - Dylan Sweetman
- School of Biosciences, University of Nottingham, Sutton Bonington, UK
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20
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El-Magd MA, Allen S, McGonnell I, Mansour AA, Otto A, Patel K. Shh regulates chick Ebf1 gene expression in somite development. Gene 2015; 554:87-95. [DOI: 10.1016/j.gene.2014.10.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 10/09/2014] [Accepted: 10/13/2014] [Indexed: 11/16/2022]
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21
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Mok GF, Cardenas R, Anderton H, Campbell KHS, Sweetman D. Interactions between FGF18 and retinoic acid regulate differentiation of chick embryo limb myoblasts. Dev Biol 2014; 396:214-23. [PMID: 25446536 DOI: 10.1016/j.ydbio.2014.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/25/2014] [Accepted: 10/10/2014] [Indexed: 10/24/2022]
Abstract
During limb development Pax3 positive myoblasts delaminate from the hypaxial dermomyotome of limb level somites and migrate into the limb bud where they form the dorsal and ventral muscle masses. Only then do they begin to differentiate and express markers of myogenic commitment and determination such as Myf5 and MyoD. However the signals regulating this process remain poorly characterised. We show that FGF18, which is expressed in the distal mesenchyme of the limb bud, induces premature expression of both Myf5 and MyoD and that blocking FGF signalling also inhibits endogenous MyoD expression. This expression is mediated by ERK MAP kinase but not PI3K signalling. We also show that retinoic acid (RA) can inhibit the myogenic activity of FGF18 and that blocking RA signalling allows premature induction of MyoD by FGF18 at HH19. We propose a model where interactions between FGF18 in the distal limb and retinoic acid in the proximal limb regulate the timing of myogenic gene expression during limb bud development.
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Affiliation(s)
- Gi Fay Mok
- Division of Animal Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington LE12 5RD, UK
| | - Ryan Cardenas
- Division of Animal Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington LE12 5RD, UK
| | - Helen Anderton
- Division of Animal Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington LE12 5RD, UK
| | - Keith H S Campbell
- Division of Animal Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington LE12 5RD, UK
| | - Dylan Sweetman
- Division of Animal Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington LE12 5RD, UK.
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22
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Chen Y, Wang G, Ma ZL, Li Y, Wang XY, Cheng X, Chuai M, Tang SZ, Lee KKH, Yang X. Adverse effects of high glucose levels on somite and limb development in avian embryos. Food Chem Toxicol 2014; 71:1-9. [PMID: 24882757 DOI: 10.1016/j.fct.2014.05.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 05/18/2014] [Accepted: 05/20/2014] [Indexed: 11/30/2022]
Abstract
Gestational diabetes has an adverse impact on fetal musculoskeletal development, but the mechanism involved is still not completely understood. In this study, we investigated the effects of high glucose on the developing somites and their derivate using the chick embryo as a model. We demonstrated that under high glucose, the number of generated somites was reduced and their morphology altered in 2-day old chick embryos. In addition, high glucose repressed the development of the limb buds in 5.5-day old chick embryos. We also demonstrated that high glucose abridged the development of the sclerotome and the cartilage in the developing limb bud. The sonic hedgehog (Shh) gene has been reported to play a crucial role in the development and differentiation of sclerotome. Hence, we examined how Shh expression in the sclerotome was affected under high glucose. We found that high glucose treatment significantly inhibited Shh expression. The high glucose also impaired myotome formation at trunk level - as revealed by immunofluorescent staining with MF20 antibodies. In the neural tube, we established that Wnt3a expression was also significantly repressed. In summary, our study demonstrates that high glucose concentrations impair somite and limb bud development in chick embryos, and suggests that Shh and Wnt genes may play a role in the underlying mechanism.
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Affiliation(s)
- Yao Chen
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Guang Wang
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Zheng-lai Ma
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Yan Li
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Xiao-yu Wang
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Xin Cheng
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China
| | - Manli Chuai
- Division of Cell and Developmental Biology, University of Dundee, Dundee DD1 5EH, UK
| | - Shu-ze Tang
- Department of Food Science and Engineering, Jinan University, Guangzhou, China
| | - Kenneth Ka Ho Lee
- Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, Hong Kong.
| | - Xuesong Yang
- Key Laboratory for Regenerative Medicine of the Ministry of Education, Division of Histology and Embryology, Medical College, Jinan University, Guangzhou 510632, China; Institute of Fetal-Preterm Labor Medicine, Jinan University, Guangzhou 510632, China.
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23
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Rossi G, Messina G. Comparative myogenesis in teleosts and mammals. Cell Mol Life Sci 2014; 71:3081-99. [PMID: 24664432 PMCID: PMC4111864 DOI: 10.1007/s00018-014-1604-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 02/17/2014] [Accepted: 03/06/2014] [Indexed: 01/02/2023]
Abstract
Skeletal myogenesis has been and is currently under extensive study in both mammals and teleosts, with the latter providing a good model for skeletal myogenesis because of their flexible and conserved genome. Parallel investigations of muscle studies using both these models have strongly accelerated the advances in the field. However, when transferring the knowledge from one model to the other, it is important to take into account both their similarities and differences. The main difficulties in comparing mammals and teleosts arise from their different temporal development. Conserved aspects can be seen for muscle developmental origin and segmentation, and for the presence of multiple myogenic waves. Among the divergences, many fish have an indeterminate growth capacity throughout their entire life span, which is absent in mammals, thus implying different post-natal growth mechanisms. This review covers the current state of the art on myogenesis, with a focus on the most conserved and divergent aspects between mammals and teleosts.
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Affiliation(s)
- Giuliana Rossi
- Department of Biosciences, University of Milan, 20133, Milan, Italy
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24
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Downregulation of Caspase-2 Expression in Somitic Cells following Coculture with Chicken Notochord. ACTA ACUST UNITED AC 2013. [DOI: 10.1155/2013/627912] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Somites are spherical aggregations of mesodermal cells located on either sides of neural tube and are differentiated into sclerotome and dermomyotome. Notochord as an axial mesoderm has a major role in somitic cell survival and differentiation in vivo. Despite secreting the survival factors, how to notochord inhibits somitic cells apoptosis remains to be elusive. So, this study was aimed to investigate downregulation of caspase-2 expression in somitic cells upon coculturing with notochord. By using alginate system to encapsulate the isolated notochord in Somite + Notochord group, the embryonic somites were cocultured with the notochord on different days. Concurrently in somite group, the somites were cultured alone. Survival assay with MTT showed that the rate of viability in somitic cells cocultured with notochord increased from 59% on day 2 to 89.7% on day 6 but decreased to 38.5% on day 10 after coculturing. Reverse transcriptase-polymerase chain reaction and spectrophotometry analysis also confirmed these findings and showed low caspase-2 and high Bcl-2 expressions and low caspase-2 enzyme activity in somitic cells cocultured with notochord, respectively. These results clearly show that the notochord enhances survival of somitic cells in vitro through downregulating of caspase-2 expression along with triggering differentiation of somitic cells to Pax-1 expressing mesenchymal cells.
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25
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Kahane N, Ribes V, Kicheva A, Briscoe J, Kalcheim C. The transition from differentiation to growth during dermomyotome-derived myogenesis depends on temporally restricted hedgehog signaling. Development 2013; 140:1740-50. [PMID: 23533174 DOI: 10.1242/dev.092726] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The development of a functional tissue requires coordination of the amplification of progenitors and their differentiation into specific cell types. The molecular basis for this coordination during myotome ontogeny is not well understood. Dermomytome progenitors that colonize the myotome first acquire myocyte identity and subsequently proliferate as Pax7-expressing progenitors before undergoing terminal differentiation. We show that the dynamics of sonic hedgehog (Shh) signaling is crucial for this transition in both avian and mouse embryos. Initially, Shh ligand emanating from notochord/floor plate reaches the dermomyotome, where it both maintains the proliferation of dermomyotome cells and promotes myogenic differentiation of progenitors that colonized the myotome. Interfering with Shh signaling at this stage produces small myotomes and accumulation of Pax7-expressing progenitors. An in vivo reporter of Shh activity combined with mouse genetics revealed the existence of both activator and repressor Shh activities operating on distinct subsets of cells during the epaxial myotomal maturation. In contrast to observations in mice, in avians Shh promotes the differentiation of both epaxial and hypaxial myotome domains. Subsequently, myogenic progenitors become refractory to Shh; this is likely to occur at the level of, or upstream of, smoothened signaling. The end of responsiveness to Shh coincides with, and is thus likely to enable, the transition into the growth phase of the myotome.
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Affiliation(s)
- Nitza Kahane
- Department of Medical Neurobiology, Hebrew University of Jerusalem-Hadassah Medical School, Jerusalem, Israel
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26
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Disturbance of SHH signalling pathway during early embryogenesis in the cadmium-induced omphalocele chick model. Pediatr Surg Int 2013; 29:165-70. [PMID: 23124188 DOI: 10.1007/s00383-012-3193-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Administration of cadmium (Cd) after 60 h (H) incubation induces ventral body wall defect (VBWD) similar to the omphalocele phenotype in the chick embryo. In this model, the earliest histological changes have been observed in somites commencing at 4-h post-treatment (4H). The molecular mechanism by which Cd acts in this critical period of embryogenesis still remains unclear. Sonic hedgehog (SHH) signalling plays an important role in vertebrate development, including somitogenesis and thus ventral body wall formation. Patched (PTCH), a cell membrane receptor for SHH, is expressed in somites and Patched knockout mice display somite dysfunction. Another transmembrane receptor, Smoothened (SMO), is also expressed in somites and transduces the SHH signal regulated by PTCH. We designed this study to test the hypothesis that SHH signalling is downregulated during the critical period of early embryogenesis in the Cd-induced omphalocele chick model. METHODS After 60 h of incubation, chicks were exposed to either chick saline or 50 μL of 50 μM cadmium acetate and divided into two groups: control and Cd (n = 24 for each group). Chicks were harvested 1, 4, and 8 h post-treatment. Real-time RT-PCR was performed to evaluate the relative mRNA expression level of SHH, PTCH and SMO. Immunofluorescence confocal microscopy was then performed to evaluate protein expression/distribution of SHH, PTCH and SMO. RESULTS The relative mRNA expression levels of SHH, PTCH and SMO were significantly downregulated in the Cd group compared to controls at 4H post treatment, whereas, there were no significant differences at the other time points. Immunohistochemistry revealed that the intensity of SHH, PTCH and SMO was markedly diminished at 4 h in Cd-treated embryos compared to controls. CONCLUSION Disturbance of the SHH signalling pathway as evidenced by SHH, PTCH and SMO downregulation during the narrow window of early embryogenesis may result in somite maldevelopment, contributing to the omphalocele phenotype in the Cd chick model.
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27
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Voronova A, Coyne E, Al Madhoun A, Fair JV, Bosiljcic N, St-Louis C, Li G, Thurig S, Wallace VA, Wiper-Bergeron N, Skerjanc IS. Hedgehog signaling regulates MyoD expression and activity. J Biol Chem 2012; 288:4389-404. [PMID: 23266826 PMCID: PMC3567689 DOI: 10.1074/jbc.m112.400184] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The inhibition of MyoD expression is important for obtaining muscle progenitors that can replenish the satellite cell niche during muscle repair. Progenitors could be derived from either embryonic stem cells or satellite cells. Hedgehog (Hh) signaling is important for MyoD expression during embryogenesis and adult muscle regeneration. To date, the mechanistic understanding of MyoD regulation by Hh signaling is unclear. Here, we demonstrate that the Hh effector, Gli2, regulates MyoD expression and associates with MyoD gene elements. Gain- and loss-of-function experiments in pluripotent P19 cells show that Gli2 activity is sufficient and required for efficient MyoD expression during skeletal myogenesis. Inhibition of Hh signaling reduces MyoD expression during satellite cell activation in vitro. In addition to regulating MyoD expression, Hh signaling regulates MyoD transcriptional activity, and MyoD activates Hh signaling in myogenic conversion assays. Finally, Gli2, MyoD, and MEF2C form a protein complex, which enhances MyoD activity on skeletal muscle-related promoters. We therefore link Hh signaling to the function and expression of MyoD protein during myogenesis in stem cells.
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Affiliation(s)
- Anastassia Voronova
- Department of Biochemistry, Microbiology, and Immunology, Dasman Diabetes Institute, Dasman 15462, Kuwait
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28
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Dubinska-Magiera M, Zaremba-Czogalla M, Rzepecki R. Muscle development, regeneration and laminopathies: how lamins or lamina-associated proteins can contribute to muscle development, regeneration and disease. Cell Mol Life Sci 2012; 70:2713-41. [PMID: 23138638 PMCID: PMC3708280 DOI: 10.1007/s00018-012-1190-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 09/28/2012] [Accepted: 10/03/2012] [Indexed: 12/22/2022]
Abstract
The aim of this review article is to evaluate the current knowledge on associations between muscle formation and regeneration and components of the nuclear lamina. Lamins and their partners have become particularly intriguing objects of scientific interest since it has been observed that mutations in genes coding for these proteins lead to a wide range of diseases called laminopathies. For over the last 10 years, various laboratories worldwide have tried to explain the pathogenesis of these rare disorders. Analyses of the distinct aspects of laminopathies resulted in formulation of different hypotheses regarding the mechanisms of the development of these diseases. In the light of recent discoveries, A-type lamins—the main building blocks of the nuclear lamina—together with other key elements, such as emerin, LAP2α and nesprins, seem to be of great importance in the modulation of various signaling pathways responsible for cellular differentiation and proliferation.
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Affiliation(s)
- Magda Dubinska-Magiera
- Department of Animal Developmental Biology, University of Wroclaw, 21 Sienkiewicza Street, 50-335, Wroclaw, Poland
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29
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Abstract
Satellite cells are a heterogeneous population of stem and progenitor cells that are required for the growth, maintenance and regeneration of skeletal muscle. The transcription factors paired-box 3 (PAX3) and PAX7 have essential and overlapping roles in myogenesis. PAX3 acts to specify embryonic muscle precursors, whereas PAX7 enforces the satellite cell myogenic programme while maintaining the undifferentiated state. Recent experiments have suggested that PAX7 is dispensable in adult satellite cells. However, these findings are controversial, and the issue remains unresolved.
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Gerhart J, Scheinfeld VL, Milito T, Pfautz J, Neely C, Fisher-Vance D, Sutter K, Crawford M, Knudsen K, George-Weinstein M. Myo/Nog cell regulation of bone morphogenetic protein signaling in the blastocyst is essential for normal morphogenesis and striated muscle lineage specification. Dev Biol 2011; 359:12-25. [PMID: 21884693 DOI: 10.1016/j.ydbio.2011.08.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/20/2011] [Accepted: 08/10/2011] [Indexed: 01/05/2023]
Abstract
Cells that express MyoD mRNA, the G8 antigen and the bone morphogenetic protein (BMP) inhibitor noggin (Nog) are present in the epiblast before gastrulation. Ablation of "Myo/Nog" cells in the blastocyst results in an expansion of canonical BMP signaling and prevents the expression of noggin and follistatin before and after the onset of gastrulation. Once eliminated in the epiblast, they are neither replaced nor compensated for as development progresses. Older embryos lacking Myo/Nog cells exhibit severe axial malformations. Although Wnts and Sonic hedgehog are expressed in ablated embryos, skeletal muscle progenitors expressing Pax3 are missing in the somites. Pax3+ cells do emerge adjacent to Wnt3a+ cells in vitro; however, few undergo skeletal myogenesis. Ablation of Myo/Nog cells also results in ectopically placed cardiac progenitors and cardiomyocytes in the somites. Reintroduction of Myo/Nog cells into the epiblast of ablated embryos restores normal patterns of BMP signaling, morphogenesis and skeletal myogenesis, and inhibits the expression of cardiac markers in the somites. This study demonstrates that Myo/Nog cells are essential regulators of BMP signaling in the early epiblast and are indispensable for normal morphogenesis and striated muscle lineage specification.
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Affiliation(s)
- Jacquelyn Gerhart
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Victoria L Scheinfeld
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Tara Milito
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Jessica Pfautz
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA
| | - Christine Neely
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Dakota Fisher-Vance
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Kelly Sutter
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Mitchell Crawford
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Karen Knudsen
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
| | - Mindy George-Weinstein
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
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Snider P, Simmons O, Rogers R, Young R, Gosnell M, Conway SJ. Notochordal and foregut abnormalities correlate with elevated neural crest apoptosis in Patch embryos. ACTA ACUST UNITED AC 2011; 91:551-64. [PMID: 21557455 DOI: 10.1002/bdra.20802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/25/2011] [Accepted: 02/04/2011] [Indexed: 01/17/2023]
Abstract
Although Patch mutants show severe abnormalities in many neural crest-derived structures including the face and the heart, there is a paucity of information characterizing the mechanisms underlying these congenital defects. Via manipulating the genetic background to circumvent early embryonic lethality, our results revealed that Patch phenotypes are most likely due to a significant decrease in migratory neural crest lineage due to diminished neural crest survival and elevated apoptosis. Homozygous mutant neural crest precursors can undergo typical expansion within the neural tube, epithelial-to-mesenchymal transformation, and initiate normal neural crest emigration. Moreover, in vitro explant culture demonstrated that when isolated from the surrounding mesenchyme, Patch mutant neural crest cells (NCCs) can migrate appropriately. Additionally, Patch foregut, notochord and somitic morphogenesis, and Sonic hedgehog expression profiles were all perturbed. Significantly, the timing of lethality and extent of apoptosis correlated with the degree of severity of Patch mutant foregut, notochord, and somite dysfunction. Finally, analysis of Balb/c-enriched surviving Patch mutants revealed that not all the neural crest subpopulations are affected and that Patch mutant neural crest-derived sympathetic ganglia and dorsal root ganglia were unaffected. We hypothesize that loss of normal coordinated signaling from the notochord, foregut, and somites underlies the diminished survival of the neural crest lineage within Patch mutants resulting in subsequent neural crest-deficient phenotypes.
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Affiliation(s)
- Paige Snider
- Developmental Biology and Neonatal Medicine Program, HB Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Stafford DA, Brunet LJ, Khokha MK, Economides AN, Harland RM. Cooperative activity of noggin and gremlin 1 in axial skeleton development. Development 2011; 138:1005-14. [PMID: 21303853 DOI: 10.1242/dev.051938] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Inductive signals from adjacent tissues initiate differentiation within the somite. In this study, we used mouse embryos mutant for the BMP antagonists noggin (Nog) and gremlin 1 (Grem1) to characterize the effects of BMP signaling on the specification of the sclerotome. We confirmed reduction of Pax1 and Pax9 expression in Nog mutants, but found that Nog;Grem1 double mutants completely fail to initiate sclerotome development. Furthermore, Nog mutants that also lack one allele of Grem1 exhibit a dramatic reduction in axial skeleton relative to animals mutant for Nog alone. By contrast, Pax3, Myf5 and Lbx1 expression indicates that dermomyotome induction occurs in Nog;Grem1 double mutants. Neither conditional Bmpr1a mutation nor treatment with the BMP type I receptor inhibitor dorsomorphin expands sclerotome marker expression, suggesting that BMP antagonists do not have an instructive function in sclerotome specification. Instead, we hypothesize that Nog- and Grem1-mediated inhibition of BMP is permissive for hedgehog (Hh) signal-mediated sclerotome specification. In support of this model, we found that culturing Nog;Grem1 double-mutant embryos with dorsomorphin restores sclerotome, whereas Pax1 expression in smoothened (Smo) mutants is not rescued, suggesting that inhibition of BMP is insufficient to induce sclerotome in the absence of Hh signaling. Confirming the dominant inhibitory effect of BMP signaling, Pax1 expression cannot be rescued in Nog;Grem1 double mutants by forced activation of Smo. We conclude that Nog and Grem1 cooperate to maintain a BMP signaling-free zone that is a crucial prerequisite for Hh-mediated sclerotome induction.
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Affiliation(s)
- David A Stafford
- Department of Molecular and Cell Biology and Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA.
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Gianakopoulos PJ, Mehta V, Voronova A, Cao Y, Yao Z, Coutu J, Wang X, Waddington MS, Tapscott SJ, Skerjanc IS. MyoD directly up-regulates premyogenic mesoderm factors during induction of skeletal myogenesis in stem cells. J Biol Chem 2010; 286:2517-25. [PMID: 21078671 DOI: 10.1074/jbc.m110.163709] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gain- and loss-of-function experiments have illustrated that the family of myogenic regulatory factors is necessary and sufficient for the formation of skeletal muscle. Furthermore, MyoD required cellular aggregation to induce myogenesis in P19 embryonal carcinoma stem cells. To determine the mechanism by which stem cells can be directed into skeletal muscle, a time course of P19 cell differentiation was examined in the presence and absence of exogenous MyoD. By quantitative PCR, the first MyoD up-regulated transcripts were the premyogenic mesoderm factors Meox1, Pax7, Six1, and Eya2 on day 4 of differentiation. Subsequently, the myoblast markers myogenin, MEF2C, and Myf5 were up-regulated, leading to skeletal myogenesis. These results were corroborated by Western blot analysis, showing up-regulation of Pax3, Six1, and MEF2C proteins, prior to myogenin protein expression. To determine at what stage a dominant-negative MyoD/EnR mutant could inhibit myogenesis, stable cell lines were created and examined. Interestingly, the premyogenic mesoderm factors, Meox1, Pax3/7, Six1, Eya2, and Foxc1, were down-regulated, and as expected, skeletal myogenesis was abolished. Finally, to identify direct targets of MyoD in this system, chromatin immunoprecipitation experiments were performed. MyoD was observed associated with regulatory regions of Meox1, Pax3/7, Six1, Eya2, and myogenin genes. Taken together, MyoD directs stem cells into the skeletal muscle lineage by binding and activating the expression of premyogenic mesoderm genes, prior to activating myoblast genes.
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Affiliation(s)
- Peter J Gianakopoulos
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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34
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Shum ASW, Tang LSC, Copp AJ, Roelink H. Lack of motor neuron differentiation is an intrinsic property of the mouse secondary neural tube. Dev Dyn 2010; 239:3192-203. [PMID: 20960561 DOI: 10.1002/dvdy.22457] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2010] [Indexed: 11/12/2022] Open
Abstract
The cranial part of the amniote neural tube is formed by folding and fusion of the ectoderm-derived neural plate (primary neurulation). After posterior neuropore closure, however, the caudal neural tube is formed by cavitation of tail bud mesenchyme (secondary neurulation). In mouse embryos, the secondary neural tube expresses several genes important in early patterning and induction, in restricted domains similar to the primary neural tube, yet it does not undergo neuronal differentiation, but subsequently degenerates. Although the secondary neural tube, isolated from surrounding tissues, is responsive to exogenous Sonic Hedgehog proteins in vitro, motor neuron differentiation is never observed. This cannot be attributed to the properties of the secondary notochord, since it is able to induce motor neuron differentiation in naive chick neural plate explants. Taken together, these results support that the lack of motor neuron differentiation is an intrinsic property of the mouse secondary neural tube.
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Affiliation(s)
- Alisa S W Shum
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
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35
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Savage J, Conley AJ, Blais A, Skerjanc IS. SOX15 and SOX7 Differentially Regulate the Myogenic Program in P19 Cells. Stem Cells 2009; 27:1231-43. [DOI: 10.1002/stem.57] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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36
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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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37
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Cairns DM, Sato ME, Lee PG, Lassar AB, Zeng L. A gradient of Shh establishes mutually repressing somitic cell fates induced by Nkx3.2 and Pax3. Dev Biol 2008; 323:152-65. [PMID: 18796301 DOI: 10.1016/j.ydbio.2008.08.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 08/14/2008] [Accepted: 08/23/2008] [Indexed: 11/25/2022]
Abstract
Wnt and Sonic Hedgehog (Shh) signals are known to pattern the somite into dermomyotomal, myotomal and sclerotomal cell fates. By employing explants of presomitic mesoderm cultured with constant levels of Wnt3a conditioned medium and increasing levels of Shh, we found that differing levels of Shh signaling elicit differing responses from somitic cells: the lowest level of Shh signaling allows dermomyotomal gene expression, intermediate levels induce loss of dermomyotomal markers and activation of myogenic differentiation, and higher levels induce loss of myotomal markers and activation of sclerotomal gene expression. In addition, we have found that in the presence of high levels of Wnt signaling, instead of inducing sclerotomal markers, Shh signals act to maintain the expression of dermomyotomal and myotomal markers. One of the sclerotomal genes induced by high levels of Shh signaling is Nkx3.2. Forced expression of Nkx3.2 blocks somitic expression of the dermomyotomal marker Pax3 both in vitro and in vivo. Conversely, forced expression of Pax3 in somites can block Shh-mediated induction of sclerotomal gene expression and chondrocyte differentiation in vitro. Thus we propose that varying levels of Shh signaling act in a morphogen-like manner to elicit differing responses from somitic cells, and that Pax3 and Nkx3.2 set up mutually repressing cell fates that promote either dermomyotome/myotome or sclerotome differentiation, respectively.
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Affiliation(s)
- Dana M Cairns
- Program in Cellular, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, 136 Harrison Avenue, Boston, MA 02111, USA
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38
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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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39
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Abstract
Recent work in teleosts has renewed interest in the dermomyotome, which was initially characterized in the late 19th century. We review the evidence for the teleost dermomyotome, comparing it to the more well-characterized amniote dermomyotome. We discuss primary myotome morphogenesis, the relationship between the primary myotome and the dermomyotome, the differentiation of axial muscle, appendicular muscle, and dermis from the dermomyotome, and the signaling molecules that regulate myotome growth from myogenic precursors within the dermomyotome. The recognition of a dermomyotome in teleosts provides a new perspective on teleost muscle growth, as well as a fruitful approach to understanding the vertebrate dermomyotome.
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Affiliation(s)
- Frank Stellabotte
- Department of Biology, Wesleyan University, Middletown, Connecticut 06459, USA
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40
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Gerhart J, Neely C, Elder J, Pfautz J, Perlman J, Narciso L, Linask KK, Knudsen K, George-Weinstein M. Cells that express MyoD mRNA in the epiblast are stably committed to the skeletal muscle lineage. ACTA ACUST UNITED AC 2007; 178:649-60. [PMID: 17698608 PMCID: PMC2064471 DOI: 10.1083/jcb.200703060] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The epiblast of the chick embryo contains cells that express MyoD mRNA but not MyoD protein. We investigated whether MyoD-positive (MyoDpos) epiblast cells are stably committed to the skeletal muscle lineage or whether their fate can be altered in different environments. A small number of MyoDpos epiblast cells were tracked into the heart and nervous system. In these locations, they expressed MyoD mRNA and some synthesized MyoD protein. No MyoDpos epiblast cells differentiated into cardiac muscle or neurons. Similar results were obtained when MyoDpos cells were isolated from the epiblast and microinjected into the precardiac mesoderm or neural plate. In contrast, epiblast cells lacking MyoD differentiated according to their environment. These results demonstrate that the epiblast contains both multipotent cells and a subpopulation of cells that are stably committed to the skeletal muscle lineage before the onset of gastrulation. Stable programming in the epiblast may ensure that MyoDpos cells express similar signaling molecules in a variety of environments.
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Affiliation(s)
- Jacquelyn Gerhart
- Center for Chronic Disorders of Aging, Philadelphia College of Osteopathic Medicine, Philadelphia, PA 19131, USA
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41
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Feng X, Adiarte EG, Devoto SH. Hedgehog acts directly on the zebrafish dermomyotome to promote myogenic differentiation. Dev Biol 2006; 300:736-46. [PMID: 17046741 DOI: 10.1016/j.ydbio.2006.08.056] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 08/23/2006] [Accepted: 08/24/2006] [Indexed: 01/03/2023]
Abstract
Vertebrate myogenesis is regulated by signaling proteins secreted from surrounding tissues. One of the most important, Sonic hedgehog, has been proposed to regulate myogenic precursor cell survival, proliferation, and differentiation in a variety of vertebrates. In zebrafish, Hedgehog signaling is both necessary and sufficient for the development of embryonic slow muscle fibers-the earliest differentiating muscle fibers. Here we investigated the function of Hedgehog signaling in another zebrafish myogenic lineage, a dermomyotomal population of cells defined by somitic pax3/7 expression. We found that Hedgehog negatively regulates the number of myogenic precursors expressing pax3/7. Hh also positively regulates the growth of embryonic fast muscle. Unlike Hedgehog's function in regulating the elongation of fast muscle fibers, this regulation is not mediated by embryonic slow muscle fibers. Instead, it is a direct Hedgehog response, cell autonomous to myogenic precursors. The regulation of myogenic precursors and their differentiation into fast fibers have a different critical time period for Hh signaling, and different requirements for specific gli gene family members of Hh activated transcription factors from the earlier promotion of embryonic slow muscle fiber differentiation. We propose that Hedgehog signaling acts at multiple times on different lineages, through different downstream pathways, to promote myogenic differentiation.
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Affiliation(s)
- Xuesong Feng
- Department of Biology, Wesleyan University, Middletown, CT 06459, USA
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42
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Gerhart J, Elder J, Neely C, Schure J, Kvist T, Knudsen K, George-Weinstein M. MyoD-positive epiblast cells regulate skeletal muscle differentiation in the embryo. J Cell Biol 2006; 175:283-92. [PMID: 17060497 PMCID: PMC2064569 DOI: 10.1083/jcb.200605037] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Accepted: 09/15/2006] [Indexed: 11/22/2022] Open
Abstract
MyoD mRNA is expressed in a subpopulation of cells within the embryonic epiblast. Most of these cells are incorporated into somites and synthesize Noggin. Ablation of MyoD-positive cells in the epiblast subsequently results in the herniation of organs through the ventral body wall, a decrease in the expression of Noggin, MyoD, Myf5, and myosin in the somites and limbs, and an increase in Pax-3-positive myogenic precursors. The addition of Noggin lateral to the somites compensates for the loss of MyoD-positive epiblast cells. Skeletal muscle stem cells that arise in the epiblast are utilized in the somites to promote muscle differentiation by serving as a source of Noggin.
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Affiliation(s)
- Jacquelyn Gerhart
- Center for Chronic Disorders of Aging, Philadelphia College of Osteopathic Medicine, Philadelphia, PA 19131, USA
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43
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Hammond CL, Hinits Y, Osborn DP, Minchin JE, Tettamanti G, Hughes SM. Signals and myogenic regulatory factors restrict pax3 and pax7 expression to dermomyotome-like tissue in zebrafish. Dev Biol 2006; 302:504-21. [PMID: 17094960 PMCID: PMC3960072 DOI: 10.1016/j.ydbio.2006.10.009] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 09/26/2006] [Accepted: 10/05/2006] [Indexed: 11/22/2022]
Abstract
Pax3/7 paired homeodomain transcription factors are important markers of muscle stem cells. Pax3 is required upstream of myod for lateral dermomyotomal cells in the amniote somite to form particular muscle cells. Later Pax3/7-dependent cells generate satellite cells and most body muscle. Here we analyse early myogenesis from, and regulation of, a population of Pax3-expressing dermomyotome-like cells in the zebrafish. Zebrafish pax3 is widely expressed in the lateral somite and, along with pax7, becomes restricted anteriorly and then to the external cells on the lateral somite surface. Midline-derived Hedgehog signals appear to act directly on lateral somite cells to repress Pax3/7. Both Hedgehog and Fgf8, signals that induce muscle formation within the somite, suppress Pax3/7 and promote expression of myogenic regulatory factors (MRFs) myf5 and myod in specific muscle precursor cell populations. Loss of MRF function leads to loss of myogenesis by specific populations of muscle fibres, with parallel up-regulation of Pax3/7. Myod is required for lateral fast muscle differentiation from pax3-expressing cells. In contrast, either Myf5 or Myod is sufficient to promote slow muscle formation from adaxial cells. Thus, myogenic signals act to drive somite cells to a myogenic fate through up-regulation of distinct combinations of MRFs. Our data show that the relationship between Pax3/7 genes and myogenesis is evolutionarily ancient, but that changes in the MRF targets for particular signals contribute to myogenic differences between species.
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Affiliation(s)
| | | | | | | | | | - Simon M. Hughes
- Corresponding author: Simon M. Hughes, 4 floor South, New Hunt’s House, Guy’s Campus, King’s College London, London SE1 1UL, UK tel: +44 (0)20 7848 6445, fax+44 (0)20 7848 6798,
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44
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Yusuf F, Brand-Saberi B. The eventful somite: patterning, fate determination and cell division in the somite. ACTA ACUST UNITED AC 2006; 211 Suppl 1:21-30. [PMID: 17024302 DOI: 10.1007/s00429-006-0119-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 08/18/2006] [Indexed: 11/29/2022]
Abstract
The segmental somites not only determine the vertebrate body plan, but also represent turntables of cell fates. The somite is initially naive in terms of its fate restriction as shown by grafting and rotation experiments whereby ectopically grafted or rotated tissue of newly formed somites yielded the same pattern of normal derivatives. Somitic derivatives are determined by local signalling between adjacent embryonic tissues, in particular the neural tube, notochord, surface ectoderm and the somitic compartments themselves. The correct spatio-temporal specification of the deriving tissues, skeletal muscle, cartilage, endothelia and connective tissue is achieved by a sequence of morphogenetic changes of the paraxial mesoderm, eventually leading to the three transitory somitic compartments: dermomyotome, myotome and sclerotome. These structures are specified along a double gradient from dorsal to ventral and from medial to lateral. The establishment and controlled disruption of the epithelial state of the somitic compartments are crucial for development. In this article, we give a synopsis of some of the most important signalling events involved in somite patterning and cell fate decisions. Particular emphasis has been laid on the issue of epithelio-mesenchymal transition and different types of cell division in the somite.
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Affiliation(s)
- Faisal Yusuf
- Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Albertstrasse 17, 79104, Freiburg, Germany.
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45
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Barrionuevo F, Taketo MM, Scherer G, Kispert A. Sox9 is required for notochord maintenance in mice. Dev Biol 2006; 295:128-40. [PMID: 16678811 DOI: 10.1016/j.ydbio.2006.03.014] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Revised: 03/01/2006] [Accepted: 03/13/2006] [Indexed: 02/06/2023]
Abstract
Sox9 encodes a HMG-box transcription factor that has been implicated in numerous developmental processes including chondrogenesis, formation of cardiac valves, and neural crest, testis and spinal cord development. Here we show that Sox9 is expressed in the notochord and the sclerotome during mouse development suggesting that the gene may play additional roles in the development of the axial skeleton. We used ubiquitous mosaic inactivation of a conditional Sox9 allele by Cre/loxP-mediated recombination in the mouse to screen for novel functions of Sox9, and revealed that its absence results in severe malformations of the vertebral column. Besides its established role in chondrogenesis, Sox9 is required for maintaining the structural integrity of the notochord. Mutant embryos establish a normal notochord; however, starting from E9.5, the notochord disintegrates in a cranial to caudal manner. The late requirement in notochord development uncovered a function of notochord-derived signals in inducing segmentation of the ventral sclerotome and chondrogenesis. Thus, Sox9 is required for axial skeletogenesis by regulating notochord survival and chondrogenesis.
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Affiliation(s)
- Francisco Barrionuevo
- Institute of Human Genetics and Anthropology, University of Freiburg, D-79106 Freiburg, Germany.
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46
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Speek M, Njunkova O, Pata I, Valdre E, Kogerman P. A potential role of alternative splicing in the regulation of the transcriptional activity of human GLI2 in gonadal tissues. BMC Mol Biol 2006; 7:13. [PMID: 16553965 PMCID: PMC1435915 DOI: 10.1186/1471-2199-7-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Accepted: 03/23/2006] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Mammalian Gli proteins are important transcription factors involved in the regulation of Sonic hedgehog signal transduction pathway. Association of Gli2 with mammalian development and human disease led us to study the structure and expression of the human GLI2. RESULTS We show that the region encoding GLI2 repressor domain is subject to alternative splicing in the gonadal tissues and different cell lines. Two major alternatively spliced forms of GLI2 mRNA arise from skipping exon 3 (GLI2Delta3) or exons 4 and 5 (GLI2Delta4-5). Both forms contain premature translational stop codons in the GLI2 open reading frame (ORF) starting from exon 2. Translation of GLI2Delta3 and GLI2Delta4-5 in vitro, initiated from downstream AUG codons, produced N-terminally truncated proteins. In Gli-dependent transactivation assay, expression of GLI2Delta3 induced activation of the reporter gene similar to that of the full-length construct (GLI2fl) containing complete ORF. However, expression of the GLI2Delta4-5 resulted in about 10-fold increase in activation, suggesting that deletion of the major part of repressor domain was responsible for the enhanced activation of GLI2 protein. CONCLUSION Our data suggest that in addition to proteolytic processing, alternative splicing may be another important regulatory mechanism for the modulation of repressor and activator properties of GLI2 protein.
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Affiliation(s)
- Mart Speek
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 19086 Tallinn, Estonia
| | - Olga Njunkova
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 19086 Tallinn, Estonia
- Department of Molecular Genetics, National Institute for Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - Illar Pata
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 19086 Tallinn, Estonia
- Department of Molecular Genetics, National Institute for Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - Eola Valdre
- Department of Molecular Genetics, National Institute for Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
- Diagnostic Clinic, East-Tallinn Central Hospital, Ravi 18, 10138 Tallinn, Estonia
| | - Priit Kogerman
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 19086 Tallinn, Estonia
- Department of Molecular Genetics, National Institute for Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
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Huh MS, Smid JK, Rudnicki MA. Muscle function and dysfunction in health and disease. ACTA ACUST UNITED AC 2005; 75:180-92. [PMID: 16187312 DOI: 10.1002/bdrc.20045] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Skeletal muscles of the trunk and limbs developmentally originate from the cells of the dermomyotomal compartment of the somite. A wealth of knowledge has been accumulated with regard to understanding the molecular regulation of embryonic skeletal myogenesis. Myogenic induction is controlled through a complex series of spatiotemporal dependent signaling cascades. Secreted signaling molecules from surrounding structures not only initiate the myogenic program, but also influence proliferation and differentiation decisions. The proper coordination of these molecular events is thus critical for the formation of physiologically functional skeletal muscles. Hereditary congenital skeletal muscle defects arise due to genetics lesions in myogenic specific components. Understanding the mechanistic routes of congenital skeletal muscle disease therefore requires a comprehensive knowledge of the developmental system. Ultimately, the application of this knowledge will improve the diagnostic and therapeutic methodologies for such diseases. The aim of this review is to overview our current understanding of skeletal muscle development and associated human congenital diseases.
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Affiliation(s)
- Michael S Huh
- Ottawa Health Research Institute, Molecular Medicine Program, and the Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
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Granata A, Quaderi NA. Asymmetric expression of Gli transcription factors in Hensen's node. Gene Expr Patterns 2005; 5:529-31. [PMID: 15749082 DOI: 10.1016/j.modgep.2004.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 11/05/2004] [Accepted: 11/08/2004] [Indexed: 11/26/2022]
Abstract
Avian left-right (L/R) axis determination involves the establishment of asymmetric gene expression in Hensen's node, resulting in two discrete signalling pathways on the left and right sides of the embryo. The extracellular signalling molecule Sonic Hedgehog (SHH) is known to be an important left-side determinant. Transcription of Shh is initially bilateral in Hensen's node (stage 4), but is restricted to the left side by stage 5. The Gli genes (Gli1, Gli2 and Gli3) are the main transcriptional mediators of the Hedgehog pathway in vertebrates. GLI1 and GLI2 are primarily transcriptional activators of Hedgehog target genes, while GLI3 is primarily a transcriptional repressor of Hedgehog targets. In order to gain insight into the mechanisms of asymmetrical Hedgehog signal transduction in the node, we have analysed the expression patterns of the Gli genes in Hensen's node from stage 4 to stage 8. Here, we reveal that the Gli genes are asymmetrically expressed in Hensen's node: Gli1 and Gli2, are expressed on the left side, while Gli3 is expressed on the right side.
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Affiliation(s)
- Alessandra Granata
- MRC Centre for Developmental Neurobiology, King's College London, 4th Floor New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UK
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Arsic D, Cameron V, Ellmers L, Quan QB, Keenan J, Beasley S. Adriamycin disruption of the Shh-Gli pathway is associated with abnormalities of foregut development. J Pediatr Surg 2004; 39:1747-53. [PMID: 15616919 DOI: 10.1016/j.jpedsurg.2004.08.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The hedgehog signalling pathway appears to have a crucial role in the embryogenesis of the foregut in vertebrates. Sonic hedgehog (Shh) protein and gene are involved in the differentiation of many organ systems such as notochord, floor plate, and limbs; development of the left-right axis in vertebrates; and differentiation of trachea and esophagus from the primitive foregut. METHODS The prenatal exposure of Sprague-Dawley fetal rats to Adriamycin between days 6 and 9 of gestation was used to induce esophageal atresia and tracheoesophageal fistula. Embryos were harvested by cesarean section on gestational days 11 to 15. Embryos were examined by microscopy, dissection, and serial histology. In situ hybridization was used to study Shh gene expression in the rat embryos. RESULTS In situ hybridization showed that the pattern and level of Shh gene expression are affected by Adriamycin. Adriamycin-treated rats have deformed notochord and undivided foregut, and some of the embryos had a lack of the dorso-ventral patterning of Shh expression seen in control embryos. CONCLUSIONS These results are consistent with the hypothesis that Adriamycin influences the Shh signalling pathway, resulting in disruption of normal development of the foregut.
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Affiliation(s)
- Dejan Arsic
- Department of Paediatric Surgery, Christchurch School of Medicine, Christchurch, New Zealand
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Cheng L, Alvares LE, Ahmed MU, El-Hanfy AS, Dietrich S. The epaxial–hypaxial subdivision of the avian somite. Dev Biol 2004; 274:348-69. [PMID: 15385164 DOI: 10.1016/j.ydbio.2004.07.020] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2003] [Revised: 07/06/2004] [Accepted: 07/07/2004] [Indexed: 01/29/2023]
Abstract
In all jaw-bearing vertebrates, three-dimensional mobility relies on segregated, separately innervated epaxial and hypaxial skeletal muscles. In amniotes, these muscles form from the morphologically continuous dermomyotome and myotome, whose epaxial-hypaxial subdivision and hence the formation of distinct epaxial-hypaxial muscles is not understood. Here we show that En1 expression labels a central subdomain of the avian dermomyotome, medially abutting the expression domain of the lead-lateral or hypaxial marker Sim1. En1 expression is maintained when cells from the En1-positive dermomyotome enter the myotome and dermatome, thereby superimposing the En1-Sim1 expression boundary onto the developing musculature and dermis. En1 cells originate from the dorsomedial edge of the somite. Their development is under positive control by notochord and floor plate (Shh), dorsal neural tube (Wnt1) and surface ectoderm (Wnt1-like signalling activity) but negatively regulated by the lateral plate mesoderm (BMP4). This dependence on epaxial signals and suppression by hypaxial signals places En1 into the epaxial somitic programme. Consequently, the En1-Sim1 expression boundary marks the epaxial-hypaxial dermomyotomal or myotomal boundary. In cell aggregation assays, En1- and Sim1-expressing cells sort out, suggesting that the En1-Sim1 expression boundary may represent a true compartment boundary, foreshadowing the epaxial-hypaxial segregation of muscle.
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Affiliation(s)
- Louise Cheng
- Department of Craniofacial Development, King's College London, London Bridge, London SE1 9RT, UK
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