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Developmental Biology Jan 1998Neural crest induction is thought to occur by a two-step process. Axially fated mesoderm induces neural plate, which is then recruited to neural crest by nonneural...
Neural crest induction is thought to occur by a two-step process. Axially fated mesoderm induces neural plate, which is then recruited to neural crest by nonneural epidermal ectoderm at the neural plate border. This model suggests a rather indirect role for mesoderm in inducing neural crest. We extensively examined the role of mesoderm in neural crest induction by determining which types of mesoderm induce neural crest cells in Xenopus embryos. We found that noggin-dorsalized ventral marginal zone (VMZ) explants differentiate as melanocytes in the absence of axial mesoderm. Dorsalized VMZ is also a potent inducer of melanocytes when juxtaposed to animal cap ectoderm in recombinant explants. Dorsalized VMZ is analogous to the dorsal-lateral marginal zone (DLMZ) region of the embryo. Neural crest-inducing activities of gastrula stage DLMZ and dorsal marginal zone (DMZ) were also compared in recombinant explants. DLMZ was a stronger inducer of neural crest than was DMZ; DLMZ induced high levels of XSlug expression and melanocyte formation in recombinants, whereas DMZ weakly induced neural crest. In whole embryos lacking DLMZ, XSlug expression and melanocyte formation were significantly reduced; in contrast, no significant reduction of XSlug expression or melanocyte formation was seen in embryos lacking a DMZ. These results suggest that paraxial-fated mesoderm plays a central role in neural crest formation by inducing a novel type of lateral neural plate. This lateral neural plate is then recruited to neural crest by adjacent nonneural epidermal ectoderm.
Topics: Animals; Biomarkers; Carrier Proteins; Cell Differentiation; Ectoderm; Embryonic Development; Embryonic Induction; Gastrula; Melanocytes; Mesoderm; Neural Crest; Proteins; Xenopus
PubMed: 9473321
DOI: 10.1006/dbio.1997.8795 -
The International Journal of... 2018Somites are epithelial blocks of paraxial mesoderm that define the vertebrate embryonic segments. They are responsible for imposing the metameric pattern observed in... (Review)
Review
Somites are epithelial blocks of paraxial mesoderm that define the vertebrate embryonic segments. They are responsible for imposing the metameric pattern observed in many tissues of the adult such as the vertebrae, and they give rise to most of the axial skeleton and skeletal muscles of the trunk. Due to its easy accessibility in the egg, the chicken embryo has provided an ideal model to study somite development. Somites were first described in the chicken embryo by Malpighi in the 17 century, soon after the invention of the microscope. Most of the major concepts relating to somite segmentation and differentiation result from studies performed in the chicken embryo (Brand-Saberi and Christ, 2000). In this review, we will discuss how studies on somites in avian embryos have contributed to our understanding of key developmental processes such as segmentation, control of bilateral symmetry or axis regionalization.
Topics: Animals; Body Patterning; Cell Differentiation; Cell Lineage; Chick Embryo; Chickens; Embryology; Embryonic Development; Gene Expression Regulation, Developmental; History, 17th Century; History, 19th Century; History, 20th Century; History, 21st Century; Humans; Mesoderm; Mice; Somites; Vertebrates; Zebrafish
PubMed: 29616740
DOI: 10.1387/ijdb.180036op -
Anatomical Record (Hoboken, N.J. : 2007) Aug 2022The process by which upper respiratory tract structures have changed over deep evolutionary time is, in part, reflected in the process of embryologic development. The...
The process by which upper respiratory tract structures have changed over deep evolutionary time is, in part, reflected in the process of embryologic development. The nasopharynx in particular is a centrally located space bounded by components of the respiratory portion of the nasal cavity, cranial base, soft palate, and Eustachian tube. The development of these components can be understood both in terms of embryologic structures such as the branchial arches and paraxial mesoderm and through fossil evidence dating as far back as the earliest agnathan fish of the Cambrian Period. Understanding both the evolution and development of these structures has been an immeasurable benefit to the otolaryngologist seeking to model disease etiology of both common and rare conditions. This discussion is a primer for those who may be unfamiliar with the central importance of the nasopharynx both in terms of our evolutionary history and early embryological development of vital cranial and upper respiratory tract structures.
Topics: Animals; Biological Evolution; Branchial Region; Developmental Biology; Mesoderm; Nasopharynx; Skull
PubMed: 35665451
DOI: 10.1002/ar.24950 -
Developmental Biology Apr 2006Tetrapod limbs, forelimbs and hindlimbs, emerge as limb buds during development from appropriate positions along the rostro-caudal axis of the main body. In this study,...
Tetrapod limbs, forelimbs and hindlimbs, emerge as limb buds during development from appropriate positions along the rostro-caudal axis of the main body. In this study, tissue interactions by which rostro-caudal level-specific limb initiation is established were analyzed. The limb bud originates from the lateral plate located laterally to the paraxial mesoderm, and we obtained evidence that level-specific tissue interactions between the paraxial mesoderm and the lateral plate mesoderm are important for the determination of the limb-type-specific gene expression and limb outgrowth. When the wing-level paraxial mesoderm was transplanted into the presumptive leg region, the wing-level paraxial mesoderm upregulated the expression of Tbx5, a wing marker gene, and down regulated the expression of Tbx4 and Pitx1, leg marker genes, in the leg-level lateral plate. The wing-level paraxial mesoderm relocated into the leg level also inhibited outgrowth of the hindlimb bud and down regulated Fgf10 and Fgf8 expression, demonstrating that the wing-level paraxial mesoderm cannot substitute for the function of the leg-level paraxial mesoderm in initiation and outgrowth of the hindlimb. The paraxial mesoderm taken from the neck- and flank-level regions also had effects on Tbx5/Tbx4 expression with different efficiencies. These findings suggest that the paraxial mesoderm has level-specific abilities along the rostro-caudal axis in the limb-type-specific mechanism for limb initiation.
Topics: Animals; Avian Proteins; Chick Embryo; Down-Regulation; Fibroblast Growth Factor 10; Fibroblast Growth Factor 8; Hindlimb; Lower Extremity; Mesoderm; Organ Culture Techniques; Paired Box Transcription Factors; T-Box Domain Proteins; Wings, Animal
PubMed: 16480709
DOI: 10.1016/j.ydbio.2006.01.002 -
Current Topics in Developmental Biology 2000
Review
Early events of somitogenesis in higher vertebrates: allocation of precursor cells during gastrulation and the organization of a meristic pattern in the paraxial mesoderm.
Topics: Animals; Body Patterning; Gastrula; Mesoderm; Somites; Vertebrates
PubMed: 10595300
DOI: 10.1016/s0070-2153(08)60720-6 -
Developmental Biology Jul 2012Paraxial mesoderm is the tissue which gives rise to the skeletal muscles and vertebral column of the body. A gene regulatory network operating in the formation of...
Paraxial mesoderm is the tissue which gives rise to the skeletal muscles and vertebral column of the body. A gene regulatory network operating in the formation of paraxial mesoderm has been described. This network hinges on three key factors, Wnt3a, Msgn1 and Tbx6, each of which is critical for paraxial mesoderm formation, since absence of any one of these factors results in complete absence of posterior somites. In this study we determined and compared the spatial and temporal patterns of expression of Wnt3a, Msgn1 and Tbx6 at a time when paraxial mesoderm is being formed. Then, we performed a comparative characterization of mutants in Wnt3a, Msgn1 and Tbx6. To determine the epistatic relationship between these three genes, and begin to decipher the complex interplay between them, we analyzed double mutant embryos and compared their phenotypes to the single mutants. Through the analysis of molecular markers in mutants, our data support the bipotential nature of the progenitor cells for paraxial mesoderm and establish regulatory relationships between genes involved in the choice between neural and mesoderm fates.
Topics: Animals; Cell Differentiation; Embryo, Mammalian; Epithelial-Mesenchymal Transition; Gene Expression Regulation, Developmental; Mesoderm; Mice; Mutation; Somites
PubMed: 22546692
DOI: 10.1016/j.ydbio.2012.04.012 -
Developmental Biology Apr 2000We used Pax-2 mRNA expression and Lim 1/2 antibody staining as markers for the conversion of chick intermediate mesoderm (IM) to pronephric tissue and Lmx-1 mRNA...
We used Pax-2 mRNA expression and Lim 1/2 antibody staining as markers for the conversion of chick intermediate mesoderm (IM) to pronephric tissue and Lmx-1 mRNA expression as a marker for mesonephros. Pronephric markers were strongly expressed caudal to the fifth somite by stage 9. To determine whether the pronephros was induced by adjacent tissues and, if so, to identify the inducing tissues and the timing of induction, we microsurgically dissected one side of chick embryos developing in culture and then incubated them for up to 3 days. The undisturbed contralateral side served as a control. Most embryos cut parallel to the rostrocaudal axis between the trunk paraxial mesoderm and IM before stage 8 developed a pronephros on the control side only. Embryos manipulated after stage 9 developed pronephric structures on both sides, but the caudal pronephric extension was attenuated on the cut side. These results suggest that a medial signal is required for pronephric development and show that the signal is propagated in a rostral to caudal sequence. In manipulated embryos cultured for 3 days in ovo, the mesonephros as well as the pronephros failed to develop on the experimental side. In contrast, embryos cut between the notochord and the trunk paraxial mesoderm formed pronephric structures on both sides, regardless of the stage at which the operation was performed, indicating that the signal arises from the paraxial mesoderm (PM) and not from axial mesoderm. This cut also served as a control for cuts between the PM and the IM and showed that signaling itself was blocked in the former experiments, not the migration of pronephric or mesonephric precursor cells from the primitive streak. Additional control experiments ruled out the need for signals from lateral plate mesoderm, ectoderm, or endoderm. To determine whether the trunk paraxial mesoderm caudal to the fifth somite maintains its inductive capacity in the absence of contact with more rostral tissue, embryos were transected. Those transected below the prospective level of the fifth somite expressed Pax-2 in both the rostral and the caudal isolates, whereas embryos transected rostral to this level expressed Pax-2 in the caudal isolate only. Thus, a rostral signal is not required to establish the normal pattern of Pax-2 expression and pronephros formation. To determine whether paraxial mesoderm is sufficient for pronephros induction, stage 7 or earlier chick lateral plate mesoderm was cocultured with caudal stage 8 or 9 quail somites in collagen gels. Pax-2 was expressed in chick tissues in 21 of 25 embryos. Isochronic transplantation of stage 4 or 5 quail node into caudal chick primitive streak resulted in the generation of ectopic somites. These somites induced ectopic pronephroi in lateral plate mesoderm, and the IM that received signals from both native and ectopic somites formed enlarged pronephroi with increased Pax-2 expression. We conclude that signals from a localized region of the trunk paraxial mesoderm are both required and sufficient for the induction of the pronephros from the chick IM. Studies to identify the molecular nature of the induction are in progress.
Topics: Animals; Chick Embryo; Coturnix; DNA-Binding Proteins; Ectoderm; Embryonic Induction; Endoderm; Homeodomain Proteins; In Situ Hybridization; Kidney; Mesoderm; Mesonephros; Nerve Tissue Proteins; PAX2 Transcription Factor; RNA, Messenger; Signal Transduction; Somites; Transcription Factors
PubMed: 10720431
DOI: 10.1006/dbio.2000.9623 -
Developmental Dynamics : An Official... Sep 2007Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of... (Review)
Review
Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of data on the complex molecular interactions leading to the formation of various somitic derivatives. In this review, we focus on the crucial role of the somites in building the body wall and limbs of amniote embryos. We give an overview on the current knowledge on the specification and differentiation of somitic cell lineages leading to the development of the vertebral column, skeletal muscle, connective tissue, meninges, and vessel endothelium, and highlight the importance of the somites in establishing the metameric pattern of the vertebrate body.
Topics: Amnion; Animals; Cell Differentiation; Cell Lineage; Chick Embryo; Embryonic Development; Endothelium; Epithelium; Extremities; Microscopy, Electron, Scanning; Models, Anatomic; Models, Biological; Muscles; Somites; Spinal Cord
PubMed: 17557304
DOI: 10.1002/dvdy.21189 -
Development (Cambridge, England) Feb 2004We provide the first analysis of how a segmentally reiterated pattern of neurons is specified along the anteroposterior axis of the vertebrate spinal cord by...
We provide the first analysis of how a segmentally reiterated pattern of neurons is specified along the anteroposterior axis of the vertebrate spinal cord by investigating how zebrafish primary motoneurons are patterned. Two identified primary motoneuron subtypes, MiP and CaP, occupy distinct locations within the ventral neural tube relative to overlying somites, express different genes and innervate different muscle territories. In all vertebrates examined so far, paraxial mesoderm-derived signals specify distinct motoneuron subpopulations in specific anteroposterior regions of the spinal cord. We show that signals from paraxial mesoderm also control the much finer-grained segmental patterning of zebrafish primary motoneurons. We examined primary motoneuron specification in several zebrafish mutants that have distinct effects on paraxial mesoderm development. Our findings suggest that in the absence of signals from paraxial mesoderm, primary motoneurons have a hybrid identity with respect to gene expression, and that under these conditions the CaP axon trajectory may be dominant.
Topics: Animals; Cell Differentiation; Heparan Sulfate Proteoglycans; Mesoderm; Motor Neurons; Mutation; Signal Transduction; Somites; Zebrafish; Zebrafish Proteins
PubMed: 14757641
DOI: 10.1242/dev.00981 -
Stem Cells (Dayton, Ohio) Jan 2013The paired box transcription factor Pax3 is well-known as a major regulator of embryonic myogenesis. Before Pax3 expression becomes restricted to the dermomyotome, this...
The paired box transcription factor Pax3 is well-known as a major regulator of embryonic myogenesis. Before Pax3 expression becomes restricted to the dermomyotome, this transcription factor is also expressed in the developing somites. The role of Pax3 at this early stage is unclear, in particular because of the scarce frequency of Pax3-positive cells in the early mouse embryo. Inducible gene expression in embryonic stem cells (ESCs) represents an excellent tool to overcome this limitation, since it can provide large quantities of otherwise rare embryonic populations expressing a factor of interest. Here we used engineered mouse ESCs to perform a functional analysis of Pax3 with the aim to identify the molecular determinants involved in the early functions of this transcription factor. We find that Pax3 induction during embryoid body differentiation results in the upregulation of genes expressed in the presomitic and somitic mesoderm. Moreover, we show that paraxial mesoderm induced by transient expression of Pax3 is not irreversibly committed to myogenesis rather requires sustained Pax3 expression. Using a series of deletion mutants of Pax3, which differentially affect its transcriptional activity, we map protein domains necessary for induction of paraxial mesoderm and induction of the myogenic program. The paired, homeo-, and transcriptional activation domains were each required for both processes, however, the paired-c-terminal RED domain showed a paraxial mesoderm-specific activity that was dispensable for myogenesis. These findings demonstrate and provide mechanistic insight into an early role for Pax3 in the generation of paraxial mesoderm.
Topics: Animals; Cell Differentiation; Cell Line; Embryonic Stem Cells; Gene Expression Profiling; Gene Expression Regulation, Developmental; Mesoderm; Mice; Muscle Development; PAX3 Transcription Factor; Paired Box Transcription Factors; Protein Structure, Tertiary; Receptor, Platelet-Derived Growth Factor alpha; Sequence Deletion; Vascular Endothelial Growth Factor Receptor-2
PubMed: 23081715
DOI: 10.1002/stem.1254