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Development (Cambridge, England) Sep 2015Neuromesodermal progenitors (NMps) contribute to both the elongating spinal cord and the adjacent paraxial mesoderm. It has been assumed that these cells arise as a... (Review)
Review
Neuromesodermal progenitors (NMps) contribute to both the elongating spinal cord and the adjacent paraxial mesoderm. It has been assumed that these cells arise as a result of patterning of the anterior neural plate. However, as the molecular mechanisms that specify NMps in vivo are uncovered, and as protocols for generating these bipotent cells from mouse and human pluripotent stem cells in vitro are established, the emerging data suggest that this view needs to be revised. Here, we review the characteristics, regulation, in vitro derivation and in vivo induction of NMps. We propose that these cells arise within primitive streak-associated epiblast via a mechanism that is separable from that which establishes neural fate in the anterior epiblast. We thus argue for the existence of two distinct routes for making central nervous system progenitors.
Topics: Animals; Body Patterning; Embryo, Mammalian; Humans; Mesoderm; Neural Stem Cells; Signal Transduction; Spinal Cord; Stem Cells
PubMed: 26329597
DOI: 10.1242/dev.119768 -
BMC Developmental Biology Jun 2008Co-ordinated cell movement is a fundamental feature of developing embryos. Massive cell movements occur during vertebrate gastrulation and during the subsequent...
BACKGROUND
Co-ordinated cell movement is a fundamental feature of developing embryos. Massive cell movements occur during vertebrate gastrulation and during the subsequent extension of the embryonic body axis. These are controlled by cell-cell signalling and a number of pathways have been implicated. Here we use long-term video microscopy in chicken embryos to visualize the migration routes and movement behaviour of mesoderm progenitor cells as they emerge from the primitive streak (PS) between HH stages 7 and 10.
RESULTS
We observed distinct cell movement behaviours along the length of the streak and determined that this is position dependent with cells responding to environmental cues. The behaviour of cells was altered by exposing embryos or primitive streak explants to cell pellets expressing Wnt3a and Wnt5a, without affecting cell fates, thus implicating these ligands in the regulation of cell movement behaviour. Interestingly younger embryos were not responsive, suggesting that Wnt3a and Wnt5a are specifically involved in the generation of posterior mesoderm, consistent with existing mouse and zebrafish mutants. To investigate which downstream components are involved mutant forms of dishevelled (dsh) and prickle1 (pk1) were electroporated into the primitive streak. These had differential effects on the behaviour of mesoderm progenitors emerging from anterior or posterior regions of the streak, suggesting that multiple Wnt pathways are involved in controlling cell migration during extension of the body axis in amniote embryos.
CONCLUSION
We suggest that the distinct behaviours of paraxial and lateral mesoderm precursors are regulated by the opposing actions of Wnt5a and Wnt3a as they leave the primitive streak in neurula stage embryos. Our data suggests that Wnt5a acts via prickle to cause migration of cells from the posterior streak. In the anterior streak, this is antagonised by Wnt3a to generate non-migratory medial mesoderm.
Topics: Animals; Body Patterning; Cell Movement; Chick Embryo; Embryonic Stem Cells; Gene Expression Regulation, Developmental; Mesoderm; Morphogenesis; Primitive Streak; Signal Transduction; Time Factors; Wnt Proteins
PubMed: 18541012
DOI: 10.1186/1471-213X-8-63 -
Journal of Anatomy Nov 2005The embryonic head is populated by two robust mesenchymal populations, paraxial mesoderm and neural crest cells. Although the developmental histories of each are... (Review)
Review
The embryonic head is populated by two robust mesenchymal populations, paraxial mesoderm and neural crest cells. Although the developmental histories of each are distinct and separate, they quickly establish intimate relations that are variably important for the histogenesis and morphogenesis of musculoskeletal components of the calvaria, midface and branchial regions. This review will focus first on the genesis and organization within nascent mesodermal and crest populations, emphasizing interactions that probably initiate or augment the establishment of lineages within each. The principal goal is an analysis of the interactions between crest and mesoderm populations, from their first contacts through their concerted movements into peripheral domains, particularly the branchial arches, and continuing to stages at which both the differentiation and the integrated three-dimensional assembly of vascular, connective and muscular tissues is evident. Current views on unresolved or contentious issues, including the relevance of head somitomeres, the processes by which crest cells change locations and constancy of cell-cell relations at the crest-mesoderm interface, are addressed.
Topics: Animals; Branchial Region; Cell Communication; Cell Lineage; Embryonic Induction; Head; Mesoderm; Morphogenesis; Neural Crest
PubMed: 16313393
DOI: 10.1111/j.1469-7580.2005.00473.x -
Developmental Dynamics : An Official... Oct 2017T-box genes encode a large transcription factor family implicated in many aspects of development. We are focusing on two related zebrafish T-box genes, tbx6l and tbx16,...
BACKGROUND
T-box genes encode a large transcription factor family implicated in many aspects of development. We are focusing on two related zebrafish T-box genes, tbx6l and tbx16, that are expressed in highly overlapping patterns in embryonic paraxial mesoderm. tbx16 mutants are deficient in trunk, but not tail, somites; we explored whether presence of tail somites in tbx16 mutants was due to compensatory function provided by the tbx6l gene.
RESULTS
We generated two zebrafish tbx6l mutant alleles. Loss of tbx6l has no apparent effect on embryonic development, nor does tbx6l loss enhance the phenotype of two other T-box gene mutants, ta and tbx6, or of the mesp family gene mutant msgn1. In contrast, loss of tbx6l function dramatically enhances the paraxial mesoderm deficiency of tbx16 mutants.
CONCLUSIONS
These data demonstrate that tbx6l and tbx16 genes function redundantly to direct tail somite development. tbx6l single mutants develop normally because tbx16 fully compensates for loss of tbx6l function. However, tbx6l only partially compensates for loss of tbx16 function. These results resolve the question of why loss of function of tbx16 gene, which is expressed throughout the ventral and paraxial mesoderm, profoundly affects somite development in the trunk but not the tail. Developmental Dynamics 246:759-769, 2017. © 2017 Wiley Periodicals, Inc.
Topics: Animals; Embryonic Development; Mesoderm; Somites; T-Box Domain Proteins; Zebrafish Proteins
PubMed: 28691257
DOI: 10.1002/dvdy.24547 -
Development (Cambridge, England) 1988Craniofacial mesenchyme is composed of three mesodermal populations - prechordal plate, lateral mesoderm and paraxial mesoderm, which includes the segmented occipital... (Review)
Review
Craniofacial mesenchyme is composed of three mesodermal populations - prechordal plate, lateral mesoderm and paraxial mesoderm, which includes the segmented occipital somites and the incompletely segmented somitomeres - and the neural crest. This paper outlines the fates of each of these, as determined using quail-chick chimaeras, and presents similarities and differences between these cephalic populations and their counterparts in the trunk. Prechordal and paraxial mesodermal populations are the sources of all voluntary muscles of the head. The latter also provides most of the connective precursors of the calvaria, occipital, otic-parietal and basisphenoid tissues. Lateral mesoderm is the source of peripharyngeal connective tissues; the most rostral skeletal tissues it forms are the laryngeal and tracheal cartilages. When migrating neural crest cells encounter segmented paraxial mesoderm (occipital and trunk somites), most move into the region between the dermamyotome and sclerotome in the cranial half of each somite. In contrast, most cephalic crest cells migrate superficial to somitomeres. There is, however, a small subpopulation of the head crest that invades somitomeric mesoderm. These cells subsequently segregate presumptive myogenic precursors of visceral arch voluntary muscles from underlying mesenchyme. In the neurula-stage avian embryo, all paraxial and lateral mesodermal populations contain precursors of vascular endothelial cells, which can be detected in chimaeric embryos using anti-quail endothelial anti-bodies. Some of these angioblasts differentiate in situ, contributing directly to pre-existing vessels or forming isolated, nonpatent, cords that subsequently vesiculate and fuse with nearby vessels. Many angioblasts migrate in all directions, invading embryonic mesenchymal and epithelial tissues and participating in new blood vessel formation in distant sites. The interactions leading to proper spatial patterning of craniofacial skeletal, muscular, vascular and peripheral neural tissues has been studied by performing heterotopic transplants of each of these mesodermal and neural crest populations. The results consistently indicate that connective tissue precursors, regardless of their origin, contain spatial information used by the precursors of muscles and blood vessels and by outgrowing peripheral nerves. Some of these connective tissue precursors (e.g. the neural crest, paraxial mesoderm) acquire their spatial programming while in association with the central nervous system or developing sensory epithelia (e.g. otic, optic, nasal epithelia).
Topics: Animals; Chick Embryo; Face; Mesoderm; Skull
PubMed: 3074905
DOI: 10.1242/dev.103.Supplement.121 -
The International Journal of... 2003In vertebrates, the primary segmented tissue of the body axis is the paraxial mesoderm, which lies bilaterally to the axial organs, neural tube and notochord. The... (Review)
Review
In vertebrates, the primary segmented tissue of the body axis is the paraxial mesoderm, which lies bilaterally to the axial organs, neural tube and notochord. The segmental pattern of the paraxial mesoderm is established during embryogenesis through the production of the somites which are transient embryonic segments giving rise to the vertebrae, the skeletal muscles and the dorsal dermis. Somitogenesis can be subdivided into three major phases (see Fig. 1). First a growth phase during which new paraxial mesoderm cells are produced by a growth zone (epiblast and blastopore margin or primitive streak and later on tail bud) and become organized as two rods of mesenchymal tissue,forming the presomitic mesoderm. Second a patterning phase occuring in the PSM, during which the segmental pattern is established at the molecular level. Third, the somitic boundaries are formed during the morphological segmentation phase. In all vertebrates, all cells of the paraxial mesoderm, during their maturation in the PSM, go successively through these three phases, which are tightly regulated at the spatio-temporal level. The first phase of paraxial mesoderm production falls out of the scope of this review, as it essentially pertains to the gastrulation process. Here, I essentially discuss the segmental patterning phase in vertebrates. Recent data suggest that establishment of the segmental pattern relies on a clock and wavefront mechanism which has been conserved in vertebrates. Furthermore, conservation of this system could extend to invertebrates, suggesting that the clock and wavefront is an ancestral mechanism.
Topics: Animals; Biological Clocks; Body Patterning; Cell Movement; Gastrula; Membrane Proteins; Mesoderm; Models, Biological; Proto-Oncogene Proteins; Receptors, Notch; Somites; Vertebrates; Wnt Proteins
PubMed: 14756335
DOI: No ID Found -
Developmental Biology Jul 2005The first morphological sign of vertebrate postcranial body segmentation is the sequential production from posterior paraxial mesoderm of blocks of cells termed somites....
The first morphological sign of vertebrate postcranial body segmentation is the sequential production from posterior paraxial mesoderm of blocks of cells termed somites. Each of these embryonic structures is polarized along the anterior/posterior axis, a subdivision first distinguished by marker gene expression restricted to rostral or caudal territories of forming somites. To better understand the generation of segment polarity in vertebrates, we have studied the zebrafish mutant fused somites (fss), because its paraxial mesoderm lacks segment polarity. Previously examined markers of caudal half-segment identity are widely expressed, whereas markers of rostral identity are either missing or dramatically down-regulated, suggesting that the paraxial mesoderm of the fss mutant embryo is profoundly caudalized. These findings gave rise to a model for the formation of segment polarity in the zebrafish in which caudal is the default identity for paraxial mesoderm, upon which is patterned rostral identity in an fss-dependent manner. In contrast to this scheme, the caudal marker gene ephrinA1 was recently shown to be down-regulated in fss embryos. We now show that notch5, another caudal identity marker and a component of the Delta/Notch signaling system, is not expressed in the paraxial mesoderm of early segmentation stage fss embryos. We use cell transplantation to create genetic mosaics between fss and wild-type embryos in order to assay the requirement for fss function in notch5 expression. In contrast to the expression of rostral markers, which have a cell-autonomous requirement for fss, expression of notch5 is induced in fss cells at short range by nearby wild-type cells, indicating a cell-non-autonomous requirement for fss function in this process. These new data suggest that segment polarity is created in a three-step process in which cells that have assumed a rostral identity must subsequently communicate with their partially caudalized neighbors in order to induce the fully caudalized state.
Topics: Animals; Body Patterning; Cell Polarity; Gene Expression Regulation, Developmental; Genetic Markers; In Situ Hybridization; Mesoderm; Morphogenesis; Zebrafish
PubMed: 15921674
DOI: 10.1016/j.ydbio.2005.04.012 -
International Journal of Molecular... Aug 2021To ensure the formation of a properly patterned embryo, multiple processes must operate harmoniously at sequential phases of development. This is implemented by mutual... (Review)
Review
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.
Topics: Animals; Cell Differentiation; Embryonic Stem Cells; Gene Expression Regulation, Developmental; Hedgehog Proteins; Humans; Mesoderm; Neural Tube
PubMed: 34502050
DOI: 10.3390/ijms22179141 -
Matrix Biology : Journal of the... Oct 2017Laminin-111 (α1β1γ1) is a member of the Laminin family of extra-cellular matrix proteins that comprises 16 members, components of basement membranes. Laminin-111, one...
Laminin-111 (α1β1γ1) is a member of the Laminin family of extra-cellular matrix proteins that comprises 16 members, components of basement membranes. Laminin-111, one of the first Laminin proteins synthesised during embryogenesis, is required for basement membrane deposition and has essential roles in tissue morphogenesis and patterning. Yet, the mechanisms controlling Laminin-111 expression are poorly understood. We generated a zebrafish transgenic reporter line that reproduces faithfully the expression pattern of lama1, the gene encoding Laminin α1, and we used this reporter line to investigate lama1 transcriptional regulation. Our findings established that lama1 expression is controlled by intronic enhancers, including an enhancer directing expression in the paraxial mesoderm, anterior spinal cord and hindbrain, located in intron 1. We show that Hedgehog signalling is necessary and sufficient for lama1 transcription in the paraxial mesoderm and identify putative Gli/Zic binding sites that may mediate this control. These findings uncover a conserved role for Hedgehog signalling in the control of basement membrane assembly via its transcriptional regulation of lama1, and provide a mechanism to coordinate muscle cell fate specification in the zebrafish embryo.
Topics: Animals; Animals, Genetically Modified; Binding Sites; Enhancer Elements, Genetic; Gene Expression Regulation, Developmental; Hedgehog Proteins; Introns; Laminin; Mesoderm; Promoter Regions, Genetic; Signal Transduction; Transcription, Genetic; Zebrafish; Zebrafish Proteins
PubMed: 27856309
DOI: 10.1016/j.matbio.2016.11.004 -
Developmental Dynamics : An Official... May 2006Fate maps based on quail-chick grafting of avian cephalic neural crest precursors and paraxial mesoderm cells have identified the majority of derivatives from each...
Fate maps based on quail-chick grafting of avian cephalic neural crest precursors and paraxial mesoderm cells have identified the majority of derivatives from each population but have not unequivocally resolved the precise locations of and population dynamics at the interface between them. The relation between these two mesenchymal tissues is especially critical for the development of skeletal muscles, because crest cells play an essential role in their differentiation and subsequent spatial organization. It is not known whether myogenic mesoderm and skeletogenic neural crest cells establish permanent relations while en route to their final destinations, or later at the sites where musculoskeletal morphogenesis is completed. We applied beta-galactosidase-encoding, replication-incompetent retroviruses to paraxial mesoderm, to crest progenitors, or at the interface between mesodermal and overlying neural crest as both were en route to branchial or periocular regions in chick embryos. With respect to skeletal structures, the results identify the avian neural crest:mesoderm boundary at the junction of the supraorbital and calvarial regions of the frontal bone, lateral to the hypophyseal foramen, and rostral to laryngeal cartilages. Therefore, in the chick embryo, most of the frontal and the entire parietal bone are of mesodermal, not neural crest, origin. Within paraxial mesoderm, the progenitors of each lineage display different behaviors. Chondrogenic cells are relatively stationary and intramembranous osteogenic cells move only in transverse planes around the brain. Angioblasts migrate invasively in all directions. Extraocular muscle precursors form tightly aggregated masses that en masse cross the crest:mesoderm interface to enter periocular territories, while branchial myogenic lineages shift ventrally coincidental with the movements of corresponding neural crest cells. En route to the branchial arches, myogenic mesoderm cells do not maintain constant, nearest-neighbor relations with adjacent, overlying neural crest cells. Thus, progenitors of individual muscles do not establish stable, permanent relations with their connective tissues until both populations reach the sites of their morphogenesis within branchial arches or orbital regions.
Topics: Animals; Chick Embryo; Head; Mesoderm; Muscle, Skeletal; Neural Crest; Stem Cells
PubMed: 16395689
DOI: 10.1002/dvdy.20663