Onset of the segmentation clock in the chick embryo: evidence for oscillations in the somite precursors in the primitive streak

Development ◽  
2002 ◽  
Vol 129 (5) ◽  
pp. 1107-1117 ◽  
Author(s):  
Caroline Jouve ◽  
Tadahiro Iimura ◽  
Olivier Pourquie
Keyword(s):  
Continuous Process ◽  
Notch Pathway ◽  
Primitive Streak ◽  
The Body ◽  
Paraxial Mesoderm ◽  
Segmentation Clock ◽  
Head Mesoderm ◽  
Dynamic Expression ◽  
Mesoderm Formation ◽  
Cyclic Gene

Vertebrate somitogenesis is associated with a molecular oscillator, the segmentation clock, which is defined by the periodic expression of genes related to the Notch pathway such as hairy1 and hairy2 or lunatic fringe (referred to as the cyclic genes) in the presomitic mesoderm (PSM). Whereas earlier studies describing the periodic expression of these genes have essentially focussed on later stages of somitogenesis, we have analysed the onset of the dynamic expression of these genes during chick gastrulation until formation of the first somite. We observed that the onset of the dynamic expression of the cyclic genes in chick correlated with ingression of the paraxial mesoderm territory from the epiblast into the primitive streak. Production of the paraxial mesoderm from the primitive streak is a continuous process starting with head mesoderm formation, while the streak is still extending rostrally, followed by somitic mesoderm production when the streak begins its regression. We show that head mesoderm formation is associated with only two pulses of cyclic gene expression. Because such pulses are associated with segment production at the body level, it suggests the existence of, at most, two segments in the head mesoderm. This is in marked contrast to classical models of head segmentation that propose the existence of more than five segments. Furthermore, oscillations of the cyclic genes are seen in the rostral primitive streak, which contains stem cells from which the entire paraxial mesoderm originates. This indicates that the number of oscillations experienced by somitic cells is correlated with their position along the AP axis.

Expression pattern of the Brachyury gene in whole-mount TWis/TWis mutant embryos

Development ◽  
1991 ◽  
Vol 113 (3) ◽  
pp. 913-917 ◽  
Author(s):  
B.G. Herrmann
Keyword(s):  
Gene Product ◽  
Gene Dosage ◽  
Primitive Streak ◽  
The Body ◽  
Primary Defect ◽  
Whole Mount ◽  
Mesoderm Formation ◽  
Axis Elongation ◽  
Severe Disturbance ◽  
Axial Development

The murine Brachyury (T) gene is required in mesoderm formation. Mutants carrying different T alleles show a graded severity of defects correlated with gene dosage along the body axis. The phenotypes range from shortening of the tail to the malformation of sacral vertebrae in heterozygotes, and to disruption of trunk development and embryonic death in homozygotes. Defects include a severe disturbance of the primitive streak, an early cessation of mesoderm formation and absence of the allantois and notochord, the latter resulting in an abnormality of the neural tube and somites. The T gene is expressed in nascent mesoderm and in the notochord of wild-type embryos. Here the expression of T in whole-mount mutant embryos homozygous for the T allele TWis is described. The TWis gene product is altered, but the TWis/TWis phenotype is very similar to that of T/T embryos which lack T. In early TWis/TWis embryos T expression is normal, but ceases prematurely during early organogenesis coincident with a cessation of mesoderm formation. The archenteron/node region is disrupted and the extension of the notochord precursor comes to a halt, followed by a decrease and finally a complete loss of T gene expression in the primitive streak and the head process/notochord precursor. It appears that the primary defect of the mutant embryo is the disruption of the notochord precursor in the node region which is required for axis elongation. Thus the T gene product is directly or indirectly involved in the organization of axial development.

Memoirs: Blastopore Mesoderm and Metameric Segmentation

1885 ◽  
Vol s2-25 (97) ◽  
pp. 15-28
Author(s):  
W. H. CALDWELL
Keyword(s):  
Rapid Growth ◽  
Primitive Streak ◽  
The Body ◽  
The Other ◽  
Terminal Position ◽  
Posterior Pair ◽  
Mesoderm Formation ◽  
Anterior Pair

Facts in the development of Phoronis-- 1. The blastopore gives rise to both mouth and anus. 2. The mesoderm arises in an anterior pair of endoblastic modified diverticula, and in a posterior pair of ectoblastic diverticula connected by a few mesodermic cells derived from the middle of a primitive streak. 3. The nephridial openings to the exterior are parts of the blastopore. Preliminary interpretation suggested by these facts of the development of Phoronis-- 1. A gastraea with slit-like mouth and a pair of lateral diverticula giving rise to mesoderm was the ancestor of Phoronis. 2. The rapid growth of ectoderm in the median ventral line nearly succeeded in destroying the continuity of the primitive streak. 3. The necessity of an early attainment of a terminal position by the anus caused the ectoderm to grow more rapidly than, the emdoblast, and resulted in a division of the mesoderm into anterior and posterior parts. 4. The nephridia, which might have remained either wholly or in part with the anterior, have attached themselves entirely to the posterior mesoderm. Extension of this interpretation to the other Tripleblastiea-- 1. Phoronis is the first step towards a complete division of the blastopore. The inducing cause of such division is the elongation of the body, while the endoblast is still in an embryonic condition. 2. The division of blastopore caused the division of mesoderm. 3. The division of mesoderm results in-- i. The masking of the original mode of mesoderm formation. ii. Metameric segmentation.

scholarly journals Dynamics of primitive streak regression controls the fate of neuro-mesodermal progenitors in the chicken embryo

2020 ◽  
Author(s):  
Charlene Guillot ◽  
Arthur Michaut ◽  
Brian Rabe ◽  
Olivier Pourquié
Keyword(s):  
Chicken Embryo ◽  
Single Cells ◽  
Primitive Streak ◽  
Clonal Analysis ◽  
Lineage Tracing ◽  
The Body ◽  
Paraxial Mesoderm ◽  
Axis Formation ◽  
Vertebrate Development ◽  
Tail Bud

AbstractIn classical descriptions of vertebrate development, the segregation of the three embryonic germ layers is completed by the end of gastrulation. Body formation then proceeds in a head to tail fashion by progressive deposition of lineage committed progenitors during regression of the Primitive Streak (PS) and tail bud (Pasteels, 1937b; Stern, 2004). Identification of Neuro-Mesodermal Progenitors (NMPs) contributing to both musculo-skeletal precursors (paraxial mesoderm) and spinal cord during axis formation by retrospective clonal analysis challenged these notions (Henrique et al., 2015; Tzouanacou et al., 2009). However, in amniotes such as mouse and chicken, the precise identity and localization of these cells has remained unclear despite a wealth of fate mapping analyses of the PS region. Here, we use lineage tracing in the chicken embryo to show that single cells located in the SOX2/T positive anterior PS region contribute to both neural and mesodermal lineages in the trunk and tail, but only express this bipotential fate with some delay. We demonstrate that posterior to anterior gradients of convergence speed and ingression along the PS gradually lead to exhaustion of all mesodermal precursor territories except for NMPs where limited ingression and increased proliferation maintain and amplify this pool of axial progenitors. As a result, most of the remaining mesodermal precursors from the PS in the tail bud are bipotential NMPs. Together, our results provide a novel understanding of the contribution of the PS and tail bud to the formation of the body of amniote embryos.

scholarly journals Dynamics of primitive streak regression controls the fate of neuromesodermal progenitors in the chicken embryo

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Charlene Guillot ◽  
Yannis Djeffal ◽  
Arthur Michaut ◽  
Brian Rabe ◽  
Olivier Pourquié
Keyword(s):  
Single Cell ◽  
Cell Population ◽  
Chicken Embryo ◽  
Primitive Streak ◽  
Lineage Tracing ◽  
The Body ◽  
Paraxial Mesoderm ◽  
Axis Formation ◽  
Tail Bud ◽  
Transcriptomic Signature

In classical descriptions of vertebrate development, the segregation of the three embryonic germ layers completes by the end of gastrulation. Body formation then proceeds in a head to tail fashion by progressive deposition of lineage-committed progenitors during regression of the primitive streak (PS) and tail bud (TB). The identification by retrospective clonal analysis of a population of neuromesodermal progenitors (NMPs) contributing to both musculoskeletal precursors (paraxial mesoderm) and spinal cord during axis formation challenged these notions. However, classical fate mapping studies of the PS region in amniotes have so far failed to provide direct evidence for such bipotential cells at the single-cell level. Here, using lineage tracing and single-cell RNA sequencing in the chicken embryo, we identify a resident cell population of the anterior PS epiblast, which contributes to neural and mesodermal lineages in trunk and tail. These cells initially behave as monopotent progenitors as classically described and only acquire a bipotential fate later, in more posterior regions. We show that NMPs exhibit a conserved transcriptomic signature during axis elongation but lose their epithelial characteristicsin the TB. Posterior to anterior gradients of convergence speed and ingression along the PS lead to asymmetric exhaustion of PS mesodermal precursor territories. Through limited ingression and increased proliferation, NMPs are maintained and amplified as a cell population which constitute the main progenitors in the TB. Together, our studies provide a novel understanding of the PS and TB contribution through the NMPs to the formation of the body of amniote embryos.

scholarly journals Reproductive biology, embryonic development and matrotrophy in the phylactolaemate bryozoan Plumatella casmiana

2021 ◽  
Author(s):  
Julian Bibermair ◽  
Andrew N. Ostrovsky ◽  
Andreas Wanninger ◽  
Thomas Schwaha
Keyword(s):  
Embryonic Development ◽  
Embryo Sac ◽  
The Body ◽  
Transcellular Transport ◽  
Cell Contacts ◽  
Transmission Electron ◽  
Distal Side ◽  
Early Embryos ◽  
Mesoderm Formation ◽  
Cytoplasmic Processes

AbstractBryozoa is a phylum of aquatic, colonial suspension-feeders within the Lophotrochozoa. In the Phylactolaemata embryonic development occurs in an internal brood sac on the body wall accompanied by extraembryonic nutrition. Owing to previous contradictive descriptions, many aspects of their sexual reproduction require restudy. Consequently, this study analyses embryogenesis of the freshwater bryozoan Plumatella casmiana by serial sections, 3D reconstruction and transmission electron microscopy. Early embryos cleave and soon develop into blastulae with a small central cavity. The mesoderm forms by delamination starting from the distal side towards the proximal end. In later embryos two polypides form on the posterior side that ultimately will be covered by a ciliated mantle in the larva. Embryos increase in size during development and form temporary cell contacts to the embryo sac. Mesodermal cells of the embryo sac show signs of transcellular transport indicating that embryos are nourished by transferring nutrients from the maternal coelom towards the brood cavity. This study clarifies several details such as mesoderm formation and the onset of bud development. Embryos are connected to their respective embryo sacs by a variety of temporary cytoplasmic processes formed by both tissues during embryogenesis, including a ‘placental’ ring zone. Although ultrastructural data of these cell contacts are not entirely conclusive about their function, we suggest that embryos absorb nutrients via the entire surface. The close opposition of embryos to the embryo sac implies placentation as matrotrophic mode in phylactolaemate bryozoans, with embryo sacs acting as placental analogues.

Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 711-720 ◽  
Author(s):  
H.V. Isaacs ◽  
D. Tannahill ◽  
J.M. Slack
Keyword(s):  
Specific Activity ◽  
Biological Properties ◽  
The Body ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Blastula Stage ◽  
Mesoderm Formation ◽  
Low Levels

We have cloned and sequenced a new member of the fibroblast growth factor family from Xenopus laevis embryo cDNA. It is most closely related to both mammalian kFGF (FGF-4) and FGF-6 but as it is not clear whether it is a true homologue of either of these genes we provisionally refer to it as XeFGF (Xenopus embryonic FGF). Two sequences were obtained, differing by 11% in derived amino acid sequence, which probably represent pseudotetraploid variants. Both the sequence and the behaviour of in vitro translated protein indicates that, unlike bFGF (FGF-2), XeFGF is a secreted molecule. Recombinant XeFGF protein has mesoderm-inducing activity with a specific activity similar to bFGF. XeFGF mRNA is expressed maternally and zygotically with a peak during the gastrula stage. Both probe protection and in situ hybridization showed that the zygotic expression is concentrated in the posterior of the body axis and later in the tailbud. Later domains of expression were found near the midbrain/hindbrain boundary and at low levels in the myotomes. Because of its biological properties and expression pattern, XeFGF is a good candidate for an inducing factor with possible roles both in mesoderm induction at the blastula stage and in the formation of the anteroposterior axis at the gastrula stage.

Mediolateral somitic origin of ribs and dermis determined by quail-chick chimeras

Development ◽  
2000 ◽  
Vol 127 (21) ◽  
pp. 4611-4617 ◽  
Author(s):  
I. Olivera-Martinez ◽  
M. Coltey ◽  
D. Dhouailly ◽  
O. Pourquie
Keyword(s):  
Skeletal Muscles ◽  
Body Wall ◽  
Primitive Streak ◽  
Axial Skeleton ◽  
Lateral Compartment ◽  
The Body ◽  
The Other ◽  
Lateral Part ◽  
Respective Contribution ◽  
Epaxial Muscles

Somites are transient mesodermal structures giving rise to all skeletal muscles of the body, the axial skeleton and the dermis of the back. Somites arise from successive segmentation of the presomitic mesoderm (PSM). They appear first as epithelial spheres that rapidly differentiate into a ventral mesenchyme, the sclerotome, and a dorsal epithelial dermomyotome. The sclerotome gives rise to vertebrae and ribs while the dermomyotome is the source of all skeletal muscles and the dorsal dermis. Quail-chick fate mapping and diI-labeling experiments have demonstrated that the epithelial somite can be further subdivided into a medial and a lateral moiety. These two subdomains are derived from different regions of the primitive streak and give rise to different sets of muscles. The lateral somitic cells migrate to form the musculature of the limbs and body wall, known as the hypaxial muscles, while the medial somite gives rise to the vertebrae and the associated epaxial muscles. The respective contribution of the medial and lateral somitic compartments to the other somitic derivatives, namely the dermis and the ribs has not been addressed and therefore remains unknown. We have created quail-chick chimeras of either the medial or lateral part of the PSM to examine the origin of the dorsal dermis and the ribs. We demonstrate that the whole dorsal dermis and the proximal ribs exclusively originates from the medial somitic compartment, whereas the distal ribs derive from the lateral compartment.

scholarly journals Comparative Study About Youth Body Height by Age Group and BMI at Medical Faculty of UMM

2020 ◽  
Vol 16 (1) ◽  
pp. 50
Author(s):  
Anung Putri Ilahika ◽  
Wiby Fahmi Wijaya
Keyword(s):  
Body Mass Index ◽  
Medical Students ◽  
Comparative Study ◽  
Body Mass ◽  
Growth And Development ◽  
Continuous Process ◽  
Age Groups ◽  
Medical Faculty ◽  
The Body ◽  
Measurement Results

Growth and development is a continuous process in the process of reaching adulthood, including the teenage stage. The problem that is often faced is physical change. Adolescent physical changes that appear are the increase in height and weight which affects the Body Mass Index (BMI). Height is one of the important things in adolescent growth and development. which is affected by genetic and environmental factors. The peak of growth in adolescents is different between boys and girls, so the pattern of height and BMI are also different. The purpose of this study was to determine differences in adolescent height based on age groups and BMI in Medical Faculty of UMM. This research is a comparative study by taking a sample of 100 medical students of UMM who have an age range of 17-20 years. The data to be taken is height measured using a MIC scale health scale ratio ratio. The measurement results have a numerical scale with units of centimeters (cm). Body mass index (BMI) is an index obtained from the division of body weight with height2. The measurement results are stated in kg / m2. All data obtained will be analyzed using the ANOVA comparative test. ANOVA test results generated p value in the two groups of students> 0.05 which concluded that the mean height of the student body based on age and BMI was not significantly different (not significant) statistically for both men and women. The conclusion from this study there were no differences in adolescent height based on age groups and BMI among medical students of UMM.

A Wnt5a pathway underlies outgrowth of multiple structures in the vertebrate embryo

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1211-1223 ◽  
Author(s):  
T.P. Yamaguchi ◽  
A. Bradley ◽  
A.P. McMahon ◽  
S. Jones
Keyword(s):  
Progenitor Cells ◽  
Primitive Streak ◽  
The Body ◽  
Loss Of Function ◽  
Proliferating Cells ◽  
Precise Control ◽  
Cellular Processes ◽  
Cell Proliferation And Differentiation ◽  
Primary Body ◽  
Multiple Structures

Morphogenesis depends on the precise control of basic cellular processes such as cell proliferation and differentiation. Wnt5a may regulate these processes since it is expressed in a gradient at the caudal end of the growing embryo during gastrulation, and later in the distal-most aspect of several structures that extend from the body. A loss-of-function mutation of Wnt5a leads to an inability to extend the A-P axis due to a progressive reduction in the size of caudal structures. In the limbs, truncation of the proximal skeleton and absence of distal digits correlates with reduced proliferation of putative progenitor cells within the progress zone. However, expression of progress zone markers, and several genes implicated in distal outgrowth and patterning including Distalless, Hoxd and Fgf family members was not altered. Taken together with the outgrowth defects observed in the developing face, ears and genitals, our data indicates that Wnt5a regulates a pathway common to many structures whose development requires extension from the primary body axis. The reduced number of proliferating cells in both the progress zone and the primitive streak mesoderm suggests that one function of Wnt5a is to regulate the proliferation of progenitor cells.

Fractured and Effaced Façades

2021 ◽  
pp. 162-185
Author(s):  
Ron J. Popenhagen
Keyword(s):  
Sensory Deprivation ◽  
The Body ◽  
Human Form ◽  
Antonin Artaud ◽  
Body Form ◽  
Dynamic Expression ◽  
Marc Chagall ◽  
Dynamic Form ◽  
The Face ◽  
Involuntary Displacement

The rise of Fascism in Europe and its aftermath rest ever in the background of Chapter Six and its collection of ‘Disfigured Bodies’. The face and gaze of Antonin Artaud best characterises the tone of this series of violent destructions, lost ones and the isolated (like Picasso in occupied Paris). Amid ‘Veiled and Displaced Faces’ and ‘Empty Gazes’, involuntary displacement and sensory deprivation haunt representations of the human form. The head and human figures presented here are almost unrecognisable when re-conceived by a metteur en scène like Étienne Decroux or a sculptor like Alberto Giacometti. Marc Chagall, in exile, invents fantasy forms that masquerade the figures of opera and ballet performers with colourful, cushioned exteriors in magical scenographic spaces. Experimentation with actor as object manipulator or manipulacteur, like the scenographic, dynamic form in some of Jacques Lecoq’s work, displace dynamic expression to ‘things’ outside of the body form itself. In Chapter Six, some non-verbal performers search for statements beyond language: texts in the materiality of space itself. The abstracted silhouette speaks as depersonalised, masquerading image.

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