A developmental pathway controlling outgrowth of the Xenopus tail bud

Development ◽  
1999 ◽  
Vol 126 (8) ◽  
pp. 1611-1620 ◽  
Author(s):  
C.W. Beck ◽  
J.M. Slack
Keyword(s):  
Normal Development ◽  
Posterior Part ◽  
Neural Plate ◽  
General Mechanism ◽  
Developmental Pathway ◽  
Tail Bud ◽  
Neural Tubes ◽  
Tailbud Stage ◽  
Tail Tip ◽  
Host Embryo

We have developed a new assay to identify factors promoting formation and outgrowth of the tail bud. A piece of animal cap filled with the test mRNAs is grafted into the posterior region of the neural plate of a host embryo. With this assay we show that expression of a constitutively active Notch (Notch ICD) in the posterior neural plate is sufficient to produce an ectopic tail consisting of neural tube and fin. The ectopic tails express the evenskipped homologue Xhox3, a marker for the distal tail tip. Xhox3 will also induce formation of an ectopic tail in our assay. We show that an antimorphic version of Xhox3, Xhox3VP16, will prevent tail formation by Notch ICD, showing that Xhox3 is downstream of Notch signalling. An inducible version of this reagent, Xhox3VP16GR, specifically blocks tail formation when induced in tailbud stage embryos, comfirming the importance of Xhox3 for tail bud outgrowth in normal development. Grafts containing Notch ICD will only form tails if placed in the posterior part of the neural plate. However, if Xwnt3a is also present in the grafts they can form tails at any anteroposterior level. Since Xwnt3a expression is localised appropriately in the posterior at the time of tail bud formation it is likely to be responsible for restricting tail forming competence to the posterior neural plate in our assay. Combined expression of Xwnt3a and active Notch in animal cap explants is sufficient to induce Xhox3, provoke elongation and form neural tubes. Conservation of gene expression in the tail bud of other vertebrates suggests that this pathway may describe a general mechanism controlling tail outgrowth and secondary neurulation.

Neural induction and regionalisation in the chick embryo

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 729-741 ◽  
Author(s):  
K.G. Storey ◽  
J.M. Crossley ◽  
E.M. De Robertis ◽  
W.E. Norris ◽  
C.D. Stern
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Molecular Markers ◽  
Chick Embryo ◽  
Normal Development ◽  
Neural Induction ◽  
Stage 4 ◽  
Embryo Chick ◽  
Host Embryo ◽  
Embryonic Region

Induction and regionalisation of the chick nervous system were investigated by transplanting Hensen's node into the extra-embryonic region (area opaca margin) of a host embryo. Chick/quail chimaeras were used to determine the contributions of host and donor tissue to the supernumerary axis, and three molecular markers, Engrailed, neurofilaments (antibody 3A10) and XlHbox1/Hox3.3 were used to aid the identification of particular regions of the ectopic axis. We find that the age of the node determines the regions of the nervous system that form: young nodes (stages 2–4) induced both anterior and posterior nervous system, while older nodes (stages 5–6) have reduced inducing ability and generate only posterior nervous system. By varying the age of the host embryo, we show that the competence of the epiblast to respond to neural induction declines after stage 4. We conclude that during normal development, the initial steps of neural induction take place before stage 4 and that anteroposterior regionalisation of the nervous system may be a later process, perhaps associated with the differentiating notochord. We also speculate that the mechanisms responsible for induction of head CNS differ from those that generate the spinal cord: the trunk CNS could arise by homeogenetic induction by anterior CNS or by elongation of neural primordia that are induced very early.

A study of the properties, morphogenetic potencies and prospective fate of outer and inner layers of ectodermal and chordamesodermal regions during gastrulation, in various Anuran amphibians

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 67-86
Author(s):  
T. A. Dettlaff
Keyword(s):  
Outer Layer ◽  
Normal Development ◽  
Neural Plate ◽  
Ependymal Cells ◽  
Epithelial Layer ◽  
Bombina Bombina ◽  
Cell Layers ◽  
The Brain ◽  
Early Gastrula

In both the ectodermal and the chordamesodermal regions of Anuran embryos, the outer layer of cells possesses epithelial properties and has the same restricted morphogenetic potencies. It is thus interchangeable between the regions, capable of epiboly and, when underlain by notochord material, of the formation of bottle-shaped cells as at the blastoporal groove, and invagination. When taken from the chordamesoderm region, this outer layer has no inducing effect on the ectoderm of the early gastrula. In normal development the outer layer of the neural plate takes an active part in forming the neural tube cavity. It gives rise to the neuroepithelial roof of the diencephalon and medulla oblongata and, when underlain by neuroblasts that develop from the inner cell layers, to ependymal cells of the brain wall. The outer layer of the notochord material is included in the epithelial layer underlying the roof of the gastrocoel - the hypochordal plate. The inner layers of these regions consist of loosely arranged cells and normally have no epithelial properties although, when taken from the ectoderm region, they may acquire such properties upon long-term contact with the environment. However they have wide morphogenetic potencies; the differences in these potencies between cells taken from the various presumptive regions being less than the differences between outer and inner cell layers in each region. Maps are provided which show the arrangement of presumptive rudiments in the ectoderm and chordamesoderm on sagittal sections through Bombina bombina embryos in early and late gastrulation.

Specification of the anterior hindbrain and establishment of a normal mid/hindbrain organizer is dependent on Gbx2 gene function

Development ◽  
1997 ◽  
Vol 124 (15) ◽  
pp. 2923-2934 ◽  
Author(s):  
K.M. Wassarman ◽  
M. Lewandoski ◽  
K. Campbell ◽  
A.L. Joyner ◽  
J.L. Rubenstein ◽  
...  
Keyword(s):  
Normal Development ◽  
Motor Nerve ◽  
Homeobox Gene ◽  
Neural Plate ◽  
Mouse Embryos ◽  
Loss Of Function ◽  
Isthmic Nuclei ◽  
Signaling Center ◽  
Derivatives Of ◽  
Anterior Posterior

Analysis of mouse embryos homozygous for a loss-of-function allele of Gbx2 demonstrates that this homeobox gene is required for normal development of the mid/hindbrain region. Gbx2 function appears to be necessary at the neural plate stage for the correct specification and normal proliferation or survival of anterior hindbrain precursors. It is also required to maintain normal patterns of expression at the mid/hindbrain boundary of Fgf8 and Wnt1, genes that encode signaling molecules thought to be key components of the mid/hindbrain (isthmic) organizer. In the absence of Gbx2 function, isthmic nuclei, the cerebellum, motor nerve V, and other derivatives of rhombomeres 1–3 fail to form. Additionally, the posterior midbrain in the mutant embryos appears to be extended caudally and displays abnormalities in anterior/posterior patterning. The failure of anterior hindbrain development is presumably due to the loss of Gbx2 function in the precursors of the anterior hindbrain. However, since Gbx2 expression is not detected in the midbrain it seems likely that the defects in midbrain anterior/posterior patterning result from an abnormal isthmic signaling center. These data provide genetic evidence for a link between patterning of the anterior hindbrain and the establishment of the mid/hindbrain organizer, and identify Gbx2 as a gene required for these processes to occur normally.

Contribution of maternal factors and cellular interaction to determination of archenteron in the starfish embryo

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2619-2628 ◽  
Author(s):  
R. Kuraishi ◽  
L. Osanai
Keyword(s):  
Alkaline Phosphatase ◽  
Normal Development ◽  
Early Stage ◽  
Posterior Part ◽  
Immature Oocyte ◽  
Cellular Interaction ◽  
Cell Stage ◽  
Cytoplasmic Factor ◽  
Animal Pole

Contribution of maternal cytoplasmic factors and cellular interaction to determination of archenteron in a starfish embryo was analyzed by (1) examining temporal and positional pattern of expression of an endoderm-specific enzyme, alkaline phosphatase, (2) deleting the vegetal polar fragment from an immature oocyte and (3) changing the orientation of a blastomere within an early stage embryo. The archenteron (and the differentiated digestive tract) of Asterina pectinifera was divided into three areas based on the time of start of alkaline phosphatase expression. At 27 hours after 1-methyladenine treatment, the whole archenteron except the anterior end started to express alkaline phosphatase. The anterior negative area differentiated into mesodermal tissues such as mesenchyme cells and anterior coelomic pouches (anterior mesodermal area). The alkaline-phosphatase-positive area 1 gave rise to the esophagus and the anterior end of the stomach. Alkaline-phosphatase-positive area 2, which was gradually added to the posterior end of the archenteron after 30 hours, became alkaline-phosphatase- positive and formed the middle-to-posterior part of the stomach and the intestine. When the vegetal oocyte fragment, the volume of which was more than 8% of that of the whole oocyte, was removed from the immature oocyte, archenteron formation was strongly suppressed. However, when the volume deleted was less than 6%, most of the larvae started archenteron formation before the intact controls reached the mesenchyme-migration stage (30 hours). Although cells in the alkaline-phosphatase-positive area 2 are added to the posterior end of the archenteron after 30 hours in normal development (R. Kuraishi and K. Osanai (1992) Biol. Bull. Mar. Biol. Lab., Woods Hole 183, 258–268), few larvae started gastrulation after 30 hours. Estimation of the movement of the oocyte cortex during the early development suggested that the area that inherits the cortex of the 7% area coincides with the combined area of anterior mesodermal area and alkaline-phosphatase-positive area 1. When one of the blastomeres was rotated 180° around the axis of apicobasal polarity at the 2-cell stage to make its vegetal pole face the animal pole of the other blastomere, two archentera formed at the separated vegetal poles. Intracellular injection of tracers showed that cells derived from the animal blastomere, which gives rise to the ectoderm in normal development, stayed in the outer layer until 30 hours; a proportion of them then entered the archenteron gradually. The involuted animal cells expressed alkaline phosphatase and were incorporated into the middle-to-posterior part of the stomach and the intestine. These results suggest that anterior mesodermal area and alkaline-phosphatase-positive area 1 are determined by cytoplasmic factor(s) that had already been localized in their presumptive areas. In contrast, alkaline-phosphatase-positive area 2 becomes the endoderm by homoiogenetic induction from the neighboring area on the vegetal side, namely alkaline-phosphatase-positive area 1.

The homeodomain-containing gene Xdbx inhibits neuronal differentiation in the developing embryo

Development ◽  
2000 ◽  
Vol 127 (13) ◽  
pp. 2945-2954 ◽  
Author(s):  
A.A. Gershon ◽  
J. Rudnick ◽  
L. Kalam ◽  
K. Zimmerman
Keyword(s):  
Neuronal Differentiation ◽  
Normal Development ◽  
Early Embryo ◽  
Neural Plate ◽  
Neural Progenitors ◽  
Expression Domain ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Early Neurogenesis

The development of the vertebrate nervous system depends upon striking a balance between differentiating neurons and neural progenitors in the early embryo. Our findings suggest that the homeodomain-containing gene Xdbx regulates this balance by maintaining neural progenitor populations within specific regions of the neuroectoderm. In posterior regions of the Xenopus embryo, Xdbx is expressed in a bilaterally symmetric stripe that lies at the middle of the mediolateral axis of the neural plate. This stripe of Xdbx expression overlaps the expression domain of the proneural basic/helix-loop-helix-containing gene, Xash3, and is juxtaposed to the expression domains of Xenopus Neurogenin related 1 and N-tubulin, markers of early neurogenesis in the embryo. Xdbx overexpression inhibits neuronal differentiation in the embryo and when co-injected with Xash3, Xdbx inhibits the ability of Xash3 to induce ectopic neurogenesis. One role of Xdbx during normal development may therefore be to restrict spatially neuronal differentiation within the neural plate, possibly by altering the neuronal differentiation function of Xash3.

Properties of the primary organization field in the embryo of Xenopus laevis

Development ◽  
1973 ◽  
Vol 30 (2) ◽  
pp. 283-300
Author(s):  
J. Cooke
Keyword(s):  
Organizer Region ◽  
Positional Information ◽  
Host Cells ◽  
Normal Embryo ◽  
Tail Bud ◽  
Essentially Normal ◽  
Head Formation ◽  
Source Data ◽  
Primary Organization ◽  
Host Embryo

Patterns of individuation occurring in the primary embryonic axis of Xenopus following excision of the organizer region of the early gastrula are described. In some 70% of cases the information for induction of the complete head is qualitatively restored by the time of cell determination, giving rise to an essentially normal embryo. In some 40% of cases a second posterior axis of bilaterality is formed, causing development of a secondary anus, tail-fin and spinal cord, and often somites. The probabilities of twinning in the tailfield and of failure to complete apical regulation (= head formation) are largely independent. After such excision of the head organizer region, a delay of some 3 h in the schedule of visible differentiation in the neurula/tail-bud embryo is commonly incurred, whether or not apical regulation is successful. When the apex is excised from a host embryo which has already contained for some hours a second apex (= head organizer) as described in an earlier paper, that grafted apex then captures a considerably increased territory in the host material, as seen from the size of the individuation field finally caused by it. Such a shift across host cells, of the boundary between fields of positional information due to two organizers, is not seen under any conditions where these are left intact, or where host excision is carried out soon after implanting the donor organizer. In discussing the results and reconciling them with earlier observations, it is shown that they strongly suggest the presence of local polar (i.e. vectorial) properties in the presumptive mesoderm, due to signals from restricted regions which have achieved a special apical state. Repolarization of cells by a new organizer is not very rapid, and may spread decrementally from the source. Data on further delays in development, caused by the presence of the second organizer during regulation in the host apex, suggest that one organizer may act directly on cells elsewhere to delay or prevent the restoration of the apical state there.

Activation of Pax6 depends on somitogenesis in the chick embryo cervical spinal cord

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 587-596 ◽  
Author(s):  
F. Pituello ◽  
F. Medevielle ◽  
F. Foulquier ◽  
A.M. Duprat
Keyword(s):  
Spinal Cord ◽  
Cervical Spinal Cord ◽  
Homeobox Gene ◽  
Neural Plate ◽  
Paraxial Mesoderm ◽  
Presomitic Mesoderm ◽  
Pax6 Expression ◽  
The Central Nervous System ◽  
Initial Activation ◽  
Host Embryo

Pax6 is a paired-type homeobox gene expressed in discrete regions of the central nervous system. In the spinal cord of 7- to 10-somite-stage chicken embryos, Pax6 is not detected within the caudal neural plate, but is progressively upregulated in the neuroepithelium neighbouring each newly formed somite. In the present study, we accumulate data suggesting that this initial activation of Pax6 is controlled via the paraxial mesoderm in correlation with somitogenesis. First, we observed that high levels of Pax6 expression occur independently of the presence of SHH-expressing cells when neural plates are maintained in culture in the presence of paraxial mesoderm. Second, grafting a somite caudally under a neural plate that has not yet expressed the gene induces a premature activation of Pax6. Furthermore, after the graft of a somite, a period of incubation corresponding to the individualization of a new somite in the host embryo produces an appreciable activation of Pax6. Conversely, Pax6 expression is delayed under conditions where somitogenesis is retarded, i.e., when the rostral part of the presomitic mesoderm is replaced by the same tissue isolated more caudally. Finally, Pax6 transcripts disappear from the neural tube when a somite is replaced by presomitic mesoderm, suggesting that the somite is also involved in the maintenance of Pax6 expression in the developing spinal cord. All together these observations lead to the proposal that Pax6 activation is triggered by the paraxial mesoderm in phase with somitogenesis in the cervical spinal cord.

Ectopic expression ofGcm1induces congenital spinal cord abnormalities

Development ◽  
2002 ◽  
Vol 129 (16) ◽  
pp. 3957-3964 ◽  
Author(s):  
Brahim Nait-Oumesmar ◽  
Barbara Stecca ◽  
Girish Fatterpekar ◽  
Thomas Naidich ◽  
Joshua Corbin ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Transgene Expression ◽  
Ectopic Expression ◽  
Spinal Column ◽  
Life Time ◽  
Tail Bud ◽  
Neural Tubes ◽  
Motor Disabilities ◽  
Transgenic Lines ◽  
Stimulation Of

Brief ectopic expression of Gcm1 in mouse embryonic tail bud profoundly affects the development of the nervous system. All mice from 5 independently derived transgenic lines exhibited either one or both of two types of congenital spinal cord pathologies: failure of the neural tube to close (spina bifida) and multiple neural tubes (diastematomyelia). Because the transgene is expressed only in a restricted caudal region and only for a brief interval (E8.5 to E13.5), there was no evidence of embryonic lethality. The dysraphisms develop during the period and within the zone of transgene expression. We present evidence that these dysraphisms result from an inhibition of neuropore closure and a stimulation of secondary neurulation. After transgene expression ceases, the spinal dysraphisms are progressively resolved and the neonatal animals, while showing signs of scarring and tissue resorption, have a closed vertebral column. The multiple spinal cords remain but are enclosed in a single spinal column as in the human diastematomyelia. The animals live a normal life time, are fertile and do not exhibit any obvious weakness or motor disabilities.

Differentiation of Ectoderm Implanted into the Primordium of the Limb Bud in the Amphibian Embryo and its Influence upon the Limb

1946 ◽  
Vol 22 (3-4) ◽  
pp. 101-106
Author(s):  
WALTER BRANDT
Keyword(s):  
Body Wall ◽  
Distal Part ◽  
The Body ◽  
Limb Bud ◽  
Muscle Fibres ◽  
Tail Bud ◽  
Amphibian Embryo ◽  
Microscopical Analysis ◽  
Proximal Half ◽  
Host Embryo

1. A microscopical analysis was made concerning the differentiation of ectoderm cut from the tip of the tail-bud of an amphibian embryo (Amblystoma mexicanum, stages 35-37, Harrison) after its implantation into the primordium of the limb-bud of a host embryo 3-5 weeks after operation. 2. The ectoderm which lay deep in the tissues of the limb differentiated either into solid epithelial cords or into cysts. 3. The ectoderm which was attached outside the limb differentiated into notched ectodermal elevations which included a mesenchymal core. 4. A microscopical analysis was made concerning the development of deformities of limbs as the result of the operation. 5. The scapula may be divided into isolated pieces, bundles of muscle fibres separating the pieces from each other. 6. A supernumerary piece of cartilage can develop close to the cartilage of the scapula. 7. The suprascapula may be absent and its place taken by a mass of muscle fibres. 8. A phocomelias may be produced when the whole length of the humerus and the elbow-joint lies inside the body wall. In this case the implanted ectoderm covers the area where the limb would normally develop. 9. The humerus may be reduplicated. 10. The humerus may be too short. 11. The proximal half of the humerus may possess a diameter different from that of the distal half. 12. One skeletal element only of the forearm (radius or ulna) may be present when the place which would normally be occupied by one of these elements was taken by implanted ectoderm. 13. The elements of the carpus and of the hand may appear irregularly scattered throughout the tissues of the distal part of the limb. In these cases the implanted ectoderm was attached to the surface of the distal end of the limb. 14. The fingers can show: (a) abnormal positions, (b) abnormal numbers, (c) syndactylias, (d) one finger too long, others too short.

Somitogenesis in amphibia

Development ◽  
1983 ◽  
Vol 76 (1) ◽  
pp. 157-176
Author(s):  
Tom Elsdale ◽  
Duncan Davidson
Keyword(s):  
Central Region ◽  
Tail Bud ◽  
Temperature Shock ◽  
Anteroposterior Axis ◽  
Tissue Change ◽  
Narrow Zone ◽  
Tail Tip

Following neurulation, the frog segments c.40 somites and concurrently undergoes a striking elongation along the anteroposterior axis. This elongation (excluding the head) is largely the result of a presegmental extension of posterior tissue with a lesser contribution from the extension of segmented tissue. Presegmental extension is entirely the result of activity within a narrow zone of extension that occupies the central region in the tail bud. Within the zone of extension, a minimum of six prospective somites undergo an eight- to ten-fold extension along the axis. The zone passes posteriorly across the tissue of the tail tip. The anterior of the tail bud contains three extended prospective somites in the course of segmentation. The anterior boundary of the zone of extension coincides in space exactly with the anterior boundary of the zone of abnormal segmentation that results from temperature shock. This means that extension ceases immediately before the sudden tissue change associated with segmentation.

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