Evolutionary dissociation between cleavage, cell lineage and embryonic axes in sea urchin embryos

Development ◽  
1992 ◽  
Vol 114 (4) ◽  
pp. 931-938 ◽  
Author(s):  
J.J. Henry ◽  
K.M. Klueg ◽  
R.A. Raff
Keyword(s):  
Sea Urchin ◽  
Cleavage Plane ◽  
Cell Lineage ◽  
Frontal Plane ◽  
Individual Species ◽  
Cleavage Pattern ◽  
Embryonic Axes ◽  
Animal Pole ◽  
Dorsoventral Axis ◽  
The Relationship

Using vital dye staining and the microinjection of fluorescent cell lineage-autonomous tracers, the relationship between the first cleavage plane and the prospective larval dorsoventral axis was examined in several sea urchin species, including: Strongylocentrotus purpuratus, S. droebachiensis, Lytechinus pictus, Clypeaster rosaceus, Heliocidaris tuberculata and H. erythrogramma. The results indicate that there is no single relationship between the early cleavage pattern and the dorsoventral axis for all sea urchins; however, specific relationships exist for individual species. In S. purpuratus the first cleavage plane occurs at an angle 45 degrees clockwise with respect to the prospective dorsoventral axis in most cases, as viewed from the animal pole. On the other hand, in S. droebachiensis, L. pictus and H. tuberculata, the first cleavage plane generally corresponds with the plane of bilateral symmetry. There does not appear to be a predominant relationship between the first cleavage plane and the dorsoventral axis in C. rosaceus. In the direct-developing sea urchin H. erythrogramma the first cleavage plane bisects the dorsoventral axis through the frontal plane. Clearly, evolutionary differences have arisen in the relationship between cleavage pattern and developmental axes. Therefore, the mechanism of cell determination is not necessarily tied to any particular pattern of cell cleavage, but to an underlying framework of axial systems resident within sea urchin eggs and embryos.

scholarly journals The oral-aboral axis of a sea urchin embryo is specified by first cleavage

Development ◽  
1989 ◽  
Vol 106 (4) ◽  
pp. 641-647 ◽  
Author(s):  
R.A. Cameron ◽  
S.E. Fraser ◽  
R.J. Britten ◽  
E.H. Davidson
Keyword(s):  
Sea Urchin ◽  
Cleavage Plane ◽  
Strongylocentrotus Purpuratus ◽  
Cell Stage ◽  
Animal Pole ◽  
Sea Urchin Embryo ◽  
The Future ◽  
Axis Specification ◽  
The Right ◽  
Lines Of Evidence

Several lines of evidence suggest that the oral-aboral axis in Strongylocentrotus purpuratus embryos is specified at or before the 8-cell stage. Were the oral-aboral axis specified independently of the first cleavage plane, then a random association of this plane with the blastomeres of the four embryo quadrants in the oral-aboral plane (viz. oral, aboral, right and left) would be expected. Lineage tracer dye injection into one blastomere at the 2-cell stage and observation of the resultant labeling patterns demonstrates instead a strongly nonrandom association. In at least ninety percent of cases, the progeny of the aboral blastomeres are associated with those of the left lateral blastomeres and the progeny of the oral blastomeres with the right lateral ones, respectively. Thus, ninety percent of the time the oral pole of the future oral-aboral axis lies 45 degrees clockwise from the first cleavage plane as viewed from the animal pole. The nonrandom association of blastomeres after labeling of the 2-cell stage implies that there is a mechanistic relation between axis specification and the positioning of the first cleavage plane.

Nuclear beta-catenin is required to specify vegetal cell fates in the sea urchin embryo

Development ◽  
1999 ◽  
Vol 126 (2) ◽  
pp. 345-357 ◽  
Author(s):  
C.Y. Logan ◽  
J.R. Miller ◽  
M.J. Ferkowicz ◽  
D.R. McClay
Keyword(s):  
Cell Fate ◽  
Sea Urchin ◽  
Beta Catenin ◽  
Cell Fate Specification ◽  
Cell Fates ◽  
Cell Stage ◽  
Animal Pole ◽  
Fate Specification ◽  
The Relationship ◽  
Vegetal Cell

Beta-catenin is thought to mediate cell fate specification events by localizing to the nucleus where it modulates gene expression. To ask whether beta-catenin is involved in cell fate specification during sea urchin embryogenesis, we analyzed the distribution of nuclear beta-catenin in both normal and experimentally manipulated embryos. In unperturbed embryos, beta-catenin accumulates in nuclei that include the precursors of the endoderm and mesoderm, suggesting that it plays a role in vegetal specification. Using pharmacological, embryological and molecular approaches, we determined the function of beta-catenin in vegetal development by examining the relationship between the pattern of nuclear beta-catenin and the formation of endodermal and mesodermal tissues. Treatment of embryos with LiCl, a known vegetalizing agent, caused both an enhancement in the levels of nuclear beta-catenin and an expansion in the pattern of nuclear beta-catenin that coincided with an increase in endoderm and mesoderm. Conversely, overexpression of a sea urchin cadherin blocked the accumulation of nuclear beta-catenin and consequently inhibited the formation of endodermal and mesodermal tissues including micromere-derived skeletogenic mesenchyme. In addition, nuclear beta-catenin-deficient micromeres failed to induce a secondary axis when transplanted to the animal pole of uninjected host embryos, indicating that nuclear beta-catenin also plays a role in the production of micromere-derived signals. To examine further the relationship between nuclear beta-catenin in vegetal nuclei and micromere signaling, we performed both transplantations and deletions of micromeres at the 16-cell stage and demonstrated that the accumulation of beta-catenin in vegetal nuclei does not require micromere-derived cues. Moreover, we demonstrate that cell autonomous signals appear to regulate the pattern of nuclear beta-catenin since dissociated blastomeres possessed nuclear beta-catenin in approximately the same proportion as that seen in intact embryos. Together, these data show that the accumulation of beta-catenin in nuclei of vegetal cells is regulated cell autonomously and that this localization is required for the establishment of all vegetal cell fates and the production of micromere-derived signals.

Commitment along the dorsoventral axis of the sea urchin embryo is altered in response to NiCl2

Development ◽  
1992 ◽  
Vol 116 (3) ◽  
pp. 671-685 ◽  
Author(s):  
J. Hardin ◽  
J.A. Coffman ◽  
S.D. Black ◽  
D.R. McClay
Keyword(s):  
Sea Urchin ◽  
Major Effect ◽  
Specific Gene ◽  
Animal Pole ◽  
Dorsoventral Axis ◽  
Dorsoventral Polarity ◽  
Normal Number ◽  
Sea Urchin Embryo ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

Few treatments are known that perturb the dorsoventral axis of the sea urchin embryo. We report here that the dorsoventral polarity of the sea urchin embryo can be disrupted by treatment of embryos with NiCl2. Lytechinus variegatus embryos treated with 0.5 mM NiCl2 from fertilization until the early gastrula stage appear morphologically normal until the midgastrula stage, when they fail to acquire the overt dorsoventral polarity characteristic of untreated siblings. The ectoderm of normal embryos possesses two ventrolateral thickenings just above the vegetal plate region. In nickel-treated embryos, these become expanded as a circumferential belt around the vegetal plate. The ectoderm just ventral to the animal pole normally invaginates to form a stomodeum, which then fuses with the tip of the archenteron to produce the mouth. In nickel-treated embryos, the stomodeal invagination is expanded to become a circumferential constriction, and it eventually pinches off as the tip of the archenteron fuses with it to produce a mouth. Primary mesenchyme cells form a ring in the lateral ectoderm, but as many as a dozen spicule rudiments can form in a radial pattern. Dorsoventral differentiation of ectodermal tissues is profoundly perturbed: nickel-treated embryos underexpress transcripts of the dorsal (aboral) gene LvS1, they overexpress the ventral (oral) ectodermal gene product, EctoV, and the ciliated band is shifted to the vegetal margin of the embryo. Although some dorsoventral abnormalities are observed, animal-vegetal differentiation of the archenteron and associated structures seems largely normal, based on the localization of region-specific gene products. Gross differentiation of primary mesenchyme cells seems unaffected, since nickel-treated embryos possess the normal number of these cells. Furthermore, when all primary mesenchyme cells are removed from nickel-treated embryos, some secondary mesenchyme cells undergo the process of “conversion” (Ettensohn, C. A. and McClay, D. R. (1988) Dev. Biol. 125, 396–409), migrating to sites where the larval skeleton would ordinarily form and subsequently producing spicule rudiments. However, the skeletal pattern formed by the converted cells is completely radialized. Our data suggest that a major effect of NiCl2 is to alter commitment of ectodermal cells along the dorsoventral axis. Among the consequences appears to be a disruption of pattern formation by mesenchyme cells.

The dorsoventral axis is specified prior to first cleavage in the direct developing sea urchin Heliocidaris erythrogramma

Development ◽  
1990 ◽  
Vol 110 (3) ◽  
pp. 875-884 ◽  
Author(s):  
J.J. Henry ◽  
G.A. Wray ◽  
R.A. Raff
Keyword(s):  
Cleavage Plane ◽  
Cell Lineage ◽  
Small Diameter ◽  
Cleavage Division ◽  
Cell Stage ◽  
Dorsoventral Axis ◽  
Fluorescent Cell ◽  
Heliocidaris Erythrogramma ◽  
Larval Stages ◽  
Set Up

Previous fate mapping studies as well as the culture of isolated blastomeres have revealed that the dorsoventral axis is specified as early as the 2-cell stage in the embryos of the direct developing echinoid, Heliocidaris erythrogramma. Normally, the first cleavage plane includes the animal-vegetal axis and bisects the embryo between future dorsal and ventral halves. Experiments were performed to establish whether the dorsoventral axis is set up prior to the first cleavage division in H. erythrogramma. Eggs were elongated and fertilized in silicone tubes of a small diameter in order to orient the cleavage spindle and thus the first plane of cell division. Following first cleavage, one of the two resulting blastomeres was then microinjected with a fluorescent cell lineage tracer dye. Fate maps were made after culturing these embryos to larval stages. The results indicate that the first cleavage division can be made to occur at virtually any angle relative to the animal-vegetal and dorsoventral axes. Therefore, the dorsoventral axis is specified prior to first cleavage. We argue that this axis resides in the unfertilized oocyte rather than being set up as a consequence of fertilization.

The establishment of bilateral asymmetry in sea urchin embryos

Development ◽  
1994 ◽  
Vol 120 (2) ◽  
pp. 395-404 ◽  
Author(s):  
E. R. McCain ◽  
D. R. McClay
Keyword(s):  
Sea Urchin ◽  
Cell Separation ◽  
New Left ◽  
Lineage Tracing ◽  
Bilateral Asymmetry ◽  
Dorsoventral Axis ◽  
Adult Rudiment ◽  
Left Right Asymmetry ◽  
Relationship Of ◽  
The Relationship

Although much is known about the specification and determination of the two primary axes (animal/vegetal and dorsoventral or oral/aboral) in a number of embryos, little is understood about bilaterality. In the sea urchin, left/right asymmetry is crucial to normal development as the echinus or adult rudiment is positioned on the left side of the larva. We examined the establishment of bilateral asymmetry in Lytechnis variegatus embryos by determining the relationship of the first cleavage planes to the left/right axis. Embryos were bisected at different times to determine when the bilateral axis is committed. These lineage tracing and cell separation experiments demonstrated that the first cleavage plane divides the embryo into left and right halves, although this is conditional until after late blastula stage. The relationship between the specification of the dorsoventral axis and the bilateral axis was examined experimentally. In other species when the dorsal and ventral halves of early echinoderm embryos (preblastula) are separated, the dorsal half often reverses (180°) its dorsoventral axis. We asked whether those larvae with an inverted dorsoventral axis would shift the position of the echinus rudiment from the original left side to the new left side. If so, it would demonstrate that the larval asymmetry is dependent upon specification of the dorsoventral axis. Using a combination of lineage tracing and cell separation techniques, we show that the left/right asymmetry is specified with respect to the dorsoventral axis.

Establishment of embryonic axes in larvae of the starfish, Asterina pectinifera

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 87-100
Author(s):  
Tetsuya Kominami
Keyword(s):  
Cleavage Plane ◽  
Anterior Part ◽  
Polar Body ◽  
Cleavage Pattern ◽  
Early Cleavage ◽  
Embryonic Axes ◽  
Cell Stage ◽  
Polar Bodies ◽  
Asterina Pectinifera ◽  
Fertilized Egg

In order to clarify the relationships between the first cleavage plane and the embryonic axes, early cleavage pattern of the fertilized eggs of the starfish, Asterina pectinifera was reexamined . It was ascertained that the polar bodies were formed at the site to which the germinal vesicle had closely located before the initiation of the meiotic division, and that the first cleavage plane passed near this site of polar body formation. While some of the early embryos of this starfish were observed to show various cleavage patterns during early cleavage stage, more than 70% of the embryos developed according to, so to say, the ‘typical’ cleavage pattern. Next, horseradish peroxidase (HRP) was injected into one of the blastomeres of the 2-cellor 8-cell-stage embryos. The embryos were allowed to develop up to either the early gastrula or the early bipinnaria stage and stained to detect the descendants of the blastomere injected with HRP. In early gastrulae still retaining radial symmetry, the activity of HRP injected at the 2-cell stage was found only in one side of the embryo partitioned by one of the symmetrical planes. When one of the four blastomeres lying nearer to the polar bodies at the 8-cell stage was marked with HRP, its descendants constituted one quarter of the anterior part of the gastrula, and descendants of a blastomere opposite the polar bodies were found in the posterior region of the embryo. It was concluded that the animal-vegetal (AV) axis was preexisting in the fertilized egg and that the first cleavage plane contained this primary axis. In early bipinnariae with their dorsoventral (DV) axes already established, the region of activity of the HRP injected at the 2-cell stage was still demarcated by a plane which passed through the AV axis, but the plane of the boundary had no fixed relation to the DV axis. The results indicate that the first cleavage plane does not necessarily correspond to the median plane of the starfish larva, unlike the case in sea-urchin eggs (Hörstadius & Wolsky, 1936). In other words, the DV axis of the starfish embryo is not predetermined in the fertilized egg, and might be established in the course of development through cell-to-cell interactions, while the AV axis is established mainly according to the pre-existing egg polarity.

Maternal mRNA encoding the orphan steroid receptor SpCOUP-TF is localized in sea urchin eggs

Development ◽  
1996 ◽  
Vol 122 (2) ◽  
pp. 521-526 ◽  
Author(s):  
A. Vlahou ◽  
M. Gonzalez-Rimbau ◽  
C.N. Flytzanis
Keyword(s):  
Sea Urchin ◽  
Hormone Receptors ◽  
Cell Lineage ◽  
Early Embryo ◽  
Steroid Hormone Receptors ◽  
Embryonic Axes ◽  
Maternal Mrna ◽  
Sea Urchin Embryo ◽  
Oral Ectoderm ◽  
Tf Gene

The SpCOUP-TF gene is a highly conserved sea urchin homologue of the vertebrate COUP-TFs and the Drosophila seven up subfamily of transcription factors, which are members of the orphan steroid hormone receptors. Whole-mount in situ hybridization experiments, using three sea urchin species, detect the maternal SpCOUP-TF mRNA deposited unevenly in the oocytes, mature eggs and the blastomeres of the early embryo. The localization pattern indicates that, in all three sea urchin species, the maternal SpCOUP-TF mRNA is placed in the egg in a fixed position relative to the embryonic axes, i.e. lateral to the animal-vegetal and at 45 degree angle to the oral-aboral (ventral-dorsal) axis. The embryonic expression of the SpCOUP-TF gene is spatially restricted in the oral ectoderm of the early embryo and, at later stages, in the cells of the ciliated band, the neurogenic cell lineage of the sea urchin embryo. The SpCOUP-TF mRNA, the first sea urchin maternal mRNA encoding a transcription factor that is specifically localized with respect to both embryonic axes in the egg, could be involved in early specification events in the sea urchin embryo.

Conditioning of a culture substratum by the ectodermal layer promotes attachment and oriented locomotion by amphibian gastrula mesodermal cells

1983 ◽  
Vol 59 (1) ◽  
pp. 43-60 ◽  
Author(s):  
N. Nakatsuji ◽  
K.E. Johnson
Keyword(s):  
Cell Migration ◽  
Time Lapse ◽  
Ambystoma Maculatum ◽  
Specific Cell ◽  
Animal Pole ◽  
Micron Diameter ◽  
The Relationship ◽  
Extracellular Fibrils ◽  
Scanning Electron

We have found that ectodermal fragments of Ambystoma maculatum gastrulae deposit immense numbers of 0.1 micron diameter extracellular fibrils on plastic coverslips. When migrating mesodermal cells from A. maculatum gastrulae are seeded on such conditioned plastic substrata, they attach and begin migrating after 15–30 min in vitro. We did a detailed analysis of the relationship between fibril orientation and cell migration using time-lapse cinemicrography, scanning electron microscopy, and a microcomputer with a graphics tablet and morphometric program. We found that cells move in directions closely related to the orientation of fibrils. Usually fibrils are oriented in dense arrays with a predominance of fibrils running parallel to the blastopore-animal pole axis of the explant, and cells move preferentially along lines parallel to the blastopore-animal pole axis. When fibrils are unaligned, cells move at random. We have also shown that cells move with a slightly stronger tendency towards the animal pole direction. These results are discussed concerning the mechanism of specific cell migration during amphibian gastrulation.

GSK3beta/shaggy mediates patterning along the animal-vegetal axis of the sea urchin embryo

Development ◽  
1998 ◽  
Vol 125 (13) ◽  
pp. 2489-2498 ◽  
Author(s):  
F. Emily-Fenouil ◽  
C. Ghiglione ◽  
G. Lhomond ◽  
T. Lepage ◽  
C. Gache
Keyword(s):  
Sea Urchin ◽  
Wnt Pathway ◽  
Dominant Negative ◽  
Early Gene ◽  
Expression Domain ◽  
Animal Pole ◽  
Axial Patterning ◽  
Sea Urchin Embryo ◽  
Vegetal Pole ◽  
Dominant Negative Activity

In the sea urchin embryo, the animal-vegetal axis is defined before fertilization and different embryonic territories are established along this axis by mechanisms which are largely unknown. Significantly, the boundaries of these territories can be shifted by treatment with various reagents including zinc and lithium. We have isolated and characterized a sea urchin homolog of GSK3beta/shaggy, a lithium-sensitive kinase which is a component of the Wnt pathway and known to be involved in axial patterning in other embryos including Xenopus. The effects of overexpressing the normal and mutant forms of GSK3beta derived either from sea urchin or Xenopus were analyzed by observation of the morphology of 48 hour embryos (pluteus stage) and by monitoring spatial expression of the hatching enzyme (HE) gene, a very early gene whose expression is restricted to an animal domain with a sharp border roughly coinciding with the future ectoderm / endoderm boundary. Inactive forms of GSK3beta predicted to have a dominant-negative activity, vegetalized the embryo and decreased the size of the HE expression domain, apparently by shifting the boundary towards the animal pole. These effects are similar to, but even stronger than, those of lithium. Conversely, overexpression of wild-type GSK3beta animalized the embryo and caused the HE domain to enlarge towards the vegetal pole. Unlike zinc treatment, GSK3beta overexpression thus appeared to provoke a true animalization, through extension of the presumptive ectoderm territory. These results indicate that in sea urchin embryos the level of GSKbeta activity controls the position of the boundary between the presumptive ectoderm and endoderm territories and thus, the relative extent of these tissue layers in late embryos. GSK3beta and probably other downstream components of the Wnt pathway thus mediate patterning both along the primary AV axis of the sea urchin embryo and along the dorsal-ventral axis in Xenopus, suggesting a conserved basis for axial patterning between invertebrate and vertebrate in deuterostomes.

scholarly journals Relationship Between 2-Dimensional Frontal Plane Measures and the Knee Abduction Angle During the Drop Vertical Jump

2019 ◽  
Vol 28 (4) ◽  
Author(s):  
Brad W. Willis ◽  
Katie Hocker ◽  
Swithin Razu ◽  
Aaron D. Gray ◽  
Marjorie Skubic ◽  
...  
Keyword(s):  
Motion Capture ◽  
Vertical Jump ◽  
Frontal Plane ◽  
Ligament Injury ◽  
Coefficient Of Determination ◽  
Abduction Angle ◽  
Initial Contact ◽  
Knee Abduction ◽  
The Relationship ◽  
Drop Vertical Jump

Context: Knee abduction angle (KAA), as measured by 3-dimensional marker-based motion capture systems during jump-landing tasks, has been correlated with an elevated risk of anterior cruciate ligament injury in females. Due to the high cost and inefficiency of KAA measurement with marker-based motion capture, surrogate 2-dimensional frontal plane measures have gained attention for injury risk screening. The knee-to-ankle separation ratio (KASR) and medial knee position (MKP) have been suggested as potential frontal plane surrogate measures to the KAA, but investigations into their relationship to the KAA during a bilateral drop vertical jump task are limited. Objective: To investigate the relationship between KASR and MKP to the KAA during initial contact of the bilateral drop vertical jump. Design: Descriptive. Setting: Biomechanics laboratory. Participants: A total of 18 healthy female participants (mean age: 24.1 [3.88] y, mass: 65.18 [10.34] kg, and height: 1.63 [0.06] m). Intervention: Participants completed 5 successful drop vertical jump trials measured by a Vicon marker-based motion capture system and 2 AMTI force plates. Main Outcome Measure: For each jump, KAA of the tibia relative to the femur was measured at initial contact along with the KASR and MKP calculated from planar joint center data. The coefficient of determination (r2) was used to examine the relationship between the KASR and MKP to KAA. Results: A strong linear relationship was observed between MKP and KAA (r2 = .71), as well as between KASR and KAA (r2 = .72). Conclusions: Two-dimensional frontal plane measures show strong relationships to the KAA during the bilateral drop vertical jump.

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