Preface

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. NP-NP
Keyword(s):  
Sea Urchin ◽  
Developmental Process ◽  
Positional Information ◽  
Body Plan ◽  
Gastrula Stage ◽  
Digestive Tube ◽  
Basic Body ◽  
Extensive Cell ◽  
Important Time ◽  
Gut Endoderm

Gastrulation is the developmental process, involving extensive cell reorganizations, which results in the formation of the mesoderm and gut endoderm of the embryo. The prefix gastr- in fact means ‘stomach’, which is perhaps both a reference to the shape of the gastrula stage of miolecithal eggs (e.g. sea urchin, Amphioxus) and to the fact that the endoderm, which lines the digestive tube, arises during gastrulation. Its importance was eulogised by Lewis Wolpert's famous statement that ‘it is not birth, marriage or death but gastrulation that is truly the most important time in your life’. Not only does the embryo become trilaminar, but it is also during gastrulation that the basic body plan is laid down, the three axes of the embryo become established and many cells receive the signals that lead them to acquire developmental fates and positional information.

scholarly journals Body Plan of Sea Urchin Embryo: An Ancestral Type Animal

2001 ◽  
Vol 18 (6) ◽  
pp. 757-770 ◽  
Author(s):  
Koji Akasaka ◽  
Hiraku Shimada
Keyword(s):  
Sea Urchin ◽  
Body Plan ◽  
Sea Urchin Embryo ◽  
Ancestral Type

The role of secondary mesenchyme cells during sea urchin gastrulation studied by laser ablation

Development ◽  
1988 ◽  
Vol 103 (2) ◽  
pp. 317-324 ◽  
Author(s):  
J. Hardin
Keyword(s):  
Laser Ablation ◽  
Sea Urchin ◽  
Normal Rate ◽  
Common Mechanism ◽  
Gastrula Stage ◽  
Mechanical Tension ◽  
Lytechinus Pictus ◽  
Final Length ◽  
Mesenchyme Cells

It has long been thought that traction exerted by filopodia of secondary mesenchyme cells (SMCs) is a sufficient mechanism to account for elongation of the archenteron during sea urchin gastrulation. The filopodial traction hypothesis has been directly tested here by laser ablation of SMCs in gastrulae of the sea urchin, Lytechinus pictus. When SMCs are ablated at the onset of secondary invagination, the archenteron doubles in length at the normal rate of elongation, but advance of the tip of the archenteron stops at the 2/3 gastrula stage. In contrast, when all SMCs are ablated at or following the 2/3 gastrula stage, further elongation does not occur. However, if a few SMCs are allowed to remain in 2/3-3/4 gastrulae, elongation continues, although more slowly than in controls. The final length of archenterons in embryos ablated at the 1/3-1/2 gastrula stage is virtually identical to the final length of everted archenterons in LiCl-induced exogastrulae; since filopodial traction is not exerted in either case, an alternate, common mechanism of elongation probably operates in both cases. These results suggest that archenteron elongation involves two processes: (1) active, filopodia-independent elongation, which depends on active cell rearrangement and (2) filopodia-dependent elongation, which depends on mechanical tension exerted by the filopodia.

scholarly journals The developmental hourglass model: a predictor of the basic body plan?

Development ◽  
2014 ◽  
Vol 141 (24) ◽  
pp. 4649-4655 ◽  
Author(s):  
N. Irie ◽  
S. Kuratani
Keyword(s):  
Body Plan ◽  
Basic Body ◽  
Hourglass Model ◽  
Developmental Hourglass

scholarly journals Dynamics of thin filopodia during sea urchin gastrulation

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2501-2511 ◽  
Author(s):  
J. Miller ◽  
S.E. Fraser ◽  
D. McClay
Keyword(s):  
Sea Urchin ◽  
Positional Information ◽  
Cell Interactions ◽  
Average Growth ◽  
Sea Urchin Embryo ◽  
Ligand Interactions ◽  
Patterning Defect ◽  
Mesenchyme Cell ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

At gastrulation in the sea urchin embryo, a dramatic rearrangement of cells establishes the three germ layers of the organism. Experiments have revealed a number of cell interactions at this stage that transfer patterning information from cell to cell. Of particular significance, primary mesenchyme cells, which are responsible for production of the embryonic skeleton, have been shown to obtain extensive positional information from the embryonic ectoderm. In the present study, high resolution Nomarski imaging reveals the presence of very thin filopodia (02-0.4 micron in diameter) extending from primary mesenchyme cells as well as from ectodermal and secondary mesenchyme cells. These thin filopodia sometimes extend to more than 80 microns in length and show average growth and retraction rates of nearly 10 microns/minute. The filopodia are highly dynamic, rapidly changing from extension to resorption; frequently, the resorption changes to resumption of assembly. The behavior, location and timing of active thin filopodial movements does not correlate with cell locomotion; instead, there is a strong correlation suggesting their involvement in cell-cell interactions associated with signaling and patterning at gastrulation. Nickel-treatment, which is known to create a patterning defect in skeletogenesis due to alterations in the ectoderm, alters the normal position-dependent differences in the thin filopodia. The effect is present in recombinant embryos in which the ectoderm alone was treated with nickel, and is absent in recombinant embryos in which only the primary mesenchyme cells were treated, suggesting that the filopodial length is substratum dependent rather than being primary mesenchyme cell autonomous. The thin filopodia provide a means by which cells can contact others several cell diameters away, suggesting that some of the signaling previously thought to be mediated by diffusible signals may instead by the result of direct receptor-ligand interactions between cell membranes.

A Basic Body Plan

1976 ◽  
Vol 11 (2) ◽  
pp. 74-77
Author(s):  
Harold J. Morowitz
Keyword(s):  
Body Plan ◽  
Basic Body

Distribution of apoptosis-like cells in sea urchin early embryogenesis

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S76-S76 ◽  
Author(s):  
Hazime Mizoguchi ◽  
Dai Kudo ◽  
Yumi Shimizu ◽  
Keiko Hirota ◽  
Shinobu Kawai ◽  
...  
Keyword(s):  
Comet Assay ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Early Embryogenesis ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Gastrula Stage ◽  
Tunel Method ◽  
Dapi Staining ◽  
Pluteus Stage ◽  
Number Of Cells

It has been reported that the number of cells per embryo increases from the cleavage stage to the pluteus stage. Also, it has been reported that the number of cells per embryo from the early gastrula stage to the mid-gastrula stage increases very slightly (Mizoguchi, 1999). A detailed analysis of cell proliferation during this period would thus seem to be necessary.On the other hand, Roccheri et al. (1997) reported spontaneous apoptosis at the early pluteus stage, especially in the regions of arm and intestine. However, it is unknown whether apoptosis occurs before the pluteus stage.Using the Tumor, Neuro and/or Cardio TACS in situ apoptosis detection kit (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling: TUNEL method, Trevigen, USA), the Comet assay kit (Trevigen, USA) and DAPI (4,6-diamidino-2-phenylinodole dihydrochloride) staining, we investigated the distribution of apoptosis-like cells in sea urchins during early embryogenesis to clarify the relationship between cell death and morphogenesis.The embryos of the sea urchin Hemicentrotus pulcherrimus were used in the present study. Three methods of detection of apoptosis signals in the embryos were performed: (1) defects in chromosomes and punctured nuclear envelopes of cells were detected by DAPI staining; (2) apoptosis-like cells were stained a brown colour by the TUNEL method; (3) some clear tails which detected the fragmentation of DNA were found by the Comet assay. These signals indicate apoptosis-like cells.

scholarly journals Origins of radial symmetry identified in an echinoderm during adult development and the inferred axes of ancestral bilateral symmetry

2007 ◽  
Vol 274 (1617) ◽  
pp. 1511-1516 ◽  
Author(s):  
Valerie B Morris
Keyword(s):  
Sea Urchin ◽  
Adult Development ◽  
Bilateral Symmetry ◽  
Radial Symmetry ◽  
Body Plan ◽  
Direct Development ◽  
The Common ◽  
Patterning Genes ◽  
Standing Problem

How the radial body plan of echinoderms is related to the bilateral body plan of their deuterostome relatives, the hemichordates and the chordates, has been a long-standing problem. Now, using direct development in a sea urchin, I show that the first radially arranged structures, the five primary podia, form from a dorsal and a ventral hydrocoele at the oral end of the archenteron. There is a bilateral plane of symmetry through the podia, the mouth, the archenteron and the blastopore. This adult bilateral plane is thus homologous with the bilateral plane of bilateral metazoans and a relationship between the radial and bilateral body plans is identified. I conclude that echinoderms retain and use the bilateral patterning genes of the common deuterostome ancestor. Homologies with the early echinoderms of the Cambrian era and between the dorsal hydrocoele, the chordate notochord and the proboscis coelom of hemichordates become evident.

scholarly journals Transcriptomic Analysis of the Highly Derived Radial Body Plan of a Sea Urchin

2014 ◽  
Vol 6 (4) ◽  
pp. 964-973 ◽  
Author(s):  
Jennifer A. Wygoda ◽  
Yee Yang ◽  
Maria Byrne ◽  
Gregory A. Wray
Keyword(s):  
Sea Urchin ◽  
Body Plan ◽  
Transcriptomic Analysis
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