Electron microscopic studies on primary mesenchyme cell ingression and gastrulation in relation to vegetal pole cell behavior in sea urchin embryos

1989 ◽  
Vol 183 (2) ◽  
pp. 453-462 ◽  
Author(s):  
Shonan Amemiya
Keyword(s):  
Sea Urchin ◽  
Cell Behavior ◽  
Electron Microscopic ◽  
Sea Urchin Embryos ◽  
Pole Cell ◽  
Vegetal Pole ◽  
Mesenchyme Cell ◽  
Microscopic Studies

scholarly journals β-Catenin is essential for patterning the maternally specified animal-vegetal axis in the sea urchin embryo

1998 ◽  
Vol 95 (16) ◽  
pp. 9343-9348 ◽  
Author(s):  
Athula H. Wikramanayake ◽  
Ling Huang ◽  
William H. Klein
Keyword(s):  
Sea Urchin ◽  
Molecular Mechanisms ◽  
Early Embryo ◽  
Cell Fates ◽  
Cell Stage ◽  
Signal Transduction Cascade ◽  
Sea Urchin Embryos ◽  
Sea Urchin Embryo ◽  
Vegetal Pole ◽  
Vegetal Cell

In sea urchin embryos, the animal-vegetal axis is specified during oogenesis. After fertilization, this axis is patterned to produce five distinct territories by the 60-cell stage. Territorial specification is thought to occur by a signal transduction cascade that is initiated by the large micromeres located at the vegetal pole. The molecular mechanisms that mediate the specification events along the animal–vegetal axis in sea urchin embryos are largely unknown. Nuclear β-catenin is seen in vegetal cells of the early embryo, suggesting that this protein plays a role in specifying vegetal cell fates. Here, we test this hypothesis and show that β-catenin is necessary for vegetal plate specification and is also sufficient for endoderm formation. In addition, we show that β-catenin has pronounced effects on animal blastomeres and is critical for specification of aboral ectoderm and for ectoderm patterning, presumably via a noncell-autonomous mechanism. These results support a model in which a Wnt-like signal released by vegetal cells patterns the early embryo along the animal–vegetal axis. Our results also reveal similarities between the sea urchin animal–vegetal axis and the vertebrate dorsal–ventral axis, suggesting that these axes share a common evolutionary origin.

scholarly journals Disruption of Primary Mesenchyme Cell Patterning by Misregulated Ectodermal Expression ofSpMsxin Sea Urchin Embryos

1998 ◽  
Vol 201 (2) ◽  
pp. 230-246 ◽  
Author(s):  
Hongying Tan ◽  
Andrew Ransick ◽  
Hailin Wu ◽  
Sonia Dobias ◽  
Yi-Hsin Liu ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Cell Patterning ◽  
Sea Urchin Embryos ◽  
Mesenchyme Cell

scholarly journals Differential behavior of centrosomes in unequally dividing blastomeres during fourth cleavage of sea urchin embryos

1991 ◽  
Vol 98 (3) ◽  
pp. 423-431
Author(s):  
J. Holy ◽  
G. Schatten
Keyword(s):  
Sea Urchin ◽  
Three Dimensional ◽  
Initial Step ◽  
Spindle Pole ◽  
Cell Cortex ◽  
Sea Urchin Embryos ◽  
Microtubular Cytoskeleton ◽  
Vegetal Pole ◽  
Dimensional Reconstruction ◽  
Dividing Cells

The fourth cleavage in sea urchin embryos is unequal and represents an initial step in cell differentiation: vegetal blastomeres divide to produce micromeres, which are precursors of the skeletogenic mesenchyme, and macromeres. The mitotic spindles of these unequally dividing cells are peripherally located and lie orthogonal to the vegetal pole plasma membrane; the aster of the micromere pole is closely apposed to the plasmalemma and presents a characteristic flattened profile. In order to investigate the role of centrosomes in the generation of the asymmetric vegetal spindle at fourth cleavage, structural dynamics of centrosomes in both equally and unequally dividing blastomeres were compared using immunofluorescence methods. Quantitation of immunofluorescence and three-dimensional reconstruction techniques demonstrate that micromere centrosomes differ from macromere centrosomes in two respects: (1) micromere spindle poles contain less centrosomal material than macromere poles, and (2) micromere centrosomes undergo a specific filiform elongation during late anaphase and telophase. The behavior of micromere centrosomes suggests that a unique spindle pole event, involving interactions of the microtubular cytoskeleton, centrosome and cell cortex, occurs during the process of unequal cleavage of vegetal blastomeres.

Disruption of collagen crosslinking during sea urchin morphogenesis

1987 ◽  
Vol 45 ◽  
pp. 786-787
Author(s):  
Jeffrey D. Hardin
Keyword(s):  
Sea Urchin ◽  
Basal Lamina ◽  
Structural Changes ◽  
Lysyl Oxidase ◽  
Three Dimensional ◽  
Specific Inhibitor ◽  
Dimensional Structure ◽  
Collagen Crosslinking ◽  
Sea Urchin Embryos ◽  
Mesenchyme Cell

The extracellular matrix (ECM) is important for many events during embryonic development. An important component of the ECM in sea urchin embryos is collagen. Collagen has been identified in the basal lamina of sea urchin embryos by morphological and immunological criteria. Recently, the need for a crosslinked collagenous matrix in the basal lamina during sea urchin embryogenesis has been demonstrated using β–aminoproprionitrile (BAPN). BAPN is a specific inhibitor of lysyl oxidase, an enzyme involved in collagen crosslinking. BAPN treatment causes completely reversible developmental arrest at the early gastrula stage, or supression of mesenchyme cell motility and archenteron elongation, depending on the time of addition of the drug. BAPN also significantly decreases the extent of collagen crosslinking, based on solubility assays. This study examines fine structural changes in cellular morphology and motility and the three-dimensional structure of the ECM induced by BAPN treatment during gastrulation and larva formation in the sea urchin embryo.

Time-lapse and electron microscopic studies of sea urchin micromeres

PROTOPLASMA ◽  
1969 ◽  
Vol 68 (3) ◽  
pp. 271-288 ◽  
Author(s):  
Berndt E. Hagstr�m ◽  
Sunniva L�nning
Keyword(s):  
Sea Urchin ◽  
Time Lapse ◽  
Electron Microscopic ◽  
Microscopic Studies
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