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.

Autonomous and non-autonomous differentiation of ectoderm in different sea urchin species

Development ◽  
1995 ◽  
Vol 121 (5) ◽  
pp. 1497-1505 ◽  
Author(s):  
A.H. Wikramanayake ◽  
B.P. Brandhorst ◽  
W.H. Klein
Keyword(s):  
Sea Urchin ◽  
Strongylocentrotus Purpuratus ◽  
Protein A ◽  
Cellular Interactions ◽  
V Protein ◽  
Lytechinus Pictus ◽  
Sea Urchin Embryo ◽  
Oral Ectoderm ◽  
Temporal And Spatial

During early embryogenesis, the highly regulative sea urchin embryo relies extensively on cell-cell interactions for cellular specification. Here, the role of cellular interactions in the temporal and spatial expression of markers for oral and aboral ectoderm in Strongylocentrotus purpuratus and Lytechinus pictus was investigated. When pairs of mesomeres or animal caps, which are fated to give rise to ectoderm, were isolated and cultured they developed into ciliated embryoids that were morphologically polarized. In animal explants from S. purpuratus, the aboral ectoderm-specific Spec1 gene was activated at the same time as in control embryos and at relatively high levels. The Spec1 protein was restricted to the squamous epithelial cells in the embryoids suggesting that an oral-aboral axis formed and aboral ectoderm differentiation occurred correctly. However, the Ecto V protein, a marker for oral ectoderm differentiation, was detected throughout the embryoid and no stomodeum or ciliary band formed. These results indicated that animal explants from S. purpuratus were autonomous in their ability to form an oral-aboral axis and to differentiate aboral ectoderm, but other aspects of ectoderm differentiation require interaction with vegetal blastomeres. In contrast to S. purpuratus, aboral ectoderm-specific genes were not expressed in animal explants from L. pictus even though the resulting embryoids were morphologically very similar to those of S. purpuratus. Recombination of the explants with vegetal blastomeres or exposure to the vegetalizing agent LiCl restored activity of aboral ectoderm-specific genes, suggesting the requirement of a vegetal induction for differentiation of aboral ectoderm cells.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Role of fibronectin in primary mesenchyme cell migration in the sea urchin.

1985 ◽  
Vol 101 (4) ◽  
pp. 1487-1491 ◽  
Author(s):  
H Katow ◽  
M Hayashi
Keyword(s):  
Cell Migration ◽  
Sea Urchin ◽  
Culture Media ◽  
Horse Serum ◽  
Time Lapse ◽  
Mesenchyme Cell ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

We studied the effect of fibronectin (FN) on the behavior of primary mesenchyme cells isolated from sea urchin mesenchyme blastulae in vitro using a time-lapse technique. The migration of isolated primary mesenchyme cells reconstituted in seawater and horse serum is dependent on the presence or absence of exogenous FN in the culture media. The cells in FN, 4 and 40 micrograms/ml, show a high percentage of migration and migrate long distances, whereas a higher concentration of FN at 400 micrograms/ml tends to inhibit migration.

scholarly journals Mechanochemical coupling in the relaxation of rigor-wave sea urchin sperm flagella.

1982 ◽  
Vol 92 (3) ◽  
pp. 733-741 ◽  
Author(s):  
S M Penningroth ◽  
A Cheung ◽  
K Olehnik ◽  
R Koslosky
Keyword(s):  
Sea Urchin ◽  
Atp Hydrolysis ◽  
Bend Angle ◽  
Flagellar Motility ◽  
Lytechinus Pictus ◽  
Mechanochemical Coupling ◽  
Mechanochemical Cycle ◽  
Hydrolysis Of

The relaxation (straightening) of flagellar rigor waves, which is known to be induced by micromolar ATP concentrations was investigated with respect to its dependence on the binding and hydrolysis of ATP. Flagellar rigor waves were formed by the dilution of demembranated, reactivated sea urchin (Lytechinus pictus) spermatozoa into ATP-free buffer. Relaxation in response to nucleotide was quantitated by measuring theta, the mean flagellar bend angle per sperm; this novel assay permitted determination of the rate of relaxation. It was found that (a) the rate of flagellar relaxation induced by 4 X 10(-6) M ATP was inhibited 80% by vanadate concentrations of 3 X 10(-6) M and above; (b) of 16 hydrolyzable and nonhydrolyzable nucleotide di-, tri-, and tetraphosphates tested, only three, each of which was hydrolyzed by the flagellar axonemal ATPase activity (ATP, dATP, and epsilon-ATP) were also capable of effecting relaxation; (c) several hundred ATP molecules were estimated to be hydrolyzed by each dynein of ATP hydrolysis, which defines the efficiency of ATP utilization, increased 30-fold as the ATP relaxation depends on ATP hydrolysis; (b) because it depends on ATP hydrolysis, flagellar relaxation is an inappropriate model system for investigating the role of ATP binding in the mechanochemical cycle of dynein; and (c) the efficiency of mechanochemical coupling in flagellar motility is an ATP-dependent phenomenon. A general model of relaxation is proposed based on active microtubule sliding.

scholarly journals A monoclonal antibody against the dynein IC1 peptide of sea urchin spermatozoa inhibits the motility of sea urchin, dinoflagellate, and human flagellar axonemes.

1994 ◽  
Vol 5 (9) ◽  
pp. 1051-1063 ◽  
Author(s):  
C Gagnon ◽  
D White ◽  
P Huitorel ◽  
J Cosson
Keyword(s):  
Sea Urchin ◽  
Cortical Microtubule ◽  
Marginal Effect ◽  
Microtubule Network ◽  
Lytechinus Pictus ◽  
Oxyrrhis Marina ◽  
Dynein Intermediate Chain ◽  
Immotile Spermatozoa ◽  
Intermediate Chain

To investigate the role of axonemal components in the mechanics and regulation of flagellar movement, we have generated a series of monoclonal antibodies (mAb) against sea urchin (Lytechinus pictus) sperm axonemal proteins, selected for their ability to inhibit the motility of demembranated sperm models. One of these antibodies, mAb D1, recognizes an antigen of 142 kDa on blots of sea urchin axonemal proteins and of purified outer arm dynein, suggesting that it acts by binding to the heaviest intermediate chain (IC1) of the dynein arm. mAb D1 blocks the motility of demembranated sea urchin spermatozoa by modifying the beating amplitude and shear angle without affecting the ATPase activity of purified dynein or of demembranated immotile spermatozoa. Furthermore, mAb D1 had only a marginal effect on the velocity of sliding microtubules in trypsin-treated axonemes. This antibody was also capable of inhibiting the motility of flagella of Oxyrrhis marina, a primitive dinoflagellate, and those of demembranated human spermatozoa. Localization of the antigen recognized by mAb D1 by immunofluorescence reveals its presence on the axonemes of flagella from sea urchin spermatozoa and O. marina but not on the cortical microtubule network of the dinoflagellate. These results are consistent with a dynamic role for the dynein intermediate chain IC1 in the bending and/or wave propagation of flagellar axonemes.

scholarly journals Effects of adenylyl imidodiphosphate, a nonhydrolyzable adenosine triphosphate analog, on reactivated and rigor wave sea urchin sperm.

1978 ◽  
Vol 79 (3) ◽  
pp. 827-832 ◽  
Author(s):  
S M Penningroth ◽  
G B Witman
Keyword(s):  
Adenosine Triphosphate ◽  
Sea Urchin ◽  
Beat Frequency ◽  
Atp Binding ◽  
Flagellar Motility ◽  
Lytechinus Pictus ◽  
Cross Bridge ◽  
Atp Concentration ◽  
Sea Urchin Sperm

A nonhydrolyzable ATP analog, adenylyl imidodiphosphate (AMP-PNP), has been used to study the role of ATP binding in flagellar motility. Sea urchin sperm of Lytechinus pictus were demembranated, reactivated, and locked in "rigor waves" by a modification of the method of Gibbons and Gibbons (11). Rigor wave sperm relaxed within 2 min after addition of 4 micrometer ATP, and reactivated upon addition of 10-12 micrometer ATP. The beat frequency of the reactivated sperm varied with ATP concentration according to Michaelis-Menten kinetics ("Km" = 0.24 mM; "Vmax" = 44 Hz) and was competitively inhibited by AMP-PNP (Ki" approximately to 8.1 mM). Rigor wave sperm were completely relaxed (straightened) within 2 min by AMP-PNP at concentrations of 2-4 mM. The possibilities that relaxation in AMP-PNP was a result of ATP contamination, AMP-PNP hydrolysis, or lowering of the free Mg++ concentration were conclusively ruled out. The results suggest that dynein cross-bridge release is dependent upon ATP binding but not hydrolysis.

Inversion of left–right asymmetry in the formation of the adult rudiment in sea urchin larvae: removal of a part of embryos at the gastrula stage

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S82-S83 ◽  
Author(s):  
Mizuki Aihara ◽  
Shonan Amemiya
Keyword(s):  
Sea Urchin ◽  
Optical Microscope ◽  
Sham Operation ◽  
Gastrula Stage ◽  
Larval Body ◽  
Lateral Region ◽  
Scaphechinus Mirabilis ◽  
Adult Rudiment ◽  
Mesenchyme Cells ◽  
Pluteus Stage

At the late pluteus stage, sea urchin larvae form an adult rudiment left–right (LR) asymmetrically, on only the left side. Little is known about how the LR asymmetry of the adult rudiment is established in earlier stages during which the larval body is basically LR symmetric. To investigate how the different regions of the embryo function to establish LR asymmetry, we removed different regions at the gastrula stage and assessed the effects of the operation on the establishment of LR asymmetry of the adult rudiment.Surgery was performed on mid- to late-gastrula embryos of two indirect developing species: Scaphechinus mirabilis and Hemicentrotus pulcherrimus. The embryos were placed under a dissecting microscope (SMZ8, Leica) and ectodermal epithelium together with underlying mesenchyme cells was dissected out with a glass needle. The region along the midline of the embryo at the width of the archenteron was designated the ‘midline region’, and the region lateral to the ‘midline region’ was designated the ‘lateral region’. When the left and/or the right side was excised, the whole lateral region was precisely removed on the animal side, but the plane of incision deviated more laterally on the vegetal side to avoid the ventro-lateral cluster of primary mesenchyme cells, so that a part of the defined ‘lateral region’ was left on the vegetal side. The vertical excision was made by cutting mid-gastrula embryos vertically to the archenteron at a level just superior to the tip of the archenteron. In the sham operation, embryos were pressed with the needle as in the vertical excision, but the incision was stopped slightly before the animal and vegetal halves of the embryos were completely divided from each other. The operated embryos were examined through an optical microscope (Optiphoto, Nikon) to confirm that the excision was correct, and they were then cultured with a food supply (diatoms, Chaetoceros gracilis). The handedness of the adult rudiment was examined at the six-armed or eight-armed pluteus stage through an optical microscope (Table 1).

scholarly journals A large-scale analysis of mRNAs expressed by primary mesenchyme cells of the sea urchin embryo

Development ◽  
2001 ◽  
Vol 128 (13) ◽  
pp. 2615-2627 ◽  
Author(s):  
Xiaodong Zhu ◽  
Gregory Mahairas ◽  
Michele Illies ◽  
R. Andrew Cameron ◽  
Eric H. Davidson ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Surface Proteins ◽  
Matrix Proteins ◽  
Specific Cell ◽  
Gastrula Stage ◽  
Sea Urchin Embryo ◽  
Expressed Sequenced Tags ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

The primary mesenchyme cells (PMCs) of the sea urchin embryo have been an important model system for the analysis of cell behavior during gastrulation. To gain an improved understanding of the molecular basis of PMC behavior, a set of 8293 expressed sequenced tags (ESTs) was derived from an enriched population of mid-gastrula stage PMCs. These ESTs represented approximately 1200 distinct proteins, or about 15% of the mRNAs expressed by the gastrula stage embryo. 655 proteins were similar (P<10−7 by BLAST comparisons) to other proteins in GenBank, for which some information is available concerning expression and/or function. Another 116 were similar to ESTs identified in other organisms, but not further characterized. We conservatively estimate that sequences encoding at least 435 additional proteins were included in the pool of ESTs that did not yield matches by BLAST analysis. The collection of newly identified proteins includes many candidate regulators of primary mesenchyme morphogenesis, including PMC-specific extracellular matrix proteins, cell surface proteins, spicule matrix proteins and transcription factors. This work provides a basis for linking specific molecular changes to specific cell behaviors during gastrulation. Our analysis has also led to the cloning of several key components of signaling pathways that play crucial roles in early sea urchin development.

Multiple signaling events specify ectoderm and pattern the oral-aboral axis in the sea urchin embryo

Development ◽  
1997 ◽  
Vol 124 (1) ◽  
pp. 13-20 ◽  
Author(s):  
A.H. Wikramanayake ◽  
W.H. Klein
Keyword(s):  
Sea Urchin ◽  
Lithium Treatment ◽  
Specific Marker ◽  
Cellular Interactions ◽  
Ciliary Band ◽  
Lytechinus Pictus ◽  
Sea Urchin Embryo ◽  
Oral Ectoderm ◽  
Multiple Signaling

In the sea urchin embryo, the animal-vegetal axis is established during oogenesis and the oral-aboral axis is specified sometime after fertilization. The mechanisms by which either of these axes are specified and patterned during embryogenesis are poorly understood. Here, we investigated the role of cellular interactions in the specification of the ectoderm territories and polarization of the ectoderm along the oral-aboral axis. Isolated animal halves (mesomeres), which are fated to give rise to oral and aboral ectoderm, developed into polarized embryoids that expressed an oral ectoderm-specific marker uniformly. These embryoids also produced neuron-like cells and serotonergic neurons, suggesting that mesomeres are autonomously specified as oral ectoderm. Mesomere-derived embryoids did not express any aboral ectoderm-specific markers, although we previously showed that aboral ectoderm-specific genes can be induced by 25 mM lithium chloride, which also induced endoderm formation (Wikramanayake, A. H., Brandhorst, B. P. and Klein, W. H.(1995). Development 121, 1497–1505). To ascertain if endoderm formation is a prerequisite for induction of aboral ectoderm by lithium and for normal ectoderm patterning in animal halves, we modulated the lithium treatment to ensure that no endoderm formed. Remarkably, treating animal halves with 10 mM LiCl at approximately 7 hours postfertilization resulted in embryoids that displayed oral-aboral axis patterning in the absence of endoderm. Application of 25 mM LiCl to animal halves at approximately 16 hours postfertilization, which also did not induce endoderm, resulted in polarized expression of the aboral ectoderm-specific LpS1 protein, but global expression of the Ecto V antigen and no induction of the stomodeum or ciliary band. These results suggest that at least two signals, a positive inductive signal to specify the aboral ectoderm and a negative suppressive signal to inactivate oral ectoderm-specific genes in the prospective aboral ectoderm territory, are needed for correct spatial expression of oral and aboral ectoderm-specific genes. Transmission of both these signals may be prerequisite for induction of secondary ectodermal structures such as the ciliary band and stomodeum. Thus, differentiation of ectoderm and polarization of the oral-aboral axis in Lytechinus pictus depends on cellular interactions with vegetal blastomeres as well as interactions along the oral-aboral axis.

T-brain homologue (HpTb) is involved in the archenteron induction signals of micromere descendant cells in the sea urchin embryo

Development ◽  
2002 ◽  
Vol 129 (22) ◽  
pp. 5205-5216 ◽  
Author(s):  
Takuya Fuchikami ◽  
Keiko Mitsunaga-Nakatsubo ◽  
Shonan Amemiya ◽  
Toshiya Hosomi ◽  
Takashi Watanabe ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Sea Urchin ◽  
Nuclear Localization ◽  
Signaling Cascade ◽  
Gastrula Stage ◽  
Blastula Stage ◽  
Sea Urchin Embryo ◽  
Mesenchyme Cells ◽  
Antisense Morpholino ◽  
Hemicentrotus Pulcherrimus

Signals from micromere descendants play a crucial role in sea urchin development. In this study, we demonstrate that these micromere descendants express HpTb, a T-brain homolog of Hemicentrotus pulcherrimus. HpTb is expressed transiently from the hatched blastula stage through the mesenchyme blastula stage to the gastrula stage. By a combination of embryo microsurgery and antisense morpholino experiments, we show that HpTb is involved in the production of archenteron induction signals. However, HpTb is not involved in the production of signals responsible for the specification of secondary mesenchyme cells, the initial specification of primary mesenchyme cells, or the specification of endoderm.HpTb expression is controlled by nuclear localization ofβ-catenin, suggesting that HpTb is in a downstream component of the Wnt signaling cascade. We also propose the possibility that HpTbis involved in the cascade responsible for the production of signals required for the spicule formation as well as signals from the vegetal hemisphere required for the differentiation of aboral ectoderm.

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