Anteroposterior patterning of the epidermis by inductive influences from the vegetal hemisphere cells in the ascidian embryo

Development ◽  
1999 ◽  
Vol 126 (22) ◽  
pp. 4955-4963 ◽  
Author(s):  
S. Wada ◽  
Y. Katsuyama ◽  
H. Saiga
Keyword(s):  
Anterior Part ◽  
Homeobox Genes ◽  
Animal Cells ◽  
Regulation Of Expression ◽  
Cell Stage ◽  
Anteroposterior Patterning ◽  
Anteroposterior Axis ◽  
Cell Ablation ◽  
Adhesive Papillae ◽  
Ascidian Embryo

Patterning along the anteroposterior axis is a critical step during animal embryogenesis. Although mechanisms of anteroposterior patterning in the neural tube have been studied in various chordates, little is known about those of the epidermis. To approach this issue, we investigated patterning mechanisms of the epidermis in the ascidian embryo. First we examined expression of homeobox genes (Hrdll-1, Hroth, HrHox-1 and Hrcad) in the epidermis. Hrdll-1 is expressed in the anterior tip of the epidermis that later forms the adhesive papillae, while Hroth is expressed in the anterior part of the trunk epidermis. HrHox-1 and Hrcad are expressed in middle and posterior parts of the epidermis, respectively. These data suggested that the epidermis of the ascidian embryo is patterned anteroposteriorly. In ascidian embryogenesis, the epidermis is exclusively derived from animal hemisphere cells. To investigate regulation of expression of the four homeobox genes in the epidermis by vegetal hemisphere cells, we next performed hemisphere isolation and cell ablation experiments. We showed that removal of the vegetal cells before the late 16-cell stage results in loss of expression of these homeobox genes in the animal hemisphere cells. Expression of Hrdll-1 and Hroth depends on contact with the anterior-vegetal (the A-line) cells, while expression of HrHox-1 and Hrcad requires contact with the posterior-vegetal (the B-line) cells. We also demonstrated that contact with the vegetal cells until the late 32-cell stage is sufficient for animal cells to express Hrdll-1, Hroth and Hrcad, while longer contact is necessary for HrHox-1 expression. Contact with the A-line cells until the late 32-cell stage is also sufficient for formation of the adhesive papillae. Our data indicate that the epidermis of the ascidian embryo is patterned along the anteroposterior axis by multiple inductive influences from the vegetal hemisphere cells and provide the first insight into mechanisms of epidermis patterning in the chordate embryos.

Acetylcholinesterase development in extra cells caused by changing the distribution of myoplasm in ascidian embryos

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 343-354
Author(s):  
J. R. Whittaker
Keyword(s):  
Cytochalasin B ◽  
Continuous Treatment ◽  
Functional Specificity ◽  
Cell Stage ◽  
Division Plane ◽  
Styela Plicata ◽  
Developmental Fate ◽  
Ascidian Embryos ◽  
Functional Autonomy ◽  
Ascidian Embryo

This research shows that myoplasmic crescent material of the ascidian egg has both functional autonomy and functional specificity in establishing the differentiation pathway of muscle lineage cells. The cytoplasmic segregation pattern in eggs of Styela plicata was altered by compression of the embryos during third cleavage. This caused a meridional division instead of the normal equatorial third cleavage; first and second cleavages are meridional. Since eggs of S. plicata have a pronounced yellow myoplasmic crescent, one observes directly that third cleavage under compression resulted in a flat 8-cell stage with four cells containing yellow myoplasm instead of the two myoplasm-containing cells that would be formed by normal equatorial division at third cleavage. If such altered 8-cell-stage embryos were released from compression and kept from undergoing further divisions by continuous treatment with cytochalasin B, some embryos eventually developed histospecific acetylcholinesterase in three and four cells instead of in just the two muscle lineage cells found in cleavage-arrested normal 8-cell stages. The wider myoplasmic distribution effected by altering the division plane at third cleavage apparently caused a change in developmental fate of the extra cells receiving myoplasm. This meridional third cleavage also resulted in a changed nuclear lineage pattern. Two nuclei that would ordinarily be in ectodermal lineage cells after third cleavage were now associated with yellow myoplasm. Acetylcholinesterase development in these cells demonstrates that nuclear lineages are not responsible for muscle acetylcholinesterase development in the ascidian embryo.

scholarly journals The Planarian HOM/HOX Homeobox Genes (Plox) Expressed along the Anteroposterior Axis

1999 ◽  
Vol 210 (2) ◽  
pp. 456-468 ◽  
Author(s):  
Hidefumi Orii ◽  
Kentaro Kato ◽  
Yoshihiko Umesono ◽  
Takashige Sakurai ◽  
Kiyokazu Agata ◽  
...  
Keyword(s):  
Homeobox Genes ◽  
Anteroposterior Axis

Most of centrin in animal cells is not centrosome-associated and centrosomal centrin is confined to the distal lumen of centrioles

1996 ◽  
Vol 109 (13) ◽  
pp. 3089-3102 ◽  
Author(s):  
A. Paoletti ◽  
M. Moudjou ◽  
M. Paintrand ◽  
J.L. Salisbury ◽  
M. Bornens
Keyword(s):  
Calcium Binding ◽  
Complex Structure ◽  
Specific Pattern ◽  
Dominant Negative ◽  
Cell Fractionation ◽  
Animal Cells ◽  
Negative Effects ◽  
Cell Stage ◽  
Centriole Duplication ◽  
Ef Hand

Centrin is a member of the calcium-binding EF-hand protein superfamily present in centrosomes of widely divergent species. Investigating the cellular distribution of human centrin by both immunofluorescence and cell fractionation, we report that centrin is biochemically complex in human cells, displaying as much as ten isoforms in 2-D electrophoresis. This suggests that centrin may be subject to multiple regulations. Strikingly, more than 90% of centrin is not associated with the centrosome fraction. The centrosome-associated centrin, however, displays a specific pattern in 2-D electrophoresis and is concentrated within the distal lumen of the centrioles, where a complex structure has been previously described. This precise localization allows the resolution of centrioles at the optical level throughout the cell cycle and provides a valuable tool for monitoring centriole duplication. To get insights on centrin function, we performed injection experiments of recombinant heterologous centrin in two-cell stage frog embryos in an attempt to produce dominant negative effects. We report that green algae and human centrin delay cleavage and promote the formation of abnormal blastomeres in which the distribution of microtubule asters and of nuclei is dramatically impaired. This suggests that centrin could be involved in the centrosome reproduction cycle, in the coordination of cytoplasmic and nuclear division or in cytokinesis.

Development and Biology of the Larva of Saccoglossus Horsti (Enteropneusta)

1952 ◽  
Vol 236 (639) ◽  
pp. 553-589 ◽  
Keyword(s):  
Anterior Part ◽  
Cell Stage ◽  
Apical Tuft ◽  
Polar Bodies ◽  
The Family ◽  
Planktonic Phase ◽  
Mode Of Life ◽  
Fertilization Membrane ◽  
Mode Of Development ◽  
Dispersal Period

Larvae of Saccoglossus horsti were reared in the laboratory, and their developmental history from the egg to the five gill-slit stage studied. The immature eggs varied from 0.23 to 0.30 mm in length and from 0.15 to 0.22 mm in breadth. They were irregular, opaque, finely granular and creamish grey in colour. They became spherical on maturing. Fertilization resulted in the rapid erection of a fertilization membrane, making the eggs buoyant. Two similar polar bodies were extruded shortly afterwards, marking the plane of the first cleavage which, with the second, was holoblastic and meridional. Subsequent cleavages were different in the animal and vegetative tiers. There was evidence of radial cleavage during the 16- to 32-cell stage. A hollow blastula was formed at the 9th to 10th cleavage stage, and gastrulation by invagination followed. The blastocoele was completely obliterated and a typical archigastrula resulted. This rapidly became uniformly ciliated and developed a telotroch around the closing blastopore. The component cilia of the telotroch imparted a slow rotatory movement to the embryo. Axial elongation and the growth of an apical tuft were accompanied by the formation of a faint annular groove. This groove marked off the definitive proboscis and the anterior part of the collar. Hatching followed 30 to 36 h after fertilization, and the larva became planktonic. During its lecithotrophic existence the larva developed a second annular groove anterior to the first, marking off the definitive proboscis from the anterior region of the collar. No definite phototaxis was detectable. Swimming movements were spasmodic. The larva rotated in a clockwise direction when viewed from the apical tuft. The spiral mode of propulsion and the propelling action of the telotroch is discussed. Settlement occurred some 2 days after hatching. A post-telotrochal adhesive patch was developed just prior to settlement, enabling the larva to adhere tenaciously to the substratum. After settlement further elongation of the main axis occurred, a well-defined proboscis, collar and trunk were rapidly differentiated. Of particular interest is the development of a long, muscular strongly ciliated post-anal tail. A dispersal period of about 6 1 2 to 7 days occurred prior to settlement. The existence of this phase prior to the animal adopting the adult mode of life demands that the mode of development of certain members of the family Harrimanidae be regarded as indirect and comparable in many respects to that known for some of the family Ptychoderidae. The mouth, anus and gill apertures became functional at much the same period, viz., at the onset of the burrowing phase. Remarkable growth movements initiated during the late planktonic phase were accelerated after settlement. This resulted in the translation of the telotroch to a latero-ventral position on the trunk and tail. The behaviour of the tail during the process of ciliary feeding, as well as during the coursing through the burrow, was observed. Ciliary reversal occurred on collar, trunk and tail. This phenomenon is discussed. Special tactile cilia have been described. They occurred on the dorsal and latero-dorsal surfaces of the trunk and tail. There was some evidence of gregariousness. The possibility of this larval habit is briefly considered in relation to the dispersal of the adults in the field. The homologies of the Enteropneusta and the Pterobranchia are discussed in some detail, with particular reference to the tail of the larval Saccoglossus horsti , and the stalk of the genus Cephalodiscus .

Effect of activin and lithium on isolated Xenopus animal blastomeres and response alteration at the midblastula transition

Development ◽  
1995 ◽  
Vol 121 (6) ◽  
pp. 1581-1589
Author(s):  
K. Kinoshita ◽  
M. Asashima
Keyword(s):  
Lithium Treatment ◽  
Treated Animal ◽  
Mesoderm Induction ◽  
Animal Cells ◽  
Cell Stage ◽  
Midblastula Transition ◽  
Amphibian Embryo ◽  
Peptide Growth Factors ◽  
Default State ◽  
Mesoderm Patterning

Dorsoventral mesoderm patterning in the amphibian embryo involves a series of interactions mediated by several peptide growth factors. Animal blastomeres isolated at the 8-cell stage are useful for studying mesoderm patterning, since they contain the prospective (uninduced) mesoderm region and allow examination of the default state of animal cells. When activin is applied to these dorsal and ventral animal half explants, a competence prepattern for responding to activin is observed. In order to investigate the characteristics of prepatterning, we treated animal blastomeres with the embryo dorsalizing agent LiCl. Treatment with lithium alone did not induce normal trunk mesoderm in either blastomere. Lithium did, however, alter the competence of animal blastomeres to activin. Dorsal mesoderm was formed in the ventral blastomeres, as well as in the dorsal blastomeres. This result reveals that the early dorsoventral polarity in the animal hemisphere is not fixed. Using goosecoid(gsc) and Xwnt-8 genes as dorsal and ventral mesoderm markers, it was verified that lithium modifies the competence to activin. Unexpectedly, lithium treatment on its own resulted in gsc expression in the animal half explants. This suggests that embryo goosecoid expression may be induced by the effect of dorsal determination activity, but not by mesoderm induction. However, lithium induced also the expression of brachyury (Xbra) gene at very low levels. This would indicate the formation of dorsal-anterior mesoderm, which was not identified by the tissue observations. Expression of Xwnt-8, a ventral mesoderm marker usually induced in blastula animal caps by activin, was hardly induced in the blastomere explants. We isolated whole animal half explants at the 8-cell stage and exposed to activin at different stages. It was found that the same concentration of activin induces gsc before the midblastula stage, and induces Xwnt-8 at later stages. This suggests that the response of animal blastomeres alters depending on the stage of activin signaling.

An FGF signal from endoderm and localized factors in the posterior-vegetal egg cytoplasm pattern the mesodermal tissues in the ascidian embryo

Development ◽  
2000 ◽  
Vol 127 (13) ◽  
pp. 2853-2862 ◽  
Author(s):  
G.J. Kim ◽  
A. Yamada ◽  
H. Nishida
Keyword(s):  
Marginal Zone ◽  
Normal Development ◽  
Cell Stage ◽  
Asymmetric Divisions ◽  
Notochord Cells ◽  
Ascidian Embryos ◽  
The Difference ◽  
Mesenchyme Cells ◽  
Time Required ◽  
Ascidian Embryo

The major mesodermal tissues of ascidian larvae are muscle, notochord and mesenchyme. They are derived from the marginal zone surrounding the endoderm area in the vegetal hemisphere. Muscle fate is specified by localized ooplasmic determinants, whereas specification of notochord and mesenchyme requires inducing signals from endoderm at the 32-cell stage. In the present study, we demonstrated that all endoderm precursors were able to induce formation of notochord and mesenchyme cells in presumptive notochord and mesenchyme blastomeres, respectively, indicating that the type of tissue induced depends on differences in the responsiveness of the signal-receiving blastomeres. Basic fibroblast growth factor (bFGF), but not activin A, induced formation of mesenchyme cells as well as notochord cells. Treatment of mesenchyme-muscle precursors isolated from early 32-cell embryos with bFGF promoted mesenchyme fate and suppressed muscle fate, which is a default fate assigned by the posterior-vegetal cytoplasm (PVC) of the eggs. The sensitivity of the mesenchyme precursors to bFGF reached a maximum at the 32-cell stage, and the time required for effective induction of mesenchyme cells was only 10 minutes, features similar to those of notochord induction. These results support the idea that the distinct tissue types, notochord and mesenchyme, are induced by the same signaling molecule originating from endoderm precursors. We also demonstrated that the PVC causes the difference in the responsiveness of notochord and mesenchyme precursor blastomeres. Removal of the PVC resulted in loss of mesenchyme and in ectopic notochord formation. In contrast, transplantation of the PVC led to ectopic formation of mesenchyme cells and loss of notochord. Thus, in normal development, notochord is induced by an FGF-like signal in the anterior margin of the vegetal hemisphere, where PVC is absent, and mesenchyme is induced by an FGF-like signal in the posterior margin, where PVC is present. The whole picture of mesodermal patterning in ascidian embryos is now known. We also discuss the importance of FGF induced asymmetric divisions, of notochord and mesenchyme precursor blastomeres at the 64-cell stage.

bFGF as a possible morphogen for the anteroposterior axis of the central nervous system in Xenopus

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3121-3130 ◽  
Author(s):  
M. Kengaku ◽  
H. Okamoto
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neural Development ◽  
Anteroposterior Patterning ◽  
Anteroposterior Axis ◽  
Spemann's Organizer ◽  
The Central Nervous System ◽  
Dorsal Ectoderm ◽  
Higher Doses

Vertebrate neural development is initiated during gastrulation by the inductive action of the dorsal mesoderm (Spemann's organizer in amphibians) on neighbouring ectoderm, which eventually gives rise to the central nervous system from forebrain to spinal cord. Here we present evidence that bFGF can mimic the organizer action by inducing Xenopus ectoderm cells in culture to express four position-specific neural markers (XeNK-2, En-2, XIHbox1 and XIHbox6) along the anteroposterior axis. bFGF also induced the expression of a general neural marker NCAM but not the expression of immediate-early mesoderm markers (goosecoid, noggin, Xbra and Xwnt-8), suggesting that bFGF directly neuralized ectoderm cells without forming mesodermal cells. The bFGF dose required to induce the position-specific markers was correlated with the anteroposterior location of their expression in vivo, with lower doses eliciting more anterior markers and higher doses more posterior markers. These data indicate that bFGF or its homologue is a promising candidate for a neural morphogen for anteroposterior patterning in Xenopus. Further, we showed that the ability of ectoderm cells to express the anterior markers in response to bFGF was lost by mid-gastrula, before the organizer mesoderm completely underlies the anterior dorsal ectoderm. Thus, an endogenous FGF-like molecule released from the involuting organizer may initiate the formation of the anteroposterior axis of the central nervous system during the early stages of gastrulation by forming a concentration gradient within the plane of dorsal ectoderm.

Interactions of different vegetal cells with mesomeres during early stages of sea urchin development

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 881-890 ◽  
Author(s):  
O. Khaner ◽  
F. Wilt
Keyword(s):  
Sea Urchin ◽  
Normal Development ◽  
Pigment Cells ◽  
Regional Differentiation ◽  
Cell Type ◽  
Animal Cells ◽  
Cell Stage ◽  
Latent Ability ◽  
A Cell ◽  
Poorly Differentiated

It has been known from results obtained in the classical experiments on sea urchin embryos that cell isolation and transplantation showed extensive interactions between the early blastomeres and/or their descendants. In the experiments reported here a systematic reexamination of recombination of mesomeres and their progeny (which come from the animal hemisphere) with various vegetal cells derived from blastomeres of the 32- and 64-cell stage was carried out. Cells were marked with lineage tracers to follow which cell gave rise to what structures, and newly available molecular markers have been used to analyze different structures characteristic of regional differentiation. Large micromeres form spicules and induce gut and pigment cells in mesomeres, conforming to previous results. Small micromeres, a cell type not heretofore examined, gave rise to no recognizable structure and had very limited ability to evoke poorly differentiated gut tissue in mesomeres. Macromeres and their descendants, Veg 1 and Veg 2, form primarily what their normal fate dictated, though both did have some capacity to form spicules, presumably by formation from secondary mesenchyme. Macromeres and their descendants were not potent inducers of vegetal structures in animal cells, but they suppress the latent ability of mesomeres to form vegetal structures. The results lead us to propose that the significant interactions during normal development may be principally suppressive effects of mesomeres on one another and of adjacent vegetal cells on mesomeres.

40 EARLY DEVELOPMENT OF RECONSTRUCTED MOUSE EMBRYOS USING BONE MARROW CELLS FROZEN WITHOUT CRYOPROTECTANT

2008 ◽  
Vol 20 (1) ◽  
pp. 100
Author(s):  
H. Kato ◽  
A. Nakao ◽  
M. Nishiwaki ◽  
M. Anzai ◽  
T. Mitani ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Cumulus Cells ◽  
Freezing Temperature ◽  
Animal Cells ◽  
Cell Stage ◽  
Fresh Bone ◽  
Nuclear Injection ◽  
Frozen Bone ◽  
Marrow Cells

Animal cells frozen with suitable cryoprotectants have been successfully cryopreserved for long periods of time, maintaining viability upon thawing. Animal cells frozen without cryoprotectant, however, may suffer serious damage and not be useful as donors in somatic cell nuclear transfer (SCNT). However, in some cases, old animal samples were frozen only as a whole body or a piece of tissue without cryoprotectant. If the cells from such old samples could be useful for SCNT, then there are potentially many candidates where individual animals could be reproduced. In this study, we examined the possibility of using mouse bone marrow cells frozen without cryoprotectant as nuclear donors in SCNT. Thigh bones were collected from B6C3F1 mice and frozen in either a –25�C or a –80�C freezer for more than one month. Thawing of frozen bones was performed by placing them in an incubator at 37�C. Bone marrow cells were collected by washing the bone cavity with saline. Recipient oocytes for SCNT were collected from B6D2F1 female mice. The enucleation of recipient oocytes and the injection of nuclei were performed as previously reported (Wakayama et al. 1998 Nature 394, 369–374) with a piezo-actuated micromanipulator system. In this study, 4 groups of mouse cells (fresh bone marrow cells, bone marrow cells frozen at –25�C, bone marrow cells frozen at –80�C, and fresh cumulus cells) were used as the nuclear donors in SCNT. After nuclear injection, embryos were kept in mCZB medium for 1 h at 37�C. Subsequently, embryos were cultured for 3 h with 5 µg mL–1 cytochalasin B and 10 mm SrCl2 for activation and cultured for an additional 20 h in mKSOM medium. The nuclear dynamics of SCNT embryos in each donor cell group was observed using 42,6-diamidino-2-phenylindole (DAPI) staining and a fluorescent microscope at 0, 1, 7, and 24 h after nuclear injection. Data were analyzed by Student's t-test. The cell viability after thawing by trypan blue vital staining was about 20% regardless of freezing temperature. At 7 h after nuclear injection, the SCNT embryos injected with frozen bone marrow cells, regardless of freezing temperature, had more single pronuclei (67%, 54/81; P < 0.05) than SCNT embryos injected with either fresh bone marrow cells (36%, 26/73) or cumulus cells (28%, 67/236). At 24 h after nuclear injection, fewer SCNT embryos injected with bone marrow cells, either fresh or frozen, developed to the 2-cell stage (fresh: 11%, 6/56; frozen at –25�C: 21%, 5/24; frozen at –80�C: 20%, 10/49) than SCNT embryos injected with cumulus cells (58%, 185/319; P < 0.05). There was no difference in the embryonic development to the 2-cell stage among SCNT embryos injected with either fresh or frozen bone marrow cells. Further studies are required to determine whether cells frozen without cryoprotectant are capable of resulting in viable clones.

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