Translocation of a localized maternal mRNA to the vegetal pole of Xenopus oocytes

Nature ◽  
1987 ◽  
Vol 328 (6125) ◽  
pp. 80-82 ◽  
Author(s):  
D. A. Melton
Keyword(s):  
Xenopus Oocytes ◽  
Maternal Mrna ◽  
Vegetal Pole

A gastrulation center in the ascidian egg

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 53-63 ◽  
Author(s):  
William R. Jeffery
Keyword(s):  
Nervous System ◽  
Uv Irradiation ◽  
Second Phase ◽  
Uv Sensitivity ◽  
Maternal Mrna ◽  
Free Translation ◽  
Vegetal Pole ◽  
Cell Embryo ◽  
Ooplasmic Segregation ◽  
Uv Dose

A gastrulation center is described in ascidian eggs. Extensive cytoplasmic rearrangements occur in ascidian eggs between fertilization and first cleavage. During ooplasmic segregation, a specific cytoskeletal domain (the myoplasm) is translocated first to the vegetal pole (VP) and then to the posterior region of the zygote. A few hours later, gastrulation is initiated by invagination of endoderm cells in the VP region of the 110-cell embryo. After the completion of gastrulation, the embryonic axis is formed, which includes induction of the nervous system, morphogenesis of the larval tail and differentiation of tail muscle cells. Microsurgical deletion or ultraviolet (UV) irradiation of the VP region during the first phase of myoplasmic segregation prevents gastrulation, nervous system induction and tail formation, without affecting muscle cell differentiation. Similar manipulations of unfertilized eggs or uncleaved zygotes after the second phase of segregation have no effect on development, suggesting that a gastrulation center is established by transient localization of myoplasm in the VP region. The function of the gastrulation center was investigated by comparing protein synthesis in normal and UV-irradiated embryos. About 5% of 433 labelled polypeptides detected in 2D gels were affected by UV irradiation. The most prominent protein is a 30 kDa cytoskeletal component (p30), whose synthesis is abolished by UV irradiation. p30 synthesis peaks during gastrulation, is affected by the same UV dose and has the same UV-sensitivity period as gastrulation. However, p30 is not a UV-sensitive target because it is absent during ooplasmic segregation, the UV-sensitivity period. Moreover, the UV target has the absorption maximum of a nucleic acid rather than a protein. Cell-free translation studies indicate that p30 is encoded by a maternal mRNA. UV irradiation inhibits the ability of this transcript to direct p30 synthesis, indicating that p30 mRNA is a UV-sensitive target The gastrulation center may function by sequestration or activation of maternal mRNAs encoding proteins that function during embryogenesis.

Nonspecific effects of oligodeoxynucleotide injection in Xenopus oocytes: a reevaluation of previous D7 mRNA ablation experiments

Development ◽  
1990 ◽  
Vol 110 (3) ◽  
pp. 769-779
Author(s):  
R.C. Smith ◽  
W.M. Bement ◽  
M.A. Dersch ◽  
E. Dworkin-Rastl ◽  
M.B. Dworkin ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Xenopus Oocytes ◽  
Cell Metabolism ◽  
Germinal Vesicle ◽  
Annulate Lamellae ◽  
Maternal Mrna ◽  
Nonspecific Effects ◽  
Abnormal Accumulation ◽  
Cellular Mrnas

Microinjection of oligodeoxynucleotides (ODNs) complementary to cellular mRNAs has been advanced as an experimental approach to degrade target mRNAs in vivo and thereby obtain information as to the function of their cognate proteins. It is shown here that ODNs can induce a variety of aberrations in cell metabolism and structure when injected into Xenopus oocytes. Examination of histological sections of ODN-injected oocytes revealed the frequent abnormal accumulation of heavily staining basophilic material in the area of the germinal vesicle (gv). Ultrastructural analysis detected further abnormalities including blebbing of the plasma membrane, anomalous cytoskeletal structures, hyperorganised annulate lamellae, hyperinvagination of the gv, and formation of irregular nucleoli within the gv. Analysis of newly synthesised proteins by [35S]methionine radiolabelling of oocytes demonstrated that ODN injection can trigger a general decrease in both label uptake and protein synthesis. Qualitative effects on protein synthesis could also be observed, particularly a decrease in synthesis of high molecular weight proteins. The severity of ODN-induced effects is dose-dependent and highly variable from ODN to ODN. The previously reported delay in progesterone-induced maturation observed in oocytes depleted of the maternal mRNA D7 by ODN-directed degradation (Smith R. C., Dworkin M. B. and Dworkin-Rastl E. (1988) Genes and Devpt. 2, 1296–1306) is most likely a result of nonspecific ODN effects in the oocyte. Oocytes injected with effective antisense D7 ODNs that do not display detectable side effects matured with normal kinetics.

scholarly journals Stability and movement of mRNAs and their encoded proteins in Xenopus oocytes.

1985 ◽  
Vol 100 (4) ◽  
pp. 1148-1156 ◽  
Author(s):  
D R Drummond ◽  
M A McCrae ◽  
A Colman
Keyword(s):  
Injection Site ◽  
Xenopus Oocytes ◽  
Secretory Proteins ◽  
Globin Mrna ◽  
Encoded Proteins ◽  
Vegetal Pole ◽  
The Stability ◽  
Chicken Ovalbumin

The stability and movement of several polyadenylated (poly A+) and nonpolyadenylated (poly A-) mRNAs in Xenopus oocytes have been examined. At least 50% of the poly A+ mRNA molecules (9S rabbit globin mRNA, chicken ovalbumin, and lysozyme) were stable in oocytes over a 48-h period, irrespective of the amount injected. About 50% of injected poly A- reovirus mRNAs was degraded within the first 24 h of injection, irrespective of the amount injected, although no further degradation was observed over an additional 24 h. The movement of all poly A+ mRNAs injected at either the animal or vegetal pole of the oocyte was very slow. Little movement of RNA from the animal half to the vegetal half was observed even 48 h after injection. In contrast, similar amounts of mRNA were present in both halves 48 h after vegetal pole injection. Similar results were obtained after injection of poly A- reovirus mRNAs. The movement of the proteins encoded by the poly A+ mRNAs was studied in the 6-h period after injection when little mRNA movement had occurred. 85% of the globin synthesized accumulated in the animal half irrespective of injection site. The movement of the sequestered secretory proteins ovalbumin and lysozyme in the same oocytes as globin was much slower; very little lysozyme appeared in the half of the oocyte opposite the site of injection.

Antisense oligodeoxyribonucleotide-directed cleavage of maternal mRNA in Xenopus oocytes and embryos

Gene ◽  
1988 ◽  
Vol 72 (1-2) ◽  
pp. 267-275 ◽  
Author(s):  
John Shuttleworth ◽  
Glenn Matthews ◽  
Les Dale ◽  
Chris Baker ◽  
Alan Colman
Keyword(s):  
Xenopus Oocytes ◽  
Maternal Mrna

The maternal mRNA Vg1 is correctly localized following injection into Xenopus oocytes

Nature ◽  
1988 ◽  
Vol 336 (6199) ◽  
pp. 592-595 ◽  
Author(s):  
Joel K. Yisraeli ◽  
D. A. Melton
Keyword(s):  
Xenopus Oocytes ◽  
Maternal Mrna

Photocrosslinking of proteins to maternal mRNA in Xenopus oocytes

1988 ◽  
Vol 128 (2) ◽  
pp. 349-358 ◽  
Author(s):  
Ruth E. Swiderski ◽  
Joel D. Richter
Keyword(s):  
Xenopus Oocytes ◽  
Maternal Mrna

A two-step model for the localization of maternal mRNA in Xenopus oocytes: involvement of microtubules and microfilaments in the translocation and anchoring of Vg1 mRNA

Development ◽  
1990 ◽  
Vol 108 (2) ◽  
pp. 289-298 ◽  
Author(s):  
J.K. Yisraeli ◽  
S. Sokol ◽  
D.A. Melton
Keyword(s):  
Xenopus Oocytes ◽  
Subcellular Fraction ◽  
Cytoplasmic Microtubule ◽  
Microtubule Array ◽  
Maternal Mrna ◽  
Step Model ◽  
Vegetal Cortex ◽  
Biochemical Fractionation

In an effort to understand how polarity is established in Xenopus oocytes, we have analyzed the process of localization of the maternal mRNA, Vg1. In fully grown oocytes, Vg1 mRNA is tightly localized at the vegetal cortex. Biochemical fractionation shows that the mRNA is preferentially associated with a detergent-insoluble subcellular fraction. The use of cytoskeletal inhibitors suggests that (1) microtubules are involved in the translocation of the message to the vegetal hemisphere and (2) microfilaments are important for the anchoring of the message at the cortex. Furthermore, immunohistochemistry reveals that a cytoplasmic microtubule array exists during translocation. These results suggest a role for the cytoskeleton in localizing information in the oocyte.

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