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.

fatvg encodes a new localized RNA that uses a 25-nucleotide element (FVLE1) to localize to the vegetal cortex of Xenopus oocytes

Development ◽  
1999 ◽  
Vol 126 (22) ◽  
pp. 4943-4953 ◽  
Author(s):  
A.P. Chan ◽  
M. Kloc ◽  
L.D. Etkin
Keyword(s):  
Cell Fate ◽  
Xenopus Oocytes ◽  
Single Copy ◽  
Biological Functions ◽  
Embryonic Patterning ◽  
Cis Acting ◽  
Maternal Transcript ◽  
Vegetal Cortex ◽  
Mitochondrial Cloud ◽  
Localization Elements

Vegetally localized transcripts have been implicated in a number of important biological functions, including cell fate determination and embryonic patterning. We have isolated a cDNA, fatvg, which encodes a localized maternal transcript that exhibits a localization pattern reminiscent of Vg1 mRNA. fatvg is the homologue of a mammalian gene expressed in adipose tissues. The fatvg transcript, unlike Vg1 which localizes strictly through the Late pathway, also associates with the mitochondrial cloud that is characteristic of the METRO or Early pathway. This suggests that fatvg mRNA may utilize both the METRO and Late pathways to localize to the vegetal cortex during oogenesis. We have dissected the cis-acting localization elements of fatvg mRNA and compared these elements with Vg1 mRNA. Our results indicate that, like most localized RNAs, in a variety of systems, transcripts of fatvg contain localization elements in the 3′UTR. The 3′UTR of fatvg mRNA contains multiple elements that are able to function independently; however, it functions most efficiently when all of the elements are present. We have defined a short 25-nucleotide element that can direct vegetal localization as a single copy. This element differs in sequence from previously described Vg1 localization elements, suggesting that different localization elements are involved in the localization of RNAs through the Late pathway.

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.

Xwnt-11: a maternally expressed Xenopus wnt gene

Development ◽  
1993 ◽  
Vol 119 (4) ◽  
pp. 1161-1173 ◽  
Author(s):  
M. Ku ◽  
D.A. Melton
Keyword(s):  
Embryonic Development ◽  
Neural Tube ◽  
Marginal Zone ◽  
Mrna Localization ◽  
Branchial Arch ◽  
Axis Formation ◽  
Maternal Mrna ◽  
Egg Maturation ◽  
Vegetal Cortex ◽  
Overexpression Phenotype

We have isolated and characterized a novel Xenopus wnt gene, Xwnt-11, whose expression pattern and overexpression phenotype suggest that it may be important for dorsal-ventral axis formation. Xwnt-11 mRNA is present during oogenesis and embryonic development through swimming tadpole stages. Xwnt-11 mRNA is ubiquitous in early oocytes and is localized during mid-oogenesis. By late oocyte stages, Xwnt-11 mRNA is localized to the vegetal cortex, with some mRNA in the vegetal cytoplasm. After egg maturation, Xwnt-11 mRNA is released from the vegetal cortex and is found in the vegetal cytoplasm. This early pattern of Xwnt-11 mRNA localization is similar to another vegetally localized maternal mRNA, Vg1 (D. A. Melton (1987) Nature 328, 80–82). In the late blastula, Xwnt-11 mRNA is found at high levels in the dorsal marginal zone. As gastrulation proceeds, Xwnt-11 mRNA appears in the lateral and ventral marginal zone and, during tadpole stages, it is found in the somites and first branchial arch. Injection of Xwnt-11 mRNA into UV-ventralized embryos can substantially rescue the UV defect by inducing the formation of dorsal tissues. The rescued embryos develop somitic muscle and neural tube; however, they lack notochord and anterior head structures.

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