scholarly journals Cytoplasmic volume and limiting nucleoplasmin scale nuclear size during Xenopus laevis development

2019 ◽  
Author(s):  
Pan Chen ◽  
Miroslav Tomschik ◽  
Katherine Nelson ◽  
John Oakey ◽  
J. C. Gatlin ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Size Control ◽  
Scaling Factor ◽  
Nuclear Size ◽  
Developmental Mechanism ◽  
Size Scaling ◽  
Biochemical Fractionation ◽  
Nuclear Histone

SUMMARYHow nuclear size is regulated relative to cell size is a fundamental cell biological question. Reductions in both cell and nuclear sizes during Xenopus laevis embryogenesis provide a robust scaling system to study mechanisms of nuclear size regulation. To test if the volume of embryonic cytoplasm is limiting for nuclear growth, we encapsulated gastrula stage embryonic cytoplasm and nuclei in droplets of defined volume using microfluidics. Nuclei grew and reached new steady-state sizes as a function of cytoplasmic volume, supporting a limiting component mechanism of nuclear size control. Through biochemical fractionation, we identified the histone chaperone nucleoplasmin (Npm2) as a putative nuclear size-scaling factor. Cellular amounts of Npm2 decrease over development, and nuclear size was sensitive to Npm2 levels both in vitro and in vivo, affecting nuclear histone levels and chromatin organization. Thus, reductions in cell volume with concomitant decreases in Npm2 amounts represent a developmental mechanism of nuclear size-scaling that may also be relevant to cancers with increased nuclear size.

scholarly journals Nucleoplasmin is a limiting component in the scaling of nuclear size with cytoplasmic volume

2019 ◽  
Vol 218 (12) ◽  
pp. 4063-4078 ◽  
Author(s):  
Pan Chen ◽  
Miroslav Tomschik ◽  
Katherine M. Nelson ◽  
John Oakey ◽  
Jesse C. Gatlin ◽  
...  
Keyword(s):  
Steady State ◽  
Xenopus Laevis ◽  
Cell Volume ◽  
Size Control ◽  
Nuclear Size ◽  
Gastrula Stage ◽  
Biochemical Fractionation ◽  
Nuclear Histone

How nuclear size is regulated relative to cell size is a fundamental cell biological question. Reductions in both cell and nuclear sizes during Xenopus laevis embryogenesis provide a robust scaling system to study mechanisms of nuclear size regulation. To test if the volume of embryonic cytoplasm is limiting for nuclear growth, we encapsulated gastrula-stage embryonic cytoplasm and nuclei in droplets of defined volume using microfluidics. Nuclei grew and reached new steady-state sizes as a function of cytoplasmic volume, supporting a limiting component mechanism of nuclear size control. Through biochemical fractionation, we identified the histone chaperone nucleoplasmin (Npm2) as a putative nuclear size effector. Cellular amounts of Npm2 decrease over development, and nuclear size was sensitive to Npm2 levels both in vitro and in vivo, affecting nuclear histone levels and chromatin organization. We propose that reductions in cell volume and the amounts of limiting components, such as Npm2, contribute to developmental nuclear size scaling.

scholarly journals Elucidating nuclear size control in the Xenopus model system

2018 ◽  
Vol 72 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Predrag Jevtic ◽  
Daniel Levy
Keyword(s):  
Functional Significance ◽  
Evolutionary Relationship ◽  
Size Control ◽  
Model System ◽  
Nuclear Size ◽  
Nuclear Lamins ◽  
Egg Extracts ◽  
Cellular Feature

Background. Nuclear size is a tightly regulated cellular feature. Mechanisms that regulate nuclear size and the functional significance of this regulation are largely unknown. Nuclear size and morphology are often altered in many diseases, such as cancer. Therefore, understanding the mechanisms that regulate nuclear size is crucial to provide insight into the role of nuclear size in disease. Scope and Approach. The goal of this review is to summarize the most recent studies about the mechanisms and functional significance of nuclear size control using the Xenopus model system. First, this review describes how Xenopus egg extracts, embryos, and embryo extracts are prepared and used in scientific research. Next, the review focuses on the mechanisms and functional effects of proper nuclear size control that have been learned using the Xenopus system. Key Findings and Conclusions. Xenopus is an excellent in vivo and in vitro experimental platform to study mechanisms of nuclear size control. Given its close evolutionary relationship with mammals and that most cellular processes and pathways are highly conserved between Xenopus and humans, the Xenopus system has been a valuable tool to advance biomedical research. Some of the mechanisms that regulate nuclear size include components of nuclear import such as importin ? and NTF2, nuclear lamins, nucleoporins, proteins that regulate the morphology of the endoplasmic reticulum, and cytoskeletal elements.

Further studies on the melanophores of periodic albino mutant of Xenopus laevis

Development ◽  
1986 ◽  
Vol 91 (1) ◽  
pp. 65-78
Author(s):  
T. Fukuzawa ◽  
H. Ide
Keyword(s):  
Xenopus Laevis ◽  
Microscopic Level ◽  
Wild Type ◽  
Light Microscopic Level ◽  
In Vitro Proliferation ◽  
Albino Mutant ◽  
Site Of Action ◽  
Periodic Albino

It is still unknown why dermal melanophores disappear during larval development, and why no or very few epidermal melanophores appear during and after metamorphosis, in Xenopus laevis showing periodic albinism (ap). To elucidate these points, we investigated (1) the occurrence of depigmentation in mutant (ap/ap) melanophores during in vitro proliferation and (2) the incidence of melanophore differentiation from mutant melanoblasts in the skin in vitro. During in vitro proliferation of mutant melanophores, ap-type melanosomes decreased in number gradually and instead the number of premelanosomes increased in the cells, which caused depigmentation at the light microscopic level in the culture. Depigmentation was observed only in mutant melanophores, and not in wild-type (+/+) melanophores. These results suggest that autonomous depigmentation of mutant dermal melanophores is the cause of the disappearance of these cells in vivo. Dopa-positive melanoblasts were demonstrated in both wild-type and mutant skins. However, the melanoblasts of metamorphosed mutant froglets did not differentiate in vitro, while those of wild-type froglets did. These results suggest that mutant melanoblasts in the skin of froglets lose the potency to differentiate into melanophores, and that this causes the lack of mutant melanophores in the froglets. The site of action of the ap gene is also discussed.

Electron microscopic studies on the structure of motile primordial germ cells of Xenopus laevis in vitro

Development ◽  
1978 ◽  
Vol 46 (1) ◽  
pp. 119-133
Author(s):  
Janet Heasman ◽  
C. C. Wylie
Keyword(s):  
Xenopus Laevis ◽  
Germ Cells ◽  
Primordial Germ Cells ◽  
Structural Features ◽  
Culture Conditions ◽  
Structural Basis ◽  
Electron Microscopic ◽  
Microscopic Studies

Primordial germ cells (PGCs) of Xenopus laevis have been isolated from early embryos and kept alive in vitro, in order to study the structural basis of their motility, using the transmission and scanning electron microscope. The culture conditions used mimicked as closely as possible the in vivo environment of migrating PGCs, in that isolated PGCs were seeded onto monolayers of amphibian mesentery cells. In these conditions we have demonstrated that: (a) No significant differences were found between the morphology of PGCs in vitro and in vivo. (b) Structural features involved in PGC movement in vitro include (i) the presence of a filamentous substructure, (ii) filopodial and blunt cell processes, (iii) cell surface specializations. These features are also characteristic of migratory PGCs studied in vivo. (c) PGCs in vitro have powers of invasion similar to those of migrating PGCs in vivo. They occasionally become completely surrounded by cells of the monolayer and, in this situation, bear striking resemblance to PGCs moving between mesentery cells to the site of the developing gonad in stage-44 tadpoles. We conclude that as far as it is possible to assess, the behaviour of isolated PGCs in these in vitro conditions mimics their activities in vivo. This allows us to study the ultrastructural basis of their migration.

Aqueous leaf extracts display endocrine activities in vitro and disrupt sexual differentiation of male Xenopus laevis tadpoles in vivo

2010 ◽  
Vol 168 (2) ◽  
pp. 245-255 ◽  
Author(s):  
Björn Hermelink ◽  
Ralph Urbatzka ◽  
Claudia Wiegand ◽  
Stephan Pflugmacher ◽  
Ilka Lutz ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Sexual Differentiation ◽  
Leaf Extracts

scholarly journals Regulation of the DNA-binding and transcriptional activities of Xenopus laevis NFI-X by a novel C-terminal domain.

1995 ◽  
Vol 15 (10) ◽  
pp. 5552-5562 ◽  
Author(s):  
E Roulet ◽  
M T Armentero ◽  
G Krey ◽  
B Corthésy ◽  
C Dreyer ◽  
...  
Keyword(s):  
Dna Replication ◽  
Dna Binding ◽  
Xenopus Laevis ◽  
Transcriptional Activation ◽  
Binding Activity ◽  
New Members ◽  
Binding Domains ◽  
Dna Binding Activity

The nuclear factor I (NFI) family consists of sequence-specific DNA-binding proteins that activate both transcription and adenovirus DNA replication. We have characterized three new members of the NFI family that belong to the Xenopus laevis NFI-X subtype and differ in their C-termini. We show that these polypeptides can activate transcription in HeLa and Drosophila Schneider line 2 cells, using an activation domain that is subdivided into adjacent variable and subtype-specific domains each having independent activation properties in chimeric proteins. Together, these two domains constitute the full NFI-X transactivation potential. In addition, we find that the X. laevis NFI-X proteins are capable of activating adenovirus DNA replication through their conserved N-terminal DNA-binding domains. Surprisingly, their in vitro DNA-binding activities are specifically inhibited by a novel repressor domain contained within the C-terminal part, while the dimerization and replication functions per se are not affected. However, inhibition of DNA-binding activity in vitro is relieved within the cell, as transcriptional activation occurs irrespective of the presence of the repressor domain. Moreover, the region comprising the repressor domain participates in transactivation. Mechanisms that may allow the relief of DNA-binding inhibition in vivo and trigger transcriptional activation are discussed.

scholarly journals Thyroid hormone induces constitutive keratin gene expression during Xenopus laevis development.

1989 ◽  
Vol 9 (5) ◽  
pp. 1823-1831 ◽  
Author(s):  
P M Mathisen ◽  
L Miller
Keyword(s):  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Constitutive Expression ◽  
High Level Expression ◽  
Keratin Gene ◽  
Explant Cultures ◽  
Extensive Cell ◽  
High Level

We have used in vitro explant cultures of Xenopus laevis skin to investigate the role that the thyroid hormone triiodothyronine (T3) plays in activating the 63-kilodalton (kDa) keratin genes. The activation of these genes in vivo requires two distinct steps, one independent of T3 and one dependent on T3. In this report we have shown that the same two steps are required to fully activate the 63-kDa keratin genes in skin explant cultures, and we have characterized the T3-mediated step in greater detail. Unlike the induction of transcription by T3 or steroid hormones in adult tissues, there was a long latent period of approximately 2 days between the addition of T3 to skin cultures and an increase in concentration of keratin mRNA. While the T3 induction of 63-kDa keratin gene transcription cannot occur until age 48, a short transient exposure of stage 40 skin cultures to T3 resulted in high-level expression of these genes 5 days later, when normal siblings had reached stage 48. This result indicates that T3 induces a stable change in epidermal cells which can be expressed much later, after extensive cell proliferation has occurred in the absence of T3. Once the 63-kDa keratin genes were induced, they were stably expressed, and by the end of metamorphosis T3 had no further effect on their expression. The results suggest that T3 induces constitutive expression of the 63-kDa keratin genes during metamorphosis.

In vivo and in vitro resistance to multiple anticholinesterases in Xenopus laevis tadpoles

1998 ◽  
Vol 102-103 ◽  
pp. 205-209 ◽  
Author(s):  
Michael Shapira ◽  
Shlomo Seidman ◽  
Nadav Livni ◽  
Hermona Soreq
Keyword(s):  
Xenopus Laevis

scholarly journals The 36-kilodalton embryonic-type cytoplasmic polyadenylation element-binding protein in Xenopus laevis is ElrA, a member of the ELAV family of RNA-binding proteins.

1997 ◽  
Vol 17 (11) ◽  
pp. 6402-6409 ◽  
Author(s):  
L Wu ◽  
P J Good ◽  
J D Richter
Keyword(s):  
Xenopus Laevis ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Dominant Negative ◽  
Cytoplasmic Polyadenylation ◽  
Element Binding Protein

The translational activation of several maternal mRNAs in Xenopus laevis is dependent on cytoplasmic poly(A) elongation. Messages harboring the UUUUUAU-type cytoplasmic polyadenylation element (CPE) in their 3' untranslated regions (UTRs) undergo polyadenylation and translation during oocyte maturation. This CPE is bound by the protein CPEB, which is essential for polyadenylation. mRNAs that have the poly(U)12-27 embryonic-type CPE (eCPE) in their 3' UTRs undergo polyadenylation and translation during the early cleavage and blastula stages. A 36-kDa eCPE-binding protein in oocytes and embryos has been identified by UV cross-linking. We now report that this 36-kDa protein is ElrA, a member of the ELAV family of RNA-binding proteins. The proteins are identical in size, antibody directed against ElrA immunoprecipitates the 36-kDa protein, and the two proteins have the same RNA binding specificity in vitro. C12 and activin receptor mRNAs, both of which contain eCPEs, are detected in immunoprecipitated ElrA-mRNP complexes from eggs and embryos. In addition, this in vivo interaction requires the eCPE. Although a number of experiments failed to define a role for ElrA in cytoplasmic polyadenylation, the expression of a dominant negative ElrA protein in embryos results in an exogastrulation phenotype. The possible functions of ElrA in gastrulation are discussed.

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