A comparative ultrastructural and physiological study on melanophores of wild-type and periodic albino mutants of Xenopus laevis

1982 ◽  
Vol 222 (1) ◽  
pp. 1-9 ◽  
Author(s):  
R. Seldenrijk ◽  
K. G. H. Huijsman ◽  
A. M. A. Heussen ◽  
F. C. G. van de Veerdonk
Keyword(s):  
Xenopus Laevis ◽  
Physiological Study ◽  
Wild Type ◽  
Periodic Albino

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.

scholarly journals Role of chromatin and Xenopus laevis heat shock transcription factor in regulation of transcription from the X. laevis hsp70 promoter in vivo.

1995 ◽  
Vol 15 (11) ◽  
pp. 6013-6024 ◽  
Author(s):  
N Landsberger ◽  
A P Wolffe
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Xenopus Laevis ◽  
Heat Shock Transcription Factor ◽  
Chromatin Assembly ◽  
Regulation Of Transcription ◽  
Wild Type ◽  
Hsp70 Promoter ◽  
Chromatin Template

Xenopus laevis oocytes activate transcription from the Xenopus hsp70 promoter within a chromatin template in response to heat shock. Expression of exogenous Xenopus heat shock transcription factor 1 (XHSF1) causes the activation of the wild-type hsp70 promoter within chromatin. XHSF1 activates transcription at normal growth temperatures (18 degrees C), but heat shock (34 degrees C) facilitates transcriptional activation. Titration of chromatin in vivo leads to constitutive transcription from the wild-type hsp70 promoter. The Y box elements within the hsp70 promoter facilitate transcription in the presence or absence of chromatin. The presence of the Y box elements prevents the assembly of canonical nucleosomal arrays over the promoter and facilitates transcription. In a mutant hsp70 promoter lacking Y boxes, exogenous XHSF1 activates transcription from a chromatin template much more efficiently under heat shock conditions. Activation of transcription from the mutant promoter by exogenous XHSF1 correlates with the disappearance of a canonical nucleosomal array over the promoter. Chromatin structure on a mutant hsp70 promoter lacking Y boxes can restrict XHSF1 access; however, on both mutant and wild-type promoters, chromatin assembly can also restrict the function of the basal transcriptional machinery. We suggest that chromatin assembly has a physiological role in establishing a transcriptionally repressed state on the Xenopus hsp70 promoter in vivo.

Fine Structure of the Nucleolus in Normal and Mutant Xenopus Embryos

1967 ◽  
Vol 2 (2) ◽  
pp. 151-162
Author(s):  
ELIZABETH D. HAY ◽  
J. B. GURDON
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Fibrous Material ◽  
Osmium Tetroxide ◽  
Wild Type ◽  
Granular Component ◽  
Basic Dyes ◽  
Fibrillar Component ◽  
Xenopus Laevis Embryos

Mutant and normal Xenopus laevis embryos (0-nu, 1-nu, 2-nu) were examined in the electron microscope after glutaraldehyde and/or osmium-tetroxide fixation. During cleavage both 0-nu and wild-type embryos contain multiple small nucleolar bodies, less than 1 µ in diameter, composed mainly of a fibrous material. By the end of cleavage or beginning of gastrulation, granular caps develop on the fibrous nucleolar bodies. In 1-and 2-nu cells, the multiple nucleolar bodies are replaced during gastrula and neurula stages by definitive nucleoli (2-5 µ in diameter) which contain abundant small (150 Å) granules intermingled with fibrous material. In 0-nu cells, one or two pseudonucleoli (1-3 µ in diameter) appear at about the same time that definitive nucleoli develop in wild-type cells. The multiple small nucleolar bodies disappear as the pseudonucleoli enlarge. Pseudonucleoli differ from definitive nucleoli in having a much smaller amount of the granular component, which is located as a cap on the periphery of the fibrous component and not mingled with it. The granular component of the 0-nu pseudonucleoli, however, is not distinguishable in its fine structure from the same component of normal nucleoli. In many 0-nu tadpoles at stage 41, the granular component of the nucleolus is entirely absent and the fibrillar component is very prominent. Both granular and fibrous components of the 0-nu pseudonucleoli contain RNA as judged by RNase sensitivity and staining affinity for basic dyes.

scholarly journals Latrophilin2 is involved in neural crest cell migration and placode patterning in Xenopus laevis

2019 ◽  
Vol 63 (1-2) ◽  
pp. 29-35
Author(s):  
Natsumi Yokote ◽  
Marianna Y. Suzuki-Kosaka ◽  
Tatsuo Michiue ◽  
Takahiko Hara ◽  
Kosuke Tanegashima
Keyword(s):  
Cell Migration ◽  
Xenopus Laevis ◽  
Neural Crest ◽  
Neural Crest Cell ◽  
Wild Type ◽  
Neural Crest Cell Migration ◽  
Guidance Molecule ◽  
G Protein Coupled ◽  
Crest Cell ◽  
Xenopus Laevis Embryos

Latrophilin2 (Lphn2) is an adhesion-class of G protein-coupled receptor with an unknown function in development. Here, we show that Xenopus laevis lphn2 (Xlphn2) is involved in the migration and differentiation of neural crest (NC) cells and placode patterning in Xenopus laevis embryos. Although Xlphn2 mRNA was detected throughout embryogenesis, it was expressed more abundantly in the placode region. Morpholino antisense oligonucleotide-mediated knockdown of Xlphn2 caused abnormal migration of NC cells, irregular epibranchial placode segmentation, and defective cartilage formation. Transplantation of fluorescently-labeled NC regions of wild-type embryos into Xlphn2 morpholino-injected embryos reproduced the defective NC cell migration, indicating that Xlphn2 regulates the migration of NC cells in a non-cell autonomous manner. Our results suggest that Xlphn2 is essential for placode patterning and as a guidance molecule for NC cells.

High tyrosinase activity in albino Xenopus laevis oocytes

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 555-559
Author(s):  
A. H. Wyllie ◽  
E. M. De Robertis
Keyword(s):  
Molecular Weight ◽  
Xenopus Laevis ◽  
Specific Activity ◽  
High Specific Activity ◽  
Low Molecular Weight ◽  
Xenopus Laevis Oocytes ◽  
Melanin Synthesis ◽  
Wild Type ◽  
Albino Mutant

Tyrosinase was measured in oocytes of the recently described albino mutant (avav) of Xenopus laevis. Although these oocytes show no pigmentation and the eggs are known to contain no melanosomes, tyrosinase — which is probably the only enzyme necessary for melanin synthesis from tyrosine — was increased more than twofold relative to the wild type. Tyrosinase recovered from albino and wild type oocytes showed the same KM with respect to tyrosine, and this was not altered by previous gonadotrophin stimulation in vivo. The tyrosi-nase assay, based on [14]tyrosine incorporation into acid-insoluble products, was of greater sensitivity than previously described methods of the same type, through removal of low molecular weight material from the oocyte homogenate prior to incubation, and the use of tyrosine of high specific activity.

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