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A G Zaraisky

Publications and source records attributed to A G Zaraisky.

12 recordsLinked to original sources
PubMed2003

Expression zones of three novel genes abut the developing anterior neural plate of Xenopus embryo.

We identified three novel genes that were expressed within the anterior non-neural ectoderm of Xenopus early neurula embryos. The expression of these genes was observed in the different areas complementary to the expression zone of a homeodomain gene Xanf-1 in the anterior neural plate. One of these genes, a Ras-like GTP-ase Ras-dva, marked the anterior placodal ectoderm area; a second, an Agr family homologous gene, XAgr2, was expressed in the anterior-most ectoderm in the cement gland primordium, and a third, novel gene Nlo was expressed in the lateral neural folds. The genes were transiently expressed in the developing cement and hatching gland primordia, and repressed in the mature cement and hatching glands. XAgr2 and Nlo were also expressed in the otic vesicles, and Ras-dva was expressed in the dorso-lateral column of the neural tube.

Amino Acid Sequence↗
PubMed2001

Subcellular localization and targeting of glucocorticoid receptor protein fusions expressed in transgenic Arabidopsis thaliana.

An animal system of inducible activation of protein fusions with the binding domain of glucocorticoid receptor (BDGR) was tested in Arabidopsis thaliana by monitoring dexamethasone (DEX)-induced nuclear targeting of reporter constructs. Two constructs containing green fluorescent protein (GFP), human homeobox protein Hanf-1 and Xenopus laevis BDGR were used, GFP/Hanf-1/BDGR and GFP/BDGR. The control construct contained GFP alone. In the absence of DEX both fusion proteins were uniformly distributed in the cytoplasm of root cells, but showed strong association with plastids in plant aerial parts. DEX treatment of roots prompted a strong and reversible nuclear accumulation of GFP/Hanf-1/BDGR, but not GFP/BDGR. Thus, in roots, the specific nuclear translocation of GFP/Hanf-1/BDGR was driven by Hanf-1 and tightly regulated by BDGR. However, in plant aerial parts treated with DEX, nuclear translocation of GFP/Hanf-1/BDGR was observed only in a few cases, and most part of the fusion protein was incorrectly and irreversibly targeted to plastids. Protease X digestion of isolated chloroplasts showed that BDGR fusion proteins were translocated into the chloroplast envelope and bound to envelope membranes, probably due to association with the chloroplast import apparatus. Thus, for efficient use of the glucocorticoid-inducible system in plants, it will be necessary to modify BDGR structure to prevent incorrect targeting of fusion proteins.

Animals↗
PubMed2000

Natural animal coloration can Be determined by a nonfluorescent green fluorescent protein homolog.

It is generally accepted that the colors displayed by living organisms are determined by low molecular weight pigments or chromoproteins that require a prosthetic group. The exception to this rule is green fluorescent protein (GFP) from Aequorea victoria that forms a fluorophore by self-catalyzed protein backbone modification. Here we found a naturally nonfluorescent homolog of GFP to determine strong purple coloration of tentacles in the sea anemone Anemonia sulcata. Under certain conditions, this novel chromoprotein produces a trace amount of red fluorescence (emission lambda(max) = 595 nm). The fluorescence demonstrates unique behavior: its intensity increases in the presence of green light but is inhibited by blue light. The quantum yield of fluorescence can be enhanced dramatically by single amino acid replacement, which probably restores the ancestral fluorescent state of the protein. Other fluorescent variants of the novel protein have emission peaks that are red-shifted up to 610 nm. They demonstrate that long wavelength fluorescence is attainable in GFP-like fluorescent proteins.

Amino Acid Sequence↗
PubMed1999

Fluorescent proteins from nonbioluminescent Anthozoa species.

We have cloned six fluorescent proteins homologous to the green fluorescent protein (GFP) from Aequorea victoria. Two of these have spectral characteristics dramatically different from GFP, emitting at yellow and red wavelengths. All the proteins were isolated from nonbioluminescent reef corals, demonstrating that GFP-like proteins are not always functionally linked to bioluminescence. The new proteins share the same beta-can fold first observed in GFP, and this provided a basis for the comparative analysis of structural features important for fluorescence. The usefulness of the new proteins for in vivo labeling was demonstrated by expressing them in mammalian cell culture and in mRNA microinjection assays in Xenopus embryos.

Amino Acid Sequence↗
PubMed1999

The homeobox gene, Xanf-1, can control both neural differentiation and patterning in the presumptive anterior neurectoderm of the Xenopus laevis embryo.

From the onset of neurectoderm differentiation, homeobox genes of the Anf class are expressed within a region corresponding to the presumptive telencephalic and rostral diencephalic primordia. Here we investigate functions of the Xenopus member of Anf, Xanf-1, in the differentiation of the anterior neurectoderm. We demonstrate that ectopic Xanf-1 can expand the neural plate at expense of adjacent non-neural ectoderm. In tadpoles, the expanded regions of the plate developed into abnormal brain outgrowths. At the same time, Xanf-1 can inhibit terminal differentiation of primary neurones. We also show that, during gastrula/neurula stages, the exogenous Xanf-1 can downregulate four transcription regulators, XBF-1, Otx-2, Pax-6 and the endogenous Xanf-1, that are expressed in the anterior neurectoderm. However, during further development, when the exogenous Xanf-1 was presumably degraded, re-activation of XBF-1, Otx-2 and Pax-6 was observed in the abnormal outgrowths developed from blastomeres microinjected with Xanf-1 mRNA. Other effects of the ectopic Xanf-1 include cyclopic phenotype and inhibition of the cement gland, both by Otx-2-dependent and -independent mechanisms. Using fusions of Xanf-1 with the repressor domain of Drosophila engrailed or activator domain of herpes virus VP16 protein, we showed that most of the observed effects of Xanf-1 were probably elicited by its functioning as a transcription repressor. Altogether, our data indicate that the repressor function of Xanf-1 may be necessary for regulation of both neural differentiation and patterning in the presumptive anterior neurectoderm.

Animals↗
PubMed1997

Anf: a novel class of vertebrate homeobox genes expressed at the anterior end of the main embryonic axis.

Five novel genes homologous to the homeobox-containing genes Xanf-1 and Xanf-2 of Xenopus and Hesx-1/Rpx of mouse have been identified as a result of a PCR survey of cDNA in sturgeon, zebrafish, newt, chicken and human. Comparative analysis of the homeodomain primary structure of these genes revealed that they belong to a novel class of homeobox genes, which we name Anf. All genes of this class investigated so far have similar patterns of expression during early embryogenesis, characterized by maximal transcript levels being present at the anterior extremity of the main embryonic body axis. The data obtained also suggest that, despite considerable high structural divergence between their homeodomains, all known Anf genes may be orthologues, and thus represent one of the most quickly evolving classes of vertebrate homeobox genes.

Amino Acid Sequence↗
PubMed1997

A novel marker of early epidermal differentiation: cDNA subtractive cloning starting on a single explant of Xenopus laevis gastrula epidermis.

To understand the molecular mechanism underlying in the earliest steps of the embryonic ectoderm subdivision into epidermis and neuroectoderm, it would be important to isolate differentially expressed genes in presumptive neuroectoderm and epidermis at the gastrula stage, the period of the divergence of the two adjacent ectodermal compartments. Meanwhile, the most direct approach for such a task, i.e. subtractive enrichment of cDNA from neuroectodermal and epidermal explants with differentially expressed gene sequences, was difficult to realize because of the high number of explants needed for this technique. In the present paper we report a novel effective and quite simple method of cDNA subtractive enrichment, based on amplification of cDNA in vitro by polymerase chain reaction (PCR) and allowing to use a very small amount of initial cDNA samples. With this method we have cloned cDNA of a novel gene of Xenopus laevis, which was named XEP-1 for its specific expression in the presumptive epidermis starting from the midgastrula stage.

Amino Acid Sequence↗
PubMed1995

Inverted terminal repeats permit the average length of amplified DNA fragments to be regulated during preparation of cDNA libraries by polymerase chain reaction.

A simple polymerase chain reaction (PCR)-based technique for construction of cDNA libraries starting with very small amounts of cells or tissues is described. The technique is based on the insertion of inverted terminal repeats into amplified cDNAs which permit short molecules to generate "pan"-type structures at each cycle of PCR amplification and thus to escape annealing with primers. This allows one to avoid amplification of primer dimers and makes it possible to perform oligonucleotide tailing of the first cDNA strands followed by PCR amplification in the same tube. Moreover, the average size of amplified cDNAs can be controlled by varying the primer concentration.

Animals↗
PubMed1995

The homeobox-containing gene XANF-1 may control development of the Spemann organizer.

At the beginning of gastrulation the homeobox-containing gene, XANF-1, is expressed at a low level throughout the animal hemisphere of Xenopus laevis embryos, with a local maximum of expression in the region of the dorsal blastopore lip. By the end of gastrulation expression ceases everywhere except in the most anterior part of the neurectoderm. We have investigated the functions of this gene by microinjecting XANF-1 mRNA in the blastomeres of the 32-cell stage embryo and have observed the following effects. First, microinjections of the mRNA in the animal blastomeres and the blastomeres of the marginal zone elicited massive migration of cells to the interior of the embryo at the early gastrula stage. Second, overexpression of XANF-1 in the ventral marginal zone (VMZ) resulted in the appearance of an additional centre of gastrulation movements and the formation of a secondary axis. In addition we showed that synthetic XANF-1 mRNA was able to cause dorsal-type differentiation in VMZ explants extirpated from the microinjected embryos at the beginning of gastrulation. These results suggest that XANF-1 may control the main functions of cells of the Spemann organizer.

Animals↗
PubMed1992

A novel homeobox gene expressed in the anterior neural plate of the Xenopus embryo.

To obtain gene sequences controlling the early steps of amphibian neurogenesis, we have performed differential screening of a subtractive cDNA library prepared by a novel PCR-based method from a single presumptive neural plate of a Xenopus laevis late-gastrula embryo. As a result we have isolated a fragment of a novel homeobox gene (named XANF-1, for Xenopus anterior neural folds). This gene is expressed predominantly in the anterior part of the developing nervous system. Such preferential localization of XANF-1 mRNA is established from its initially homogenous distribution in ectoderm of early gastrula. This change in the expression pattern is conditioned by a differential influence of various mesoderm regions on ectoderm: anterior mesoderm activates XANF-1 expression in the overlying ectoderm, whereas posterior axial and ventral mesoderm areas inhibit it. The data obtained demonstrate for the first time that selection of genes for specific expression in the CNS of the early vertebrate embryo is affected not only by chordamesoderm (a neural inductor) but also by ventral mesoderm.

Amino Acid Sequence↗
PubMed1987

Model of pattern formation in epithelial morphogenesis.

One of the most universal events in morphogenesis is the formation of domains of morphologically polarized cells in the initially homogeneous epithelial sheets. We investigate the possibility of considering this process as a phenomenon of self-organization which is based upon the following experimentally proven mechanochemical cell properties: (1) a capacity of individual cells for morphological polarization considered as a bistable "all-or-none" transition of a cell from a non-polarized to a polarized state; (2) transmission of this capacity from one cell to another on their contacts; (3) feedback relations between co-operative cell polarization and tangential elastic tensions in a cell sheet: cell polarization increases tangential tensions whereas the latter inhibit further cell polarization. We have constructed a phenomenological model which formally expresses the above properties. Its mathematical description includes but few macroscopic parameters available to experimental investigation and controlled changes. The analysis of the collective dynamic regimes of cell polarization demonstrates that variations of some non-specific parameters leads to spontaneous transition in the morphology of cell layers accompanied by symmetry breaking (Turing's instability). Under these conditions either long-range ordered patterns of cell polarization (including hexagonal cell nets) or non-regular spotted structures can emerge. In the particular case of a sheet having fixed complete dimensions and lacking any external elastic bonds a stable macrostate is created; it corresponds to the sheet's binary subdivision into polarized and non-polarized cell domains of size-invariant proportions. The model conclusions are compared with the morphogenetical processes in sea-urchin development, the morphogenesis of skin derivates and artificially induced budding in hydrozoa.

Animals↗