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At least 235 records · Page 13Linked to original sources
PubMed1992

Retinoic acid induces changes in the localization of homeobox proteins in the antero-posterior axis of Xenopus laevis embryos.

We have studied the localization of the proteins of Xeb1 and Xeb2, two homeobox (hbx)-containing genes that are expressed during the early development of Xenopus laevis. Both proteins are expressed in juxtaposed and partially overlapping domains along the antero-posterior axis of Xenopus laevis embryos, with clearly defined anterior boundaries. Xeb2 is predominantly expressed in the caudal region of the hindbrain, whereas the Xeb1 protein is located in the most rostral region of the spinal cord. Furthermore, both proteins are expressed in single cells dispersed in the lateral flanks of the embryo in positions that correlate with the expression domains in the neural tube. We suggest that these cells are migratory neural crest cells that have acquired positional information in the neural tube prior to migration. The Xeb2 protein was also detected in the most posterior branchial arches and the pronephros. In stage 45 embryos, nuclei of the IX-X cranial ganglia, the lung buds and cells spreading into the forelimb rudiment express the Xeb2 antigen. The Xeb1 protein was also detected in the lung buds and the forelimb rudiment. To examine the effect of retinoic acid on expression, gastrula embryos were treated with all-trans retinoic acid (RA). Increasing concentrations of RA caused progressive truncation of anterior structures. The most severely affected embryos lacked eyes, nasal pits, forebrain, midbrain and otic vesicles, and the anterior boundary of the hindbrain seemed to be displaced rostrally. This alteration correlates with a progressive displacement of the anterior boundary of the expression domain of Xeb2. On the other hand, 10(-6) M RA induces an ectopic site of Xeb1 expression at the anterior end of the central nervous system, located just anterior to the extended domain of Xeb2 whereas expression in the spinal cord remains unaffected.

Animals↗
PubMed1995

XIdx, a dominant negative regulator of bHLH function in early Xenopus embryos.

We have identified a divergent member of the Xenopus Id family, XIdx, which disrupts binding of myogenic factor/E-protein complexes to DNA in vitro and inhibits transactivation of the E-box regulated cardiac actin gene by MyoD in embryonic tissue. XIdx transcripts accumulate from the early neurula stage in discrete domains of the anterior neural plate and subsequently identify regions of the developing nervous system, including the eye rudiments and the rhombencephalon. These results suggest that bHLH proteins and their Id protein regulators may participate in patterning of embryonic neural tissue. Phylogenetic analysis indicates that XIdx is the product of a novel Id gene and is distinct from XId2, which is expressed primarily in the developing pronephros.

Amino Acid Sequence↗
PubMed1994

Pagliaccio, a member of the Eph family of receptor tyrosine kinase genes, has localized expression in a subset of neural crest and neural tissues in Xenopus laevis embryos.

Cranial neural crest cells arise from neural folds in the embryonic head and differentiate to produce most of the cartilages and bones of the skull and the somatosensory ganglia of several cranial nerves, among other tissues. Since the molecular basis of the determination of these cells is poorly understood, we have begun a search for molecules involved in signal transduction in cranial neural crest. From a Xenopus laevis cranial neural crest cDNA bank, we have cloned a cDNA encoding a putative receptor tyrosine kinase, which we call Pagliaccio (Pag). Pag RNA is present transiently in visceral arch 3, probably representing neural crest cells in this tissue. Pag is also expressed in the forebrain, rhombomeres r3 and r5 of the hindbrain and in the pronephros. Based on this localized expression, we propose that Pag may play a role in the differentiation of cranial neural crest and other tissues.

Animals↗
PubMed1994

Cloning and developmental expression of LFB3/HNF1 beta transcription factor in Xenopus laevis.

We have cloned the Xenopus laevis homologue of the LFB3/HNF1 beta transcription factor. RNase protection and in situ hybridisation experiments show that XLFB3 transcription starts in the gastrulating endoderm at stage 10.5 (mid-gastrula). At later stages, XLFB3 transcripts within the endoderm are restricted to mid- and hindgut and to their derivative organs and tissues. XLFB3 is also expressed in the neuroectoderm and in the pronephros anlage. XLFB3 is not expressed in the rostral part of all three germ layers, with coincident anterior borders that are shifted anteriorly by treatment of developing embryos with retinoic acid. XLFB3 is a useful marker of early endoderm differentiation and its expression pattern along the antero-posterior axis, as well as the response to retinoic acid treatment, suggests a role in early morphogenesis.

Amino Acid Sequence↗
PubMed1995

Wnt4 affects morphogenesis when misexpressed in the zebrafish embryo.

The Wnts are a family of secreted glycoproteins involved in cell-cell signalling and pattern formation during development, although the extent to which various Wnts are functionally equivalent remains unclear. We have cloned zebrafish (Danio rerio) wnt4, characterized its expression, and compared its activity relative to other Wnts. The wnt4 transcript is first detected early in somitogenesis, in the dorsocaudal region of the forebrain, and then appears in the dorsal and lateral regions of the caudal hindbrain and neural keel. During somitogenesis, wnt4 appears in the floor plate, and this expression is absent in cyclops mutants, which lack floor plate. wnt4 is also expressed in the developing pronephros and gill slit. To characterize the biological activity of wnt4, synthetic zebrafish wnt4 mRNA was injected into embryos of zebrafish and Xenopus laevis. The phenotypic effects of misexpression in the zebrafish include cyclopia, misfolding in the brain, and an anteriorly forking notochord. Comparison of the phenotypes arising from misexpression of wnt4 and Xwnt-5A in both organisms suggests close parallels in the response to these Wnts. Our data suggest that wnt4, like Xwnt-5A, inhibits cell movements, and that these Wnts define a functional class distinct from the class which includes Wnt-1, Xwnt-3A and Xwnt-8.

Amino Acid Sequence↗
PubMed2004

The role of Xenopus frizzled-8 in pronephric development.

Vertebrates use two or three forms of kidney successively during development and the nephric duct is essential for this succession of kidney induction. While transcripts of many Wnt ligands and Wnt receptor Frizzled genes have been localized in developing kidney, the relationship between Wnt signaling and nephric duct development remains unknown. This study investigated the role of Xenopus frizzled-8 (Xfz8) in pronephros development. Translational inhibition of Xfz8 caused a significant reduction in the staining of a duct-specific antibody, but did not affect the expression of early pronephric maker genes in the duct region. Defects in pronephric tubule branching were also observed following inhibition of Xfz8. Histological analysis revealed that the Xfz8-inhibited cells failed to form a normal epithelium structure. These results suggest that Xfz8 is involved in the process of normal epithelium formation in the developing pronephric duct and tubules after specification.

Animals↗
PubMed2006

Cold-inducible RNA binding protein is required for the expression of adhesion molecules and embryonic cell movement in Xenopus laevis.

We have previously shown that the Xenopus homologue of cold-inducible RNA binding protein, XCIRP-1, is required for the morphogenetic migration of the pronephros during embryonic development. However, the underlying molecular mechanisms remain elusive. Here, we report that XCIRP is essential for embryonic cell movement, as suppression of XCIRP by microinjection of anti-sense mRNA and morpholino antisense oligonucleotides (MOs) significantly reduced protein expression, inhibited the cell migration rate, and inhibited eFGF and activin-induced animal cap elongation. By immunoprecipitation and RT-PCR, we further showed that the mRNA of a panel of adhesion molecules, including alphaE- and beta-catenin, C- and E-cadherin, and paraxial proto-cadherin, are the targets of XCIRP. Consistently, in animal cap explant studies, suppression of XCIRP by MOs inhibited the expression of these adhesion molecules, while over-expression of sense XCIRP-1 mRNA fully rescued this inhibition. Taken together, these results suggest for the first time that XCIRP is required to maintain the expression of adhesion molecules and cell movement during embryonic development.

Animals↗
PubMed2006

Cloning, embryonic expression, and functional characterization of two novel connexins from Xenopus laevis.

Vertebrate gap junctions are constituted of connexin (Cx) proteins. In Xenopus laevis, only seven different Cxs have been described so far. Here, we identify two new Cxs from X. laevis. Cx28.6 displays > 60% amino acid identity with human Cx25, Cx29 displays strong homology with mouse Cx26 and Cx30. Cx29 is expressed throughout embryonic development. Cx28.6 mRNA is only transiently found from stage 22 to 26 of development. While no Cx28.6 expression could be detected by whole mount in situ hybridization, expression of Cx29 was found in the developing endoderm, lateral mesoderm, liver anlage, pronephros, and proctodeum. Ectopic expression of Cx28.6 failed to produce functional gap-junctions. In contrast, ectopic expression of full-length Cx29 in HEK293 and COS-7 cells resulted in the formation of gap junction-like structures at the cell-cell interfaces. Ectopic expression of Cx29 in communication deficient N2A cell pairs led to functional electrical coupling.

Amino Acid Sequence↗
PubMed2004

T cells and the thymus in developing zebrafish.

The expression of genes encoding T cell receptor (TCR) alpha was used to follow the development of the thymus and to analyze the distribution of T cells in zebrafish. In the thymus, expression was first detected, by in situ hybridization, at four days post fertilization. In RNA extracted from whole fish, TCRalpha transcripts were also detected at four days and reached adult levels at three weeks. At six weeks, TCRalpha was expressed throughout the thymus, whereas rag1 expression was localized to the peripheral regions. Expression of TCRalpha outside the thymus was detected at nine days. In adult peripheral organs, the greatest expression was in the pronephros, mesonephros and intestine; expression in the spleen became greater as fish age. Three new, relatively highly expressed, TCR Valpha families were identified.

Amino Acid Sequence↗
PubMed2005

The immunomodulatory effects of the dimer of lysozyme (KLP-602) in carp (Cyprinus carpio L)--in vivo study.

The dimer of lysozyme was administered to carp (Cyprinus carpio L.) in an attempt to reduce the suppression of response in fish exposed to the cypermethrin. Experimental studies were carried out on cells isolated from blood and pronephros of carp. In the in vivo studies fish were intoxicated with cypermethrin (synthetic pesticide) at a dose of LD5. After 24 h fish were injected intraperitoneally with a modulator-the dimer of lysozyme (KLP-602) at a dose of 0.02 mg/kg of body weight. In the study we determined the metabolic activity of phagocyte cells and the proliferative ability of lymphocytes stimulated by ConA and LPS. The results indicate that this modulator is useful for stimulation of cellular and humoral immunity after experimentally induced suppression by selected pesticide.

Animals↗
PubMed2005

The ontogeny of MHC class I expression in rainbow trout (Oncorhynchus mykiss).

In the present study, clonal rainbow trout (Oncorhynchus mykiss) embryos and larvae were assayed for the expression of key molecules involved in specific cell-mediated cytotoxicity using an anti-MHC class I monoclonal Ab and by RT-PCR using specific primers derived from classical MHC class I (class Ia), TCR and CD8. Whereas RT-PCR revealed that MHC class Ia and CD8 were expressed from at least 1 week after fertilisation (p.f.) on, TCR expression was detectable from 2 weeks p.f. Immunohistochemistry indicated an early and distinct expression of MHC class I protein in the thymus. Positive lymphoid, epithelial and endothelial cells were found in the pronephros, in the spleen and in the inner and outer epithelia at later stages. Whereas in older rainbow trout the intestine is counted among the organs of the highest class I expression, during ontogeny it was the last site (39 days after hatching) where such expression was detectable. Knowledge on the appearance of the assayed key molecules during fish development is relevant for the pathogenesis of infections as well as for early vaccine delivery. Besides such information regarding the development of the adaptive immune system, immunohistochemistry revealed that in early larvae MHC class I was expressed in neurons whereas in older rainbow trout this was not observed.

Animals↗
PubMed2006

In vitro effects of pure microcystin-LR on the lymphocyte proliferation in rainbow trout (Oncorhynchus mykiss).

The aim of this study was to determine the in vitro influence of microcystin-LR on the viability and mitogenic response of rainbow trout (Oncorhynchus mykiss) lymphocytes since few data are available in the literature on the influence of cyanotoxins on fish immunocompetent cells. Lymphocytes were isolated from blood and haematopoietic organs (pronephros and spleen) and cultivated in RPMI 1640 medium with different concentrations of the toxin (1, 5, 10, 20, 40 mg ml-1 of cell suspension). Dose-dependent effects of microcystin-LR on the lymphocyte viability were shown. The lymphocyte proliferation was inhibited after application of microcystin at a concentration of 40 mg ml-1 but significantly increased at a concentration of 1mg ml-1 in comparison to the control group. The results suggest the modulatory effects of microcystin-LR dependent on the applied concentration.

Animals↗
PubMed2005

Cloning and expression of the amphibian homologue of the human PKD1 gene.

PKD1 is the gene responsible for autosomal dominant polycystic kidney disease (ADPKD) type 1 in humans. The PKD1 gene product is likely to be a calcium channel regulator. In this paper, we describe the isolation and characterization of the Xenopus homologue of the human PKD1 gene. We isolated and cloned genomic fragments corresponding to the amphibian homologue of PKD1 from a BAC library, and after sequencing the clones, we designed primers for the amplification of the transcript and sequenced 10 kb of ORF. The sequence of the putative protein clearly demonstrated that this gene is the homologue of human PKD1. Analysis of the tissue expression patterns of xPKD1 demonstrated a high level of expression in the kidney. A similar analysis in developing embryos and in an in vitro nephrogenic system suggests that xPKD1 is associated with, and probably involved in, the development of the amphibian pronephros.

Amphibian Proteins↗
PubMed2005

[To live or to die, an embryonic dilemma].

The development and formation of an organ needs both cell proliferation and cell death. It is commonly possible to decipher three types of basic cell death: 1) the so-called morphogenetic cell death (an example is the formation of the digits); 2) the histogenetic cell death like the apoptotic processes taking place in the spinal cord and allowing to regulate the number of motoneurons according to their targets; and 3) the phylogenetic cell death in which vestigial structures are selectively removed (e.g. destruction of the pronephros or removal of the tail in the anuran larva).

Animals↗
PubMed2004

Embryonic expression of pre-initiation DNA replication factors in Xenopus laevis.

We examined the expression of various DNA replication factors, including: cdc45, the factors of the GINS heterotetramer (Sld5, Psf1, Psf2, Psf3), and PCNA, in Xenopus laevis during embryonic development via whole mount in situ hybridization. For the most part, these factors were expressed in similar patterns, with some subtle variations, throughout development within the anterior CNS, pharyngeal arches, and various placodes. More significant variations were also observed, including expression of only Psf1 and Psf2 in the pronephros and unique Psf2 expression in the somitic mesoderm. Overall, these results suggest that common regulatory mechanisms are involved in the transcriptional deployment of these factors. Significantly, expression of these factors does not directly coincide with elevated patterns of DNA replication, suggesting that different replication factors are utilized in different developmental regions.

Animals↗
PubMed2004

Cloning and characterisation of the immunophilin X-CypA in Xenopus laevis.

This paper reports the cloning of Xenopus laevis, cyclophilin A gene, X-CypA. This study is the first developmental and functional characterisation in vivo of cyclophilin A in a vertebrate. X-CypA belongs to the superfamily of the immunophilin/PPIase proteins that can bind the immunosuppressant drug Cyclosporin A. Sequence analysis showed that X-CypA is highly conserved during evolution. RT-PCR and in situ hybridisation analysis showed that X-CypA expression is regulated during development and its transcripts are found in three major expression domains: nervous system, sensory organs and pronephros. Over-expression of X-CypA in embryos, analysed by in situ hybridisation and RT-PCR, leads to an expansion and disorganisation of the neural crest domain.

Amino Acid Sequence↗
PubMed2004

The developmental expression of two Xenopus laevis steel homologues, Xsl-1 and Xsl-2.

We have investigated the expression patterns of two Xenopus laevis genes with similarity to mouse steel (sl) using whole-mount in situ hybridization. Areas of overlapping expression include the epidermis, stomodeum, proctodeum, and otic placodes. Xsl-1 is specifically expressed in the pronephros, neural tube, gil arches, and a superficial region of the somite, while Xsl-2 is in the ganglion and facial nerve projecting to visceral arch 3, the mandibular arch, and the clefts of anterior somites. Thus, both transcripts exhibit partially overlapping expression patterns, but their tissue distribution differs significantly from that of sl expression in the mouse and chicken.

Amino Acid Sequence↗
PubMed2004

The FoxO-subclass in Xenopus laevis development.

Transcription factors of the Fox (fork head box) family are involved in cellular specification and determination processes. Here, we report on the isolation and first characterisation of two members of the FoxO subclass in Xenopus laevis, xFoxO1 and xFoxO3. These sequences exhibit 68% (67%) and 69% (70%) identity to their mouse (human) orthologues, respectively. Serine and threonine residues, which are phosphorylated upon insulin signalling, are evolutionarily conserved from frogs to mammals. xFoxO1 and xFoxO3 genes are maternally transcribed, but transcripts disappear during early cleavage stages. Zygotic transcription of both genes starts at the late neurula stages and transcripts accumulate at the end of organogenesis. While maternal transcripts of both genes are found within the animal half of the early embryo, zygotic transcripts show distinct patterns. xFoxO1 expression is observed in the pronephros, within head mesenchyme in front of the eye, within the branchial arches and in the liver primordium. At the late neurula, xFoxO3 is found to be specifically expressed in the anterior neural plate and in neural crest cells. Later, expression of xFoxO3 is observed in a variety of organs and tissues, like the head, the branchial arches and the somites.

Amino Acid Sequence↗