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At least 865 records · Page 48Linked to original sources
PubMed1990

Complex karyotypic anomalies, including an i(5p) marker chromosome, in malignant mixed mesodermal tumor of the ovary.

Cytogenetic analysis of short-term cultures initiated from an ovarian malignant mixed mesodermal tumor yielded the following karyotype: 59-61, XX,t(1;?)(p36;?), +t(1;9) (q43;q21), +t(2;?)(p25;?), +i(5p), +i(5p), +7, +t(7;?)(p13;?), +8,der(11) (pter----cen----q23::q13----q23::q13----q23::?), +12, + der(13)t(13;15)(q21;q15), -15,der(16) (16qter----cen----16p13::hsr::8q21----8qter), +19, + der(20)t(X;20)(q13;p13), -22, +4 - 6mar. Because the only other cytogenetically characterized ovarian neoplasm of this rare histopathologic subtype also had a small metacentric marker interpreted as an isochromosome for the short arm of a B-group chromosome, we suggest that i(5p) constitutes a nonrandom anomaly in mixed mesodermal tumors.

Adenocarcinoma↗
PubMed1992

Mesoderm induction and development of the embryonic axis in amniotes.

The mechanisms controlling the formation of the embryonic axis, and specifically those that give rise to the mesoderm, have received renewed attention recently. In the frog, some of these mechanisms have begun to be elucidated, and several factors have been found to cause uncommitted ectoderm cells to differentiate into mesoderm. All of the factors identified to date are related either to fibroblast growth factor (FGF) or to transforming growth factor beta (TGF-beta). Do the mechanisms that generate the embryonic axis of amphibians also operate in chick and mouse embryos? Here I address how amphibian and amniote embryos might provide complementary pieces of a puzzle.

Amphibians↗
PubMed1986

Intraspecific chick/chick chimaeras: dystrophic somitic mesoderm transplanted to a normal host forms muscles with a dystrophic phenotype.

Intraspecific chick/chick chimaeras were prepared by transplanting thoracic somitic mesoderm from donor chick embryos with hereditary muscular dystrophy to replace extirpated brachial somites of normal host embryos at stage 13 (48-52 h in ovo). Since the wings of unoperated dystrophic embryos exhibit significantly reduced motility between day-10 in ovo (day-10E) to day-15E, this parameter was used as a marker both to verify the viability of the transplant and to assess if the dystrophic phenotype of impaired functional activity is preserved in the mutant wing muscles innervated by brachial nerves of normal embryos. Our motility analyses of the chimaeras confirmed that transplanted thoracic somitic mesoderm gives rise to brachial musculature and that the experimental muscles maintained the inherent dystrophic phenotype.

Animals↗
PubMed1988

Isolation of mesoderm-specific genes expressed in the Drosophila embryo.

Tissue differentiation during embryonic development involves activation of specific genes. To isolate genes selectively expressed in mesoderm and nervous system in the Drosophila embryo, we have screened a cDNA library with molecular probes enriched in specific gene sequences from both tissues. In this way, we have isolated six mesoderm-specific genes, as demonstrated by in situ hybridization to embryo sections. Two of these genes, expressed during muscle differentiation, are described here for the first time. These genes have been localized in the 17A region of the first chromosome and in the 60A region of the second chromosome, respectively. No neural-specific genes were identified using this approach, most probably because of the low sensitivity of detection methods which combine filter hybridization techniques with the use of complex probes.

Animals↗
PubMed1988

Mesodermal cell lineage determination and proto-oncogene expression.

Previously, we have established a rat embryo fibroblastic cell line that is characterized as immortal, nontumorigenic and retains a diploid karyotype. We report here that this cell line will spontaneously differentiate along mesodermal cell lineages to form myotubes and adipocytes. We have isolated and characterized lineage-determined (nondifferentiated) preadipocytes and myoblasts. Using these cell lines we have investigated the expression of proto-oncogenes concomitant with lineage-specific determination. No major changes in proto-oncogene RNA levels were observed that correlated with lineage determination. These results would suggest that none of the 15 proto-oncogenes used in these experiments are involved in mesodermal lineage determination; but this does not rule out the possibility that other proto-oncogenes not tested or currently unknown may be involved. However, these differentiating subclones and nondifferentiating fibroblasts that exhibit a normal karyotype will be an excellent model-system to investigate the molecular basis of cell lineage determination.

Adipose Tissue↗
PubMed1995

Mesodermal expression of the chicken erg gene associated with precartilaginous condensation and cartilage differentiation.

The ets gene superfamily encodes a class of transcription factors that bind to a purine rich sequence through a 85 amino-acid ETS domain. Among them, the human erg gene has been found to be involved in Ewing's sarcoma, primitive neurectodermal tumour of childhood and acute myeloid leukaemia. Nevertheless, little is known about human erg expression. Northern blot analyses have shown a human erg expression restricted to few cell lines and thymus, but the status concerning expression during development remains unknown probably because no homologue of this gene has yet been isolated and studied in other vertebrates. We thus choose to clone the chicken erg gene (ck-erg) and to study its expression during chicken development. We obtained a bona fide clone of ck-erg and defined the transcriptional modulating properties of its product. The ck-Erg protein acts as a transcriptional activator through a conventional consensus ETS binding site. Northern blot studies on various chicken tissues, in situ analyses and comparison with the well-characterised c-ets-1 expression show that ck-erg is expressed in mesoderm- and, to a lesser extent, in ectoderm-derived tissues. During chicken development, two salient features could be observed. From stage E1 to E3.5, ck-erg expression was widely distributed in mesodermal derivatives and neural crest, resembling c-ets-1 expression. However, by E6, the expression of ck-erg exhibited, unlike c-ets-1, a drastically new and strong signal in precartilaginous condensation zones and cartilaginous skeletal primordia. These stages are the first steps of bone formation during skeletal elaboration. Our results show for the first time a possible specific involvement of ck-erg in cartilage morphogenesis.

Amino Acid Sequence↗
PubMed1994

Suramin and heparin: aspecific inhibitors of mesoderm induction in the Xenopus laevis embryo.

Xenopus embryos in solutions containing suramin show a dose-dependent decrease in the formation of dorsoanterior structures. Continuous treatment with 1 mM suramin produces embryos without mesodermal derivatives but with mesenchymal cells. Brief immersions of 20 min were used to determine the most sensitive stages and to establish dose-effect curves: a 20 min treatment with 3 mM suramin at stages 7-8.5 produces blastula-like embryos, never classified before, with atypical epidermis, cells full of yolk and mesenchyme in between. The lack of dorsal mesoderm was confirmed by an RNase protection assay with alpha-cardiac actin probe. Heparin also causes a reduction in dorsal structures, but its action is weaker and and there are also strong toxic effects such as superficial cell dissociation. The effect of heparin is dose-dependent and brief immersions show a very sensitive period around stage 6.5. The lowest DAI obtained is 1.5, an extremely microcephalic embryo with forked tail codes, a stocky notochord, and abnormally shaped, abundant neural tissue. Immunofluorescence shows that the distribution of fibronectin-containing fibrils is normal in heparin-treated embryos, whereas there are no such fibrils in suramin-treated embryos at control stage 12.

Animals↗
PubMed1993

The community effect, dorsalization and mesoderm induction.

The community effect is an interaction among muscle progenitor cells of amphibian gastrula, and is necessary for the initiation of muscle-specific gene expression. Dorsalization provides a signal that can convert ventral mesoderm cells to a muscle fate. Neither process involves mesoderm-inducing molecules. We suggest that the developmental significance of the community effect is to generate homogeneous but clearly demarcated groups of cells from progenitor cells arranged in a continuous gradient of developmental potential.

Animals↗
PubMed1992

Mesodermal control of neural cell identity in vertebrates.

It has long been appreciated that the differentiation and patterning of neural cells is controlled in part by inductive signals from the mesoderm. Several recent experiments have revealed that distinct mesodermal signals act throughout early neural development and have begun to address the nature and sources of such signals.

Animals↗
PubMed2004

A crucial interaction between embryonic red blood cell progenitors and paraxial mesoderm revealed in spadetail embryos.

Zebrafish embryonic red blood cells (RBCs) develop in trunk intermediate mesoderm (IM), and early macrophages develop in the head, suggesting that local microenvironmental cues regulate differentiation of these two blood lineages. spadetail (spt) mutant embryos, which lack trunk paraxial mesoderm (PM) due to a cell-autonomous defect in tbx16, fail to produce embryonic RBCs but retain head macrophage development. In spt mutants, initial hematopoietic gene expression is absent in trunk IM, although endothelial and pronephric expression is retained, suggesting that early blood progenitor development is specifically disrupted. Using cell transplantation, we reveal that spt is required cell autonomously for early hematopoietic gene expression in trunk IM. Further, we uncover an interaction between embryonic trunk PM and blood progenitors that is essential for RBC development. Importantly, our data identify a hematopoietic microenvironment that allows embryonic RBC production in the zebrafish.

Animals↗
PubMed2005

Groucho-associated transcriptional repressor ripply1 is required for proper transition from the presomitic mesoderm to somites.

Concomitant with the transition from the presomitic mesoderm (PSM) to somites, the periodical gene expression characteristic of the PSM is drastically changed and translated into the segmental structure. However, the molecular mechanism underlying this transition has remained obscure. Here, we show that ripply1, encoding a nuclear protein associated with the transcriptional corepressor Groucho, is required for this transition. Zebrafish ripply1 is expressed in the anterior PSM and in several newly formed somites. Ripply1 represses mesp-b expression in the PSM through a Groucho-interacting motif. In ripply1-deficient embryos, somite boundaries do not form, the characteristic gene expression in the PSM is not properly terminated, and the initially established rostrocaudal polarity in the segmental unit is not maintained, whereas paraxial mesoderm cells become differentiated. Thus, ripply1 plays dual roles in the transition from the PSM to somites: termination of the segmentation program in the PSM and maintenance of the rostrocaudal polarity.

Amino Acid Sequence↗
PubMed2006

Oscillations of the snail genes in the presomitic mesoderm coordinate segmental patterning and morphogenesis in vertebrate somitogenesis.

The segmented body plan of vertebrate embryos arises through segmentation of the paraxial mesoderm to form somites. The tight temporal and spatial control underlying this process of somitogenesis is regulated by the segmentation clock and the FGF signaling wavefront. Here, we report the cyclic mRNA expression of Snail 1 and Snail 2 in the mouse and chick presomitic mesoderm (PSM), respectively. Whereas Snail genes' oscillations are independent of NOTCH signaling, we show that they require WNT and FGF signaling. Overexpressing Snail 2 in the chick embryo prevents cyclic Lfng and Meso 1 expression in the PSM and disrupts somite formation. Moreover, cells mis-expressing Snail 2 fail to express Paraxis, remain mesenchymal, and are thereby inhibited from undergoing the epithelialization event that culminates in the formation of the epithelial somite. Thus, Snail genes define a class of cyclic genes that coordinate segmentation and PSM morphogenesis.

Animals↗
PubMed2004

Structural and functional evidences for a type 1 TGF-beta sensu stricto receptor in the lophotrochozoan Crassostrea gigas suggest conserved molecular mechanisms controlling mesodermal patterning across bilateria.

The transforming growth factor beta (TGFbeta) superfamily includes bone morphogenetic proteins, activins and TGF-betasensu stricto (s.s.). These ligands have been shown to play a key role in numerous biological processes including early embryonic development and immune regulation. They transduce their signal through a hetromeric complex of type I and type II receptors. Such receptors have been identified in ecdysozoans but none have been found as yet in the other major protostomal clade, the lophotrochozoans. Here, we report the identification of the first lophotrochozoan TGFbetas.s. type I receptor (Cg-TGFbetaRI) from the mollusk Crassostrea gigas. The phylogenetic and structural analyses as well as the expression pattern during early development suggest Cg-TGFbetaRI to belong to the TGFbetas.s./activin type I receptor clade and functional studies corroborate these deductions. The use of the zebrafish embryo as a reporter organism reveals that either Cg-TGFbetaRI or its dominant negative acting truncated form, when overexpressed during gastrulation, resulted in a range of phenotypes displaying severe disturbance of anterioposterior patterning due to a strong modulation of ventrolateral mesoderm patterning. Finally, a Cg-TGFbetaRI cytokine activity during immune regulation in C. gigas has been investigated by real-time PCR in haemocytes and mantle edge during an in vivo bacterial LPS challenge. One piece of evidence from this study suggests that the molecular mechanisms controlling mesodermal patterning and some immune regulations across all bilateria could be conserved through a functional TGF-beta s.s. pathway in lophotrochozoans.

Activin Receptors, Type I↗
PubMed2004

Identification of distinct genes with restricted expression in the somitic mesoderm in Xenopus embryo.

We have used whole-mount in situ hybridisation to identify genes expressed in the somitic mesoderm during Xenopus early development. We report here the analysis of eight genes whose expression pattern has not been described previously. They include the Xenopus homologues of eukaryotic initiation factor 2beta, methionine adenosyltransferase II, serine dehydratase, alpha-adducin, oxoglutarate dehydrogenase, fragile X mental retardation syndrome related protein 1, monocarboxylate transporter and voltage-dependent anion channel 1. Interestingly, these genes exhibit very dynamic expression pattern during early development. At early gastrula stages several genes do not show localised expression pattern, while other genes are expressed in the marginal mesoderm or in ectoderm. As development proceeds, the expression of these genes is gradually restricted to different compartments of somite. This study thus reveals an unexpected dynamic expression pattern for various genes with distinct function in vertebrates.

Animals↗
PubMed2005

CyNodal, the Japanese newt nodal-related gene, is expressed in the left side of the lateral plate mesoderm and diencephalon.

The nodal and nodal-related genes play fundamental roles during deuterostome left-right axis formation. Several of these genes show left-sided expression in the lateral plate mesoderm and brain region. We have isolated the nodal-related gene, CyNodal, from Cynops pyrrhogaster. CyNodal mRNA is detected at the marginal zone and left side of several tissues. The left-sideness of CyNodal mRNA expression is highly conserved throughout vertebrate evolution. However, CyNodal mRNA expression shows little variation from the Xenopus nodal-related gene 1, in that CyNodal gene expression in the left lateral plate mesoderm shifts from posterior to anterior at least twice.

Amino Acid Sequence↗
PubMed2004

Expression of Pax2 in the intermediate mesoderm is regulated by YY1.

The transcription factor Pax2 is essential for the development of the urogenital system. Pax2 expression can be detected by mouse embryonic day 8.5 (E8.5) in the region of intermediate mesoderm fated to become the nephric duct, pronephros, and mesonephros. Elements that direct Pax2 expression to nephrogenic precursor cells must be responding to positional information that controls nephrogenic fate. A 4.1-kb Pax2 promoter/enhancer fragment directs expression of a lacZ reporter to the nephrogenic region and the midbrain-hindbrain junction in transgenic mice. As kidney development proceeds, transgene expression is limited to the nephric duct and its derivatives, but not the metanephric mesenchyme. The early expression driven by the 4.1 promoter does not require the Pax2 protein, demonstrating that it receives positional information in the absence of a developing pro- or mesonephros. We have identified two DNAseI hypersensitive regions within this promoter, one at the start site of transcription initiation and a second approximately 2-kb upstream. Deletion of the more distal site significantly attenuates lacZ expression in the nephrogenic region but not in the midbrain-hindbrain region. DNA footprinting of this fragment revealed a highly conserved sequence between mouse and human Pax2 promoter sequences. Using fractionated nuclear extracts, we identified the transcription factor Yin Yang 1 (YY1) as the protein that binds to this conserved sequence. Deletion of the YY1 element significantly attenuated expression of a full-length 4.1 promoter. Moreover, inclusion of this YY1 binding element significantly enhanced expression of a minimal Pax2 promoter/enhancer transgene in E12 embryos. These data point to a novel role for YY1 in the establishment of high level tissue-specific expression within the intermediate mesoderm.

Animals↗
PubMed2004

ALK4 functions as a receptor for multiple TGF beta-related ligands to regulate left-right axis determination and mesoderm induction in Xenopus.

In Xenopus, several TGF betas, including nodal-related 1 (Xnr1), derriere, and chimeric forms of Vg1, elicit cardiac and visceral organ left-right (LR) defects when ectopically targeted to right mesendoderm cell lineages, suggesting that LR axis determination may require activity of one or more TGF betas. However, it is not known which, if any, of these ligands is required for LR axis determination, nor is it known which type I TGF beta receptor(s) are involved in mediating left-side TGF beta signaling. We report here that similar to effects of ectopic TGF betas, right-side expression of constitutively active activin-like kinase (ALK) 4 results in LR organ reversals as well as altered Pitx2 expression in the lateral plate mesoderm. Moreover, left-side expression of a kinase-deficient, dominant-negative ALK4 (DN-ALK4) or an ALK4 antisense morpholino also results in abnormal embryonic body situs, demonstrating a left-side requirement for ALK4 signaling. To determine which TGF beta(s) utilize the ALK4 pathway to mediate LR development, biochemical and functional assays were performed using an Activin-Vg1 chimera (AVg), Xnr1, and derriere. Whereas ALK4 can co-immunoprecipitate all of these TGF betas, including endogenous Vg1 protein from embryo homogenates, functional assays demonstrate that not all of these ligands require an intact ALK4 signaling pathway to modulate LR asymmetry. When AVg and DN-ALK4 are co-expressed, LR defects otherwise induced by AVg alone are attenuated by DN-ALK4; however, when functional assays are performed with Xnr1 or derriere, LR defects otherwise elicited by these ligands alone still occur in the presence of DN-ALK4. Intriguingly, when any of these TGF betas is expressed at a higher concentration to elicit primary axis defects, DN-ALK4 blocks gastrulation and dorsoanterior/ventroposterior defects that otherwise occur following ligand-only expression. Together, these results suggest not only that ALK4 interacts with multiple TGF betas to generate embryonic pattern, but also that ALK4 ligands differentially utilize the ALK4 pathway to regulate distinct aspects of axial pattern, with Vg1 as a modulator of ALK4 function in LR axis determination and Vg1, Xnr1, and derriere as modulators of ALK4 function in mesoderm induction during primary axis formation.

Activin Receptors↗
PubMed2004

Wnt 6 regulates the epithelialisation process of the segmental plate mesoderm leading to somite formation.

In higher vertebrates, the paraxial mesoderm undergoes a mesenchymal to epithelial transformation to form segmentally organised structures called somites. Experiments have shown that signals originating from the ectoderm overlying the somites or from midline structures are required for the formation of the somites, but their identity has yet to be determined. Wnt6 is a good candidate as a somite epithelialisation factor from the ectoderm since it is expressed in this tissue. In this study, we show that injection of Wnt6-producing cells beneath the ectoderm at the level of the segmental plate or lateral to the segmental plate leads to the formation of numerous small epithelial somites. Ectopic expression of Wnt6 leads to sustained expression of markers associated with the epithelial somites and reduced or delayed expression of markers associated with mesenchymally organised somitic tissue. More importantly, we show that Wnt6-producing cells are able to rescue somite formation after ectoderm ablation. Furthermore, injection of Wnt6-producing cells following the isolation of the neural tube/notochord from the segmental plate was able to rescue somite formation at both the structural (epithelialisation) and molecular level, as determined by the expression of marker genes like Paraxis or Pax-3. We show that Wnts are indeed responsible for the epithelialisation of somites by applying Wnt antagonists, which result in the segmental plate being unable to form somites. These results show that Wnt6, the only known member of this family to be localised to the chick paraxial ectoderm, is able to regulate the development of epithelial somites and that cellular organisation is pivotal in the execution of the differentiation programmes. We propose a model in which the localisation of Wnt6 and its antagonists regulates the process of epithelialisation in the paraxial mesoderm.

Animals↗