Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “germ layer specification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1990

Immunocytochemical analysis of embryonic compartmentation with a monoclonal antibody against a cytokeratin-related antigen.

Mab 113F4, a monoclonal antibody recognizing an antigen in the outer synaptic layer of the chick neural retina, also recognizes an antigen appearing in all three germ layers of the gastrulating chick embryo. However, as neurulation proceeds, the antigen is down-regulated in three distinct patterns. First, the antigen is lost specifically from those trunk ectodermal cells destined to form the neural plate and, later, the neural tube. It remains absent from any neural derivative until day 13 when it appears in the outer synaptic layer of the neural retina, coincident with synaptogenesis in this region. Second, the entirety of the head ectoderm loses this antigen as the head lifts off the blastoderm. This down-regulation is followed later by a similar loss of antigen expression in the trunk ectoderm. Third, expression in the mesoderm becomes limited to the lateral plate and extraembryonic epithelia. Endodermal derivatives continue to express the antigen throughout development. Antigen 113F4 is localized within the cytoplasm and is organized in a fibrillar pattern. The intracellular localization of this antigen and its characteristic spatio-temporal tissue distribution are consistent with the antigen being a cytokeratin or cytokeratin-related antigen. The changes in tissue distribution suggest a possible role in tissue modelling in response to inductive interactions during development.

Animals↗
PubMed1999

Basonuclin, a zinc finger protein of keratinocytes and reproductive germ cells, binds to the rRNA gene promoter.

Basonuclin is a protein containing three pairs of C(2)H(2) zinc fingers. The protein has been found in the basal (germinal) cell layer of stratified squamous epithelia, such as the epidermis, and in germ cells of the testis and ovary. We show here that the human protein has specific affinity for a segment of the promoter of the gene for rRNA. Basonuclin interacts with two separate parts of the promoter, each possessing dyad symmetry. The upstream part, but not the downstream part, is known to bind UBF1, a transcription factor for rDNA. Basonuclin is likely to be a cell-type-specific regulatory protein for rDNA transcription.

DNA↗
PubMed2002

Differentiation of monkey embryonic stem cells into neural lineages.

Embryonic stem (ES) cells are self-renewing, pluripotent, and capable of differentiating into all of the cell types found in the adult body. Therefore, they have the potential to replace degenerated or damaged cells, including those in the central nervous system. For ES cell-based therapy to become a clinical reality, translational research involving nonhuman primates is essential. Here, we report monkey ES cell differentiation into embryoid bodies (EBs), neural progenitor cells (NPCs), and committed neural phenotypes. The ES cells were aggregated in hanging drops to form EBs. The EBs were then plated onto adhesive surfaces in a serum-free medium to form NPCs and expanded in serum-free medium containing fibroblast growth factor (FGF)-2 before neural differentiation was induced. Cells were characterized at each step by immunocytochemistry for the presence of specific markers. The majority of cells in complex/cystic EBs expressed antigens (alpha-fetal protein, cardiac troponin I, and vimentin) representative of all three embryonic germ layers. Greater than 70% of the expanded cell populations expressed antigenic markers (nestin and musashi1) for NPCs. After removal of FGF-2, approximately 70% of the NPCs differentiated into neuronal phenotypes expressing either microtubule-associated protein-2C (MAP2C) or neuronal nuclear antigen (NeuN), and approximately 28% differentiated into glial cell types expressing glial fibrillary acidic protein. Small populations of MAP2C/NeuN-positive cells also expressed tyrosine hydroxylase (approximately 4%) or choline acetyltransferase (approximately 13%). These results suggest that monkey ES cells spontaneously differentiate into cells of all three germ layers, can be induced and maintained as NPCs, and can be further differentiated into committed neural lineages, including putative neurons and glial cells.

Animals↗
PubMed1989

Cell allocation and lineage in the early mouse embryo.

In the early mammalian embryo, initially asymmetric cell contacts appear to induce blastomere polarization, elements of which can persists through cytokinesis. This leads to the generation of inner and outer populations of blastomeres which may subsequently diverge as a result of residing in distinct microenvironments. Similar processes may account for the generation of primitive endoderm versus primitive ectoderm, and that of trophectoderm versus inner cell mass. However, if this is the case, the response of cells to positional cues must change as a function of either their previous positional history or the number of cycles they have completed. Once these primary tissues have been established, specific interactions between them lead to further cellular diversification.

Animals↗
PubMed1987

A stage-specific sialoglycoprotein in encysting cells of Entamoeba invadens.

A novel sialoglycoprotein with an apparent molecular mass of approximately 250 kDa was detected on the surface of cysts of Entamoeba invadens. Sialic acid was identified in this glycoprotein by gas chromatography after methanolysis; N-acetyl- and N-glycolyl neuraminic acid were identified by thin layer chromatography in hydrolysates of partially purified preparations of the 250 kDa glycoprotein as well as in whole cysts. The sialoglycoprotein is stage-specific and could be detected by binding of wheat germ agglutinin and a specific monoclonal antibody (JAM3) only to precysts and mature cysts but not to trophozoites. A 250 kDa protein could be metabolically labeled with [35S]methionine. This, together with the absence of such a glycoprotein in the encystation medium, suggests that the 250 kDa sialoglycoprotein is not an adsorbed serum glycoprotein. Indirect evidence suggests that the parasite may utilize serum components as a source for sialic acid.

Animals↗
PubMed2005

Stem cell plasticity and issues of stem cell therapy.

Today, there is much evidence suggesting that organ-specific stem cells need not rely completely on their own sources for maintenance and regeneration of an organism. In certain circumstances, mostly related to tissue damage, stem cell populations residing past the affected organ can contribute to its recovery--that means from different cell lines and also in tissues from another germ layer. The key factor in formation of self-renewing cellular clones is the presence of stem cells either from the tissue of origin or stem cells migrating from other areas and their successful settlement in an empty niche of the damaged tissue. Stem cell plasticity is the ability of adult tissue-specific stem cells to switch to new identities. The term plasticity also means stem cell phenotypic potential, which is broader than phenotypes of differentiated cells in their original tissues. Many laboratories have given evidence on stem cell plasticity; however, the presented results met with many objections from others. In the first part of our report we wish to refer to several issues associated with stem cell plasticity, transdifferentiation and fusion. Recent experimental results show that stem cells will play a key role in cell therapy. But there are still many questions to answer for scientists engaged in stem cell research. Is it possible to induce cells from one type of tissue to look and act as cells of another tissue? Do these changes occur naturally? Could plasticity be used in the treatment of fatal diseases? Cell therapy is one of the methods to treat damaged myocardial tissue. However, recent results with autologous bone marrow cells in the treatment of damaged myocardium show that this method has still many unanswered questions concerning cells, cytokines, microenvironment and other factors responsible for reparation. To date, there are many opinions either recommending or denying this method in different modifications. One question has not yet been definitely solved: What are the conditions for us to accept this method--its safety and efficacy? The future will show whether these our hopes and expectations will be fulfiled. Many experiments are needed before at least some of these questions may be answered and cell therapy become an important method for the benefit of our patients.

Cell Differentiation↗
PubMed2004

Mosaicism of a TCOF1 mutation in an individual clinically unaffected with Treacher Collins syndrome.

Treacher Collins syndrome (TCS) or mandibulofacial dysostosis is an autosomal dominant disorder of craniofacial development with 60% of its cases arising de novo. Other modes of inheritance such as autosomal recessive, gonadal mosaicism, and chromosomal rearrangement have also been proposed. This syndrome can result from TCOF1 gene mutations. In this study we identified a TCOF1 1408delAG heterozygous mutation in a patient with the clinical diagnosis of TCS. This same mutation was found in the clinically unaffected mother's leukocytes, hair root bulbs, buccal mucosa, urine, and stool. The mother has a clinically unaffected child and the maternal grandparents do not have the mutation. Because the mother has the mutation in cells derived from all three germ layers, we suspected the mutation was nonpenetrant. However, we could not detect the mutation in her skin fibroblasts, suggesting she is mosaic secondary to cell type specific selection.

Adult↗
PubMed1989

Regional identity is established before gastrulation in the Xenopus embryo.

Regional differences in cell recognition properties along the animal-vegetal axis of Xenopus laevis embryos were investigated by using an in vitro cell sorting assay. Dissociated cells were obtained from defined regions of blastula- and early gastrula-stage embryos. Binary combinations of cells from different regions, or from the same region at different ages, were aggregated in stationary culture. Labelling of one population in each pair with a cell-autonomous dye allowed the degree of sorting out in the resulting aggregates to be scored. In combinations of cells from animal caps (prospective ectoderm) and vegetal masses (prospective endoderm), sorting was detectable at the equivalent of late blastula stage and increased with developmental age to the gastrula stage. In addition, cells from the same region but different stages sorted from each other, indicating temporal changes in regional identity. Marginal cells (prospective mesoderm) sorted strongly from vegetal cells but only weakly from animal cells. These results indicate the presence of regional identity in the form of specific recognition properties in cells of the Xenopus blastula. We suggest that these properties act to establish and maintain coherent cell populations, corresponding to the primary germ layers, prior to gastrulation. These results account for the gradual restriction in developmental capacity of blastomeres seen previously in single-cell transplantation experiments from this laboratory.

Animals↗
PubMedDate not supplied

Issues in stem cell plasticity.

Experimental biology and medicine work with stem cells more than twenty years. The method discovered for in vitro culture of human embryonal stem cells acquired at abortions or from "surplus" embryos left from in vitro fertilization, evoked immediately ideas on the possibility to aim development and differentiation of these cells at regeneration of damaged tissues. Recently, several surprising observations proved that even tissue-specific (multipotent) stem cells are capable, under suitable conditions, of producing a whole spectrum of cell types, regardless, whether these tissues are derived from the same germ layer or not. This ability is frequently called stem cell plasticity but other authors also use different names - "non-orthodox differentiation" or "transdifferentiation". In this paper we wish to raise several important questions and problems related to this theme. Let us remind some of them: Is it possible to force cells of one-type tissue to look and act as cells of another tissue? Are these changes natural? Could these transformations be used to treat diseases? What about the bioethic issue? However, the most serious task "still remains to be solved - how to detect, harvest and culture stem cells for therapy of certain diseases".

Animals↗
PubMedDate not supplied

[Screening for Y chromosome sequences in patients with Turner syndrome].

The Turner syndrome (TS) has been described in association with different sex chromosome aberrations. Although most TS patients show no evidence of Y chromosome sequences, according to different authors some TS patients may have Y chromosome material present in a few cells that are not detected by standard cytogenetic analysis. The importance of identification of this low level Y mosaicism is of clinical relevance due to the patient's increased risk of developing gonadoblastoma. In the present study, standard chromosome analysis performed on peripheral blood lymphocytes from 22 TS patients showed 12 patients with 45,X karyotype, 7 patients were mosaics with or without structural abnormalities in one X chromosome and, the remaining three patients had the following karyotypes: 46,X,i(X)(q10); 46,X,+mar/47,X,idic(Y),+mar and 45,X/46,X,+r. Molecular studies were performed on genomic DNA extracted from peripheral blood lymphocytes and mouth epithelial cells, which derive from two different embryonic germ layers, mesoderm and ectoderm, respectively. The screening for low level Y mosaicism was carried out by simplex PCR and by nested PCR of the following Y specific loci: SRY (sex determining region Y), TSPY (testis specific protein Y encoded), DYZ3 (centromeric locus) and DAZ1 (deleted in azoospermia). In two TS patients a set of STSs of the Y long and short arms were used to characterize the idic(Y) and the ring chromosomes. The high sensitivity of the nested PCR (1 male cell/125,000 female cells) allowed for exclusion of the presence of low level Y mosaicism in 20 out of 22 TS patients. In the patient with the idic(Y), PCR analysis was positive for all Y loci tested excluding the heterochromatic region. This result identified the breakpoint between sY158 and sY159 on the long arm and, by fluorescence in situ hybridization (FISH) it was confirmed that the euchromatic part of the long arm, centromere and short arm of the Y chromosome were duplicated. The characterization of the ring chromosome, detected in one of the TS patients, was only possible to analyse by FISH and PCR. In this ring, derived from the Y chromosome, a deletion was identified including the pseudoautosomal region 1 (PARY1) and Y intervals 6 and 7. However, the ring Y was positive for SRY, RPS4Y, AMGY, TSPY loci on the short arm, DYZ3 (centromere) and, sY85, DFFRY, GY6, sY87, sY113, sY119, sY122, sY126 and RBMY1 on the long arm. This study excluded the presence of low level Y mosaicism in two tissues collected from 20 TS patients. FISH and molecular analysis allowed us to characterize, in 2 out of 22 patients, one idic(Y) and one ring chromosome. The nature of the latter had not been completely identified by standard cytogenetics. The potential increased risk of gonadoblastoma in TS patients carrying Y chromosome sequences justifies the application of FISH and PCR for the characterization of marker chromosomes and the application of nested PCR for the detection of low level Y mosaicisms when Y chromosome material is not detected by standard cytogenetic analysis in patients with a 45,X karyotype and/or with virilization.

Adolescent↗
PubMed2004

[Study of embryonic stem cells induced to express hepatic cell functions in vitro in a pathologic niche containing cholestatic serum].

OBJECTIVE: To study the role of a pathologic niche inducing mouse embryonic stem cells (ESC) to express hepatic cell functions in vitro. METHODS: Embryoid bodies were developed from 5 to 7 day hanging-drop culture of mouse ESC, and their dissociated cells were planted in three differential systems: nothing added; with 20 ng/ml hepatocyte growth factor (HGF); and 5% rat cholestatic serum plus 20 ng/ml HGF added. Their differentiation was observed with inverted microscopes daily, and their hepatic functions were analyzed against their synthesis of glycogen, triglycerides, albumin, and urea nitrogen, and by their staining of indocyanine green (ICG) and fluorescein diacetate (FDA). RESULTS: ESC spontaneous differentiation was hardly being controlled to form three germ layers. HGF prompted the ESC to develop further into visceral endoderm and mesoderm (myocardium), but both of them only expressed a low level of hepatocyte-specific metabolic functions. With cholestatic serum added into the HGF-induced system, differentiated cells grew into similar angular cells, and had a higher level synthesis of glycogen, triglycerides, albumin and urea nitrogen with positive ICG and FDA staining. CONCLUSIONS: Spontaneous or HGF-induced ESC differentiation has only limited hepatic functions expressed. A pathologic niche in vitro induces ESC to develop into hepatic lineages, with a higher level of hepatic metabolic functions.

Animals↗
PubMed1985

Initial appearance and regional distribution of the neuron-glia cell adhesion molecule in the chick embryo.

This study represents a global survey of the times of the first appearance of the neuron-glia cell adhesion molecule (Ng-CAM) in various regions and on particular cells of the chick embryonic nervous system. Ng-CAM, originally characterized by means of an in vitro binding assay between glial cells and brain membrane vesicles, first appears in development at the surface of early postmitotic neurons. By 3 d in the chick embryo, the first neurons detected by antibodies to Ng-CAM are located in the ventral neural tube; these precursors of motor neurons emit well-stained fibers to the periphery. To identify locations of appearance of Ng-CAM in the peripheral nervous system (PNS), we used a monoclonal antibody called NC-1 that is specific for neural crest cells in early embryos to show the presence of numerous crest cells in the neuritic outgrowth from the neural tube; neither these crest cells nor those in ganglion rudiments bound anti-Ng-CAM antibodies. The earliest neurons in the PNS stained by anti-Ng-CAM appeared by 4 d of development in the cranial ganglia. At later stages and progressively, all the neurons and neurities of the PNS were found to contain Ng-CAM both in vitro and in vivo. Many central nervous system (CNS) neurons also showed Ng-CAM at these later stages, but in the CNS, the molecule was mostly associated with neuronal processes (mainly axons) rather than with cell bodies; this regional distribution at the neuronal cell surface is an example of polarity modulation. In contrast to the neural cell adhesion molecule and the liver cell adhesion molecule, both of which are found very early in derivatives of more than one germ layer, Ng-CAM is expressed only on neurons of the CNS and the PNS during the later epoch of development concerned with neural histogenesis. Ng-CAM is thus a specific differentiation product of neuroectoderm. Ng-CAM was found on developing neurons at approximately the same time that neurofilaments first appear, times at which glial cells are still undergoing differentiation from neuroepithelial precursors. The present findings and those of previous studies suggest that together the neural cell adhesion molecule and Ng-CAM mediate specific cellular interactions during the formation of neuronal networks by means of modulation events that govern their prevalence and polarity on neuronal cell surfaces.

Age Factors↗
PubMedDate not supplied

Human embryonic stem cells: culture, differentiation, and genetic modification for regenerative medicine applications.

Human embryonic stem (hES) cells can proliferate extensively in culture and can differentiate into representatives of all three embryonic germ layers in vitro and in vivo. The undifferentiated hES cells have now been cultured for more than 50 passages in vitro, yet maintain a normal karyotype. The hES cells express a series of specific surface antigens, as well as OCT-4 and human telomerase, proteins associated with a pluripotent and immortal phenotype. On differentiation, OCT-4 and human telomerase expression decreases with the emergence of a maturing population of cells. During hES cell differentiation, modulation of the expression of many genes has been evaluated using microarray analysis. To improve the ease, reproducibility, and scalability of hES culture, methods have been developed to propagate the cells in the absence of mouse embryonic cell feeders. hES cells maintained in culture using extracellular matrix factors together with mouse embryonic cell conditioned medium proliferate indefinitely while maintaining a normal karyotype, proliferation rate, and complement of undifferentiated cell markers. hES cells cultured without feeder layers retain their capacity to differentiate into cells of all three germ layers in vitro and in teratomas. The hES cells can also be genetically modified transiently or stably using both plasmid and viral gene transfer agents. These analyses and technological developments will aid in the realization of the full potential of hES cells for both research and therapeutic applications.

Animals↗
PubMed2006

Axis specification and morphogenesis in the mouse embryo require Nap1, a regulator of WAVE-mediated actin branching.

Dynamic cell movements and rearrangements are essential for the generation of the mammalian body plan, although relatively little is known about the genes that coordinate cell movement and cell fate. WAVE complexes are regulators of the actin cytoskeleton that couple extracellular signals to polarized cell movement. Here, we show that mouse embryos that lack Nap1, a regulatory component of the WAVE complex, arrest at midgestation and have defects in morphogenesis of all three embryonic germ layers. WAVE protein is not detectable in Nap1 mutants, and other components of the WAVE complex fail to localize to the surface of Nap1 mutant cells; thus loss of Nap1 appears to inactivate the WAVE complex in vivo. Nap1 mutants show specific morphogenetic defects: they fail to close the neural tube, fail to form a single heart tube (cardia bifida), and show delayed migration of endoderm and mesoderm. Other morphogenetic processes appear to proceed normally in the absence of Nap1/WAVE activity: the notochord, the layers of the heart, and the epithelial-to-mesenchymal transition (EMT) at gastrulation appear normal. A striking phenotype seen in approximately one quarter of Nap1 mutants is the duplication of the anteroposterior body axis. The axis duplications arise because Nap1 is required for the normal polarization and migration of cells of the Anterior Visceral Endoderm (AVE), an early extraembryonic organizer tissue. Thus, the Nap1 mutant phenotypes define the crucial roles of Nap1/WAVE-mediated actin regulation in tissue organization and establishment of the body plan of the mammalian embryo.

Actins↗
PubMed2005

Basement membrane composition in the early mouse embryo day 7.

Basement membranes (BM) are specialized structures of the extracellular matrix known to be involved in various early developmental processes. Despite numerous investigations on the localization of BM components, it remains unknown which molecules are expressed in early developmental stages and by which germ layers these proteins are produced. Therefore, we tested for all known laminin chains, nidogens, collagen type IV, and perlecan by means of light microscopic immunostaining and performed in situ reverse transcriptase-polymerase chain reaction to detect the mRNAs specific for laminin alpha1, laminin beta1, the alpha1 chain of collagen type IV, nidogen-2, and perlecan in the early mouse embryo, day 7, in vivo. Only the laminin chains alpha1, beta1, and gamma1 were detected immunohistochemically throughout the entire endodermal and ectodermal BM zones of the embryo proper. The mRNA of laminin alpha1, laminin beta1, collagen type IV, nidogen-2 and perlecan were expressed in the ectoderm-derived mesoderm, in the endoderm as well as in the ectoderm. In contrast, Reichert's membrane was positive for all laminin chains except for the alpha4, alpha5, beta3, and gamma3 chains. Moreover, maternal epithelial as well as mesenchymal cells expressed laminins, nidogen-1 and nidogen-2, collagen type IV, and perlecan. In conclusion, laminin-1 might be the only laminin isoform in the early mouse embryo that, together with the other main BM components, nidogens, collagen type IV, and perlecan, is synthesized by all three germ layers.

Animals↗
PubMed2000

Skeletal myogenic potential of human and mouse neural stem cells.

Distinct cell lineages established early in development are usually maintained throughout adulthood. Thus, adult stem cells have been thought to generate differentiated cells specific to the tissue in which they reside. This view has been challenged; for example, neural stem cells can generate cells that normally originate from a different germ layer. Here we show that acutely isolated and clonally derived neural stem cells from mice and humans could produce skeletal myotubes in vitro and in vivo, the latter following transplantation into adult animals. Myogenic conversion in vitro required direct exposure to myoblasts, and was blocked if neural cells were clustered. Thus, a community effect between neural cells may override such myogenic induction. We conclude that neural stem cells, which generate neurons, glia and blood cells, can also produce skeletal muscle cells, and can undergo various patterns of differentiation depending on exposure to appropriate epigenetic signals in mature tissues.

Age Factors↗