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PubMed1995

Mutations of the Connexin43 gap-junction gene in patients with heart malformations and defects of laterality.

BACKGROUND: Gap junctions are thought to have a crucial role in the synchronized contraction of the heart and in embryonic development. Connexin43, the major protein of gap junctions in the heart, is targeted by several protein kinases that regulate myocardial cell-cell coupling. We hypothesized that mutations altering sites critical to this regulation would lead to functional or developmental abnormalities of the heart. METHODS: Connexin43 DNA from 25 normal subjects and 30 children with a variety of congenital heart diseases was amplified by the polymerase chain reaction and sequenced. Mutant DNA was expressed in cell culture and examined for its effect on the regulation of cell-cell communication. RESULTS: The 25 normal subjects and 23 of the 30 children with heart disease had no amino acid substitutions in connexin43. All six children with syndromes that included complex heart malformations had substitutions of one or more phosphorylatable serine or threonine residues. Four of these children had two independent mutations, suggesting an autosomal recessive disorder. Five of these children had substitutions of proline for serine at position 364. A seventh child, with a different heart condition, also had a point mutation in connexin43. Transfected cells expressing the Ser364Pro mutant connexin43 sequence showed abnormalities in the regulation of cell-cell communication, as compared with cells expressing normal connexin43. CONCLUSIONS: Mutations in the connexin43 gap-junction gene, which lead to abnormally regulated cell-cell communication, are associated with visceroatrial heterotaxia.

Adolescent↗
PubMedDate not supplied

Communication of agonist-induced electrical responses along 'capillaries' in vitro can be modulated by lipopolysaccharide, but not nitric oxide.

Communication of agonist-induced membrane potential changes along blood vessels has been proposed to contribute to the coordination of microvascular function. Factors mediating septic shock may compromise this coordination. Using electrophysiology in a simplified in vitro model of endothelial cells grown as capillary-like structures, we aimed to determine (i) the effect of lipopolysaccharide (LPS) on endothelial cell membrane potential responses to ATP and KCl and (ii) the effect of LPS and nitric oxide (NO) on cell-to-cell communication. Treatment of 'capillaries' with LPS (10 microg/ml for 1 h) did not affect local responsiveness to ATP or KCl, but reduced cell communication by a tyrosine-kinase-dependent mechanism. Treatment of 'capillaries' with the NO donor DETA (100 microM) or the NO synthase inhibitor L-NAME (100 microM) had no effect on cell communication or the response to LPS. Endogenous NO production, stimulated by LPS + interferon-gamma (100 U/ml) treatment, also had no effect on cell communication beyond that of LPS alone. We conclude that LPS, but not NO, can modulate conduction of agonist-induced electrical responses along endothelial capillary-like structures in vitro.

Adenosine Triphosphate↗
PubMed2006

Bystander effect: biological endpoints and microarray analysis.

In cell populations exposed to ionizing radiation, the biological effects occur in a much larger proportion of cells than are estimated to be traversed by radiation. It has been suggested that irradiated cells are capable of providing signals to the neighboring unirradiated cells resulting in damage to these cells. This phenomenon is termed the bystander effect. The bystander effect induces persistent, long-term, transmissible changes that result in delayed death and neoplastic transformation. Because the bystander effect is relevant to carcinogenesis, it could have significant implications for risk estimation for radiation exposure. The nature of the bystander effect signal and how it impacts the unirradiated cells remains to be elucidated. Examination of the changes in gene expression could provide clues to understanding the bystander effect and could define the signaling pathways involved in sustaining damage to these cells. The microarray technology serves as a tool to gain insight into the molecular pathways leading to bystander effect. Using medium from irradiated normal human diploid lung fibroblasts as a model system we examined gene expression alterations in bystander cells. The microarray data revealed that the radiation-induced gene expression profile in irradiated cells is different from unirradiated bystander cells suggesting that the pathways leading to biological effects in the bystander cells are different from the directly irradiated cells. The genes known to be responsive to ionizing radiation were observed in irradiated cells. Several genes were upregulated in cells receiving media from irradiated cells. Surprisingly no genes were found to be downregulated in these cells. A number of genes belonging to extracellular signaling, growth factors and several receptors were identified in bystander cells. Interestingly 15 genes involved in the cell communication processes were found to be upregulated. The induction of receptors and the cell communication processes in bystander cells receiving media from irradiated cells supports the active involvement of these processes in inducing bystander effect.

Apoptosis↗
PubMed2004

Downregulation of tissue factor by RNA interference in human melanoma LOX-L cells reduces pulmonary metastasis in nude mice.

Tissue factor (TF) is the membrane receptor of the serine protease coagulation factor VIIa (FVIIa). Formation of the TF/FVIIa complex initiates the coagulation cascade. We used short hairpin RNA (shRNA)-mediated RNA interference to knock down TF expression in the human metastatic melanoma cell line LOX-L. After transfection with the shRNA construct, 3 stable clones with significantly downregulated TF expression were established. They exhibited decreased proliferation in vitro as determined by (14)C thymidine incorporation and soft agar assay. The in vivo metastatic potential was assessed in an experimental pulmonary metastasis model in which cells from different clones were injected into the tail vein of nude mice. The incidence of pulmonary tumors was significantly lower in mice receiving shRNA-expressing cells (33% +/- 15%) than in control mice injected with wild-type cells or cells stably transfected with empty expression vector (90% +/- 10%). The mice injected with TF-downregulated cells had markedly longer survival time (69 +/- 17 days) compared to the control mice (35.6 +/- 5 days; p = 0.03). Thus, reduction of TF levels in LOX-L cells significantly delayed and reduced lung tumor formation. As a first step in elucidating the molecular basis for this effect, we compared the global gene expression profile in TF-downregulated cells and control cells by using cDNA microarray analysis. Forty-four known human genes were found to be significantly upregulated (> 2-fold; p < 0.05) and 228 genes significantly downregulated (>or= 3-fold; p < 0.05) in TF-downregulated cells compared to control cells. The differentially expressed genes encode proteins functioning in transcription, translation, cell communication and cell growth/death. The results provide a basis for investigating molecular mechanisms underlying the effects of TF on the metastatic capacity of LOX-L melanoma cells.

Animals↗
PubMed1999

Sequences of 596 cDNA Clones (565,977 bp) of Japanese Flounder (Paralichthys olivaceus) Leukocytes Infected with Hirame Rhabdovirus.

: We have partially sequenced 785 sequences of 596 independent complementary DNA clones isolated from a cDNA library of Japanese flounder leukocytes infected with hirame rhabdovirus. These sequences consist of a total of 565,977 base pairs. The average size of the sequenced lengths was 721 bp. Of 596 clones, 386 (64.8%) were identified as previously reported genes by the BLASTN and BLASTX programs. About 30% of the identified clones could be recognized by only the BLASTX program. A total of 251 distinct genes were identified, and 181 of these genes are the first such genes reported from the teleostei. Approximately 27% of the identified Japanese flounder genes appear to be associated with cell division, cell structure or motility, and basic energy metabolism, 29% with gene or protein expression, and 17% with cell signaling, cell communication, and cell or organism defense. The most frequently identified expressed sequence tags of leukocytes of Japanese flounder were gelatinase b and ribosomal protein L23, which both had 1.34% prevalence.

Journal Article↗
PubMed2001

Autocrine up-regulation of glucocorticoid receptors by interleukin-6 in human osteoblast-like cells.

Interleukin (IL)-6 is a bone-resorbing cytokine that acts primarily on osteoclast progenitors to stimulate both proliferation and differentiation. Glucocorticoids (GC) down-regulate IL-6 synthesis in different cell types, including osteoblasts. Given the fact that bone remodeling is a tightly controlled process, it is reasonable to think of auto-regulatory mechanisms in the bone microenvironment able to prevent excess IL-6 production. We have studied two human osteosarcoma cell lines (Saos-2 and MG-63) with different degrees of differentiation and different constitutive IL-6 production (3.4 +/- 0.2 (mean +/- SE) and 2,898 +/- 401 pg/10(6) cells, respectively). We measured the expression of glucocorticoid receptor (GR) in terms of specific binding sites after exposure of cells to different amounts of IL-6. Incubation for 20 hours with IL-6 at increasing concentrations up to 2,000 pg/ml yielded significant increase of GR binding sites in both cell lines. IL-6 was also able to revert the inhibitory effect of dexamethasone (1 microM) on GR in both cell lines. In MG-63 cells, that express higher concentrations of GR, IL-6 deprivation via a specific anti-IL-6 antibody (100 ng/ml) significantly decreased GR, as it was noticed, although to a lesser degree, using a specific anti-IL-6 receptor antibody. In Saos-2, cells that express lower concentrations of GR, a 40-hour treatment with human IL-1beta (10 ng/ml) significantly increased both IL-6 production and GR. This latter effect was completely abolished by co-treating the cells with the anti-IL-6 antibody. Our data are consistent with an autocrine up-regulation of GR expression by IL-6 in human osteoblast-like cells. This phenomenon, which is also relevant to paracrine cell-to-cell communication, subserves a feedback loop in the bone microenvironment that restrains excess inducible IL-6 production. In patients having high levels of IL-6 and given GCs, it could offer an additional explanation for the biphasic pattern of bone loss in the course of therapy.

Antibodies, Monoclonal↗
PubMed2001

Expression of connexin 37, 40, and 43 mRNA and protein in renal preglomerular arterioles.

Gap junctions allow direct intercellular coupling between many cells including those in the vascular wall. Studies of connexin expression in cells of the microcirculatory system are very few in number. However, cell-to-cell communication between cells of the arteriolar wall may be particularly important in microcirculatory control. We investigated the expression of connexins 43, 40, and 37 (Cx43, Cx40, Cx37) mRNA and proteins in primary cultures of smooth muscle cells (SMC) from rat renal preglomerular arterioles and in the aortic cell line A7r5. Furthermore protein expression in preglomerular arterioles in frozen sections was evaluated. SMC were isolated from kidneys using an iron oxide sieve method and explant technique. Total RNA from these cultures was tested by RT-PCR analysis for the expression of the three connexins mRNA. Using immunofluorescence we examined whether the expression pattern of connexin protein in the cell culture and frozen sections corresponded to the mRNA expression. The data show that A7r5 and preglomerular SMC express mRNA for Cx37 in addition to Cx43 and Cx40. In A7r5 cells the mRNA for Cx43, Cx40, and Cx37 are translated to protein, whereas cultured preglomerular SMC and the media of afferent arterioles in frozen sections only showed Cx40 immunoreactivity.

Animals↗
PubMed1992

Mechanically induced electrical and intracellular calcium responses in normal and cancerous mammary cells.

Mechanically induced channel activities and increase of intracellular calcium ([Ca2+]i) in normal and cancerous murine mammary cells (MMT 060562) were investigated using the patch clamp technique and Fura-2 fluorescence. Both cell types showed similar properties. Upon mechanical stimulation, activation of the Ca(2+)-dependent K+ channel or outward membrane current was recorded in cells which were several cells distant from the stimulated cell. Mechanical stimulation also induced an increase of [Ca2+]i in the touched cell, and this increase of [Ca2+]i spread to the surrounding cells. The [Ca2+]i signal travelled a distance of 100-200 microns within 20-40 s and then diminished. The presence of cell-to-cell communication between adjacent mammary cells through gap junction was indicated by injection of lucifer yellow and measurements of electrical coupling (coupling constant = 0.2-0.3). The mechanically induced increase of the [Ca2+]i signal spread to adjacent cells even when the stimulated cell had no physical contact with them. In the absence of fluid movement, the pattern of the spread of the [Ca2+]i signal was a concentric circle. However, in the presence of fluid movement, the pattern changed to elongate to the direction of the flow. These findings suggested that a certain factor was released from the mechanically stimulated cell to the extracellular space, and this factor induces the increase of [Ca2+]i in surrounding cells.

Animals↗
PubMed1991

A review of cancer induction by extremely low frequency electromagnetic fields. Is there a plausible mechanism?

A body of epidemiological evidence suggests an association between residential or occupational exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and an increased incidence of cancer in children and adults. Experimental studies at the whole-animal and cellular level are ambiguous; bioeffects suggestive of a carcinogenic effect have been reported, but a similar volume of negative reports can also be assembled. This literature is critically reviewed based on the hypothesis that the epidemiological results are correct, and asking what plausible mechanism could explain a small increase in the incidence of a range of tumors with a non-specific increased exposure to ELF EMF? We focus on four likely mechanisms: 1) disruption of cell communication, 2) modulation of cell growth via changes in calcium ion flux, 3) activation of specific oncogenic gene sequences, and 4) action as a stress factor operating through disruption of hormonal and immune system tumor control mechanisms. We discuss the implications of epidemiologic and experimental results in the context of hypothetical mechanisms of cancer induction, and suggest experiments likely to help define putative EMF hazards.

Adult↗
PubMed2006

Cluster analysis and gene expression profiles: a cDNA microarray system-based comparison between human dental pulp stem cells (hDPSCs) and human mesenchymal stem cells (hMSCs) for tissue engineering cell therapy.

We investigated gene expression patterns and functional classifications regarding the clusters of human dental pulp stem cells (hDPSCs) and human mesenchymal stem cells (hMSCs)--which possess a multipotent ability--because little is known about the precise moleculobiological clues by which these cells activate their differentiating ability or functionality to eventually form dentin and bone, respectively. We first verified the expressions of the alkaline phosphatase (ALP) gene, dentin matrix protein 1 (DMP-1), and dentinsialophosphoprotein (DSPP) by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) and consequently discovered the high expressions of these genes. Total RNA was also followed by hybridization with a human microarray system consisting of 12,814 genes. Analyses of gene expression patterns indicated several genes which encode extracellular matrix components, cell adhesion molecules, growth factors, and transcription regulators. Functional and clustering analyses of differences in gene expression levels revealed cell signaling, cell communication, or cell metabolism. In the future, information on the gene expression patterns of hDPSCs and hMSCs might be useful in determining the detailed functional roles of the relevant genes and applicable to stem cell therapies, and these cells could also be used as multipotent cell sources for gene technology and tissue engineering technology.

Adult↗
PubMed2004

Compensatory proliferation induced by cell death in the Drosophila wing disc requires activity of the apical cell death caspase Dronc in a nonapoptotic role.

Achieving proper organ size requires a balance between proliferation and cell death. For example, at least 40%-60% of cells in the Drosophila wing disc can be lost, yet these discs go on to give rise to normal-looking adult wings as a result of compensatory proliferation. The signals that drive this proliferation are unknown. One intriguing possibility is that they derive, at least in part, from the dying cells. To explore this hypothesis, we activated cell death signaling in specific populations of cells in the developing wing but prevented these cells from dying through expression of the baculovirus p35 protein, which inhibits the activity of effector caspases that mediate apoptosis. This allowed us to uncouple the activation steps of apoptosis from death itself. Here we report that stimulation of cell death signaling in the wing disc-in the absence of cell death-results in increased proliferation and ectopic expression of Wingless, a known mitogen in the wing. Activation of the apical cell death caspase Dronc is necessary and sufficient to drive both of these processes. Our results demonstrate an unanticipated function, the nonautonomous induction of proliferation, of an apical cell death caspase. This activity is likely to contribute to tissue homeostasis by promoting local compensatory proliferation in response to cell death. We speculate that dying cells may communicate cell fate or behavior instructions to their neighbors in other contexts as well.

Animals↗
PubMed2004

Periodic Delta-like 4 expression in developing retinal arteries.

During vascular development, Notch signalling plays important roles in cell-cell communication and cell fate decisions. We studied expression of Notch 1-4 and its ligand Delta-like 4 (Dll4) in the developing retinal vasculature. Dll4 mRNA is strongly expressed in endothelial cells at the very tips of growing vessels ('tip cells') and also in arteries, where it is expressed in a segmented 'tiger's tail' pattern. This implies that developing retinal arteries contain different types of endothelial cells, Dll4-positive and Dll4-negative. The Dll4-positive stripes do not correspond to any obvious morphological property of the vascular network but correlate to some extent with the distribution of platelet derived growth factor B (PDGF-B) mRNA. However, PDGF-B expression is neither as artery-specific nor as clearly segmented as Dll4. Possible target cells for Dll4 signalling are retinal astrocytes (Notch1 positive), arterial pericytes (Notch3 positive) or arterial endothelial cells themselves (Notch4 positive). However, there is no clear reciprocity of Notch and Dll4 expression that allows identification of the interacting cells. Nevertheless, Dll4 stripes are a novel property of immature arteries, the origin and function of which remain to be explained.

Animals↗
PubMed2006

Gene expression profiling studies on Caenorhabditis elegans dystrophin mutants dys-1(cx-35) and dys-1(cx18).

The Caenorhabditis elegans genome contains a single dystrophin/utrophin orthologue, dys-1. Point mutations in this gene, dys-1(cx35) and dys-1(cx18), result in truncated proteins. Such mutants offer potentially valuable worm models of human Duchenne muscular dystrophy. We have used microarrays to examine genes expressed differentially between wild-type C. elegans and dys-1 mutants. We found 106 genes (115 probe sets) to be differentially expressed when the two mutants are compared to wild-type worms, 49 of which have been assigned to six functional categories. The main categories of regulated genes in C. elegans are genes encoding intracellular signalling, cell-cell communication, cell-surface, and extracellular matrix proteins; genes in these same categories have been shown by others to be differentially expressed in muscle biopsies of muscular dystrophy patients. The C. elegans model may serve as a convenient vehicle for future genetic and chemical screens to search for new drug targets.

Animals↗
PubMed2004

The exocyst complex in polarized exocytosis.

Exocytosis is an essential membrane traffic event mediating the secretion of intracellular protein contents such as hormones and neurotransmitters as well as the incorporation of membrane proteins and lipids to specific domains of the plasma membrane. As a fundamental cell biological process, exocytosis is crucial for cell growth, cell-cell communication, and cell polarity establishment. For most eukaryotic cells exocytosis is polarized. A multiprotein complex, named the exocyst, is required for polarized exocytosis from yeast to mammals. The exocyst consists of eight components: Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84. They are localized to sites of active exocytosis, where they mediate the targeting and tethering of post-Golgi secretory vesicles for subsequent membrane fusion. Here we review the progress made in the understanding of the exocyst and its role in polarized exocytosis.

Animals↗
PubMed2003

Eph receptors and ephrins.

Eph receptors, the largest subfamily of receptor tyrosine kinases (RTKs), and their ephrin ligands are important mediators of cell-cell communication regulating cell attachment, shape, and mobility. Eph signaling is crucial for the development of many tissues and organs including the nervous and cardiovascular systems. Both Ephs and ephrins are membrane-bound and their interactions at sites of cell-cell contact initiate unique bi-directional signaling cascades where information is transduced in both the receptor- and the ligand-expressing cells. Recent studies summarized in this review reveal how the signaling process is triggered upon ligand-receptor binding via the formation of a 2:2 circular heterotetramer. This fixes the orientation of the participating molecules and facilitates phosphorylation of their cytoplasmic domains which then interact with downstream signaling factors. The elucidation of the structural details of Eph-ephrin recognition and binding should yield insight into the future development of novel therapeutic agents targeting cardiovascular function, nerve regeneration, and cancer.

Animals↗
PubMed2004

Micropatterning neuronal cells on polyelectrolyte multilayers.

This paper describes an approach to adhere retinal cells on micropatterned polyelectrolyte multilayer (PEM) lines adsorbed on poly(dimethylsiloxane) (PDMS) surfaces using microfluidic networks. PEMs were patterned on flat, oxidized PDMS surfaces by sequentially flowing polyions through a microchannel network that was placed in contact with the PDMS surface. Polyethyleneimine (PEI) and poly(allylamine hydrochloride) (PAH) were the polyions used as the top layer cellular adhesion material. The microfluidic network was lifted off after the patterning was completed and retinal cells were seeded on the PEM/PDMS surfaces. The traditional practice of using blocking agents to prevent the adhesion of cells on unpatterned areas was avoided by allowing the PDMS surface to return to its uncharged state after the patterning was completed. The adhesion of rat retinal cells on the patterned PEMs was observed 5 h after seeding. Cell viability and morphology on the patterned PEMs were assayed. These materials proved to be nontoxic to the cells used in this study regardless of the number of stacked PEM layers. Phalloidin staining of the cytoskeleton revealed no apparent morphological differences in retinal cells compared with those plated on polystyrene or the larger regions of PEI and PAH; however, cells were relatively more elongated when cultured on the PEM lines. Cell-to-cell communication between cells on adjacent PEM lines was observed as interconnecting tubes containing actin that were a few hundred nanometers in diameter and up to 55 microm in length. This approach provides a simple, fast, and inexpensive method of patterning cells onto micrometer-scale features.

Animals↗
PubMed2006

A nanofabricated planar aperture as a mimic of the nerve-muscle contact during synaptogenesis.

The release of synaptogenic factors by the nerve terminal plays a central role in the aggregation of neurotransmitter receptors at the postsynaptic membrane, a precisely timed and localized process that is essential for the correct formation and functioning of the synapse. This process has been difficult to re-capitulate in cell culture because present cell stimulation methods do not have sufficient spatiotemporal control of the delivery of soluble signals. We cultured myotubes atop nanofabricated planar apertures (2-8 microm diameter) to focally stimulate the muscle cell membrane with neural agrin, a synaptogenic factor released by motor neurons during development. Focal agrin delivery through the apertures after myotube fusion results in local aggregation of acetylcholine receptors (AChRs) in the vicinity of the apertures, a process reminiscent of AChR clustering at innervation sites. Since the apertures are spatially organized in microarrays, multiple experiments can be run in parallel on one device. The technique has wide applicability in cell-cell communication studies and cell-based bioassays.

Animals↗
PubMed1996

Cellular and molecular features of lens differentiation: a review of recent advances.

In this paper, the more recent literature pertaining to differentiation in the developing vertebrate lens is reviewed in relation to previous work. The literature reviewed reveals that the developing lens has been, and will continue to be, a useful model system for the examination of many fundamental processes occurring during embryonic development. Areas of lens development reviewed here include: the induction and early embryology of the lens; lens cell culture techniques; the role of growth factors and cytokines; the involvement of gap junctions in lens cell-cell communication; the role of cell adhesion molecules, integrins, and the extracellular matrix; the role of the cytoskeleton; the processes of programmed cell death (apoptosis) and lens fibre cell denucleation; the involvement of Pax and Homeobox genes; and crystallin gene regulation. Finally, some speculation is provided as to possible directions for further research in lens development.

Animals↗