Regulation of body length and male tail ray pattern formation of Caenorhabditis elegans by a member of TGF-beta family.
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We have identified a new member of the TGF-beta superfamily, CET-1, from Caenorhabditis elegans, which is expressed in the ventral nerve cord and other neurons. cet-1 null mutants have shortened bodies and male tail abnormal phenotype resembling sma mutants, suggesting cet-1, sma-2, sma-3 and sma-4 share a common pathway. Overexpression experiments demonstrated that cet-1 function requires wild-type sma genes. Interestingly, CET-1 appears to affect body length in a dose-dependent manner. Heterozygotes for cet-1 displayed body lengths ranging between null mutant and wild type, and overexpression of CET-1 in wild-type worms elongated body length close to lon mutants. In male sensory ray patterning, lack of cet-1 function results in ray fusions. Epistasis analysis revealed that mab-21 lies downstream and is negatively regulated by the cet-1/sma pathway in the male tail. Our results show that cet-1 controls diverse biological processes during C. elegans development probably through different target genes. (+info)
Activities of citrate synthase, NAD+-linked and NADP+-linked isocitrate dehydrogenases, glutamate dehydrogenase, aspartate aminotransferase and alanine aminotransferase in nervous tissues from vertebrates and invertebrates.
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1. The activities of citrate synthase and NAD+-linked and NADP+-linked isocitrate dehydrogenases were measured in nervous tissue from different animals in an attempt to provide more information about the citric acid cycle in this tissue. In higher animals the activities of citrate synthase are greater than the sum of activities of the isocitrate dehydrogenases, whereas they are similar in nervous tissues from the lower animals. This suggests that in higher animals the isocitrate dehydrogenase reaction is far-removed from equilibrium. If it is assumed that isocitrate dehydrogenase activities provide an indication of the maximum flux through the citric acid cycle, the maximum glycolytic capacity in nervous tissue is considerably greater than that of the cycle. This suggest that glycolysis can provide energy in excess of the aerobic capacity of the tissue. 2. The activities of glutamate dehydrogenase are high in most nervous tissues and the activities of aspartate aminotransferase are high in all nervous tissue investigated. However, the activities of alanine aminotransferase are low in all tissues except the ganglia of the waterbug and cockroach. In these insect tissues, anaerobic glycolysis may result in the formation of alanine rather than lactate. (+info)
Acute and persistent infection of human neural cell lines by human coronavirus OC43.
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Human coronaviruses (HuCV) are recognized respiratory pathogens. Data accumulated by different laboratories suggest their neurotropic potential. For example, primary cultures of human astrocytes and microglia were shown to be susceptible to an infection by the OC43 strain of HuCV (A. Bonavia, N. Arbour, V. W. Yong, and P. J. Talbot, J. Virol. 71:800-806, 1997). We speculate that the neurotropism of HuCV will lead to persistence within the central nervous system, as was observed for murine coronaviruses. As a first step in the verification of our hypothesis, we have characterized the susceptibility of various human neural cell lines to infection by HuCV-OC43. Viral antigen, infectious virus progeny, and viral RNA were monitored during both acute and persistent infections. The astrocytoma cell lines U-87 MG, U-373 MG, and GL-15, as well as neuroblastoma SK-N-SH, neuroglioma H4, oligodendrocytic MO3.13, and the CHME-5 immortalized fetal microglial cell lines, were all susceptible to an acute infection by HuCV-OC43. Viral antigen and RNA and release of infectious virions were observed during persistent HuCV-OC43 infections ( approximately 130 days of culture) of U-87 MG, U-373 MG, MO3.13, and H4 cell lines. Nucleotide sequences of RNA encoding the putatively hypervariable viral S1 gene fragment obtained after 130 days of culture were compared to that of initial virus input. Point mutations leading to amino acid changes were observed in all persistently infected cell lines. Moreover, an in-frame deletion was also observed in persistently infected H4 cells. Some point mutations were observed in some molecular clones but not all, suggesting evolution of the viral population and the emergence of viral quasispecies during persistent infection of H4, U-87 MG, and MO3.13 cell lines. These results are consistent with the potential persistence of HuCV-OC43 in cells of the human nervous system, accompanied by the production of infectious virions and molecular variation of viral genomic RNA. (+info)
The mouse GATA-2 gene is expressed in the para-aortic splanchnopleura and aorta-gonads and mesonephros region.
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We previously reported that the mouse GATA-2 gene is regulated by two alternative promoters (Minegishi et al, J Biol Chem, 273:3625, 1998). Although the more proximal IG (general) promoter is active in almost all GATA-2-expressing cells, the distal IS (specific) promoter activity was selectively detected in hematopoietic tissues but not in other mesodermal tissues. We report here in vivo analysis of the GATA-2 locus and its regulatory characteristics in hematopoietic tissues of transgenic mice. Transgenes containing 6 or 7 kbp of sequence flanking the 5' end of the IS first exon direct expression of beta-galactosidase or green fluorescent protein (GFP) reporter genes specifically to the para-aortic splanchnopleura, aorta-gonads, and mesonephros (AGM) region, and in the neural tissues. In situ hybridization analysis showed that reporter gene expression specifically recapitulates the endogenous expression profile of GATA-2 in these tissues. The flk-1, CD34, c-kit, and CD45 antigens were identified in the GFP-positive cells from the AGM region and fetal liver, indicating that GATA-2 is expressed in immature hematopoietic cells. Deletion of 3.5 kbp from the 5' end of the 6.0 kbp IS promoter construct, including one of the DNase I hypersensitive sites, completely abolished hematopoietic expression. These experiments describe an early developmental GATA-2 hematopoietic enhancer located between 6.0 and 2.5 kbp 5' to the IS exon. (+info)
Co-ordinate variations in methylmalonyl-CoA mutase and methionine synthase, and the cobalamin cofactors in human glioma cells during nitrous oxide exposure and the subsequent recovery phase.
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We investigated the co-ordinate variations of the two cobalamin (Cbl)-dependent enzymes, methionine synthase (MS) and methylmalonyl-CoA mutase (MCM), and measured the levels of their respective cofactors, methylcobalamin (CH3Cbl) and adenosylcobalamin (AdoCbl) in cultured human glioma cells during nitrous oxide exposure and during a subsequent recovery period of culture in a nitrous oxide-free atmosphere (air). In agreement with published data, MS as the primary target of nitrous oxide was inactivated rapidly (initial rate of 0.06 h(-1)), followed by reduction of CH3Cbl (to <20%). Both enzyme activity and cofactor levels recovered rapidly when the cells were subsequently cultured in air, but the recovery was completely blocked by the protein-synthesis inhibitor, cycloheximide. During MS inactivation, there was a reduction of cellular AdoCbl and holo-MCM activity (measured in the absence of exogenous AdoCbl) to about 50% of pre-treatment levels. When the cells were transferred to air, both AdoCbl and holo-MCM activity recovered, albeit more slowly than the MS system. Notably, the regain of the holo-MCM and AdoCbl was enhanced rather than inhibited by cycloheximide. These findings confirm irreversible damage of MS by nitrous oxide; hence, synthesis of the enzyme is required to restore its activity. In contrast, restoration of holo-MCM activity is only dependent on repletion of the AdoCbl cofactor. We also observed a synchronous fluctuation in AdoCbl and the much larger hydroxycobalamin pool during the inactivation and recovery phase, suggesting that the loss and repletion of AdoCbl reflect changes in intracellular Cbl homoeostasis. Our data demonstrate that the nitrous oxide-induced changes in MS and CH3Cbl are associated with reversible changes in both MCM holoactivity and the AdoCbl level, suggesting co-ordinate distribution of Cbl cofactors during depletion and repletion. (+info)
Alternatively spliced isoforms of nerve- and muscle-derived agrin: their roles at the neuromuscular junction.
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Agrin induces synaptic differentiation at the skeletal neuromuscular junction (NMJ); both pre- and postsynaptic differentiation are drastically impaired in its absence. Multiple alternatively spliced forms of agrin that differ in binding characteristics and bioactivity are synthesized by nerve and muscle cells. We used surgical chimeras, isoform-specific mutant mice, and nerve-muscle cocultures to determine the origins and nature of the agrin required for synaptogenesis. We show that agrin containing Z exons (Z+) is a critical nerve-derived inducer of postsynaptic differentiation, whereas neural isoforms containing a heparin binding site (Y+) and all muscle-derived isoforms are dispensable for major steps in synaptogenesis. Our results also suggest that the requirement of agrin for presynaptic differentiation is mediated indirectly by its ability to promote postsynaptic production or localization of appropriate retrograde signals. (+info)
Identification of a nervous tissue-specific chondroitin sulfate proteoglycan, neurocan, in developing rat retina.
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PURPOSE: To identify the expression of neurocan, a nervous tissue-specific chondroitin sulfate proteoglycan, in retina and to elucidate its changes during development. METHODS: Expressional changes of neurocan mRNAs in developing rat retinas were investigated by a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). The localization and characterization of neurocan core proteins were also investigated with the use of Western blot analysis and immunohistochemistry. RESULTS: Gene expression of neurocan was identified in retinas by RT-PCR. Semiquantitative analysis using Southern blot analysis revealed that mRNA expression for neurocan increased at increasing postnatal stages and that it reached its peak around postnatal day 7 (P7). Immunohistochemical studies demonstrated that in differentiating rat retinal (neuroblast) cells weak neurocan immunoreactivities were observed throughout the retina on embryonal days 14 (E14) and E16. During the early postnatal period, the immunoreactivities became most conspicuous in the inner and outer plexiform layers on P7 through P14. In adult retinas, only faint immunostaining was detected. Immunoblot analysis showed two positive bands of 220- and 150-kDa core glycoproteins after treatment with chondroitinase ABC. Further immunoblot analysis revealed that the expression of these two immunolabeled variants was regulated differently during retinal development. CONCLUSIONS: The temporal and spatial regulation of expression of neurocan and its proteolytic variant during retinal development suggest that it may play a role in differentiation and neural network formation. (+info)
SCL expression in the mouse embryo detected with a targeted lacZ reporter gene demonstrates its localization to hematopoietic, vascular, and neural tissues.
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The helix-loop-helix transcription factor SCL (TAL1) is indispensable for blood cell formation in the mouse embryo. We have explored the localization and developmental potential of cells fated to express SCL during murine development using SCL-lacZ mutant mice in which the Escherichia coli lacZ reporter gene was 'knocked in' to the SCL locus. In addition to the hematopoietic defect associated with SCL deficiency, the yolk sac blood vessels in SCL(lacZ/lacZ) embryos formed an abnormal primary vascular plexus, which failed to undergo subsequent remodeling and formation of large branching vessels. Intraembryonic vasculogenesis in precirculation SCL(lacZ/lacZ) embryos appeared normal but, in embryos older than embryonic day (E) 8.5 to E9, absolute anemia leading to severe hypoxia precluded an accurate assessment of further vascular development. In heterozygous SCL(lacZ/w) embryos, lacZ was expressed in the central nervous system, vascular endothelia, and primitive and definitive hematopoietic cells in the blood, aortic wall, and fetal liver. Culture of fetal liver cells sorted for high and low levels of beta galactosidase activity from SCL(lacZ/w) heterozygous embryos indicated that there was a correlation between the level of SCL expression and the frequency of hematopoietic progenitor cells. (+info)