green fluorescent protein

/Tag:green fluorescent protein

Establishment of an Embryotoxicity Assay with Green Fluorescence Protein-expressing Embryonic Cell-derived Cardiomyocytes

Susanne Bremer, Maaike van Dooren, Martin Paparella, Eugen Kossolov, Bernd Fleischmann and Juergen Hescheler

Transgenic embryonic stem cells were used to determine the embryotoxic effects of chemicals on the development of embryonic tissues. This investigation supports an ongoing validation study, aimed at reducing the time-consuming procedure currently in use, and at providing more-objective and more-detailed information on the embryotoxic potentials of chemicals. Green fluorescence protein (GFP) was used as a reporter gene and was linked to a human α-cardiac-specific promoter. The expression of GFP was switched on after specific activation of the human α-actin promoter. This permitted the easy quantification of cardiac cells by using a fluorescence-activated cell sorter (FACS). The percentage of cardiac precursor cells was calculated from the FACS-distribution pattern of cells which fluoresced versus the total number of cells. The percentage of cardiac precursor cells increased from 25% in embryoid bodies on day 3, to 86% on day 7. However, in 11-day-old embryoid bodies, the percentage decreased to 35%. Five chemicals with known embryotoxic potentials were compared with respect to the IC50 (concentration causing 50% inhibition of measured effect) values obtained by various in vitro endpoints (for example, cytotoxicity, morphology). The results showed a higher sensitivity of endpoints used for the analysis of specific effects on the selected target tissue. The data also showed the need to develop in vitro methods with specific endpoints which account for the complexity of embryotoxicology.
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Development of a Testing Strategy for Detecting Embryotoxic Hazards of Chemicals In Vitro by using Embryonic Stem Cell Models

Susanne Bremer, Cristian Pellizzer, Sarah Adler, Martin Paparella and Jan de Lange

The importance of developing in vitro tests for embryotoxicity is discussed, and ECVAM's work with its collaborators is summarised. Studies are in progress to find new endpoints for use in the scientifically validated embryonic stem (ES) cell test, so that the potential for chemical effects on endodermal, mesodermal and/or ectodermal differentiation can be identified. This involves, inter alia, the use of genetically modified ES cells.
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The Detection of Differentiation-inducing Chemicals by using Green Fluorescent Protein Expression in Genetically Engineered Teratocarcinoma Cells

Sarah Adler, Martin Paparella, Cristian Pellizzer, Thomas Hartung and Susanne Bremer

The murine embryonal teratocarcinoma cell line, P19, was genetically manipulated in order to provide preliminary information on compounds that induce differentiation. Without chemical induction, P19 cells remain in an undifferentiated state, but can be induced to differentiate into specific cell types. For example, dimethyl sulphoxide (DMSO) induces cardiac and skeletal muscle differentiation, whereas retinoic acid stimulates neuronal differentiation. P19 cells were transfected with a construct containing a segment of the murineTert (mTert) promoter sequence combined with the green fluorescent protein (GFP) gene, which acts as a reporter gene. mTert expression, the reverse transcriptase component of murine telomerase, is closely linked to telomerase activity and is down-regulated during differentiation. Three retinoids and DMSO induced the differentiation of P19 cells, which was determined by a reduction in mTert_GFP expression, detected by flow cytometry and confocal microscopy as independent methods of detection. A test substance, ethanol, and a control substance, saccharin, did not cause a decrease in mTert_GFP expression. In addition, it could be demonstrated that the mTert_GFP test detects developmentally relevant effects at non-cytotoxic concentrations. The ID50 values derived for the reduction of mTert_GFP expression were lower than the IC50 values detected with the MTT test, by a factor of 21.4 for all-trans retinoic acid, 12.7 for 9-cis retinoic acid, 29.6 for 13-cis retinoic acid, and 8.7 for DMSO. In comparison to the IC50 value for the P19 cell line, a similar IC50 value was obtained with 3T3 cells for ethanol, but there was a 2-fold
increase for DMSO. The retinoids were not cytotoxic to 3T3 cells at the concentrations tested. This newly developed test is capable of detecting differentiation-inducing compounds at non-cytotoxic concentrations within 4 days. It offers a method for detecting chemicals with specific toxicological mechanisms, such as the retinoids, which could provide additional information in embryotoxicity testing as different promoters could be employed. Here, we report the use of this novel test system for the successful analysis of DMSO and three retinoids with different in vivo teratogenic potentials.
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The Developmental Expression of Fluorescent Proteins in Organotypic Hippocampal Slice Cultures from Transgenic Mice and its Use in the Determination of Excitotoxic Neurodegeneration

Jens Noraberg, Carsten V. Jensen, Christian Bonde, Maria Montero, Jakob V. Nielsen,Niels A. Jensen and Jens Zimmer

Transgenic mice, expressing fluorescent proteins in neurons and glia, provide new opportunities for real-time microscopic monitoring of degenerative and regenerative structural changes. We have previously validated and compared a number of quantifiable markers for neuronal damage and cell death in organotypic brain slice cultures, such as cellular uptake of propidium iodide (PI), loss of microtubuleassociated protein 2 (MAP2), Fluoro-Jade (FJ) cell staining, and the release of cytosolic lactate dehydrogenase (LDH). An important supplement to these markers would be data on corresponding morphological changes, as well as the opportunity to monitor reversible changes or long-term effects in the event of minor damage. As a first step, we present: a) the developmental expression in organotypic hippocampal brain slice cultures of transgenic fluorescent proteins, useful for the visualisation of neuronal subpopulations and astroglial cells; and b) examples of excitotoxic, glutamate receptor-induced degeneration of hippocampal CA1 pyramidal cells, with corresponding astroglial reactivity in such cultures. The slice cultures were set up according to standard techniques, by using one-week old pups from four transgenic mouse strains which express fluorescent proteins in their neurons and/or astroglial cells. From the time of explantation, and subsequently for up to nine weeks in culture, the transgenic neuronal fluorescence displayed the expected characteristics of a developmental, in vivo-like increase, including both the number and localisation of cells, as well as the intensity of fluorescence. At that stage and later, the transgenic fluorescence clearly permitted the visualisation of cell bodies, larger and smaller dendritic branches, spines and axons. In separate experiments, with a 24-hour exposure of matured sliced cultures to 100μM of the glutamate agonist, N-methyl-D-aspartate (NMDA), we observed, by time-lapse recording, a gradual, but rapid loss of fluorescent CA1 pyramidal cells, accompanied by astrogliosis of transgene fluorescent astroglial cells. Based on these results, we consider that organotypic brain slice cultures from transgenic mice, with fluorescent neurons and glia, combined with detailed visualisation by time-lapse fluorescence microscopy, have great potential for investigating both major irreversible and minor reversible structural changes in neurons and glia, induced by neurotoxins and other neurodegenerative compounds and conditions.
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