Telomere dysfunction-induced loss of genome integrity and its associated DNA damage signaling and checkpoint responses are well-established drivers that cause tissue degeneration during ageing. Cancer, with incidence rates greatly increasing with age, is characterized by short telomere lengths and high telomerase activity. To study the roles of telomere dysfunction and telomerase reactivation in ageing and cancer, the protocol shows how to generate two murine inducible telomerase knock-in alleles 4-Hydroxytamoxifen (4-OHT)-inducible TERT-Estrogen Receptor (mTERT-ER) and Lox-Stopper-LoxTERT (LSL-mTERT). The protocol describes the procedures to induce telomere dysfunction and reactivate telomerase activity in mTERT-ER and LSL-mTERT mice in vivo. The representative data show that reactivation of telomerase activity can ameliorate the tissue degenerative phenotypes induced by telomere dysfunction. In order to determine the impact of telomerase reactivation on tumorigenesis, we generated prostate tumor model G4 PB-Cre4 PtenL/L p53L/L LSL-mTERTL/L and thymic T-cell lymphoma model G4 Atm-/- mTERTER/ER. The representative data show that telomerase reactivation in the backdrop of genomic instability induced by telomere dysfunction can greatly enhance tumorigenesis. The protocol also describes the procedures used to isolate neural stem cells (NSCs) from mTERT-ER and LSL-mTERT mice and reactivate telomerase activity in NSCs in vitro. The representative data show that reactivation of telomerase can enhance the self-renewal capability and neurogenesis in vitro. Finally, the protocol describes the procedures for performing telomere FISH (Fluorescence In Situ Hybridization) on both mouse FFPE (Formalin Fixed and Paraffin Embedded) brain tissues and metaphase chromosomes of cultured cells.
17 Related JoVE Articles!
Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol (TRAP) Assay
Institutions: Ben-Gurion University of the Negev.
Telomerase, a ribonucleoprotein, is responsible for maintaining the telomere length and therefore promoting genomic integrity, proliferation, and lifespan. In addition, telomerase protects the mitochondria from oxidative stress and confers resistance to apoptosis, suggesting its possible importance for the surviving of non-mitotic, highly active cells such as neurons. We previously demonstrated the ability of novel telomerase activators to increase telomerase activity and expression in the various mouse brain regions and to protect motor neurons cells from oxidative stress. These results strengthen the notion that telomerase is involved in the protection of neurons from various lesions. To underline the role of telomerase in the brain, we here compare the activity of telomerase in male and female mouse brain and its dependence on age. TRAP assay is a standard method for detecting telomerase activity in various tissues or cell lines. Here we demonstrate the analysis of telomerase activity in three regions of the mouse brain by non-denaturing protein extraction using CHAPS lysis buffer followed by modification of the standard TRAP assay.
In this 2-step assay, endogenous telomerase elongates a specific telomerase substrate (TS primer) by adding TTAGGG 6 bp repeats (telomerase reaction). The telomerase reaction products are amplified by PCR reaction creating a DNA ladder of 6 bp increments. The analysis of the DNA ladder is made by 4.5% high resolution agarose gel electrophoresis followed by staining with highly sensitive nucleic acid stain.
Compared to the traditional TRAP assay that utilize 32
P labeled radioactive dCTP's for DNA detection and polyacrylamide gel electrophoresis for resolving the DNA ladder, this protocol offers a non-toxic time saving TRAP assay for evaluating telomerase activity in the mouse brain, demonstrating the ability to detect differences in telomerase activity in the various female and male mouse brain region.
Neuroscience, Issue 91, telomerase, telomeres, TRAP assay, PCR, gel electrophoresis, frontal lobe, cerebellum, brain stem
Mouse Embryonic Lung Culture, A System to Evaluate the Molecular Mechanisms of Branching
Institutions: Childrens Hospital Los Angeles.
Lung primordial specification as well as branching morphogenesis, and the formation of various pulmonary cell lineages requires a specific interaction of the lung endoderm with its surrounding mesenchyme and mesothelium. Lung mesenchyme has been shown to be the source of inductive signals for lung branching morphogenesis. Epithelial-mesenchymal-mesothelial interactions are also critical to embryonic lung morphogenesis. Early embryonic lung organ culture is a very useful system to study epithelial-mesenchymal interactions. Both epithelial and mesenchymal morphogenesis proceeds under specific conditions that can be readily manipulated in this system (in the absence of maternal influence and blood flow). More importantly this technique can be readily done in a serumless, chemically defined culture media. Gain and loss of function can be achieved using expressed proteins, recombinant viral vectors and/or analysis of transgenic mouse strains, antisense RNA, as well as RNA interference gene knockdown.
Developmental Biology, Issue 40, lung, mice, culture
Generation of Lymphocytic Microparticles and Detection of their Proapoptotic Effect on Airway Epithelial Cells
Institutions: University of Montréal, Third Military Medical University.
Interest in the biological roles of cell membrane–derived vesicles in cell–cell communication has increased in recent years. Microparticles (MPs) are one such type of vesicles, ranging in diameter from 0.1 μm to 1 μm, and typically shed from the plasma membrane of eukaryotic cells undergoing activation or apoptosis. Here we describe the generation of T lymphocyte–derived microparticles (LMPs) from apoptotic CEM T cells stimulated with actinomycin D. LMPs are isolated through a multistep differential centrifugation process and characterized using flow cytometry. This protocol also presents an in situ
cell death detection method for demonstrating the proapoptotic effect of LMPs on bronchial epithelial cells derived from mouse primary respiratory bronchial tissue explants. Methods described herein provide a reproducible procedure for isolating abundant quantities of LMPs from apoptotic lymphocytes in vitro
. LMPs derived in this manner can be used to evaluate the characteristics of various disease models, and for pharmacology and toxicology testing. Given that the airway epithelium offers a protective physical and functional barrier between the external environment and underlying tissue, use of bronchial tissue explants rather than immortalized epithelial cell lines provides an effective model for investigations requiring airway tract tissue.
Immunology, Issue 96, T lymphocytes, microparticles, FACS analysis, bronchial tissue explants, bronchial epithelial cells, apoptosis, H&E staining, in situ cell death detection
Isolation and Immortalization of Patient-derived Cell Lines from Muscle Biopsy for Disease Modeling
Institutions: UT Southwestern Medical Center, National Institute of Health, Medical College of Wisconsin, Boston Children's Hospital.
The generation of patient-specific cell lines represents an invaluable tool for diagnostic or translational research, and these cells can be collected from skin or muscle biopsy tissue available during the patient’s diagnostic workup. In this protocol, we describe a technique for live cell isolation from small amounts of muscle or skin tissue for primary cell culture. Additionally, we provide a technique for the immortalization of myogenic cell lines and fibroblast cell lines from primary cells. Once cell lines are immortalized, substantial expansion of patient-derived cells can be achieved. Immortalized cells are amenable to many downstream applications, including drug screening and in vitro
correction of the genetic mutation. Altogether, these protocols provide a reliable tool to generate and preserve patient-derived cells for downstream applications.
Medicine, Issue 95, Biopsy, skeletal muscle, skin, tissue dissociation, myoblast purification, myoblast immortalization, cell freezing
Isolation, Cryopreservation and Culture of Human Amnion Epithelial Cells for Clinical Applications
Institutions: Wake Forest University Health Sciences, Monash University.
Human amnion epithelial cells (hAECs) derived from term or pre-term amnion membranes have attracted attention from researchers and clinicians as a potential source of cells for regenerative medicine. The reason for this interest is evidence that these cells have highly multipotent differentiation ability, low immunogenicity, and anti-inflammatory functions. These properties have prompted researchers to investigate the potential of hAECs to be used to treat a variety of diseases and disorders in pre-clinical animal studies with much success.
hAECs have found widespread application for the treatment of a range of diseases and disorders. Potential clinical applications of hAECs include the treatment of stroke, multiple sclerosis, liver disease, diabetes and chronic and acute lung diseases. Progressing from pre-clinical animal studies into clinical trials requires a higher standard of quality control and safety for cell therapy products. For safety and quality control considerations, it is preferred that cell isolation protocols use animal product-free reagents.
We have developed protocols to allow researchers to isolate, cryopreserve and culture hAECs using animal product-free reagents. The advantage of this method is that these cells can be isolated, characterized, cryopreserved and cultured without the risk of delivering potentially harmful animal pathogens to humans, while maintaining suitable cell yields, viabilities and growth potential. For researchers moving from pre-clinical animal studies to clinical trials, these methodologies will greatly accelerate regulatory approval, decrease risks and improve the quality of their therapeutic cell population.
Medicine, Issue 94, Amnion Membrane, Amniotic, Stem Cells, Epithelial, Cell Therapy, Perinatal, Placenta
Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis
Institutions: Johns Hopkins University Bloomberg School of Public Health, Chinese University of Hong Kong, Johns Hopkins University School of Medicine.
Anastasis (Greek for “rising to life”) refers to the recovery of dying cells. Before these cells recover, they have passed through important checkpoints of apoptosis, including mitochondrial fragmentation, release of mitochondrial cytochrome c
into the cytosol, activation of caspases, chromatin condensation, DNA damage, nuclear fragmentation, plasma membrane blebbing, cell shrinkage, cell surface exposure of phosphatidylserine, and formation of apoptotic bodies. Anastasis can occur when apoptotic stimuli are removed prior to death, thereby allowing dying cells to reverse apoptosis and potentially other death mechanisms. Therefore, anastasis appears to involve physiological healing processes that could also sustain damaged cells inappropriately. The functions and mechanisms of anastasis are still unclear, hampered in part by the limited tools for detecting past events after the recovery of apparently healthy cells. Strategies to detect anastasis will enable studies of the physiological mechanisms, the hazards of undead cells in disease pathology, and potential therapeutics to modulate anastasis. Here, we describe effective strategies using live cell microscopy and a mammalian caspase biosensor for identifying and tracking anastasis in mammalian cells.
Cellular Biology, Issue 96, Anastasis, apoptosis, apoptotic bodies, caspase, cell death, cell shrinkage, cell suicide, cytochrome c, DNA damage, genetic alterations, mitochondrial outer membrane permeabilization (MOMP), programmed cell death, reversal of apoptosis
Measuring Respiratory Function in Mice Using Unrestrained Whole-body Plethysmography
Institutions: Monash Institute of Medical Research, Monash Medical Centre, Animal Resource Centre, Perth, Australia, Wake Forest Institute for Regenerative Medicine.
Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative assessment of lung function in rodent models is an important tool in the development of future therapies. Commonly used techniques for assessing respiratory function including invasive plethysmography and forced oscillation. While these techniques provide valuable information, data collection can be fraught with artefacts and experimental variability due to the need for anesthesia and/or invasive instrumentation of the animal. In contrast, unrestrained whole-body plethysmography (UWBP) offers a precise, non-invasive, quantitative way by which to analyze respiratory parameters. This technique avoids the use of anesthesia and restraints, which is common to traditional plethysmography techniques. This video will demonstrate the UWBP procedure including the equipment set up, calibration and lung function recording. It will explain how to analyze the collected data, as well as identify experimental outliers and artefacts that results from animal movement. The respiratory parameters obtained using this technique include tidal volume, minute volume, inspiratory duty cycle, inspiratory flow rate and the ratio of inspiration time to expiration time. UWBP does not rely on specialized skills and is inexpensive to perform. A key feature of UWBP, and most appealing to potential users, is the ability to perform repeated measures of lung function on the same animal.
Physiology, Issue 90, Unrestrained Whole Body Plethysmography, Lung function, Respiratory Disease, Rodents
In vitro Coculture Assay to Assess Pathogen Induced Neutrophil Trans-epithelial Migration
Institutions: Harvard Medical School, MGH for Children, Massachusetts General Hospital.
Mucosal surfaces serve as protective barriers against pathogenic organisms. Innate immune responses are activated upon sensing pathogen leading to the infiltration of tissues with migrating inflammatory cells, primarily neutrophils. This process has the potential to be destructive to tissues if excessive or held in an unresolved state. Cocultured in vitro
models can be utilized to study the unique molecular mechanisms involved in pathogen induced neutrophil trans-epithelial migration. This type of model provides versatility in experimental design with opportunity for controlled manipulation of the pathogen, epithelial barrier, or neutrophil. Pathogenic infection of the apical surface of polarized epithelial monolayers grown on permeable transwell filters instigates physiologically relevant basolateral to apical trans-epithelial migration of neutrophils applied to the basolateral surface. The in vitro
model described herein demonstrates the multiple steps necessary for demonstrating neutrophil migration across a polarized lung epithelial monolayer that has been infected with pathogenic P. aeruginosa
(PAO1). Seeding and culturing of permeable transwells with human derived lung epithelial cells is described, along with isolation of neutrophils from whole human blood and culturing of PAO1 and nonpathogenic K12 E. coli
(MC1000). The emigrational process and quantitative analysis of successfully migrated neutrophils that have been mobilized in response to pathogenic infection is shown with representative data, including positive and negative controls. This in vitro
model system can be manipulated and applied to other mucosal surfaces. Inflammatory responses that involve excessive neutrophil infiltration can be destructive to host tissues and can occur in the absence of pathogenic infections. A better understanding of the molecular mechanisms that promote neutrophil trans-epithelial migration through experimental manipulation of the in vitro
coculture assay system described herein has significant potential to identify novel therapeutic targets for a range of mucosal infectious as well as inflammatory diseases.
Infection, Issue 83, Cellular Biology, Epithelium, Neutrophils, Pseudomonas aeruginosa, Respiratory Tract Diseases, Neutrophils, epithelial barriers, pathogens, transmigration
Noninvasive Intratracheal Intubation to Study the Pathology and Physiology of Mouse Lung
Institutions: National Institutes of Health.
The use of a model that mimics the condition of lung diseases in humans is critical for studying the pathophysiology and/or etiology of a particular disease and for developing therapeutic intervention. With the increasing availability of knockout and transgenic derivatives, together with a vast amount of genetic information, mice provide one of the best models to study the molecular mechanisms underlying the pathology and physiology of lung diseases. Inhalation, intranasal instillation, intratracheal instillation, and intratracheal intubation are the most widely used techniques by a number of investigators to administer materials of interest to mouse lungs. There are pros and cons for each technique depending on the goals of a study. Here a noninvasive intratracheal intubation method that can directly deliver exogenous materials to mouse lungs is presented. This technique was applied to administer bleomycin to mouse lungs as a model to study pulmonary fibrosis.
Medicine, Issue 81, mouse, rodents, intratracheal intubation, delivery of exogenous substances, lung, study of airway pathology and physiology, pulmonary fibrosis
Induction and Analysis of Epithelial to Mesenchymal Transition
Institutions: R&D Systems, Inc., R&D Systems, Inc..
Epithelial to mesenchymal transition (EMT) is essential for proper morphogenesis during development. Misregulation of this process has been implicated as a key event in fibrosis and the progression of carcinomas to a metastatic state. Understanding the processes that underlie EMT is imperative for the early diagnosis and clinical control of these disease states. Reliable induction of EMT in vitro
is a useful tool for drug discovery as well as to identify common gene expression signatures for diagnostic purposes. Here we demonstrate a straightforward method for the induction of EMT in a variety of cell types. Methods for the analysis of cells pre- and post-EMT induction by immunocytochemistry are also included. Additionally, we demonstrate the effectiveness of this method through antibody-based array analysis and migration/invasion assays.
Molecular Biology, Issue 78, Cellular Biology, Biochemistry, Biomedical Engineering, Stem Cell Biology, Cancer Biology, Medicine, Bioengineering, Anatomy, Physiology, biology (general), Pathological Conditions, Signs and Symptoms, Wounds and Injuries, Neoplasms, Diagnosis, Therapeutics, Epithelial to mesenchymal transition, EMT, cancer, metastasis, cancer stem cell, cell, assay, immunohistochemistry
Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence
Institutions: Albert Einstein College of Medicine , Albert Einstein College of Medicine , Albert Einstein College of Medicine .
Telomeres are repeating DNA sequences at the tip ends of the chromosomes that are diverse in length and in humans can reach a length of 15,000 base pairs. The telomere serves as a bioprotective mechanism of chromosome attrition at each cell division. At a certain length, telomeres become too short to allow replication, a process that may lead to chromosome instability or cell death. Telomere length is regulated by two opposing mechanisms: attrition and elongation. Attrition occurs as each cell divides. In contrast, elongation is partially modulated by the enzyme telomerase, which adds repeating sequences to the ends of the chromosomes. In this way, telomerase could possibly reverse an aging mechanism and rejuvenates cell viability. These are crucial elements in maintaining cell life and are used to assess cellular aging. In this manuscript we will describe an accurate, short, sophisticated and cheap method to assess telomere length in multiple tissues and species. This method takes advantage of two key elements, the tandem repeat of the telomere sequence and the sensitivity of the qRT-PCR to detect differential copy numbers of tested samples. In addition, we will describe a simple assay to assess telomerase activity as a complementary backbone test for telomere length.
Genetics, Issue 75, Molecular Biology, Cellular Biology, Medicine, Biomedical Engineering, Genomics, Telomere length, telomerase activity, telomerase, telomeres, telomere, DNA, PCR, polymerase chain reaction, qRT-PCR, sequencing, aging, telomerase assay
Preparation of Cell-lines for Conditional Knockdown of Gene Expression and Measurement of the Knockdown Effects on E4orf4-Induced Cell Death
Institutions: Technion - Israel Institute of Technology.
Functional inactivation of gene expression in mammalian cells is crucial for the study of the contribution of a protein of interest to various pathways1,2
. However, conditional knockdown of gene expression is required in cases when constitutive knockdown is not tolerated by cells for a long period of time3-5
. Here we describe a protocol for preparation of cell lines allowing conditional knockdown of subunits of the ACF chromatin remodeling factor. These cell lines facilitate the determination of the contribution of ACF to induction of cell death by the adenovirus E4orf4 protein6
. Sequences encoding short hairpin RNAs for the Acf1 and SNF2h subunits of the ACF chromatin remodeling factor were cloned next to a doxycycline-inducible promoter in a plasmid also containing a gene for the neomycin resistance gene. Neomycin-resistant cell clones were selected in the presence of G418 and isolated. The resulting cell lines were induced by doxycycline treatment, and once Acf1 or SNF2h expression levels were reduced, the cells were transfected with a plasmid encoding E4orf4 or an empty vector. To confirm the specific effect of the shRNA constructs, Acf1 or SNF2h protein levels were restored to WT levels by cotransfection with a plasmid expressing Acf1 or SNF2h which were rendered resistant to the shRNA by introduction of silent mutations. The ability of E4orf4 to induce cell death in the various samples was determined by a DAPI assay, in which the frequency of appearance of nuclei with apoptotic morphologies in the transfected cell population was measured7-9
The protocol described here can be utilized for determination of the functional contribution of various proteins to induction of cell death by their protein partners in cases when constitutive knockdown may be cell lethal.
Genetics, Issue 68, Cellular Biology, Molecular Biology, Microbiology, Medicine, Cell death, adenovirus, E4orf4, DAPI assay, conditional knockdown, shRNA
Heterotypic Three-dimensional In Vitro Modeling of Stromal-Epithelial Interactions During Ovarian Cancer Initiation and Progression
Institutions: University of Southern California, University College London.
Epithelial ovarian cancers (EOCs) are the leading cause of death from gynecological malignancy in Western societies. Despite advances in surgical treatments and improved platinum-based chemotherapies, there has been little improvement in EOC survival rates for more than four decades 1,2
. Whilst stage I tumors have 5-year survival rates >85%, survival rates for stage III/IV disease are <40%. Thus, the high rates of mortality for EOC could be significantly decreased if tumors were detected at earlier, more treatable, stages 3-5
. At present, the molecular genetic and biological basis of early stage disease development is poorly understood. More specifically, little is known about the role of the microenvironment during tumor initiation; but known risk factors for EOCs (e.g.
age and parity) suggest that the microenvironment plays a key role in the early genesis of EOCs. We therefore developed three-dimensional heterotypic models of both the normal ovary and of early stage ovarian cancers. For the normal ovary, we co-cultured normal ovarian surface epithelial (IOSE) and normal stromal fibroblast (INOF) cells, immortalized by retrovrial transduction of the catalytic subunit of human telomerase holoenzyme (hTERT
) to extend the lifespan of these cells in culture. To model the earliest stages of ovarian epithelial cell transformation, overexpression of the CMYC
oncogene in IOSE cells, again co-cultured with INOF cells. These heterotypic models were used to investigate the effects of aging and senescence on the transformation and invasion of epithelial cells. Here we describe the methodological steps in development of these three-dimensional model; these methodologies aren't specific to the development of normal ovary and ovarian cancer tissues, and could be used to study other tissue types where stromal and epithelial cell interactions are a fundamental aspect of the tissue maintenance and disease development.
Cancer Biology, Issue 66, Medicine, Tissue Engineering, three-dimensional cultures, stromal-epithelial interactions, epithelial ovarian cancer, ovarian surface epithelium, ovarian fibroblasts, tumor initiation
An Experimental System to Study Mechanotransduction in Fetal Lung Cells
Institutions: Alpert Medical School of Brown University.
Mechanical forces generated in utero
by repetitive breathing-like movements and by fluid distension are critical for normal lung development. A key component of lung development is the differentiation of alveolar type II epithelial cells, the major source of pulmonary surfactant. These cells also participate in fluid homeostasis in the alveolar lumen, host defense, and injury repair. In addition, distal lung parenchyma cells can be directly exposed to exaggerated stretch during mechanical ventilation after birth. However, the precise molecular and cellular mechanisms by which lung cells sense mechanical stimuli to influence lung development and to promote lung injury are not completely understood. Here, we provide a simple and high purity method to isolate type II cells and fibroblasts from rodent fetal lungs. Then, we describe an in vitro
system, The Flexcell Strain Unit, to provide mechanical stimulation to fetal cells, simulating mechanical forces in fetal lung development or lung injury. This experimental system provides an excellent tool to investigate molecular and cellular mechanisms in fetal lung cells exposed to stretch. Using this approach, our laboratory has identified several receptors and signaling proteins that participate in mechanotransduction in fetal lung development and lung injury.
Bioengineering, Issue 60, Mechanical stretch, differentiation, lung injury, isolation, fetal, type II epithelial cells, fibroblasts
In vitro Reconstitution of the Active T. castaneum Telomerase
Institutions: University of Pennsylvania.
Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (Tc
TERT) and the reconstitution of the active T. castaneum
telomerase ribonucleoprotein (RNP) complex in vitro
Telomerase is a specialized reverse transcriptase1
that adds short DNA repeats, called telomeres, to the 3' end of linear chromosomes2
that serve to protect them from end-to-end fusion and degradation. Following DNA replication, a short segment is lost at the end of the chromosome3
and without telomerase, cells continue dividing until eventually reaching their Hayflick Limit4
. Additionally, telomerase is dormant in most somatic cells5
in adults, but is active in cancer cells6
where it promotes cell immortality7
The minimal telomerase enzyme consists of two core components: the protein subunit (TERT), which comprises the catalytic subunit of the enzyme and an integral RNA component (TER), which contains the template TERT uses to synthesize telomeres8,9
. Prior to 2008, only structures for individual telomerase domains had been solved10,11
. A major breakthrough in this field came from the determination of the crystal structure of the active12
, catalytic subunit of T. castaneum
Here, we present methods for producing large quantities of the active, soluble Tc
TERT for structural and biochemical studies, and the reconstitution of the telomerase RNP complex in vitro
for telomerase activity assays. An overview of the experimental methods used is shown in Figure 1.
Molecular Biology, Issue 53, Telomerase, protein expression, purification, chromatography, RNA isolation, TRAP
Experimental Metastasis and CTL Adoptive Transfer Immunotherapy Mouse Model
Institutions: Medical College of Georgia.
Experimental metastasis mouse model is a simple and yet physiologically relevant metastasis model. The tumor cells are injected intravenously (i.v) into mouse tail veins and colonize in the lungs, thereby, resembling the last steps of tumor cell spontaneous metastasis: survival in the circulation, extravasation and colonization in the distal organs. From a therapeutic point of view, the experimental metastasis model is the simplest and ideal model since the target of therapies is often the end point of metastasis: established metastatic tumor in the distal organ. In this model, tumor cells are injected i.v into mouse tail veins and allowed to colonize and grow in the lungs. Tumor-specific CTLs are then injected i.v into the metastases-bearing mouse. The number and size of the lung metastases can be controlled by the number of tumor cells to be injected and the time of tumor growth. Therefore, various stages of metastasis, from minimal metastasis to extensive metastasis, can be modeled. Lung metastases are analyzed by inflation with ink, thus allowing easier visual observation and quantification.
Immunology, Issue 45, Metastasis, CTL adoptive transfer, Lung, Tumor Immunology
Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling
Institutions: Friedrich-Alexander-Universität, Friedrich-Loeffler-Institut, Universitätsklinikum Erlangen.
The technique presented here allows one to analyze at which step a target protein, or alternatively a small molecule, interacts with the components of a signaling pathway. The method is based, on the one hand, on the inducible expression of a specific protein to initiate a signaling event at a defined and predetermined step in the selected signaling cascade. Concomitant expression, on the other hand, of the gene of interest then allows the investigator to evaluate if the activity of the expressed target protein is located upstream or downstream of the initiated signaling event, depending on the readout of the signaling pathway that is obtained. Here, the apoptotic cascade was selected as a defined signaling pathway to demonstrate protocol functionality. Pathogenic bacteria, such as Coxiella burnetii
, translocate effector proteins that interfere with host cell death induction in the host cell to ensure bacterial survival in the cell and to promote their dissemination in the organism. The C. burnetii
effector protein CaeB effectively inhibits host cell death after induction of apoptosis with UV-light or with staurosporine. To narrow down at which step CaeB interferes with the propagation of the apoptotic signal, selected proteins with well-characterized pro-apoptotic activity were expressed transiently in a doxycycline-inducible manner. If CaeB acts upstream of these proteins, apoptosis will proceed unhindered. If CaeB acts downstream, cell death will be inhibited. The test proteins selected were Bax, which acts at the level of the mitochondria, and caspase 3, which is the major executioner protease. CaeB interferes with cell death induced by Bax expression, but not by caspase 3 expression. CaeB, thus, interacts with the apoptotic cascade between these two proteins.
Infection, Issue 100, Apoptosis, Bax, Caspase 3, Coxiella burnetii, Doxycycline, Effector protein, Inducible expression, stable cell line, Tet system, Type IV Secretion System