Measurement of γHV68 Infection in Mice

γ-Herpesviruses (γ-HVs) are notable for their ability to establish latent infections of lymphoid cells¹. The narrow host range of human γ-HVs, such as EBV and KSHV, has severely hindered detailed pathogenic studies. Murine γ-herpesvirus 68 (γHV68) shares extensive genetic and biological similarities with human γ-HVs and is a natural pathogen of murid rodents². As such, evaluation of γHV68 infection of mice inbred strains at different stages of viral infection provides an important model for understanding viral lifecycle and pathogenesis during γ-HVs infection.Upon intranasal inoculation, γHV68 infection results in acute viremia in the lung that is later resolved into a latent infection of splenocytes and other cells, which may be reactivated throughout the life of the host^3,4. In this protocol, we will describe how to use the plaque assay to assess infectious virus titer in the lung homogenates on Vero cell monolayers at the early stage (5 - 7 days) of post-intranasal infection (dpi). While acute infection is largely cleared 2 - 3 weeks postinfection, a latent infection of γHV68 is established around 14 dpi and maintained later on in the spleen of the mice. Latent infection usually affects a very small population of cells in the infected tissues, whereby the virus stays dormant and shuts off most of its gene expression. Latently-infected splenocytes spontaneously reactivate virus upon explanting into tissue culture, which can be recapitulated by an infectious center (IC) assay to determine the viral latent load. To further estimate the amount of viral genome copies in the acutely and/or latently infected tissues, quantitative real-time PCR (qPCR) is used for its maximal sensitivity and accuracy. The combined analyses of the results of qPCR and plaque assay, and/or IC assay will reveal the spatiotemporal profiles of viral replication and infectivity in vivo.Download video file.^{(81M, mov)}     

Quantitation of γH2AX Foci in Tissue Samples

DNA double-strand breaks (DSBs) are particularly lethal and genotoxic lesions, that can arise either by endogenous (physiological or pathological) processes or by exogenous factors, particularly ionizing radiation and radiomimetic compounds. Phosphorylation of the H2A histone variant, H2AX, at the serine-139 residue, in the highly conserved C-terminal SQEY motif, forming γH2AX, is an early response to DNA double-strand breaks¹. This phosphorylation event is mediated by the phosphatidyl-inosito 3-kinase (PI3K) family of proteins, ataxia telangiectasia mutated (ATM), DNA-protein kinase catalytic subunit and ATM and RAD3-related (ATR)². Overall, DSB induction results in the formation of discrete nuclear γH2AX foci which can be easily detected and quantitated by immunofluorescence microscopy². Given the unique specificity and sensitivity of this marker, analysis of γH2AX foci has led to a wide range of applications in biomedical research, particularly in radiation biology and nuclear medicine. The quantitation of γH2AX foci has been most widely investigated in cell culture systems in the context of ionizing radiation-induced DSBs. Apart from cellular radiosensitivity, immunofluorescence based assays have also been used to evaluate the efficacy of radiation-modifying compounds. In addition, γH2AX has been used as a molecular marker to examine the efficacy of various DSB-inducing compounds and is recently being heralded as important marker of ageing and disease, particularly cancer³. Further, immunofluorescence-based methods have been adapted to suit detection and quantitation of γH2AX foci ex vivo and in vivo^4,5. Here, we demonstrate a typical immunofluorescence method for detection and quantitation of γH2AX foci in mouse tissues.Download video file.^{(284M, mp4)}     

Recombinant Murine Gamma Herpesvirus 68 Carrying KSHV G Protein-Coupled Receptor Induces Angiogenic Lesions in Mice

Human gamma herpesviruses, including Kaposi’s sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are capable of inducing tumors, particularly in in immune-compromised individuals. Due to the stringent host tropism, rodents are resistant to infection by human gamma herpesviruses, creating a significant barrier for the in vivo study of viral genes that contribute to tumorigenesis. The closely-related murine gamma herpesvirus 68 (γHV68) efficiently infects laboratory mouse strains and establishes robust persistent infection without causing apparent disease. Here, we report that a recombinant γHV68 carrying the KSHV G protein-coupled receptor (kGPCR) in place of its murine counterpart induces angiogenic tumors in infected mice. Although viral GPCRs are conserved in all gamma herpesviruses, kGPCR potently activated downstream signaling and induced tumor formation in nude mouse, whereas γHV68 GPCR failed to do so. Recombinant γHV68 carrying kGPCR demonstrated more robust lytic replication ex vivo than wild-type γHV68, although both viruses underwent similar acute and latent infection in vivo. Infection of immunosuppressed mice with γHV68 carrying kGPCR, but not wild-type γHV68, induced tumors in mice that exhibited angiogenic and inflammatory features shared with human Kaposi’s sarcoma. Immunohistochemistry staining identified abundant latently-infected cells and a small number of cells supporting lytic replication in tumor tissue. Thus, mouse infection with a recombinant γHV68 carrying kGPCR provides a useful small animal model for tumorigenesis induced by a human gamma herpesvirus gene in the setting of a natural course of infection.     

Live-imaging of PKC Translocation in Sf9 Cells and in Aplysia Sensory Neurons

Protein kinase Cs (PKCs) are serine threonine kinases that play a central role in regulating a wide variety of cellular processes such as cell growth and learning and memory. There are four known families of PKC isoforms in vertebrates: classical PKCs (α, βI, βII and γ), novel type I PKCs (ε and η), novel type II PKCs (δ and θ), and atypical PKCs (ζ and ι). The classical PKCs are activated by Ca²⁺ and diacylclycerol (DAG), while the novel PKCs are activated by DAG, but are Ca²⁺-independent. The atypical PKCs are activated by neither Ca²⁺ nor DAG. In Aplysia californica, our model system to study memory formation, there are three nervous system specific PKC isoforms one from each major class, namely the conventional PKC Apl I, the novel type I PKC Apl II and the atypical PKC Apl III. PKCs are lipid-activated kinases and thus activation of classical and novel PKCs in response to extracellular signals has been frequently correlated with PKC translocation from the cytoplasm to the plasma membrane. Therefore, visualizing PKC translocation in real time in live cells has become an invaluable tool for elucidating the signal transduction pathways that lead to PKC activation. For instance, this technique has allowed for us to establish that different isoforms of PKC translocate under different conditions to mediate distinct types of synaptic plasticity and that serotonin (5HT) activation of PKC Apl II requires production of both DAG and phosphatidic acid (PA) for translocation ^1-2. Importantly, the ability to visualize the same neuron repeatedly has allowed us, for example, to measure desensitization of the PKC response in exquisite detail ³. In this video, we demonstrate each step of preparing Sf9 cell cultures, cultures of Aplysia sensory neurons have been described in another video article ⁴, expressing fluorescently tagged PKCs in Sf9 cells and in Aplysia sensory neurons and live-imaging of PKC translocation in response to different activators using laser-scanning microscopy.Download video file.^{(60M, mov)}     

SDS-PAGE/Immunoblot Detection of Aβ Multimers in Human Cortical Tissue Homogenates using Antigen-Epitope Retrieval

The anomalous folding and polymerization of the β-amyloid (Aβ) peptide is thought to initiate the neurodegenerative cascade in Alzheimer''s disease pathogenesis¹. Aβ is predominantly a 40- or 42-amino acid peptide that is prone to self-aggregation into β-sheet-rich amyloid fibrils that are found in the cores of cerebral senile plaques in Alzheimer''s disease. Increasing evidence suggests that low molecular weight, soluble Aβ multimers are more toxic than fibrillar Aβ amyloid². The identification and quantification of low- and high-molecular weight multimeric Aβ species in brain tissue is an essential objective in Alzheimer''s disease research, and the methods employed also can be applied to the identification and characterization of toxic multimers in other proteopathies³. Naturally occurring Aβ multimers can be detected by SDS-polyacrylamide gel electrophoresis followed by immunoblotting with Aβ-specific antibodies. However, the separation and detection of multimeric Aβ requires the use of highly concentrated cortical homogenates and antigen retrieval in small pore-size nitrocellulose membranes. Here we describe a technique for the preparation of clarified human cortical homogenates, separation of proteins by SDS-PAGE, and antigen-epitope retrieval/Western blotting with antibody 6E10 to the N-terminal region of the Aβ peptide. Using this protocol, we consistently detect Aβ monomers, dimers, trimers, tetramers, and higher molecular weight multimers in cortical tissue from humans with Alzheimer''s pathology.Download video file.^{(121M, mp4)}     

Preparation of Oligomeric β-amyloid1-42 and Induction of Synaptic Plasticity Impairment on Hippocampal Slices

Impairment of synaptic connections is likely to underlie the subtle amnesic changes occurring at the early stages of Alzheimer s Disease (AD). β-amyloid (Aβ), a peptide produced in high amounts in AD, is known to reduce Long-Term Potentiation (LTP), a cellular correlate of learning and memory. Indeed, LTP impairment caused by Aβ is a useful experimental paradigm for studying synaptic dysfunctions in AD models and for screening drugs capable of mitigating or reverting such synaptic impairments. Studies have shown that Aβ produces the LTP disruption preferentially via its oligomeric form. Here we provide a detailed protocol for impairing LTP by perfusion of oligomerized synthetic Aβ1-42 peptide onto acute hippocampal slices. In this video, we outline a step-by-step procedure for the preparation of oligomeric Aβ_1-42. Then, we follow an individual experiment in which LTP is reduced in hippocampal slices exposed to oligomerized Aβ_1-42 compared to slices in a control experiment where no Aβ_1-42 exposure had occurred.Download video file.^{(55M, mp4)}     

Fluorescent Labeling of Drosophila Heart Structures

The Drosophila melanogaster dorsal vessel, or heart, is a tubular structure comprised of a single layer of contractile cardiomyocytes, pericardial cells that align along each side of the heart wall, supportive alary muscles and, in adults, a layer of ventral longitudinal muscle cells. The contractile fibers house conserved constituents of the muscle cytoarchitecture including densely packed bundles of myofibrils and cytoskeletal/submembranous protein complexes, which interact with homologous components of the extracellular matrix. Here we describe a protocol for the fixation and the fluorescent labeling of particular myocardial elements from the hearts of dissected larvae and semi-intact adult Drosophila. Specifically, we demonstrate the labeling of sarcomeric F-actin and of α-actinin in larval hearts. Additionally, we perform labeling of F-actin and α-actinin in myosin-GFP expressing adult flies and of α-actinin and pericardin, a type IV extracellular matrix collagen, in wild type adult hearts. Particular attention is given to a mounting strategy for semi-intact adult hearts that minimizes handling and optimizes the opportunity for maintaining the integrity of the cardiac tubes and the associated tissues. These preparations are suitable for imaging via fluorescent and confocal microscopy. Overall, this procedure allows for careful and detailed analysis of the structural characteristics of the heart from a powerful genetically tractable model system.Download video file.^{(130M, mp4)}     

Generation of Recombinant Influenza Virus from Plasmid DNA

Efforts by a number of influenza research groups have been pivotal in the development and improvement of influenza A virus reverse genetics. Originally established in 1999 ^1,2 plasmid-based reverse genetic techniques to generate recombinant viruses have revolutionized the influenza research field because specific questions have been answered by genetically engineered, infectious, recombinant influenza viruses. Such studies include virus replication, function of viral proteins, the contribution of specific mutations in viral proteins in viral replication and/or pathogenesis and, also, viral vectors using recombinant influenza viruses expressing foreign proteins ³.Download video file.^{(133M, mp4)}     

Toxoplasma gondii Cyst Wall Formation in Activated Bone Marrow-derived Macrophages and Bradyzoite Conditions

Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of warm-blooded animals. During infection, T. gondii disseminates as a fast replicating form called the tachyzoite. Tachyzoites convert into a slow-growing encysted form called the bradyzoite by a signaling process that is not well characterized. Within animals, bradyzoite cysts are found in the central nervous system and muscle tissue and represent the chronic stage of infection. Conversion to bradyzoites can be simulated in tissue culture by CO₂ starvation, using medium with high a pH, or the addition of interferon gamma (IFNγ). Bradyzoites are characterized by the presence of a cyst wall, to which the lectin Dolichos biflorus agglutinin (DBA) binds. Fluorescently labeled DBA is used to visualize the cyst wall in parasites grown in human foreskin fibroblasts (HFFs) that have been exposed to low CO₂ and high pH medium. Similarly, parasites residing in murine bone marrow-derived macrophages (BMMs) display a cyst wall detectable by DBA after the BMMs are activated with IFNγ and lipopolysaccharide (LPS). This protocol will demonstrate how to induce conversion of T. gondii to bradyzoites using a high pH growth medium with low CO₂ and activation of BMMs. Host cells will be cultured on coverslips, infected with tachyzoites and either activated with addition of IFNγ and LPS (BMMs) or exposed to a high pH growth medium (HFFs) for three days. Upon completion of infections, host cells will be fixed, permeabilized, and blocked. Cyst walls will be visualized using rhodamine DBA with fluorescence microscopy.Download video file.^{(115M, mp4)}     

Visualization of UV-induced Replication Intermediates in E. coli using Two-dimensional Agarose-gel Analysis

Inaccurate replication in the presence of DNA damage is responsible for the majority of cellular rearrangements and mutagenesis observed in all cell types and is widely believed to be directly associated with the development of cancer in humans. DNA damage, such as that induced by UV irradiation, severely impairs the ability of replication to duplicate the genomic template accurately. A number of gene products have been identified that are required when replication encounters DNA lesions in the template. However, a remaining challenge has been to determine how these proteins process lesions during replication in vivo. Using Escherichia coli as a model system, we describe a procedure in which two-dimensional agarose-gel analysis can be used to identify the structural intermediates that arise on replicating plasmids in vivo following UV-induced DNA damage. This procedure has been used to demonstrate that replication forks blocked by UV-induced damage undergo a transient reversal that is stabilized by RecA and several gene products associated with the RecF pathway. The technique demonstrates that these replication intermediates are maintained until a time that correlates with the removal of the lesions by nucleotide excision repair and replication resumes.Download video file.^{(62M, mov)}     

Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly ¹. This guided cell migration is referred as chemotaxis, which is essential for various cells to carry out their functions such as trafficking of immune cells and patterning of neuronal cells ^{2, 3}. A large family of G-protein coupled receptors (GPCRs) detects variable small peptides, known as chemokines, to direct cell migration in vivo⁴. The final goal of chemotaxis research is to understand how a GPCR machinery senses chemokine gradients and controls signaling events leading to chemotaxis. To this end, we use imaging techniques to monitor, in real time, spatiotemporal concentrations of chemoattractants, cell movement in a gradient of chemoattractant, GPCR mediated activation of heterotrimeric G-protein, and intracellular signaling events involved in chemotaxis of eukaryotic cells ^5-8. The simple eukaryotic organism, Dictyostelium discoideum, displays chemotaxic behaviors that are similar to those of leukocytes, and D. discoideum is a key model system for studying eukaryotic chemotaxis. As free-living amoebae, D. discoideum cells divide in rich medium. Upon starvation, cells enter a developmental program in which they aggregate through cAMP-mediated chemotaxis to form multicullular structures. Many components involved in chemotaxis to cAMP have been identified in D. discoideum. The binding of cAMP to a GPCR (cAR1) induces dissociation of heterotrimeric G-proteins into Gγ and Gβγ subunits ^{7, 9, 10}. Gβγ subunits activate Ras, which in turn activates PI3K, converting PIP₂ into PIP₃ on the cell membrane ^11-13. PIP₃ serve as binding sites for proteins with pleckstrin Homology (PH) domains, thus recruiting these proteins to the membrane ^{14, 15}. Activation of cAR1 receptors also controls the membrane associations of PTEN, which dephosphorylates PIP₃ to PIP₂^{16, 17}. The molecular mechanisms are evolutionarily conserved in chemokine GPCR-mediated chemotaxis of human cells such as neutrophils ¹⁸. We present following methods for studying chemotaxis of D. discoideum cells. 1. Preparation of chemotactic component cells. 2. Imaging chemotaxis of cells in a cAMP gradient. 3. Monitoring a GPCR induced activation of heterotrimeric G-protein in single live cells. 4. Imaging chemoattractant-triggered dynamic PIP₃ responses in single live cells in real time. Our developed imaging methods can be applied to study chemotaxis of human leukocytes.Download video file.^{(59M, mov)}     

Recording Multicellular Behavior in Myxococcus xanthus Biofilms using Time-lapse Microcinematography

A swarm of the δ-proteobacterium Myxococcus xanthus contains millions of cells that act as a collective, coordinating movement through a series of signals to create complex, dynamic patterns as a response to environmental cues. These patterns are self-organizing and emergent; they cannot be predicted by observing the behavior of the individual cells. Using a time-lapse microcinematography tracking assay, we identified a distinct emergent pattern in M. xanthus called chemotaxis, defined as the directed movement of a swarm up a nutrient gradient toward its source ¹.In order to efficiently characterize chemotaxis via time-lapse microcinematography, we developed a highly modifiable plate complex (Figure 1) and constructed a cluster of 8 microscopes (Figure 2), each capable of capturing time-lapse videos. The assay is rigorous enough to allow consistent replication of quantifiable data, and the resulting videos allow us to observe and track subtle changes in swarm behavior. Once captured, the videos are transferred to an analysis/storage computer with enough memory to process and store thousands of videos. The flexibility of this setup has proven useful to several members of the M. xanthus community.Download video file.^{(133M, mp4)}     

Selection of Aptamers for Amyloid β-Protein,the Causative Agent of Alzheimer's Disease

Alzheimer''s disease (AD) is a progressive, age-dependent, neurodegenerative disorder with an insidious course that renders its presymptomatic diagnosis difficult¹. Definite AD diagnosis is achieved only postmortem, thus establishing presymptomatic, early diagnosis of AD is crucial for developing and administering effective therapies^2,3.Amyloid β-protein (Aβ) is central to AD pathogenesis. Soluble, oligomeric Aβ assemblies are believed to affect neurotoxicity underlying synaptic dysfunction and neuron loss in AD^4,5. Various forms of soluble Aβ assemblies have been described, however, their interrelationships and relevance to AD etiology and pathogenesis are complex and not well understood⁶. Specific molecular recognition tools may unravel the relationships amongst Aβ assemblies and facilitate detection and characterization of these assemblies early in the disease course before symptoms emerge. Molecular recognition commonly relies on antibodies. However, an alternative class of molecular recognition tools, aptamers, offers important advantages relative to antibodies^7,8. Aptamers are oligonucleotides generated by in-vitro selection: systematic evolution of ligands by exponential enrichment (SELEX)^9,10. SELEX is an iterative process that, similar to Darwinian evolution, allows selection, amplification, enrichment, and perpetuation of a property, e.g., avid, specific, ligand binding (aptamers) or catalytic activity (ribozymes and DNAzymes).Despite emergence of aptamers as tools in modern biotechnology and medicine¹¹, they have been underutilized in the amyloid field. Few RNA or ssDNA aptamers have been selected against various forms of prion proteins (PrP)^12-16. An RNA aptamer generated against recombinant bovine PrP was shown to recognize bovine PrP-β¹⁷, a soluble, oligomeric, β-sheet-rich conformational variant of full-length PrP that forms amyloid fibrils¹⁸. Aptamers generated using monomeric and several forms of fibrillar β₂-microglobulin (β₂m) were found to bind fibrils of certain other amyloidogenic proteins besides β₂m fibrils¹⁹. Ylera et al. described RNA aptamers selected against immobilized monomeric Aβ40²⁰. Unexpectedly, these aptamers bound fibrillar Aβ40. Altogether, these data raise several important questions. Why did aptamers selected against monomeric proteins recognize their polymeric forms? Could aptamers against monomeric and/or oligomeric forms of amyloidogenic proteins be obtained? To address these questions, we attempted to select aptamers for covalently-stabilized oligomeric Aβ40²¹ generated using photo-induced cross-linking of unmodified proteins (PICUP)^22,23. Similar to previous findings^17,19,20, these aptamers reacted with fibrils of Aβ and several other amyloidogenic proteins likely recognizing a potentially common amyloid structural aptatope²¹. Here, we present the SELEX methodology used in production of these aptamers²¹.Download video file.^{(175M, mp4)}     

Expansion of Human Peripheral Blood γδ T Cells using Zoledronate

Human γδ T cells can recognize and respond to a wide variety of stress-induced antigens, thereby developing innate broad anti-tumor and anti-infective activity.¹ The majority of γδ T cells in peripheral blood have the Vγ9Vδ2 T cell receptor. These cells recognize antigen in a major histocompatibility complex-independent manner and develop strong cytolytic and Th1-like effector functions.¹Therefore, γδ T cells are attractive candidate effector cells for cancer immunotherapy. Vγ9Vδ2 T cells respond to phosphoantigens such as (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), which is synthesized in bacteria via isoprenoid biosynthesis;² and isopentenyl pyrophosphate (IPP), which is produced in eukaryotic cells through the mevalonate pathway.³ In physiological condition, the generation of IPP in nontransformed cell is not sufficient for the activation of γδ T cells. Dysregulation of mevalonate pathway in tumor cells leads to accumulation of IPP and γδ T cells activation.³ Because aminobisphosphonates (such as pamidronate or zoledronate) inhibit farnesyl pyrophosphate synthase (FPPS), the enzyme acting downstream of IPP in the mevalonate pathway, intracellular levels of IPP and sensitibity to γδ T cells recognition can be therapeutically increased by aminobisphosphonates. IPP accumulation is less efficient in nontransfomred cells than tumor cells with a pharmacologically relevant concentration of aminobisphosphonates, that allow us immunotherapy for cancer by activating γδ T cells with aminobisphosphonates. ⁴ Interestingly, IPP accumulates in monocytes when PBMC are treated with aminobisphosphonates, because of efficient drug uptake by these cells. ⁵ Monocytes that accumulate IPP become antigen-presenting cells and stimulate Vγ9Vδ2 T cells in the peripheral blood.⁶ Based on these mechanisms, we developed a technique for large-scale expansion of γδ T cell cultures using zoledronate and interleukin-2 (IL-2).⁷ Other methods for expansion of γδ T cells utilize the synthetic phosphoantigens bromohydrin pyrophosphate (BrHPP)⁸ or 2-methyl-3-butenyl-1-pyrophosphate (2M3B1PP).⁹ All of these methods allow ex vivo expansion, resulting in large numbers of γδ T cells for use in adoptive immunotherapy. However, only zoledronate is an FDA-approved commercially available reagent. Zoledronate-expanded γδ T cells display CD27^-CD45RA^- effector memory phenotype and thier function can be evaluated by IFN-γ production assay. ⁷Download video file.^{(76M, mov)}     

Collecting and Measuring Nociceptive and Inflammatory Mediators in Surgical Wounds

The objectives of this study were to test the feasibility of collecting and measuring inflammatory and nociceptive biochemical mediators at the surgical site; to evaluate the relationship between wound and serum levels; and to determine any associations between mediator release, pain and analgesic consumption post-cesarean delivery. Twenty healthy women undergoing elective cesarean delivery with spinal anesthesia were enrolled. Wound exudate and serum mediators, pain scores and analgesics consumption were measured at 1, 6, 24, and 48 hours post-cesarean. In wound exudate, 19 out of 20 mediators were reliably detected including IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, TNFα, INFγ, G-CSF, GM-CSF, MCP-1 and MIP-1β, nerve growth factor (NGF), prostaglandin E2 (PG-E2) and substance P. Wound PG-E2 and various cytokines peaked early, whereas NGF showed a more delayed release. There were no correlations between the concentration versus time profile of wound and serum cytokines. This study demonstrates the feasibility of collecting and measuring nociceptive and inflammatory mediators in surgical wounds at specific time points. The lack of significant correlations between wound and serum levels emphasizes the importance of determining site-specific release if localized pathologies are to be studied. Download video file.^{(61M, mp4)}     

Transnuclear Mice with Pre-defined T Cell Receptor Specificities Against Toxoplasma gondii Obtained Via SCNT

Lymphocytes, such as T cells, undergo genetic V(D)J recombination, to generate a receptor with a certain specificity¹. Mice transgenic for a rearranged antigen-specific T cell receptor (TCR) have been an indispensable tool to study T cell development and function. However, such TCRs are usually isolated from the relevant T cells after long-term culture often following repeated antigen stimulation, which unavoidably selects for T cells with high affinity. Random genomic integration of the TCR α- and β-chain and expression from non-endogenous promoters can lead to variations in expression level and kinetics.Epigenetic reprogramming via somatic cell nuclear transfer provides a tool to generate embryonic stem cells and mice from any cell of interest. Consequently, when SCNT is applied to T cells of known specificity, these genetic V(D)J rearrangements are transferred to the SCNT-embryonic stem cells (ESCs) and the mice derived from them, while epigenetic marks are reset. We have demonstrated that T cells with pre-defined specificities against Toxoplasma gondii can be used to generate mouse models that express the specific TCR from their endogenous loci, without experimentally introduced genetic modification. The relative ease and speed with which such transnuclear models can be obtained holds promise for the construction of other disease models.Download video file.^{(82M, mov)}