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Semen abnormalities, sperm DNA damage and global hypermethylation in health workers occupationally exposed to ionizing radiation.
PUBLISHED: 01-01-2013
Cytogenetic studies have demonstrated that low levels of chronic radiation exposure can potentially increase the frequency of chromosomal aberrations and aneuploidy in somatic cells. Epidemiological studies have shown that health workers occupationally exposed to ionizing radiation bear an increased risk of hematological malignancies.
Fluorescence in situ hybridization (FISH) is a technique that allows specific DNA sequences to be detected on metaphase or interphase chromosomes in cell nuclei1. The technique uses DNA probes with unique sequences that hybridize to whole chromosomes or specific chromosomal regions, and serves as a powerful adjunct to classic cytogenetics. For instance, many earlier studies reported the frequent detection of increased chromosome aberrations in leukemia patients related with benzene exposure, benzene-poisoning patients, and healthy workers exposed to benzene, using classic cytogenetic analysis2. Using FISH, leukemia-specific chromosomal alterations have been observed to be elevated in apparently healthy workers exposed to benzene3-6, indicating the critical roles of cytogentic changes in benzene-induced leukemogenesis. Generally, a single FISH assay examines only one or a few whole chromosomes or specific loci per slide, so multiple hybridizations need to be conducted on multiple slides to cover all of the human chromosomes. Spectral karyotyping (SKY) allows visualization of the whole genome simultaneously, but the requirement for special software and equipment limits its application7. Here, we describe a novel FISH assay, OctoChrome-FISH, which can be applied for Chromosomics, which we define here as the simultaneous analysis of all 24 human chromosomes on one slide in human studies, such as chromosome-wide aneuploidy study (CWAS)8. The basis of the method, marketed by Cytocell as the Chromoprobe Multiprobe System, is an OctoChrome device that is divided into 8 squares, each of which carries three different whole chromosome painting probes (Figure 1). Each of the three probes is directly labeled with a different colored fluorophore, green (FITC), red (Texas Red), and blue (Coumarin). The arrangement of chromosome combinations on the OctoChrome device has been designed to facilitate the identification of the non-random structural chromosome alterations (translocations) found in the most common leukemias and lymphomas, for instance t(9;22), t(15;17), t(8;21), t(14;18)9. Moreover, numerical changes (aneuploidy) in chromosomes can be detected concurrently. The corresponding template slide is also divided into 8 squares onto which metaphase spreads are bound (Figure 2), and is positioned over the OctoChrome device. The probes and target DNA are denatured at high-temperature and hybridized in a humid chamber, and then all 24 human chromosomes can be visualized simultaneously. OctoChrome FISH is a promising technique for the clinical diagnosis of leukemia and lymphoma and for detection of aneuploidies in all chromosomes. We have applied this new Chromosomic approach in a CWAS study of benzene-exposed Chinese workers8,10.
21 Related JoVE Articles!
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Spectral Karyotyping to Study Chromosome Abnormalities in Humans and Mice with Polycystic Kidney Disease
Authors: Wissam A. AbouAlaiwi, Ingrid Rodriguez, Surya M. Nauli.
Institutions: University of Toledo, College of Pharmacy and Pharmaceutical Sciences, ProMedica Sponsored Research.
Conventional method to identify and classify individual chromosomes depends on the unique banding pattern of each chromosome in a specific species being analyzed 1, 2. This classical banding technique, however, is not reliable in identifying complex chromosomal aberrations such as those associated with cancer. To overcome the limitations of the banding technique, Spectral Karyotyping (SKY) is introduced to provide much reliable information on chromosome abnormalities. SKY is a multicolor fluorescence in-situ hybridization (FISH) technique to detect metaphase chromosomes with spectral microscope 3, 4. SKY has been proven to be a valuable tool for the cytogenetic analysis of a broad range of chromosome abnormalities associated with a large number of genetic diseases and malignancies 5, 6. SKY involves the use of multicolor fluorescently-labelled DNA probes prepared from the degenerate oligonucleotide primers by PCR. Thus, every chromosome has a unique spectral color after in-situ hybridization with probes, which are differentially labelled with a mixture of fluorescent dyes (Rhodamine, Texas Red, Cy5, FITC and Cy5.5). The probes used for SKY consist of up to 55 chromosome specific probes 7-10. The procedure for SKY involves several steps (Figure 1). SKY requires the availability of cells with high mitotic index from normal or diseased tissue or blood. The chromosomes of a single cell from either a freshly isolated primary cell or a cell line are spread on a glass slide. This chromosome spread is labeled with a different combination of fluorescent dyes specific for each chromosome. For probe detection and image acquisition,the spectral imaging system consists of sagnac interferometer and a CCD camera. This allows measurement of the visible light spectrum emitted from the sample and to acquire a spectral image from individual chromosomes. HiSKY, the software used to analyze the results of the captured images, provides an easy identification of chromosome anomalies. The end result is a metaphase and a karyotype classification image, in which each pair of chromosomes has a distinct color (Figure 2). This allows easy identification of chromosome identities and translocations. For more details, please visit Applied Spectral Imaging website ( SKY was recently used for an identification of chromosome segregation defects and chromosome abnormalities in humans and mice with Autosomal Dominant Polycystic Kidney Disease (ADPKD), a genetic disease characterized by dysfunction in primary cilia 11-13. Using this technique, we demonstrated the presence of abnormal chromosome segregation and chromosomal defects in ADPKD patients and mouse models 14. Further analyses using SKY not only allowed us to identify chromosomal number and identity, but also to accurately detect very complex chromosomal aberrations such as chromosome deletions and translocations (Figure 2).
Medicine, Issue 60, Chromosome, Polycystic Kidney Disease, Primary Cilia, Spectral Karyotyping, Cytogenetics
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Stereotactic Radiosurgery for Gynecologic Cancer
Authors: Charles Kunos, James M. Brindle, Robert Debernardo.
Institutions: University Hospitals Case Medical Center and Case Western Reserve University School of Medicine, University Hospitals Case Medical Center and Case Western Reserve University School of Medicine.
Stereotactic body radiotherapy (SBRT) distinguishes itself by necessitating more rigid patient immobilization, accounting for respiratory motion, intricate treatment planning, on-board imaging, and reduced number of ablative radiation doses to cancer targets usually refractory to chemotherapy and conventional radiation. Steep SBRT radiation dose drop-off permits narrow 'pencil beam' treatment fields to be used for ablative radiation treatment condensed into 1 to 3 treatments. Treating physicians must appreciate that SBRT comes at a bigger danger of normal tissue injury and chance of geographic tumor miss. Both must be tackled by immobilization of cancer targets and by high-precision treatment delivery. Cancer target immobilization has been achieved through use of indexed customized Styrofoam casts, evacuated bean bags, or body-fix molds with patient-independent abdominal compression.1-3 Intrafraction motion of cancer targets due to breathing now can be reduced by patient-responsive breath hold techniques,4 patient mouthpiece active breathing coordination,5 respiration-correlated computed tomography,6 or image-guided tracking of fiducials implanted within and around a moving tumor.7-9 The Cyberknife system (Accuray [Sunnyvale, CA]) utilizes a radiation linear accelerator mounted on a industrial robotic arm that accurately follows patient respiratory motion by a camera-tracked set of light-emitting diodes (LED) impregnated on a vest fitted to a patient.10 Substantial reductions in radiation therapy margins can be achieved by motion tracking, ultimately rendering a smaller planning target volumes that are irradiated with submillimeter accuracy.11-13 Cancer targets treated by SBRT are irradiated by converging, tightly collimated beams. Resultant radiation dose to cancer target volume histograms have a more pronounced radiation "shoulder" indicating high percentage target coverage and a small high-dose radiation "tail." Thus, increased target conformality comes at the expense of decreased dose uniformity in the SBRT cancer target. This may have implications for both subsequent tumor control in the SBRT target and normal tissue tolerance of organs at-risk. Due to the sharp dose falloff in SBRT, the possibility of occult disease escaping ablative radiation dose occurs when cancer targets are not fully recognized and inadequate SBRT dose margins are applied. Clinical target volume (CTV) expansion by 0.5 cm, resulting in a larger planning target volume (PTV), is associated with increased target control without undue normal tissue injury.7,8 Further reduction in the probability of geographic miss may be achieved by incorporation of 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET).8 Use of 18F-FDG PET/CT in SBRT treatment planning is only the beginning of attempts to discover new imaging target molecular signatures for gynecologic cancers.
Medicine, Issue 62, radiosurgery, Cyberknife stereotactic radiosurgery, radiation, ovarian cancer, cervix cancer
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Characterization of Molecular Mechanisms of In vivo UVR Induced Cataract
Authors: Konstantin Galichanin, Nooshin Talebizadeh, Per Söderberg.
Institutions: Karolinska Institutet, Uppsala University .
Cataract is the leading cause of blindness in the world 1. The World Health Organization defines cataract as a clouding of the lens of the eye which impedes the transfer of light. Cataract is a multi-factorial disease associated with diabetes, smoking, ultraviolet radiation (UVR), alcohol, ionizing radiation, steroids and hypertension. There is strong experimental 2-4 and epidemiological evidence 5,6 that UVR causes cataract. We developed an animal model for UVR B induced cataract in both anesthetized 7 and non-anesthetized animals 8. The only cure for cataract is surgery but this treatment is not accessible to all. It has been estimated that a delay of onset of cataract for 10 years could reduce the need for cataract surgery by 50% 9. To delay the incidence of cataract, it is needed to understand the mechanisms of cataract formation and find effective prevention strategies. Among the mechanisms for cataract development, apoptosis plays a crucial role in initiation of cataract in humans and animals 10. Our focus has recently been apoptosis in the lens as the mechanism for cataract development 8,11,12. It is anticipated that a better understanding of the effect of UVR on the apoptosis pathway will provide possibilities for discovery of new pharmaceuticals to prevent cataract. In this article, we describe how cataract can be experimentally induced by in vivo exposure to UVR-B. Further RT-PCR and immunohistochemistry are presented as tools to study molecular mechanisms of UVR-B induced cataract.
Medicine, Issue 69, Neuroscience, Molecular Biology, Ophthalmology, Immunology, UVR-B, lens, cataract, qRT-PCR, PCR, immunohistochemistry, rat restrainer, animal model
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Measuring Intracellular Ca2+ Changes in Human Sperm using Four Techniques: Conventional Fluorometry, Stopped Flow Fluorometry, Flow Cytometry and Single Cell Imaging
Authors: Esperanza Mata-Martínez, Omar José, Paulina Torres-Rodríguez, Alejandra Solís-López, Ana A. Sánchez-Tusie, Yoloxochitl Sánchez-Guevara, Marcela B. Treviño, Claudia L. Treviño.
Institutions: Instituto de Biotecnología-Universidad Nacional Autónoma de México, Edison State College.
Spermatozoa are male reproductive cells especially designed to reach, recognize and fuse with the egg. To perform these tasks, sperm cells must be prepared to face a constantly changing environment and to overcome several physical barriers. Being in essence transcriptionally and translationally silent, these motile cells rely profoundly on diverse signaling mechanisms to orient themselves and swim in a directed fashion, and to contend with challenging environmental conditions during their journey to find the egg. In particular, Ca2+-mediated signaling is pivotal for several sperm functions: activation of motility, capacitation (a complex process that prepares sperm for the acrosome reaction) and the acrosome reaction (an exocytotic event that allows sperm-egg fusion). The use of fluorescent dyes to track intracellular fluctuations of this ion is of remarkable importance due to their ease of application, sensitivity, and versatility of detection. Using one single dye-loading protocol we utilize four different fluorometric techniques to monitor sperm Ca2+ dynamics. Each technique provides distinct information that enables spatial and/or temporal resolution, generating data both at single cell and cell population levels.
Cellular Biology, Issue 75, Medicine, Molecular Biology, Genetics, Biophysics, Anatomy, Physiology, Spermatozoa, Ion Channels, Cell Physiological Processes, Calcium Signaling, Reproductive Physiological Processes, fluorometry, Flow cytometry, stopped flow fluorometry, single-cell imaging, human sperm, sperm physiology, intracellular Ca2+, Ca2+ signaling, Ca2+ imaging, fluorescent dyes, imaging
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Assessing Cell Cycle Progression of Neural Stem and Progenitor Cells in the Mouse Developing Brain after Genotoxic Stress
Authors: Olivier Etienne, Amandine Bery, Telma Roque, Chantal Desmaze, François D. Boussin.
Institutions: CEA DSV iRCM SCSR, INSERM, U967, Université Paris Diderot, Sorbonne Paris Cité, Université Paris Sud, UMR 967.
Neurons of the cerebral cortex are generated during brain development from different types of neural stem and progenitor cells (NSPC), which form a pseudostratified epithelium lining the lateral ventricles of the embryonic brain. Genotoxic stresses, such as ionizing radiation, have highly deleterious effects on the developing brain related to the high sensitivity of NSPC. Elucidation of the cellular and molecular mechanisms involved depends on the characterization of the DNA damage response of these particular types of cells, which requires an accurate method to determine NSPC progression through the cell cycle in the damaged tissue. Here is shown a method based on successive intraperitoneal injections of EdU and BrdU in pregnant mice and further detection of these two thymidine analogues in coronal sections of the embryonic brain. EdU and BrdU are both incorporated in DNA of replicating cells during S phase and are detected by two different techniques (azide or a specific antibody, respectively), which facilitate their simultaneous detection. EdU and BrdU staining are then determined for each NSPC nucleus in function of its distance from the ventricular margin in a standard region of the dorsal telencephalon. Thus this dual labeling technique allows distinguishing cells that progressed through the cell cycle from those that have activated a cell cycle checkpoint leading to cell cycle arrest in response to DNA damage. An example of experiment is presented, in which EdU was injected before irradiation and BrdU immediately after and analyzes performed within the 4 hr following irradiation. This protocol provides an accurate analysis of the acute DNA damage response of NSPC in function of the phase of the cell cycle at which they have been irradiated. This method is easily transposable to many other systems in order to determine the impact of a particular treatment on cell cycle progression in living tissues.
Neuroscience, Issue 87, EdU, BrdU, in utero irradiation, neural stem and progenitor cells, cell cycle, embryonic cortex, immunostaining, cell cycle checkpoints, apoptosis, genotoxic stress, embronic mouse brain
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Effect of Male Accessory Gland Products on Egg Laying in Gastropod Molluscs
Authors: Sander van Iersel, Elferra M. Swart, Yumi Nakadera, Nico M. van Straalen, Joris M. Koene.
Institutions: VU University.
In internally fertilizing animals, seminal fluid is usually added to the spermatozoa, together forming the semen or ejaculate. Besides nourishing and activating sperm, the components in the seminal fluid can also influence female physiology to augment fertilization success of the sperm donor. While many studies have reported such effects in species with separate sexes, few studies have addressed this in simultaneously hermaphroditic animals. This video protocol presents a method to study effects of seminal fluid in gastropods, using a simultaneously hermaphroditic freshwater snail, the great pond snail Lymnaea stagnalis, as model organism. While the procedure is shown using complete prostate gland extracts, individual components (i.e., proteins, peptides, and other compounds) of the seminal fluid can be tested in the same way. Effects of the receipt of ejaculate components on egg laying can be quantified in terms of frequency of egg laying and more subtle estimates of female reproductive performance such as egg numbers within each egg masses. Results show that seminal fluid proteins affect female reproductive output in this simultaneous hermaphrodite, highlighting their importance for sexual selection.
Physiology, Issue 88, Allohormone, Fresh-water snail, Gastropod, Lymnaea stagnalis, Mollusc, Pond snail, Prostate, Semen, Seminal fluid Sexual selection, Sperm
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Fluorescence in situ hybridization (FISH) Protocol in Human Sperm
Authors: Zaida Sarrate, Ester Anton.
Institutions: Universitat Autónoma de Barcelona.
Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic process in the parents. In human males, these errors can lead to the production of spermatozoa with numerical chromosome abnormalities which represent an increased risk of transmitting these anomalies to the offspring. For this reason, the technique of fluorescence in situ hybridization (FISH) on sperm nuclei has become a protocol widely incorporated in the context of clinical diagnosis. This practice provides an estimate of the frequencies of numerical chromosome abnormalities in the gametes of the patients that seek for genetic reproductive advice. To date, the chromosomes most frequently included in sperm FISH analysis are chromosomes X, Y, 13, 18 and 21. This video-article describes, step by step, how to process and fix a human semen sample, how to decondense and denature the sperm chromatin, how to proceed to obtain sperm FISH preparations, and how to visualize the results at the microscope. Special remarks of the most relevant steps are given to achieve the best results.
Cellular Biology, Issue 31, Fluorescence in situ hybridization, human, infertility, numerical chromosome abnormalities, spermatozoa
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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Authors: Chryssostomos Chatgilialoglu, Carla Ferreri, Annalisa Masi, Michele Melchiorre, Anna Sansone, Michael A. Terzidis, Armida Torreggiani.
Institutions: Consiglio Nazionale delle Ricerche.
The involvement of free radicals in life sciences has constantly increased with time and has been connected to several physiological and pathological processes. This subject embraces diverse scientific areas, spanning from physical, biological and bioorganic chemistry to biology and medicine, with applications to the amelioration of quality of life, health and aging. Multidisciplinary skills are required for the full investigation of the many facets of radical processes in the biological environment and chemical knowledge plays a crucial role in unveiling basic processes and mechanisms. We developed a chemical biology approach able to connect free radical chemical reactivity with biological processes, providing information on the mechanistic pathways and products. The core of this approach is the design of biomimetic models to study biomolecule behavior (lipids, nucleic acids and proteins) in aqueous systems, obtaining insights of the reaction pathways as well as building up molecular libraries of the free radical reaction products. This context can be successfully used for biomarker discovery and examples are provided with two classes of compounds: mono-trans isomers of cholesteryl esters, which are synthesized and used as references for detection in human plasma, and purine 5',8-cyclo-2'-deoxyribonucleosides, prepared and used as reference in the protocol for detection of such lesions in DNA samples, after ionizing radiations or obtained from different health conditions.
Chemistry, Issue 74, Biochemistry, Chemical Engineering, Chemical Biology, chemical analysis techniques, chemistry (general), life sciences, radiation effects (biological, animal and plant), biomarker, biomimetic chemistry, free radicals, trans lipids, cyclopurine lesions, DNA, chromatography, spectroscopy, synthesis
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Quantitation of γH2AX Foci in Tissue Samples
Authors: Michelle M. Tang, Li-Jeen Mah, Raja S. Vasireddy, George T. Georgiadis, Assam El-Osta, Simon G. Royce, Tom C. Karagiannis.
Institutions: The Alfred Medical Research and Education Precinct, The Alfred Medical Research and Education Precinct, The University of Melbourne, Royal Children's Hospital, The University of Melbourne.
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 vivo4,5. Here, we demonstrate a typical immunofluorescence method for detection and quantitation of γH2AX foci in mouse tissues.
Cellular Biology, Issue 40, immunofluorescence, DNA double-strand breaks, histone variant, H2AX, DNA damage, ionising radiation, reactive oxygen species
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2D and 3D Chromosome Painting in Malaria Mosquitoes
Authors: Phillip George, Atashi Sharma, Igor V Sharakhov.
Institutions: Virginia Tech.
Fluorescent in situ hybridization (FISH) of whole arm chromosome probes is a robust technique for mapping genomic regions of interest, detecting chromosomal rearrangements, and studying three-dimensional (3D) organization of chromosomes in the cell nucleus. The advent of laser capture microdissection (LCM) and whole genome amplification (WGA) allows obtaining large quantities of DNA from single cells. The increased sensitivity of WGA kits prompted us to develop chromosome paints and to use them for exploring chromosome organization and evolution in non-model organisms. Here, we present a simple method for isolating and amplifying the euchromatic segments of single polytene chromosome arms from ovarian nurse cells of the African malaria mosquito Anopheles gambiae. This procedure provides an efficient platform for obtaining chromosome paints, while reducing the overall risk of introducing foreign DNA to the sample. The use of WGA allows for several rounds of re-amplification, resulting in high quantities of DNA that can be utilized for multiple experiments, including 2D and 3D FISH. We demonstrated that the developed chromosome paints can be successfully used to establish the correspondence between euchromatic portions of polytene and mitotic chromosome arms in An. gambiae. Overall, the union of LCM and single-chromosome WGA provides an efficient tool for creating significant amounts of target DNA for future cytogenetic and genomic studies.
Immunology, Issue 83, Microdissection, whole genome amplification, malaria mosquito, polytene chromosome, mitotic chromosomes, fluorescence in situ hybridization, chromosome painting
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Quantitation and Analysis of the Formation of HO-Endonuclease Stimulated Chromosomal Translocations by Single-Strand Annealing in Saccharomyces cerevisiae
Authors: Lauren Liddell, Glenn Manthey, Nicholas Pannunzio, Adam Bailis.
Institutions: Irell & Manella Graduate School of Biological Sciences, City of Hope Comprehensive Cancer Center and Beckman Research Institute, University of Southern California, Norris Comprehensive Cancer Center.
Genetic variation is frequently mediated by genomic rearrangements that arise through interaction between dispersed repetitive elements present in every eukaryotic genome. This process is an important mechanism for generating diversity between and within organisms1-3. The human genome consists of approximately 40% repetitive sequence of retrotransposon origin, including a variety of LINEs and SINEs4. Exchange events between these repetitive elements can lead to genome rearrangements, including translocations, that can disrupt gene dosage and expression that can result in autoimmune and cardiovascular diseases5, as well as cancer in humans6-9. Exchange between repetitive elements occurs in a variety of ways. Exchange between sequences that share perfect (or near-perfect) homology occurs by a process called homologous recombination (HR). By contrast, non-homologous end joining (NHEJ) uses little-or-no sequence homology for exchange10,11. The primary purpose of HR, in mitotic cells, is to repair double-strand breaks (DSBs) generated endogenously by aberrant DNA replication and oxidative lesions, or by exposure to ionizing radiation (IR), and other exogenous DNA damaging agents. In the assay described here, DSBs are simultaneously created bordering recombination substrates at two different chromosomal loci in diploid cells by a galactose-inducible HO-endonuclease (Figure 1). The repair of the broken chromosomes generates chromosomal translocations by single strand annealing (SSA), a process where homologous sequences adjacent to the chromosome ends are covalently joined subsequent to annealing. One of the substrates, his3-Δ3', contains a 3' truncated HIS3 allele and is located on one copy of chromosome XV at the native HIS3 locus. The second substrate, his3-Δ5', is located at the LEU2 locus on one copy of chromosome III, and contains a 5' truncated HIS3 allele. Both substrates are flanked by a HO endonuclease recognition site that can be targeted for incision by HO-endonuclease. HO endonuclease recognition sites native to the MAT locus, on both copies of chromosome III, have been deleted in all strains. This prevents interaction between the recombination substrates and other broken chromosome ends from interfering in the assay. The KAN-MX-marked galactose-inducible HO endonuclease expression cassette is inserted at the TRP1 locus on chromosome IV. The substrates share 311 bp or 60 bp of the HIS3 coding sequence that can be used by the HR machinery for repair by SSA. Cells that use these substrates to repair broken chromosomes by HR form an intact HIS3 allele and a tXV::III chromosomal translocation that can be selected for by the ability to grow on medium lacking histidine (Figure 2A). Translocation frequency by HR is calculated by dividing the number of histidine prototrophic colonies that arise on selective medium by the total number of viable cells that arise after plating appropriate dilutions onto non-selective medium (Figure 2B). A variety of DNA repair mutants have been used to study the genetic control of translocation formation by SSA using this system12-14.
Genetics, Issue 55, translocation formation, HO-endonuclease, Genomic Southern blot, Chromosome blot, Pulsed-field gel electrophoresis, Homologous recombination, DNA double-strand breaks, Single-strand annealing
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Chromosome Preparation From Cultured Cells
Authors: Bradley Howe, Ayesha Umrigar, Fern Tsien.
Institutions: Louisiana State University Health Science Center.
Chromosome (cytogenetic) analysis is widely used for the detection of chromosome instability. When followed by G-banding and molecular techniques such as fluorescence in situ hybridization (FISH), this assay has the powerful ability to analyze individual cells for aberrations that involve gains or losses of portions of the genome and rearrangements involving one or more chromosomes. In humans, chromosome abnormalities occur in approximately 1 per 160 live births1,2, 60-80% of all miscarriages3,4, 10% of stillbirths2,5, 13% of individuals with congenital heart disease6, 3-6% of infertility cases2, and in many patients with developmental delay and birth defects7. Cytogenetic analysis of malignancy is routinely used by researchers and clinicians, as observations of clonal chromosomal abnormalities have been shown to have both diagnostic and prognostic significance8,9.  Chromosome isolation is invaluable for gene therapy and stem cell research of organisms including nonhuman primates and rodents10-13. Chromosomes can be isolated from cells of live tissues, including blood lymphocytes, skin fibroblasts, amniocytes, placenta, bone marrow, and tumor specimens. Chromosomes are analyzed at the metaphase stage of mitosis, when they are most condensed and therefore more clearly visible. The first step of the chromosome isolation technique involves the disruption of the spindle fibers by incubation with Colcemid, to prevent the cells from proceeding to the subsequent anaphase stage. The cells are then treated with a hypotonic solution and preserved in their swollen state with Carnoy's fixative. The cells are then dropped on to slides and can then be utilized for a variety of procedures. G-banding involves trypsin treatment followed by staining with Giemsa to create characteristic light and dark bands. The same procedure to isolate chromosomes can be used for the preparation of cells for procedures such as fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH), and spectral karyotyping (SKY)14,15.
Basic Protocol, Issue 83, chromosome, cytogenetic, harvesting, karyotype, fluorescence in situ hybridization, FISH
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Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH
Authors: Sarah M. Misenko, Samuel F. Bunting.
Institutions: Rutgers, the State University of New Jersey.
Defective DNA repair leads to increased genomic instability, which is the root cause of mutations that lead to tumorigenesis. Analysis of the frequency and type of chromosome aberrations in different cell types allows defects in DNA repair pathways to be elucidated. Understanding mammalian DNA repair biology has been greatly helped by the production of mice with knockouts in specific genes. The goal of this protocol is to quantify genomic instability in mouse B lymphocytes. Labeling of the telomeres using PNA-FISH probes (peptide nucleic acid - fluorescent in situ hybridization) facilitates the rapid analysis of genomic instability in metaphase chromosome spreads. B cells have specific advantages relative to fibroblasts, because they have normal ploidy and a higher mitotic index. Short-term culture of B cells therefore enables precise measurement of genomic instability in a primary cell population which is likely to have fewer secondary genetic mutations than what is typically found in transformed fibroblasts or patient cell lines.
Immunology, Issue 90, genomic instability, DNA repair, mouse, metaphase spread, FISH, primary culture
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Transgenic Rodent Assay for Quantifying Male Germ Cell Mutant Frequency
Authors: Jason M. O'Brien, Marc A. Beal, John D. Gingerich, Lynda Soper, George R. Douglas, Carole L. Yauk, Francesco Marchetti.
Institutions: Environmental Health Centre.
De novo mutations arise mostly in the male germline and may contribute to adverse health outcomes in subsequent generations. Traditional methods for assessing the induction of germ cell mutations require the use of large numbers of animals, making them impractical. As such, germ cell mutagenicity is rarely assessed during chemical testing and risk assessment. Herein, we describe an in vivo male germ cell mutation assay using a transgenic rodent model that is based on a recently approved Organisation for Economic Co-operation and Development (OECD) test guideline. This method uses an in vitro positive selection assay to measure in vivo mutations induced in a transgenic λgt10 vector bearing a reporter gene directly in the germ cells of exposed males. We further describe how the detection of mutations in the transgene recovered from germ cells can be used to characterize the stage-specific sensitivity of the various spermatogenic cell types to mutagen exposure by controlling three experimental parameters: the duration of exposure (administration time), the time between exposure and sample collection (sampling time), and the cell population collected for analysis. Because a large number of germ cells can be assayed from a single male, this method has superior sensitivity compared with traditional methods, requires fewer animals and therefore much less time and resources.
Genetics, Issue 90, sperm, spermatogonia, male germ cells, spermatogenesis, de novo mutation, OECD TG 488, transgenic rodent mutation assay, N-ethyl-N-nitrosourea, genetic toxicology
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Functional Interrogation of Adult Hypothalamic Neurogenesis with Focal Radiological Inhibition
Authors: Daniel A. Lee, Juan Salvatierra, Esteban Velarde, John Wong, Eric C. Ford, Seth Blackshaw.
Institutions: California Institute of Technology, Johns Hopkins University School of Medicine, Johns Hopkins University School of Medicine, University Of Washington Medical Center, Johns Hopkins University School of Medicine.
The functional characterization of adult-born neurons remains a significant challenge. Approaches to inhibit adult neurogenesis via invasive viral delivery or transgenic animals have potential confounds that make interpretation of results from these studies difficult. New radiological tools are emerging, however, that allow one to noninvasively investigate the function of select groups of adult-born neurons through accurate and precise anatomical targeting in small animals. Focal ionizing radiation inhibits the birth and differentiation of new neurons, and allows targeting of specific neural progenitor regions. In order to illuminate the potential functional role that adult hypothalamic neurogenesis plays in the regulation of physiological processes, we developed a noninvasive focal irradiation technique to selectively inhibit the birth of adult-born neurons in the hypothalamic median eminence. We describe a method for Computer tomography-guided focal irradiation (CFIR) delivery to enable precise and accurate anatomical targeting in small animals. CFIR uses three-dimensional volumetric image guidance for localization and targeting of the radiation dose, minimizes radiation exposure to nontargeted brain regions, and allows for conformal dose distribution with sharp beam boundaries. This protocol allows one to ask questions regarding the function of adult-born neurons, but also opens areas to questions in areas of radiobiology, tumor biology, and immunology. These radiological tools will facilitate the translation of discoveries at the bench to the bedside.
Neuroscience, Issue 81, Neural Stem Cells (NSCs), Body Weight, Radiotherapy, Image-Guided, Metabolism, Energy Metabolism, Neurogenesis, Cell Proliferation, Neurosciences, Irradiation, Radiological treatment, Computer-tomography (CT) imaging, Hypothalamus, Hypothalamic Proliferative Zone (HPZ), Median Eminence (ME), Small Animal Radiation Research Platform (SARRP)
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CometChip: A High-throughput 96-Well Platform for Measuring DNA Damage in Microarrayed Human Cells
Authors: Jing Ge, Somsak Prasongtanakij, David K. Wood, David M. Weingeist, Jessica Fessler, Panida Navasummrit, Mathuros Ruchirawat, Bevin P. Engelward.
Institutions: Massachusetts Institute of Technology, Chulabhorn Graduate Institute, University of Minnesota.
DNA damaging agents can promote aging, disease and cancer and they are ubiquitous in the environment and produced within human cells as normal cellular metabolites. Ironically, at high doses DNA damaging agents are also used to treat cancer. The ability to quantify DNA damage responses is thus critical in the public health, pharmaceutical and clinical domains. Here, we describe a novel platform that exploits microfabrication techniques to pattern cells in a fixed microarray. The ‘CometChip’ is based upon the well-established single cell gel electrophoresis assay (a.k.a. the comet assay), which estimates the level of DNA damage by evaluating the extent of DNA migration through a matrix in an electrical field. The type of damage measured by this assay includes abasic sites, crosslinks, and strand breaks. Instead of being randomly dispersed in agarose in the traditional assay, cells are captured into an agarose microwell array by gravity. The platform also expands from the size of a standard microscope slide to a 96-well format, enabling parallel processing. Here we describe the protocols of using the chip to evaluate DNA damage caused by known genotoxic agents and the cellular repair response followed after exposure. Through the integration of biological and engineering principles, this method potentiates robust and sensitive measurements of DNA damage in human cells and provides the necessary throughput for genotoxicity testing, drug development, epidemiological studies and clinical assays.
Bioengineering, Issue 92, comet assay, electrophoresis, microarray, DNA damage, DNA repair
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Metabolic Labeling of Leucine Rich Repeat Kinases 1 and 2 with Radioactive Phosphate
Authors: Jean-Marc Taymans, Fangye Gao, Veerle Baekelandt.
Institutions: KU Leuven and Leuven Institute for Neuroscience and Disease (LIND).
Leucine rich repeat kinases 1 and 2 (LRRK1 and LRRK2) are paralogs which share a similar domain organization, including a serine-threonine kinase domain, a Ras of complex proteins domain (ROC), a C-terminal of ROC domain (COR), and leucine-rich and ankyrin-like repeats at the N-terminus. The precise cellular roles of LRRK1 and LRRK2 have yet to be elucidated, however LRRK1 has been implicated in tyrosine kinase receptor signaling1,2, while LRRK2 is implicated in the pathogenesis of Parkinson's disease3,4. In this report, we present a protocol to label the LRRK1 and LRRK2 proteins in cells with 32P orthophosphate, thereby providing a means to measure the overall phosphorylation levels of these 2 proteins in cells. In brief, affinity tagged LRRK proteins are expressed in HEK293T cells which are exposed to medium containing 32P-orthophosphate. The 32P-orthophosphate is assimilated by the cells after only a few hours of incubation and all molecules in the cell containing phosphates are thereby radioactively labeled. Via the affinity tag (3xflag) the LRRK proteins are isolated from other cellular components by immunoprecipitation. Immunoprecipitates are then separated via SDS-PAGE, blotted to PVDF membranes and analysis of the incorporated phosphates is performed by autoradiography (32P signal) and western detection (protein signal) of the proteins on the blots. The protocol can readily be adapted to monitor phosphorylation of any other protein that can be expressed in cells and isolated by immunoprecipitation.
Cellular Biology, Issue 79, biology (general), biochemistry, bioengineering (general), LRRK1, LRRK2, metabolic labeling, 32P orthophosphate, immunoprecipitation, autoradiography
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Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Authors: Alexandra Amaro-Ortiz, Jillian C. Vanover, Timothy L. Scott, John A. D'Orazio.
Institutions: University of Kentucky College of Medicine, University of Kentucky College of Medicine, University of Kentucky College of Medicine, University of Kentucky College of Medicine.
Fairness of skin, UV sensitivity and skin cancer risk all correlate with the physiologic function of the melanocortin 1 receptor, a Gs-coupled signaling protein found on the surface of melanocytes. Mc1r stimulates adenylyl cyclase and cAMP production which, in turn, up-regulates melanocytic production of melanin in the skin. In order to study the mechanisms by which Mc1r signaling protects the skin against UV injury, this study relies on a mouse model with "humanized skin" based on epidermal expression of stem cell factor (Scf). K14-Scf transgenic mice retain melanocytes in the epidermis and therefore have the ability to deposit melanin in the epidermis. In this animal model, wild type Mc1r status results in robust deposition of black eumelanin pigment and a UV-protected phenotype. In contrast, K14-Scf animals with defective Mc1r signaling ability exhibit a red/blonde pigmentation, very little eumelanin in the skin and a UV-sensitive phenotype. Reasoning that eumelanin deposition might be enhanced by topical agents that mimic Mc1r signaling, we found that direct application of forskolin extract to the skin of Mc1r-defective fair-skinned mice resulted in robust eumelanin induction and UV protection 1. Here we describe the method for preparing and applying a forskolin-containing natural root extract to K14-Scf fair-skinned mice and report a method for measuring UV sensitivity by determining minimal erythematous dose (MED). Using this animal model, it is possible to study how epidermal cAMP induction and melanization of the skin affect physiologic responses to UV exposure.
Medicine, Issue 79, Skin, Inflammation, Photometry, Ultraviolet Rays, Skin Pigmentation, melanocortin 1 receptor, Mc1r, forskolin, cAMP, mean erythematous dose, skin pigmentation, melanocyte, melanin, sunburn, UV, inflammation
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Ex vivo Culture of Drosophila Pupal Testis and Single Male Germ-line Cysts: Dissection, Imaging, and Pharmacological Treatment
Authors: Stefanie M. K. Gärtner, Christina Rathke, Renate Renkawitz-Pohl, Stephan Awe.
Institutions: Philipps-Universität Marburg, Philipps-Universität Marburg.
During spermatogenesis in mammals and in Drosophila melanogaster, male germ cells develop in a series of essential developmental processes. This includes differentiation from a stem cell population, mitotic amplification, and meiosis. In addition, post-meiotic germ cells undergo a dramatic morphological reshaping process as well as a global epigenetic reconfiguration of the germ line chromatin—the histone-to-protamine switch. Studying the role of a protein in post-meiotic spermatogenesis using mutagenesis or other genetic tools is often impeded by essential embryonic, pre-meiotic, or meiotic functions of the protein under investigation. The post-meiotic phenotype of a mutant of such a protein could be obscured through an earlier developmental block, or the interpretation of the phenotype could be complicated. The model organism Drosophila melanogaster offers a bypass to this problem: intact testes and even cysts of germ cells dissected from early pupae are able to develop ex vivo in culture medium. Making use of such cultures allows microscopic imaging of living germ cells in testes and of germ-line cysts. Importantly, the cultivated testes and germ cells also become accessible to pharmacological inhibitors, thereby permitting manipulation of enzymatic functions during spermatogenesis, including post-meiotic stages. The protocol presented describes how to dissect and cultivate pupal testes and germ-line cysts. Information on the development of pupal testes and culture conditions are provided alongside microscope imaging data of live testes and germ-line cysts in culture. We also describe a pharmacological assay to study post-meiotic spermatogenesis, exemplified by an assay targeting the histone-to-protamine switch using the histone acetyltransferase inhibitor anacardic acid. In principle, this cultivation method could be adapted to address many other research questions in pre- and post-meiotic spermatogenesis.
Developmental Biology, Issue 91, Ex vivo culture, testis, male germ-line cells, Drosophila, imaging, pharmacological assay
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Non-invasive 3D-Visualization with Sub-micron Resolution Using Synchrotron-X-ray-tomography
Authors: Michael Heethoff, Lukas Helfen, Peter Cloetens.
Institutions: University of Tubingen, European Synchrotron Radiation Facility.
Little is known about the internal organization of many micro-arthropods with body sizes below 1 mm. The reasons for that are the small size and the hard cuticle which makes it difficult to use protocols of classical histology. In addition, histological sectioning destroys the sample and can therefore not be used for unique material. Hence, a non-destructive method is desirable which allows to view inside small samples without the need of sectioning. We used synchrotron X-ray tomography at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France) to non-invasively produce 3D tomographic datasets with a pixel-resolution of 0.7µm. Using volume rendering software, this allows us to reconstruct the internal organization in its natural state without the artefacts produced by histological sectioning. These date can be used for quantitative morphology, landmarks, or for the visualization of animated movies to understand the structure of hidden body parts and to follow complete organ systems or tissues through the samples.
Developmental Biology, Issue 15, Synchrotron X-ray tomography, Acari, Oribatida, micro-arthropods, non-invasive investigation
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Minimal Erythema Dose (MED) Testing
Authors: Carolyn J. Heckman, Rachel Chandler, Jacqueline D. Kloss, Amy Benson, Deborah Rooney, Teja Munshi, Susan D. Darlow, Clifford Perlis, Sharon L. Manne, David W. Oslin.
Institutions: Fox Chase Cancer Center , University of Pennsylvania , Drexel University , Fox Chase Cancer Center , The Cancer Institute of New Jersey.
Ultraviolet radiation (UV) therapy is sometimes used as a treatment for various common skin conditions, including psoriasis, acne, and eczema. The dosage of UV light is prescribed according to an individual's skin sensitivity. Thus, to establish the proper dosage of UV light to administer to a patient, the patient is sometimes screened to determine a minimal erythema dose (MED), which is the amount of UV radiation that will produce minimal erythema (sunburn or redness caused by engorgement of capillaries) of an individual's skin within a few hours following exposure. This article describes how to conduct minimal erythema dose (MED) testing. There is currently no easy way to determine an appropriate UV dose for clinical or research purposes without conducting formal MED testing, requiring observation hours after testing, or informal trial and error testing with the risks of under- or over-dosing. However, some alternative methods are discussed.
Medicine, Issue 75, Anatomy, Physiology, Dermatology, Analytical, Diagnostic, Therapeutic Techniques, Equipment, Health Care, Minimal erythema dose (MED) testing, skin sensitivity, ultraviolet radiation, spectrophotometry, UV exposure, psoriasis, acne, eczema, clinical techniques
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