Name: analysis of the ambient particulate matter-induced chromosomal aberrations using an in vitro system
Uploaded: 2016-12-21T15:00:00
Description: Watch this Scientific Journal Video about Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System at JoVE.com

The work was supported, in part, by the National Institute of Health Center of Biological Research Excellence [grant number 1P20GM109005], the Arkansas Space Grant Consortium through National Aeronautics and Space Administration [grant number NNX15AK32A], and the National Institute for Occupational Safety and Health (NIOSH) [grant number 2T420H008436]. The authors would like to thank Christopher Fettes for proofreading and editing this manuscript.

1. Particle Collection and Preparation
<ol>
	<li>Calibration of the high volume total suspended particles sampler
	<ol>
		<li>Disconnect the sampler motor from the mass flow controller and connect the motor to a stable AC power source (Figure 1). 
		NOTE: A filter is not used during this procedure.</li>
		<li>Mount the calibrator orifice and top loading adapter plate to the sampler. Tighten the top loading adapter hold-down nuts securely to ensure that no air leaks are present. Al...

<ol>
	<li>Lim, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+risk+assessment+of+burden+of+disease+and+injury+attributable+to+67+risk+factors+and+risk+factor+clusters+in+21+regions,+1990-2010:+a+systematic+analysis+for+the+Global+Burden+of+Disease+Study+2010.">A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010.</a> Lancet. 380, 2224-2260 (2012).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> IARC: Outdoor air pollution a leading environmental cause of cancer deaths. , (2013).</li><li>Putaud, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+European+aerosol+phenomenology-2:+chemical+characteristics+of+particulate+matter+at+kerbside,+urban,+rural+and+background+sites+in+Europe.">A European aerosol phenomenology-2: chemical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe.</a> Atmos. Environ. 38 (16), 2579-2595 (2004).</li><li>Hand, J., Schichtel, B., Pitchford, M., Malm, W., Frank, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seasonal+composition+of+remote+and+urban+fine+particulate+matter+in+the+United+States.">Seasonal composition of remote and urban fine particulate matter in the United States.</a> J Geophys Res-Atmos. 117 (5), (2012).</li><li>Schauer, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Source+apportionment+of+airborne+particulate+matter+using+organic+compounds+as+tracers.">Source apportionment of airborne particulate matter using organic compounds as tracers.</a> Atmos. Environ. 30 (22), 3837-3855 (1996).</li><li>Simoneit, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+biomarker+compounds+as+source+indicators+and+tracers+for+air+pollution.">A review of biomarker compounds as source indicators and tracers for air pollution.</a> Environ. Sci. Pollut. Res. 6 (3), 159-169 (1999).</li><li>Kavouras, I. G., Stephanou, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+size+distribution+of+organic+primary+and+secondary+aerosol+constituents+in+urban,+background+marine,+and+forest+atmosphere.">Particle size distribution of organic primary and secondary aerosol constituents in urban, background marine, and forest atmosphere.</a> J Geophys Res-Atmos. 107 (8), (2002).</li><li>Graber, E., Rudich, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atmospheric+HULIS:+How+humic-like+are+they?+A+comprehensive+and+critical+review.">Atmospheric HULIS: How humic-like are they? A comprehensive and critical review.</a> Atmos. Chem. Phys. 6 (3), 729-753 (2006).</li><li>P&#246;schl, U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atmospheric+aerosols:+composition,+transformation,+climate+and+health+effects.">Atmospheric aerosols: composition, transformation, climate and health effects.</a> Angew. Chem. Int. 44 (46), 7520-7540 (2005).</li><li>Hou, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+methylation+in+tandem+repeat+element+and+elemental+component+levels+in+inhalable+air+particles.">Altered methylation in tandem repeat element and elemental component levels in inhalable air particles.</a> Environ. Mol. Mutagen. 55 (3), 256-265 (2014).</li><li>Miousse, I. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+alterations+induced+by+ambient+particulate+matter+in+mouse+macrophages.">Epigenetic alterations induced by ambient particulate matter in mouse macrophages.</a> Environ. Mol. Mutagen. 55 (5), 428-435 (2014).</li><li>Miousse, I. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Vitro+Toxicity+and+Epigenotoxicity+of+Different+Types+of+Ambient+Particulate+Matter.">In Vitro Toxicity and Epigenotoxicity of Different Types of Ambient Particulate Matter.</a> Toxicol. Sci. 148 (2), 473-487 (2015).</li><li>Ehrlich, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic+instability+in+cancer+development.">Genomic instability in cancer development.</a> Genome Instability in Cancer Development. , 363-392 (2005).</li><li>Michael, S., Montag, M., Dott, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pro-inflammatory+effects+and+oxidative+stress+in+lung+macrophages+and+epithelial+cells+induced+by+ambient+particulate+matter.">Pro-inflammatory effects and oxidative stress in lung macrophages and epithelial cells induced by ambient particulate matter.</a> Environ Pollut. 183, 19-29 (2013).</li><li>Li, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+heme+oxygenase-1+expression+in+macrophages+by+diesel+exhaust+particle+chemicals+and+quinones+via+the+antioxidant-responsive+element.">Induction of heme oxygenase-1 expression in macrophages by diesel exhaust particle chemicals and quinones via the antioxidant-responsive element.</a> J Immunol. 165 (6), 3393-3401 (2000).</li><li>Pathak, R., Ramakumar, A., Subramanian, U., Prasanna, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+radio-sensitivities+of+human+chromosomes+1+and+2+in+one+donor+in+interphase-+and+metaphase-spreads+after+60Co+gamma-irradiation.">Differential radio-sensitivities of human chromosomes 1 and 2 in one donor in interphase- and metaphase-spreads after 60Co gamma-irradiation.</a> BMC Med. Phys. 9, 6649 (2009).</li><li>Pathak, R., Dey, S. K., Sarma, A., Khuda-Bukhsh, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genotoxic+effects+in+M5+cells+and+Chinese+hamster+V79+cells+after+exposure+to+7+Li-beam+(LET=+60keV/&#181;m)+and+correlation+of+their+survival+dynamics+to+nuclear+damages+and+cell+death.">Genotoxic effects in M5 cells and Chinese hamster V79 cells after exposure to 7 Li-beam (LET= 60keV/&#181;m) and correlation of their survival dynamics to nuclear damages and cell death.</a> Mutat. Res. Genet. Toxicol. Environ. Mutagen. 628 (1), 56-66 (2007).</li><li>Pathak, R., Dey, S. K., Sarma, A., Khuda-Bukhsh, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+killing,+nuclear+damage+and+apoptosis+in+Chinese+hamster+V79+cells+after+irradiation+with+heavy-ion+beams+of+16+O,+12+C+and+7+Li.">Cell killing, nuclear damage and apoptosis in Chinese hamster V79 cells after irradiation with heavy-ion beams of 16 O, 12 C and 7 Li.</a> Mutat. Res. Genet. Toxicol. Environ. Mutagen. 632 (1), 58-68 (2007).</li><li>Chalbot, M. C., Kavouras, I. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+magnetic+resonance+spectroscopy+for+determining+the+functional+content+of+organic+aerosols:+a+review.">Nuclear magnetic resonance spectroscopy for determining the functional content of organic aerosols: a review.</a> Environ. Pollut. 191, 232-249 (2014).</li></ol>

Cytogenetic study or microscopic analysis of the numbers or structures of chromosomes, primarily in metaphase spreads, provides information crucial for prognosis, risk assessment, and treatment for various diseases. It is now well-established that cytogenetic abnormalities are linked with the progression and development of several diseases, including cancer. To date, CAs have been found in all major tumor types. CAs may arise spontaneously or by either external or internal stimuli, such as ionizing radiation (IR) &#8212;...

It has been estimated that exposure to particulate matter (PM) causes over 3 million excess deaths annually, primarily from cardiopulmonary disease and lung cancer1. Indeed, PM was recognized as carcinogenic to humans by the International Agency for Research on Cancer (Group 1), as an increased risk of lung cancer with increasing levels of exposure to PM has been shown2. Interestingly, almost all the cancer cells harbor numerical and/or structural chromosomal abnormalities. Particulate organic carbon is a variant, complex, and heterogeneous mixture, whose composition and size distribution depends on emissions as well as physical and chemical transformations. It accounts from 35-55% of urban PM2.5 mass (PM 2.5 &#181;m in size and smaller) and more than 60% of rural and continental background PM2.5 mass3, 4. The water soluble fraction accounts for 30-90% of organic aerosol. A large number of organic compounds have been identified, including aliphatic hydrocarbons, polycyclic aromatic hydrocarbons, and their oxygenated and nitrated derivatives, aliphatic aldehydes and alcohols, free fatty acids and their salts, di-carboxylic acids, multifunctional compounds, proteins, and humic-like macromolecules (HULIS) using chromatographic methods coupled with mass spectrometric techniques5-8. These compounds represent less than 10-20% of particulate organic carbon, thus most of organic carbon is unknown9.
Experimental evidence suggests that cytotoxicity, oxidative stress, and inflammation are involved in the development of PM-associated pathological states. It has been recently shown, however, that exposure to PM also results in a number of epigenetic alterations, including alterations in DNA methylation of repetitive elements, in both experimental in vitro systems and in human subjects10-12. Of particular interest are the effects of PM on satellite DNA &#8212; major and minor satellites &#8212; which are found in the heterochromatic region around the centromere of chromosomes. It was shown that these effects may be persistent by nature, as they can be detected for at least 72 hr after exposure12. Alterations in DNA methylation, particularly around centromeres, may lead to accumulation of satellite DNA mRNA transcripts, compromise chromosomal integrity during cell division and, subsequently, result in the development of a variety of pathological states13.
Adaptation of cytogenetic approach for the analysis of CAs as an end-point of epigenetic alterations caused by PM, thus, is of high importance. Here, we report the approach for the ambient PM collection and preparation, in vitro exposure and analysis of CAs using the murine macrophage RAW264.7 model system. Macrophages comprise the first line of defense against the inhaled foreign objects and, therefore, this cell line serves as an established and the most frequently used model in particle toxicology11, 12, 14, 15.

<table border="0" cellpadding="0" cellspacing="0" width="726">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Total suspended particulate sampler</td>
			<td style="width:179px;">Tisch Environmental</td>
			<td style="width:119px;">TE-5170</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:261px;">Bruker Avance III NMR spectrometer&#160;</td>
			<td style="width:179px;">Bruker</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">TopSpin 3.5/pl2 software</td>
			<td style="width:179px;">Bruker</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:261px;">ACD/NMR Processor Academic Edition</td>
			<td style="width:179px;">ACD/Labs</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RAW264.7 murine macrophages</td>
			<td style="width:179px;">ATCC</td>
			<td style="width:119px;">ATCC TIB-71</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:261px;">High glucose DMEM GlutaMAX media</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">10569010</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Fetal Bovine Serum</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">16000044</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:261px;">Penicillin-Streptomycin (10,000 U/mL)</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">15140163</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Trypsin-EDTA (0.25%)</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">25200056</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">PBS, pH 7.4</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">10010049</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:261px;">KaryoMAX Colcemid Solution in PBS</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">15212012</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:261px;">KaryoMAX Potassium Chloride Solution</td>
			<td style="width:179px;">ThermoFisher</td>
			<td align="right" style="width:119px;">10575090</td>
			<td>Warm in a 37&#176;C waterbath before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Methanol (HPLC)</td>
			<td style="width:179px;">Fisher Scientific</td>
			<td style="width:119px;">A452N1-19</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Acetic Acid, Glacial</td>
			<td style="width:179px;">Fisher Scientific</td>
			<td style="width:119px;">BP1185-500</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:261px;">Decon Contrad 70 Liquid Detergent</td>
			<td style="width:179px;">Fisher Scientific</td>
			<td style="width:119px;">04-355-1</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:261px;">Wright and Wright-Giemsa Stain Solutions</td>
			<td style="width:179px;">Fisher Scientific</td>
			<td style="width:119px;">23-200733</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Permount Mounting Medium</td>
			<td style="width:179px;">Fisher Scientific</td>
			<td style="width:119px;">SP15-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Axio Imager 2</td>
			<td style="width:179px;">Zeiss</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

analysis of the ambient particulate matter-induced chromosomal aberrations using an in vitro system

Exposure to particulate matter (PM) is a major world health concern, which may damage various cellular components, including the nuclear genetic material. To assess the impact of PM on nuclear genetic integrity, structural chromosomal aberrations are scored in the metaphase spreads of mouse RAW264.7 macrophage cells. PM is collected from ambient air with a high volume total suspended particles sampler. The collected material is solubilized and filtered to retain the water-soluble, fine portion. The particles are characterized for chemical composition by nuclear magnetic resonance (NMR) spectroscopy. Different concentrations of particle suspension are added onto an in vitro culture of RAW264.7 mouse macrophages for a total exposure time of 72 hr, along with untreated control cells. At the end of exposure, the culture is treated with colcemid to arrest cells in metaphase. Cells are then harvested, treated with hypotonic solution, fixed in acetomethanol, dropped onto glass slides and finally stained with Giemsa solution. Slides are examined to assess the structural chromosomal aberrations (CAs) in metaphase spreads at 1,000X magnification using a bright-field microscope. 50 to 100 metaphase spread are scored for each treatment group. This technique is adapted for the detection of structural chromosomal aberrations (CAs), such as chromatid-type breaks, chromatid-type exchanges, acentric fragments, dicentric and ring chromosomes, double minutes, endoreduplication, and Robertsonian translocations in vitro after exposure to PM. It is a powerful method to associate a well-established cytogenetic endpoint to epigenetic alterations.

Great care should be taken in choosing the location of the TSP sampler, as well as the time of the year when collection is performed. The chemical composition as well as the size of particles may substantially influence the results. The material collected should be visible against the white filter. A normal mouse metaphase spread will have 40 acentric chromosomes. The goal of the technique is to demonstrate a change (or absence thereof) in the proportion of abnormal chromosomes in treated...

Watch this Scientific Journal Video about Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System at JoVE.com

Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System

This protocol describes techniques for the quantification and characterization of chromosomal aberrations in vitro in RAW264.7 mouse macrophages after treatment with ambient air particulate matter.

Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System

Exposure to particulate matter (PM) is a major world health concern, which may damage various cellular components, including the nuclear genetic material. ...

The overall goal of this experiment, is to detect chromosomal damage induced by exposure of cells to particulate matter, extracted from ambient air. This method can help answer one key question in the field of particulate matter, and that is does particulate matter exposure induce chromosomal damage? The main advantage of this technique, is it allows direct visualization of the damage induced in the genetic material.After collecting and analyzing particles according to the text protocol, carry out particle exposure by warming complete growth medium, 0.25%trypsin, and PBS in a water bath at 37 degrees celsius, for at least 30 minutes before culture initiation. After washing raw 264.7 cells, add one milliliter of the warm trypsin solution to the dish and dislodge the cells from the bottom of the tissue culture vessel by scraping. Then collect the cells and make a single-cell suspension by repeated pipetting.With trypan blue, count the number of cells, then use pre-warmed complete medium to plate them at a density of 8000 per square centimeter in a 100 millimeter tissue culture dish. Then use complete medium to adjust the volume to 10 milliliters for a final concentration of 50, 000 cells per milliliter. Incubate the cells at 37 degrees celsius, and 5%CO2 for 24 hours to allow them to attach.In a bio-safety cabinet, use sterile PBS to dilute filtered particles at a concentration of 0.5 milligrams per milliliter, for a 5 microgram per milliliter treatment dose, and at 5 milligrams per milliliter, for a 50 microgram per milliliter treatment dose. To treat cells with particulate matter, check the cultured cells under a microscope with 10x magnification for cell growth, cell morphology, culture condition, and contamination. The cells should be at least 30%confluent at this stage.Using a sterile pipette, aseptically aspirate the medium and use two milliliters of 37 degrees celsius PBS to wash the culture vessel two times. Add a pre-determined dose of particulate matter with fresh medium and incubate the cultures at 37 degrees celsius and 5%CO2 to parallel the exposure used for concurrent genotoxic and epigenotoxic analysis. To arrest cells at metaphase, after washing the cells add two milliliters of pre-warmed medium with five microliters per milliliter of colcemid solution to the culture, and incubate at 37 degrees celsius and 5%CO2 for two hours.After the incubation, completely remove the medium and use warm PBS to wash the cells two times. Then add trypsin solution and incubate the cultures at 37 degrees celsius for one minute. Using a cell scraper, detach the cells and add 10 milliliters of PBS to inactivate the trypsin.Then pipette the cells up and down at least ten times to create a single-cell suspension, and transfer the cells into a 15 milliliter, conical centrifuge tube. Place the tubes in a swing out centrifuge, and spin the cell suspension at 400 times g and room temperature for five minutes. To carry out hypotonic treatment, remove the supernatant from the tubes without disturbing the cell pellet, and leave approximately 0.5 milliliters of PBS.Gently break the cell pellet and use a P200 pipette to make a single cell suspension. Then add four milliliters of pre-warmed potassium chloride solution drop wise with gentle shaking. Incubate the cell suspension in a 37 degree celsius water bath for 20 minutes.After the hypotonic treatment, fix the cells by adding an equal volume of fixative to the tube, and gently mix by inverting the tube. Centrifuge the tubes at 400 times g at room temperature for five minutes and remove the supernatant. This stage, the cell pellet will have increased in size and become whitish in color and more visible.Remove the supernatant. Add four milliliters of fresh fixative, and incubate the tubes at room temperature for 30 minutes. Then centrifuge the tubes, remove the supernatant, and use four milliliters of fixative to wash the cells two more times.Immerse glass slides completely in 10%liquid detergent for 30 minutes. Then rinse the slides thoroughly in cold running tap water for 30 minutes. Use distilled water to rinse the slides three times to completely remove the detergent.Then immerse them in distilled water, and store the slides in the refrigerator overnight. Drop ten microliters of cell suspension on a chilled wet slide, and allow it to dry overnight at room temperature. To stain and mount the samples, prepare 50 milliters of giemsa staining solution by mixing one part of giemsa stain solution, with one part of PBS, and pour into a coplin jar.Immerse the slides in staining solution for 20 minutes, then rinse the slides in distilled water to remove excess stain, and immediately use a hair dryer to dry the slides. Leave the slides at room temperature overnight. The following morning, apply a single drop of mounting medium on the slide.Gently place a cover slip on top, and allow the mounting medium to slowly spread over the slide. Then use a paper towel to remove excess medium. Finally, use a bright field microscope at 100x magnification to examine the structural chromosomal aberrations in the metaphase spreads.This image shows that a normal mouse metaphase spread, will have 40 acentric chromosomes. Treatment with particulate matter induces various chromosomal aberrations, such as a chromatid break, an acentric fragment, a ring chromosome, a dicentric chromosome, double minutes, a Robertsonian translocation, and an endoreduplication. While attempting this procedure, it is important to remember that only proliferating cells should be used.Following this procedure, other methods, like M-FISH and SKY, can be used to answer additional questions. Like whether inter-chromosomal, stable aberrations are present. Don't forget the cautions and carcinogens, and precautions such as wearing gloves, should always be taking while performing this procedure.

analysis-ambient-particulate-matter-induced-chromosomal-aberrations

Research

JoVE Journal

Genetics

In Vitro Transcription Assays and Their Application in Drug Discovery

In vitro transcription assays have been developed and widely used for many years to study the molecular mechanisms involved in transcription. This process requires multi-subunit DNA-dependent RNA polymerase (RNAP) and a series of transcription factors that act to modulate the activity of RNAP during gene expression. Sequencing gel electrophoresis of radiolabeled transcripts is used to provide detailed mechanistic information on how transcription proceeds and what parameters can affect it. In this paper we describe the protocol to study how the essential elongation factor NusA regulates transcriptional pausing, as well as a method to identify an antibacterial agent targeting transcription initiation through inhibition of RNAP holoenzyme formation. These methods can be used a as platform for the development of additional approaches to explore the mechanism of action of the transcription factors which still remain unclear, as well as new antibacterial agents targeting transcription which is an underutilized drug target in antibiotic research and development.

In Vitro Transcription Assays and Their Application in Drug Discovery

In this manuscript, we describe a protocol to functionally examine transcription and the inhibitory activity of antibacterial agents targeting bacterial transcription.

In vitro transcription assays have been developed and widely used for many years to study the molecular mechanisms involved in transcription. This process ...

Detection of Inter-chromosomal Stable Aberrations by Multiple Fluorescence In Situ Hybridization (mFISH) and Spectral Karyotyping (SKY) in Irradiated Mice

Ionizing radiation (IR) induces numerous stable and unstable chromosomal aberrations. Unstable aberrations, where chromosome morphology is substantially compromised, can easily be identified by conventional chromosome staining techniques. However, detection of stable aberrations, which involve exchange or translocation of genetic materials without considerable modification in the chromosome morphology, requires sophisticated chromosome painting techniques that rely on in situ hybridization of fluorescently labeled DNA probes, a chromosome painting technique popularly known as fluorescence in situ hybridization (FISH). FISH probes can be specific for whole chromosome/s or precise sub-region on chromosome/s. The method not only allows visualization of stable aberrations, but it can also allow detection of the chromosome/s or specific DNA sequence/s involved in a particular aberration formation. A variety of chromosome painting techniques are available in cytogenetics; here two highly sensitive methods, multiple fluorescence in situ hybridization (mFISH) and spectral karyotyping (SKY), are discussed to identify inter-chromosomal stable aberrations that form in the bone marrow cells of mice after exposure to total body irradiation. Although both techniques rely on fluorescent labeled DNA probes, the method of detection and the process of image acquisition of the fluorescent signals are different. These two techniques have been used in various research areas, such as radiation biology, cancer cytogenetics, retrospective radiation biodosimetry, clinical cytogenetics, evolutionary cytogenetics, and comparative cytogenetics.

Detection of Inter-chromosomal Stable Aberrations by Multiple Fluorescence In Situ Hybridization mFISH and Spectral Karyotyping SKY in Irradiated Mice

The present protocol describes the usefulness of multiple fluorescence in situ hybridization (mFISH) and spectral karyotyping (SKY) in identifying inter-chromosomal stable aberrations in the bone marrow cells of mice after exposure to total body irradiation.

Ionizing radiation (IR) induces numerous stable and unstable chromosomal aberrations. Unstable aberrations, where chromosome morphology is substantially ...

Analysis of the c-KIT Ligand Promoter Using Chromatin Immunoprecipitation

Multiple cellular processes, including DNA replication and repair, DNA recombination, and gene expression, require interactions between proteins and DNA. Therefore, DNA-protein interactions regulate multiple physiological, pathophysiological, and biological functions, such as cell differentiation, cell proliferation, cell cycle control, chromosome stability, epigenetic gene regulation, and cell transformation. In eukaryotic cells, the DNA interacts with histone and nonhistone proteins and is condensed into chromatin. Several technical tools can be used to analyze DNA-protein interactions, such as the Electrophoresis (gel) Mobility Shift Assay (EMSA) and DNase I footprinting. However, these techniques analyze the protein-DNA interaction in vitro, not within the cellular context. Chromatin immunoprecipitation (ChIP) is a technique that captures proteins at their specific DNA binding sites, thereby allowing for the identification of DNA-protein interactions within their chromatin context. It is done by fixation&#160;of the DNA-protein interaction, followed by&#160;immunoprecipitation of the protein of interest. Subsequently, the genomic site that the protein was bound to is characterized. Here, we describe and discuss ChIP and demonstrate its analytical value for the identification of the Transforming Growth Factor-&#946; (TGF-&#946;)-induced binding of the transcription factor SMAD2 to SMAD Binding Elements (SBE) within the promoter region of the tyrosine-protein kinase Kit (c-KIT) receptor ligand Stem Cell Factor (SCF).

DNA-protein interactions are essential for multiple biological processes. During the evaluation of cellular functions, the analysis of DNA-protein interactions is indispensable for understanding gene regulation. Chromatin immunoprecipitation (ChIP) is a powerful tool to analyze such interactions in vivo.

Multiple cellular processes, including DNA replication and repair, DNA recombination, and gene expression, require interactions between proteins and DNA. ...

Determination of the Optimal Chromosomal Location(s) for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach

The optimal chromosomal position(s) of a given DNA element was/were determined by transposon-mediated random insertion followed by fitness selection. In bacteria, the impact of the genetic context on the function of a genetic element can be difficult to assess. Several mechanisms, including topological effects, transcriptional interference from neighboring genes, and/or replication-associated gene dosage, may affect the function of a given genetic element. Here, we describe a method that permits the random integration of a DNA element into the chromosome of Escherichia coli and select the most favorable locations using a simple growth competition experiment. The method takes advantage of a well-described transposon-based system of random insertion, coupled with a selection of the fittest clone(s) by growth advantage, a procedure that is easily adjustable to experimental needs. The nature of the fittest clone(s) can be determined by whole-genome sequencing on a complex multi-clonal population or by easy gene walking for the rapid identification of selected clones. Here, the non-coding DNA region DARS2, which controls the initiation of chromosome replication in E. coli, was used as an example. The function of DARS2 is known to be affected by replication-associated gene dosage; the closer DARS2 gets to the origin of DNA replication, the more active it becomes. DARS2 was randomly inserted into the chromosome of a DARS2-deleted strain. The resultant clones containing individual insertions were pooled and competed against one another for hundreds of generations. Finally, the fittest clones were characterized and found to contain DARS2 inserted in close proximity to the original DARS2 location.

Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach

Here, the power of a transposon-mediated random insertion of a non-coding DNA element was used to resolve its optimal chromosomal position.

The optimal chromosomal position(s) of a given DNA element was/were determined by transposon-mediated random insertion followed by fitness selection. In ...

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA mutation rates. Changes in replication timing occur during development and in cancer, but the role replication timing plays in development and disease is not known. Zebrafish were recently established as an in vivo model system to study replication timing. Here is detailed the protocols for using the zebrafish to determine DNA replication timing. After sorting cells from embryos and adult zebrafish, high-resolution genome-wide DNA replication timing patterns can be constructed by determining changes in DNA copy number through analysis of next generation sequencing data. The zebrafish model system allows for evaluation of the replication timing changes that occur in vivo throughout development, and can also be used to assess changes in individual cell types, disease models, or mutant lines. These methods will enable studies investigating the mechanisms and determinants of replication timing establishment and maintenance during development, the role replication timing plays in mutations and tumorigenesis, and the effects of perturbing replication timing on development and disease.

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

Zebrafish were recently used as an in vivo model system to study DNA replication timing during development. Here is detailed the protocols for using zebrafish embryos to profile replication timing. This protocol can be easily adapted to study replication timing in mutants, individual cell types, disease models, and other species.

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA ...

CRISPR-Mediated Reorganization of Chromatin Loop Structure

Recent studies have clearly shown that long-range, three-dimensional chromatin looping interactions play a significant role in the regulation of gene expression, but whether looping is responsible for or a result of alterations in gene expression is still unknown. Until recently, how chromatin looping affects the regulation of gene activity and cellular function has been relatively ambiguous, and limitations in existing methods to manipulate these structures prevented in-depth exploration of these interactions. To resolve this uncertainty, we engineered a method for selective and reversible chromatin loop re-organization using CRISPR-dCas9 (CLOuD9). The dynamism of the CLOuD9 system has been demonstrated by successful localization of CLOuD9 constructs to target genomic loci to modulate local chromatin conformation. Importantly, the ability to reverse the induced contact and restore the endogenous chromatin conformation has also been confirmed. Modulation of gene expression with this method establishes the capacity to regulate cellular gene expression and underscores the great potential for applications of this technology in creating stable de novo chromatin loops that markedly affect gene expression in the contexts of cancer and development.

Chromatin looping plays a significant role in gene regulation; however, there have been no technological advances that allow for selective and reversible modification of chromatin loops. Here we describe a powerful system for chromatin loop re-organization using CRISPR-dCas9 (CLOuD9), demonstrated to selectively and reversibly modulate gene expression at targeted loci.

Recent studies have clearly shown that long-range, three-dimensional chromatin looping interactions play a significant role in the regulation of gene ...

Measuring Exercise Levels in Drosophila melanogaster Using the Rotating Exercise Quantification System (REQS)

Drosophila melanogaster is a new model organism for studies in exercise biology. To date, two main exercise systems, the Power Tower and the Treadwheel have been described. However, a method to measure the amount of additional animal activity induced through the exercise treatment has been lacking. The Rotating Exercise Quantification System (REQS) fills this need, providing a measure of animal activity for animals experiencing rotational exercise. This protocol details how to use the REQS to assess animal activity during rotational exercise and illustrates the type of data that can be generated. Here, we demonstrate how the REQS is used to measure sex- and strain-specific differences in exercise induced activity. The REQS can also be used to evaluate the impact of various other experimental parameters such as age, diet, or population size on exercise induced activity. In addition, it can be used to compare the efficacy of different exercise training protocols. Importantly, it provides an opportunity to standardize exercise treatments between strains, allowing the researcher to achieve equal amounts of activity between groups if needed. Thus, the REQS is a notable new resource for exercise biologists working with the Drosophila model system and complements existing exercise systems.

Measuring Exercise Levels in Drosophila melanogaster Using the Rotating Exercise Quantification System REQS

The Rotating Exercise Quantification System (REQS) can induce exercise in Drosophila melanogaster through rotation while simultaneously measuring the amount of activity performed by the animals. Here, we present a point-by-point protocol detailing how to measure activity levels of animals experiencing rotational exercise treatments using the REQS.

Drosophila melanogaster is a new model organism for studies in exercise biology. To date, two main exercise systems, the Power Tower and the Treadwheel ...

Using In Vitro and In-cell SHAPE to Investigate Small Molecule Induced Pre-mRNA Structural Changes

In the process of drug development of RNA-targeting small molecules, elucidating the structural changes upon their interactions with target RNA sequences is desired. We herein provide a detailed in vitro and in-cell selective 2&#39;-hydroxyl acylation analyzed by primer extension (SHAPE) protocol to study the RNA structural change in the presence of an experimental drug for spinal muscular atrophy (SMA), survival of motor neuron (SMN)-C2, and in exon 7 of the pre-mRNA of the SMN2 gene. In in vitro SHAPE, an RNA sequence of 140 nucleotides containing SMN2 exon 7 is transcribed by T7 RNA polymerase, folded in the presence of SMN-C2, and subsequently modified by a mild 2&#39;-OH acylation reagent, 2-methylnicotinic acid imidazolide (NAI). This 2&#39;-OH-NAI adduct is further probed by a 32P-labeled primer extension and resolved by polyacrylamide gel electrophoresis (PAGE). Conversely, 2&#39;-OH acylation in in-cell SHAPE takes place in situ with SMN-C2 bound cellular RNA in living cells. The pre-mRNA sequence of exon 7 in the SMN2 gene, along with SHAPE-induced mutations in the primer extension, was then amplified by PCR and subject to next-generation sequencing. Comparing the two methodologies, in vitro SHAPE is a more cost-effective method and does not require computational power to visualize results. However, the in vitro SHAPE-derived RNA model sometimes deviates from the secondary structure in a cellular context, likely due to the loss of all interactions with RNA-binding proteins. In-cell SHAPE does not need a radioactive material workplace and yields a more accurate RNA secondary structure in the cellular context. Furthermore, in-cell SHAPE is usually applicable for a larger range of RNA sequences (~1,000 nucleotides) by utilizing next-generation sequencing, compared to in vitro SHAPE (~200 nucleotides) that usually relies on PAGE analysis. In case of exon 7 in SMN2 pre-mRNA, the in vitro and in-cell SHAPE derived RNA models are similar to each other.

Detailed protocols for both in vitro and in-cell selective 2&#39;-hydroxyl acylation analyzed by primer extension (SHAPE) experiments to determine the secondary structure of pre-mRNA sequences of interest in the presence of an RNA-targeting small molecule are presented in this article.

In the process of drug development of RNA-targeting small molecules, elucidating the structural changes upon their interactions with target RNA sequences ...

The Use of Mouse Mammary Tumor Cells in an In Vitro Invasion Assay as a Measure of Oncogenic Cell Behavior

The in vitro invasion assay uses a protein-rich matrix in a Boyden chamber to measure the ability of cultured cells to pass through the matrix and a porous membrane in a process analogous to the initial steps of cancer cell metastasis. The tested cells can be altered for the gene expression or treated with inhibitors to test for changes in the invasion potential. This experiment tests the aggressive phenotype of the mouse mammary tumor cells to discover and characterize the potential oncogenes that promote cell invasion. This technique, however, can be versatile and adapted to many different applications. The experiment itself can be done in one day and the results are acquired by light microscopy in less than a day. The results include counts of the number of invading cells for comparison and analysis. The in vitro invasion assay is a rapid, inexpensive, and clear-cut method for determining cell behavior in a culture that can be used as an initial assessment before more involved in vivo assays.

The in vitro cell invasion assay is used to measure the potential of cancer metastasis by quantifying the cellular potential for invasion and migration using cell culture inserts containing protein matrix. Cells are challenged to migrate through the protein matrix and a porous membrane, towards a chemoattractant, and then quantified by light microscopy.

The in vitro invasion assay uses a protein-rich matrix in a Boyden chamber to measure the ability of cultured cells to pass through the matrix and a ...

In Vitro Biochemical Assays using Biotin Labels to Study Protein-Nucleic Acid Interactions

Protein-nucleic acid interactions play important roles in biological processes such as transcription, recombination, and RNA metabolism. Experimental methods to study protein-nucleic acid interactions require the use of fluorescent tags, radioactive isotopes, or other labels to detect and analyze specific target molecules. Biotin, a non-radioactive nucleic acid label, is commonly used in electrophoretic mobility shift assays (EMSA) but has not been regularly employed to monitor protein activity during nucleic acid processes. This protocol illustrates the utility of biotin labeling during in vitro enzymatic reactions, demonstrating that this label works well with a range of different biochemical assays. Specifically, in alignment with previous findings using radioisotope 32P-labeled substrates, it is confirmed via biotin-labeled EMSA that MEIOB (a protein specifically involved in the meiotic recombination) is a DNA-binding protein, that MOV10 (an RNA helicase) resolves biotin-labeled RNA duplex structures, and that MEIOB cleaves biotin-labeled single-stranded DNA. This study demonstrates that biotin is capable of substituting 32P in various nucleic acid-related biochemical assays in vitro.&#160;

Presented here are protocols for in vitro biochemical assays using biotin labels that may be widely&#160;applicable for studying protein-nucleic acid interactions.

Protein-nucleic acid interactions play important roles in biological processes such as transcription, recombination, and RNA metabolism. Experimental ...