This work is supported by NIH grant R00 CA160574 (SFB) and by a fellowship of the Rutgers Biotechnology Training Program (to SMM).

This procedure was approved by the Institutional Animal Care and Use Committee at Rutgers, the State University of New Jersey. Mice were treated in accordance with the NIH Guide for the Care and Use of Laboratory Animals. Scientists should consult their national and institutional animal organizations for established and approved guidelines.
Before beginning, prepare the solutions listed in Table 1.
1. B Cell Isolation and Activation
Euthanize a mouse using CO2 followed by cervical dislocation. Position the mouse so the left side of the body is up and spray the mouse with 70% ethanol until the fur is damp. Dissect the spleen and place in a 35 mm tissue culture dish with 2 ml wash buffer. In a laminar flow hood, gently break up the spleen in the tissue culture dish using the flat end of a 5 ml syringe.
<ol>
	<li>Insert a 70 &#956;m nylon mesh into a 50 ml tube and transfer the spleen sample in 2 ml wash buffer into the nylon mesh. Gently disrupt the spleen in the mesh using the flat end of the syringe.</li>
	<li>Rinse the back of the syringe and the 35 mm plate with 8 ml of wash buffer and filter through the 70 &#956;m nylon mesh. Centrifuge at 300 x g for 10 min at 4 &#176;C.</li>
	<li>Aspirate and discard the supernatant and resuspend the pellet in 3 ml of ACK lysis buffer. Pipette up and down briefly to disrupt clumps and incubate for 5 min. Add 10 ml of wash buffer and centrifuge at 300 x g for 10 min at 4 &#176;C.</li>
	<li>Aspirate and discard the supernatant and resuspend the pellet by tapping the bottom of the tube then by pipetting in 1 ml of wash buffer. Add 50 &#956;l of anti-CD43 MACS micro-beads and incubate on ice for 30 min. Add 10 ml of wash buffer, mix gently, and centrifuge at 300 x g for 10 min at 4 &#176;C. Add 10 ml of wash buffer, mix gently, and centrifuge at 300 x g for 10 min at 4 &#176;C.</li>
	<li>Set up a Mini-MACS column by placing a column on the MACS magnet. Position a labeled 15 ml conical tube below the column. Add 1 ml of wash buffer to column and allow to run through to the 15 ml tube.</li>
	<li>Aspirate the supernatant and resuspend in 1 ml of wash buffer. Load the sample in the column after the wash buffer has run through.</li>
	<li>After the sample has run through the column, add 1 ml wash buffer to wash the column. Add 7 ml of wash buffer directly to the collected sample in the 15 ml tube.</li>
	<li>Count the cells using a hemocytometer. Transfer the required volume of cells needed for 5,000,000 cells/well into a 50 ml tube. Centrifuge at 300 x g for 10 min at 4 &#176;C. Supplement B cell medium with LPS 1:500 and IL4 1:1,000.</li>
	<li>Aspirate the supernatant and add the appropriate volume of supplemented B cell medium needed for final concentration of 1,000,000 cells/ml.</li>
	<li>Plate cells in 6-well plates with 5 ml of cells at 1,000,000 cell/ml and place in a humidified cell culture incubator at 37 &#176;C, 5% CO2.</li>
</ol>
2. B Cell Fixation
<ol>
	<li>Add 50 &#956;l of colcemid to the well containing 5 ml of B cells (for a final concentration of 100 ng/ml) and incubate 1 hr at 37 &#176;C. Prewarm 75 mM KCl solution in a 37 &#176;C water bath. Transfer the B cells to a labeled 15 ml tube. Cover the label with tape and centrifuge at 300 x g for 10 min at 4 &#176;C.</li>
	<li>Aspirate the supernatant leaving 1 ml in the tube and resuspend the pellet by pipetting. Add 5 ml of the prewarmed KCl drop by drop while tapping or pulsing on a vortex.</li>
	<li>Add 10 ml of KCl and mix by inverting. Incubate in a 37 &#176;C water bath for 15 min. Add 5 drops of fresh fixative and mix by inverting. Centrifuge at 300 x g for 10 min at 4 &#176;C. Aspirate the supernatant leaving 1 ml in the tube and resuspend pellet by pipetting up and down.</li>
	<li>Add 5 ml of fresh fixative drop by drop while tapping or pulsing on a vortex. Add an additional 10 ml of fixative and incubate for 30 min at room temperature.</li>
	<li>Centrifuge at 300 x g for 10 min at 4 &#176;C. Aspirate the supernatant leaving 1 ml in tube and resuspend by pipetting. Add 14 ml of fresh fixative and centrifuge at 300 x g for 10 min at 4 &#176;C.</li>
	<li>Repeat step 2.7 twice more.</li>
	<li>Add 14 ml of fresh fixative. Seal the caps with Parafilm and store overnight at -20 &#176;C.</li>
</ol>
3. Preparation of Metaphase Chromosome Spreads
<ol>
	<li>Set a regulated environmental chamber to 22.9 &#176;C and 52% humidity.</li>
	<li>Centrifuge the fixed B cells at 300 x g for 10 min at 4 &#176;C. Aspirate fixative leaving 70 &#956;l in the tube and resuspend by pipetting.</li>
	<li>Place labeled slides in the humidity chamber at a 35&#176; angle. Drop 35 &#956;l of the resuspended B cells onto a slide and drop two slides per sample. Allow the slides to dry in the humidity chamber for 30 min then store the slides in a slide box at 37 &#176;C.</li>
</ol>
4. Telomere PNA FISH
<ol>
	<li>Preparation of Probe
	<ol>
		<li>Pre-warm deionized formamide to 37 &#176;C. Mix 2 &#956;l of telomere PNA probe with 7 &#956;l deionized pre-warmed formamide and incubate at 37 &#176;C with shaking for 1 hr.</li>
		<li>Pre-warm FISH master mix to 37 &#176;C. Add 7 &#956;l pre-warmed FISH master mix to the mixture from step 4.1.1 and incubate at 37 &#176;C for 1-3 hr.</li>
		<li>Denature the probe mixture for 8 min at 80 &#176;C. Pre-anneal the probe for 1 hr at 37 &#176;C.</li>
	</ol>
	</li>
	<li>Pretreatment of Chromosome Slides
	<ol>
		<li>Pre-warm a glass slide-staining jar containing 50 ml of 0.01 M HCl to 37 &#176;C in a water bath.</li>
		<li>Place slides in a different glass slide-staining jar containing 2x SSC for 5 min at room temperature.</li>
		<li>Add 2 &#956;l of pepsin stock to the pre-warmed glass slide-staining jar and mix by inverting. Transfer the slides to this glass slide-staining jar and incubate 90 sec at 37 &#176;C.</li>
		<li>Wash the slides 2x in a different glass slide-staining jar containing 1x PBS for 5 min each at room temperature, shaking. Then wash the slides for 5 min in 1x PBS/MgCl2 at room temperature, shaking.</li>
		<li>Transfer the slides to a glass slide-staining jar containing freshly-prepared 1% formaldehyde/1x PBS/MgCl2 for 10 min at room temperature.</li>
		<li>Wash the slides for 5 min in a different glass slide-staining jar containing 1x PBS at room temperature, shaking.</li>
		<li>Prepare an ethanol dehydration series by having separate glass slide-staining jars containing 70%, 90%, and 100% ethanol.</li>
		<li>Transfer the slides to each jar for 3 min, starting with 70% ethanol, then 90% ethanol, and then 100% ethanol. Place ethanol jars at -20 &#176;C when finished.</li>
		<li>Allow the slides to air dry by tapping excess ethanol onto a paper towel and propping slides at a 35&#176; angle. Once dry, mark an 18 x 18 mm area for hybridization on the back of the slides using a diamond pen.</li>
	</ol>
	</li>
	<li>Denaturation of Slides for FISH
	<ol>
		<li>Apply 120 &#956;l 70% deionized formamide/2X SSC to a 24 x 60 mm coverslip. Touch the slide to the coverslip. Denature the slide at 80 &#176;C on a hot plate for 90 sec.</li>
		<li>Quickly and carefully slide off the coverslip and place the slide in ice cold 70% ethanol for 3 min, followed by 90% ethanol, and 100% ethanol each for 3 min. Allow the slides to air dry.</li>
		<li>Prepare a humid chamber by lining a plastic box with a tight lid and wet tissue paper. The paper should be damp, but not saturated with water.</li>
		<li>In a humid chamber, apply the pre-annealed probe mix from step 4.1.3 to the marked area on the slide, cover with an 18 x 18 mm cover slip and incubate at 37 &#176;C for 1 hr.</li>
	</ol>
	</li>
	<li>Post-incubation Washes
	<ol>
		<li>Pre-warm 50% formamide/2x SSC, 1x SSC, and 4x SSC/0.1% Tween-20 in a 45 &#176;C water bath.</li>
		<li>Carefully remove the coverslips and wash the slides in pre-warmed 50% formamide/2x SSC 3xfor 5 min each in the dark and shaking. Wash the slides in pre-warmed 1x SSC 3xfor 5 min each, shaking. Finally, wash the slides in pre-warmed 4x SSC/0.1% Tween-20 3xfor 5 min each.</li>
		<li>Stain the slides for 3 min in DAPI in a light protected glass slide-staining jar.</li>
		<li>Wash the slides for 5 min in 2x SSC, shaking. Apply 35 &#956;l of Mowiol mounting medium, cover with 24 x 60 mm coverslips and store the slides at 4 &#176;C.</li>
	</ol>
	</li>
</ol>
5. Microscopic Analysis of Chromosomes
<ol>
	<li>Analyze the metaphase slides using a standard epi-fluorescence microscope. Use an imaging platform with an automated stage such as the MetaSystems Metafer platform to obtain best results. For each metaphase spread, collect one image for DAPI fluorescence to visualize chromosomes, and one image for the fluorescent signal from the telomere probe. (e.g., Cy3- other fluors are available and work equally well.)</li>
	<li>Overlay the images with an image analysis program and analyze.</li>
</ol>

<ol>
	<li>Sancar, A., Lindsey-Boltz, L. A., Unsal-Kacmaz, K., Linn, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+mammalian+DNA+repair+and+the+DNA+damage+checkpoints.">Molecular mechanisms of mammalian DNA repair and the DNA damage checkpoints.</a> Ann Rev Biochem. 73, 39-85 (2004).</li><li>Sperka, T., Wang, J., Rudolph, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+damage+checkpoints+in+stem+cells,+ageing+and+cancer.">DNA damage checkpoints in stem cells, ageing and cancer.</a> Nature reviews Mol Cell Biol. 13 (9), 579-590 (2012).</li><li>Alexandrov, L. B., 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=Signatures+of+mutational+processes+in+human+cancer.">Signatures of mutational processes in human cancer.</a> Nature. 500 (7463), 415-421 (2013).</li><li>Bunting, S. F., 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=53BP1+inhibits+homologous+recombination+in+Brca1-deficient+cells+by+blocking+resection+of+DNA+breaks.">53BP1 inhibits homologous recombination in Brca1-deficient cells by blocking resection of DNA breaks.</a> Cell. 141 (2), 243-254 (2010).</li><li>Padilla-Nash, H. M., Barenboim-Stapleton, L., Difilippantonio, M. J., Ried, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectral+karyotyping+analysis+of+human+and+mouse+chromosomes.">Spectral karyotyping analysis of human and mouse chromosomes.</a> Nat Protoc. 1 (6), 3129-3142 (2006).</li><li>Callen, E., 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=Chimeric+IgH-TCRalpha/delta+translocations+in+T+lymphocytes+mediated+by+RAG.">Chimeric IgH-TCRalpha/delta translocations in T lymphocytes mediated by RAG.</a> Cell Cycle. 8 (15), 2408-2412 (2009).</li><li>Boboila, C., 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=Alternative+end-joining+catalyzes+robust+IgH+locus+deletions+and+translocations+in+the+combined+absence+of+ligase+4+and+Ku70.">Alternative end-joining catalyzes robust IgH locus deletions and translocations in the combined absence of ligase 4 and Ku70.</a> Natl Acad Sci USA. 107 (7), 3034-3039 (2010).</li><li>Benn, P., Delach, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+lymphocyte+culture+and+chromosome+analysis.">Human lymphocyte culture and chromosome analysis.</a> Cold Spring Harb Protoc. 2008, (2008).</li><li>Nguyen, H. N., Reijo Pera, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metaphase+spreads+and+spectral+karyotyping+of+human+embryonic+stem+cells.">Metaphase spreads and spectral karyotyping of human embryonic stem cells.</a> Cold Spring Harb Protoc. 2008, (2008).</li><li>Schreck, R. R., Disteche, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+4.">Chapter 4.</a> Chromosome banding techniques. Unit 2, (2001).</li><li>Gilley, D., 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=DNA-PKcs+is+critical+for+telomere+capping.">DNA-PKcs is critical for telomere capping.</a> Proc Natl Acad Sci USA. 98 (26), 15084-15088 (2001).</li><li>Bolzan, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosomal+aberrations+involving+telomeres+and+interstitial+telomeric+sequences.">Chromosomal aberrations involving telomeres and interstitial telomeric sequences.</a> Mutagenesis. 27 (1), 1-15 (2012).</li><li>Bolzan, A. D., Telomeres Bianchi, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=interstitial+telomeric+repeat+sequences+and+chromosomal+aberrations.">interstitial telomeric repeat sequences and chromosomal aberrations.</a> Mutat Res. 612 (3), 189-214 (2006).</li><li>Poon, S. S., Lansdorp, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+18.">Chapter 18.</a> Quantitative fluorescence in situ hybridization (Q-FISH). Unit 18 14, (2001).</li><li>Morales, J. C., 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=53BP1+and+p53+synergize+to+suppress+genomic+instability+and+lymphomagenesis.">53BP1 and p53 synergize to suppress genomic instability and lymphomagenesis.</a> Proc Natl Acad Sci USA. 103 (9), 3310-3315 (2006).</li><li>Halaby, M. 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=Synergistic+interaction+of+Rnf8+and+p53+in+the+protection+against+genomic+instability+and+tumorigenesis.">Synergistic interaction of Rnf8 and p53 in the protection against genomic instability and tumorigenesis.</a> PLoS Genet. 9 (1), e1003259 (2013).</li></ol>

The authors have no conflicting interests.

Whereas activated B lymphocytes are particularly suited to preparation of mitotic chromosome spreads, other cell types can also be used. T lymphocytes share many of the advantages of B cells, as they can be purified from the spleen or lymph nodes, and have a high mitotic index when stimulated by growth in medium containing appropriate mitogens8. Embryonic Stem cells (ES cells) are also suited for metaphase chromosome analysis9. If these are not available, fibroblast cells can be used, although a lon...

A correction was made to: Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH.&#160;Table 1 (the list of solutions to prepare) was omitted from the Protocol section. The contents of Table 1 are as follows:
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Solution</td>
			<td>Reagents</td>
			<td>Comments</td>
			<td>Storage</td>
		</tr>
		<tr>
			<td rowspan="3">B Cell Wash Buffer</td>
			<td>500 ml 1x Hanks Balanced Salt Solution</td>
			<td rowspan="3">Filter through 0.22 &#956;m stericup filtration unit</td>
			<td rowspan="3">4 &#176;C</td>
		</tr>
		<tr>
			<td>5 ml 50 &#176;C heat inactivated FCS</td>
		</tr>
		<tr>
			<td>5 ml 100x Pen/Strep</td>
		</tr>
		<tr>
			<td rowspan="8">B Cell Medium</td>
			<td>418.5 ml RPMI-1640</td>
			<td rowspan="8">Filter through 0.22 &#956;m stericup filtration unit</td>
			<td rowspan="8">4 &#176;C</td>
		</tr>
		<tr>
			<td>50 ml 50 &#176;C heat inactivated FCS</td>
		</tr>
		<tr>
			<td>5 ml 100x Pen/Strep</td>
		</tr>
		<tr>
			<td>5 ml glutamine</td>
		</tr>
		<tr>
			<td>5 ml nonessential amino acids</td>
		</tr>
		<tr>
			<td>5 ml sodium pyruvate</td>
		</tr>
		<tr>
			<td>1.8 ml 14.2 M 2-mercaptoethanol</td>
		</tr>
		<tr>
			<td>5 ml 1M HEPES</td>
		</tr>
		<tr>
			<td>Fixative</td>
			<td>3:1 v/v methanol/glacial acetic acid</td>
			<td></td>
			<td>Make fresh</td>
		</tr>
		<tr>
			<td rowspan="2">0.075 M KCl</td>
			<td>1.395 g KCl</td>
			<td rowspan="2"></td>
			<td rowspan="2">Room Temperature</td>
		</tr>
		<tr>
			<td>250 ml distilled H2O</td>
		</tr>
		<tr>
			<td rowspan="3">FISH Master Mix</td>
			<td>40 ml 50% Dextran sulfate</td>
			<td rowspan="3">Vortex the solution and leave in a shaking platform overnight</td>
			<td rowspan="3">Aliquot and store at -20 &#176;C</td>
		</tr>
		<tr>
			<td>20 ml 20x SSC</td>
		</tr>
		<tr>
			<td>40 ml sterile distilled H2O</td>
		</tr>
		<tr>
			<td rowspan="3">70% Formamide/2x SSC</td>
			<td>10 ml 20x SSC</td>
			<td rowspan="3">Adjust to pH 7 with 1M HCl</td>
			<td rowspan="3">Aliquot and store at -20 &#176;C</td>
		</tr>
		<tr>
			<td>20 ml distilled H2O</td>
		</tr>
		<tr>
			<td>70 ml deionized formamide</td>
		</tr>
		<tr>
			<td rowspan="2">0.01 M HCl</td>
			<td>1 ml 1M HCl</td>
			<td rowspan="2">Adjust to pH 2.0</td>
			<td rowspan="2">Room Temperature</td>
		</tr>
		<tr>
			<td>99 ml distilled H2O</td>
		</tr>
		<tr>
			<td rowspan="2">1x PBS/MgCl2</td>
			<td>50 ml 1M MgCl2</td>
			<td rowspan="2"></td>
			<td rowspan="2">Room Temperature</td>
		</tr>
		<tr>
			<td>950 ml 1x PBS</td>
		</tr>
		<tr>
			<td rowspan="3">50% Formamide/2x SSC</td>
			<td>20 ml 20x SSC</td>
			<td rowspan="3">Adjust to pH 7.25 
			Formamide used in this step does not have to be deionized.</td>
			<td rowspan="3">Make fresh</td>
		</tr>
		<tr>
			<td>80 ml distilled H2O</td>
		</tr>
		<tr>
			<td>100 ml formamide</td>
		</tr>
		<tr>
			<td rowspan="3">4x SSC/0.1% Tween20</td>
			<td>50 ml 20x SSC</td>
			<td rowspan="3"></td>
			<td rowspan="3">Room Temperature</td>
		</tr>
		<tr>
			<td>200 ml distilled H2O</td>
		</tr>
		<tr>
			<td>250 &#956;l Tween20</td>
		</tr>
		<tr>
			<td rowspan="2">DAPI staining solution (80 ng/ml)</td>
			<td>40 &#956;l 0.2mg/ml DAPI stock</td>
			<td rowspan="2"></td>
			<td rowspan="2">4 &#176;C in light protected staining jar</td>
		</tr>
		<tr>
			<td>100 ml 2x SSC</td>
		</tr>
		<tr>
			<td rowspan="5">Mowiol Mounting Medium</td>
			<td>6 g glycerol</td>
			<td rowspan="5">Incubate at 50 &#176;C with stirring for 2hrs</td>
			<td rowspan="5">Aliquot and store at 4 &#176;C</td>
		</tr>
		<tr>
			<td>2.4 g Mowiol 4-88</td>
		</tr>
		<tr>
			<td>6 ml distilled H2O</td>
		</tr>
		<tr>
			<td>12 ml 0.2 M TrisCl pH 8.5</td>
		</tr>
		<tr>
			<td>230 &#956;l 1% Thimerosal (w/v in water)</td>
		</tr>
	</tbody>
</table>
Table 1. List of solutions.&#160;

A correction was made to: Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH.

Erratum: Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH

Cancer is caused by the accumulation of mutations affecting genes that regulate normal cell growth. Mutation is a consequence of changes to the structure and sequence of the genome caused by damage to DNA. DNA damage can occur through a variety of process, including exogenous agents such as ionizing radiation, and as a by-product of normal cellular metabolism, such as spontaneous deamination of nucleotide bases or damage occurring by contact with reactive oxygen species1.
Although mammalian cells possess a range of repair activities which can reverse DNA damage or restore the sequence at break sites, mutations nonetheless accumulate throughout the lifetime of a cell. DNA damage can furthermore contribute to senescence and loss of potency of stem cells, two processes which are associated with aging-associated disease2. Understanding the repair of DNA damage is therefore of central importance in addressing two significant issues in public health. Increasing evidence suggests that mammalian DNA repair pathways can contribute to the evolution of the cancer cell genome3,4, making it even more imperative to understand the processes involved in suppressing mutation at the molecular level.
Direct visualization of chromosome aberrations is a powerful and quantitative means of determining the extent of genomic instability in a particular cell type. Condensed chromosomes from cells at metaphase can be isolated and inspected using light or fluorescent microscopy. Such cytogenetic approaches have been in practice for several decades and can be used to demonstrate the appearance of translocations or specific types of chromosome aberrations associated with loss of DNA repair activities. The protocol lends itself to several potential extensions: chromosomes can be labeled with probes for spectral karyotyping (SKY) or multicolor fluorescent in situ hybridization (mFISH) to identify translocations5,6. These techniques also enable the frequency of chromosome translocations and the structure of complex chromosome translocations to be determined, which provides additional information beyond what is possible with this protocol. Alternatively, sequence-specific probes can be generated and used to test the frequency of DNA breakage at selected genomic sites7.
In this protocol, we describe preparation of metaphase chromosome spreads from B lymphocytes. A fluorescently-labeled peptide nucleic acid (PNA) probe for telomeric repeats is used, which efficiently marks telomeres in metaphase chromosome spreads This protocol has several advantages. B cells can be induced to grow at high mitotic index so that high-quality spreads can consistently be produced. B cells from genetically-modified mice are also much less likely to contain secondary genetic mutations that can confound the analysis of the contribution of specific genes to genomic integrity. The PNA-FISH approach can be completed in one day, and allows more accurate scoring of chromosome breaks. By using this approach, particularly in combination with specific equipment described in this protocol, it is possible to produce very consistent, high-quality spreads and rapidly analyze the rate and type of genomic instability.

<table border="0" cellpadding="0" cellspacing="0" width="679">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Name</td>
			<td style="width:116px;">Company&#160;</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:176px;">&#160;Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">50% Dextran sulfate</td>
			<td>Intergen</td>
			<td>S4030</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Deionized formamide&#160;</td>
			<td>Ambion</td>
			<td>9342</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pepsin (5g)</td>
			<td>Sigma</td>
			<td>P 6887&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FCS</td>
			<td>Gemini</td>
			<td>100-106</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LPS (100mg)</td>
			<td>Sigma</td>
			<td>L2630</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">IL-4 (5&#956;g)</td>
			<td>Sigma</td>
			<td>I1020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PNA Telomere Probe</td>
			<td>PNA Bio Inc</td>
			<td>F1002</td>
			<td>(CCCTAACCCTAACCCTAA)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Colcemid</td>
			<td>Roche</td>
			<td>295892</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mowiol 4-88</td>
			<td>Sigma</td>
			<td>81381-50g</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CD43 (ly-48_) micro-beads</td>
			<td>Miltenyl Biotec.&#160;</td>
			<td>130-049-801</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAPI</td>
			<td>Sigma</td>
			<td>32670-5MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Eclipse E800</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AxioImager.Z2</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CDS-5 Cytogenetic Drying Chamber</td>
			<td>Thermotron</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

rapid analysis of chromosome aberrations in mouse b lymphocytes by pna-fish

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.

Metaphase chromosomes derived from one cell should form a discrete cluster containing 40 chromosomes (if using mouse cells) (Figure 1A). Each chromosome has a centromere at one end, which is visible as a light blue sphere. In normal chromosomes, two telomere signals are seen at the end of the chromatids and two signals by each centromere. Interphase nuclei will be present on the slide as well. These will be visible as blue spheres, with red telomere signals, but no condensed chromosomes (see for example ...

Watch this Scientific Journal Video about Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH at JoVE.com

Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH

DNA repair pathways are essential for maintenance of genomic integrity and preventing mutation and cancer. The goal of this protocol is to quantify genomic instability by direct observation of chromosome aberrations in metaphase spreads from mouse B cells using fluorescent in situ hybridization (FISH) for telomeric DNA repeats.

Defective DNA repair leads to increased genomic instability, which is the root cause of mutations that lead to tumorigenesis. Analysis of the frequency ...

rapid-analysis-chromosome-aberrations-mouse-b-lymphocytes-pna

Research

JoVE Journal

Immunology and Infection

16.8K Views.  Rutgers, the State University of New Jersey. DNA repair pathways are essential for maintenance of genomic integrity and preventing mutation and cancer. The goal of this protocol is to quantify genomic instability by direct observation of chromosome aberrations in metaphase spreads from mouse B cells using fluorescent in situ hybridization (FISH) for telomeric DNA repeats.

Video: Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in situ hybridization (FISH) for rapid culture-independent detection of Salmonella spp. Cell-charged tapes can also be placed face-down on selective agar for solid-phase enrichment prior to detection. Alternatively, low-volume liquid enrichments (liquid surface miniculture) can be performed on the surface of the tape in non-selective broth, followed by FISH and analysis via flow cytometry. To begin, sterile adhesive tape is brought into contact with fresh produce, gentle pressure is applied, and the tape is removed, physically extracting microbes present on these surfaces. Tapes are mounted sticky-side up onto glass microscope slides and the sampled cells are fixed with 10% formalin (30 min) and dehydrated using a graded ethanol series (50, 80, and 95%; 3 min each concentration). Next, cell-charged tapes are spotted with buffer containing a Salmonella-targeted DNA probe cocktail and hybridized for 15 - 30 min at 55&deg;C, followed by a brief rinse in a washing buffer to remove unbound probe. Adherent, FISH-labeled cells are then counterstained with the DNA dye 4',6-diamidino-2-phenylindole (DAPI) and results are viewed using fluorescence microscopy. For solid-phase enrichment, cell-charged tapes are placed face-down on a suitable selective agar surface and incubated to allow in situ growth of Salmonella microcolonies, followed by FISH and microscopy as described above. For liquid surface miniculture, cell-charged tapes are placed sticky side up and a silicone perfusion chamber is applied so that the tape and microscope slide form the bottom of a water-tight chamber into which a small volume (&le; 500 &mu;L) of Trypticase Soy Broth (TSB) is introduced. The inlet ports are sealed and the chambers are incubated at 35 - 37&deg;C, allowing growth-based amplification of tape-extracted microbes. Following incubation, inlet ports are unsealed, cells are detached and mixed with vigorous back and forth pipetting, harvested via centrifugation and fixed in 10% neutral buffered formalin. Finally, samples are hybridized and examined via flow cytometry to reveal the presence of Salmonella spp. As described here, our "tape-FISH" approach can provide simple and rapid sampling and detection of Salmonella on tomato surfaces. We have also used this approach for sampling other types of fresh produce, including spinach and jalape&ntilde;o peppers.

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple adhesive-tape-based approach for sampling of tomato and other fresh produce surfaces, followed by rapid whole cell detection of Salmonella using fluorescence in situ hybridization (FISH).

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in ...

Methods to Assess Beta Cell Death Mediated by Cytotoxic T Lymphocytes

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease. During the pathogenesis, patients become progressively more insulinopenic as 
insulin production is lost, presumably this results from the destruction of pancreatic beta cells by T cells. Understanding the mechanisms of beta cell death during 
the development of T1D will provide insights to generate an effective cure for this disease. Cell-mediated lymphocytotoxicity (CML) assays have historically used the 
radionuclide Chromium 51 (51Cr) to label target cells. These targets are then exposed to effector cells and the release of 51Cr from target 
cells is read as an indication of lymphocyte-mediated cell death. Inhibitors of cell death result in decreased release of 51Cr.
 As effector cells, we used an activated autoreactive clonal population of CD8+ Cytotoxic T lymphocytes (CTL) isolated from a mouse stock transgenic for both the alpha and beta chains of the AI4 T cell receptor (TCR). Activated AI4 T cells were co-cultured with 51Cr labeled target NIT cells for 16 hours, release of 51Cr was recorded to calculate specific lysis 
Mitochondria participate in many important physiological events, such as energy production, regulation of signaling transduction, and apoptosis. The study of beta cell mitochondrial functional changes during the development of T1D is a novel area of research. Using the mitochondrial membrane potential dye Tetramethyl Rhodamine Methyl Ester (TMRM) and confocal microscopic live cell imaging, we monitored mitochondrial membrane potential over time in the beta cell line NIT-1. For imaging studies, effector AI4 T cells were labeled with the fluorescent nuclear staining dye Picogreen. NIT-1 cells and T cells were co-cultured in chambered coverglass and mounted on the microscope stage equipped with a live cell chamber, controlled at 37&deg;C, with 5% CO2, and humidified. During these experiments images were taken of each cluster every 3 minutes for 400 minutes.
Over a course of 400 minutes, we observed the dissipation of mitochondrial membrane potential in NIT-1 cell clusters where AI4 T cells were attached. In the simultaneous control experiment where NIT-1 cells were co-cultured with MHC mis-matched human lymphocyte Jurkat cells, mitochondrial membrane potential remained intact. This technique can be used to observe real-time changes in mitochondrial membrane potential in cells under attack of cytotoxic lymphocytes, cytokines, or other cytotoxic reagents.

Cell-mediated lymphocytotoxicity (CML) assays can be used to test autoreactive responses and study mechanisms of cell death in vitro. However, using live-cell confocal microscopic imaging techniques with fluorescent dyes, the type and kinetics of cell death as well as the pathways utilized can be studied in greater detail.

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease.  During the pathogenesis, patients become progressively more insulinopenic as 
insulin ...

Isolation of Lymphocytes from Mouse Genital Tract Mucosa

Mucosal surfaces, including in the gastrointestinal, urogenital, and respiratory tracts, provide portals of entry for pathogens, such as viruses and bacteria 1. Mucosae are also inductive sites in the host to generate immunity against pathogens, such as the Peyers patches in the intestinal tract and the nasal-associated lymphoreticular tissue in the respiratory tract. This unique feature brings mucosal immunity as a crucial player of the host defense system. Many studies have been focused on gastrointestinal and respiratory mucosal sites. However, there has been little investigation of reproductive mucosal sites. The genital tract mucosa is the primary infection site for sexually transmitted diseases (STD), including bacterial and viral infections. STDs are one of the most critical health challenges facing the world today. Centers for Disease Control and Prevention estimates that there are 19 million new infectious every year in the United States. STDs cost the U.S. health care system $17 billion every year 2, and cost individuals even more in immediate and life-long health consequences. In order to confront this challenge, a greater understanding of reproductive mucosal immunity is needed and isolating lymphocytes is an essential component of these studies. Here, we present a method to reproducibly isolate lymphocytes from murine female genital tracts for immunological studies that can be modified for adaption to other species. The method described below is based on one mouse.&#x2003;

An efficient way to isolate lymphocytes from mouse genital tract is described. This method takes advantage of enzyme digestion and Percoll gradient separation to allow efficient isolation. This technique is also adaptable to for use in other species

Mucosal surfaces, including in the gastrointestinal, urogenital, and respiratory tracts, provide portals of entry for pathogens, such as viruses and ...

Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling

Cells respond to chemokine stimulation by losing their round shape in a process called polarization, and by altering the subcellular localization of many proteins. Classic imaging techniques have been used to study these phenomena. However, they required the manual acquisition of many cells followed by time consuming quantification of the morphology and the co-localization of the staining of tens of cells. Here, a rapid and powerful method is described to study these phenomena on samples consisting of several thousands of cells using an imaging flow cytometry technology that combines the advantages of a microscope with those of a cytometer. Using T lymphocytes stimulated with CCL19 and staining for MHC Class I molecules and filamentous actin, a gating strategy is presented to measure simultaneously the degree of shape alterations and the extent of co-localization of markers that are affected by CCL19 signaling. Moreover, this gating strategy allowed us to observe the segregation of filamentous actin (at the front) and phosphorylated Ezrin-Radixin-Moesin (phospho-ERM) proteins (at the rear) in polarized T cells after CXCL12 stimulation. This technique was also useful to observe the blocking effect on polarization of two different elements: inhibition of actin polymerization by a pharmacological inhibitor and expression of mutants of the Par6/atypical PKC signaling pathway. Thus, evidence is shown that this technique is useful to analyze both morphological alterations and protein redistributions.

Chemokine signaling elicits marked alterations of cellular morphology and some important redistributions of intracellular proteins. Here, a rapid and detailed protocol is provided to study these events.

Cells respond to chemokine stimulation by losing their round shape in a process called polarization, and by altering the subcellular localization of many ...

Detection of True IgE-expressing Mouse B Lineage Cells

B lymphocyte immunoglobulin heavy chain (IgH) class switch recombination (CSR) is a process wherein initially expressed IgM switches to other IgH isotypes, such as IgA, IgE and IgG. Measurement of IgH CSR in vitro is a key method for the study of a number of biologic processes ranging from DNA recombination and repair to aspects of molecular and cellular immunology. In vitro CSR assay involves the flow cytometric measurement surface Ig expression on activated B cells. While measurement of IgA and IgG subclasses is straightforward, measurement of IgE by this method is problematic due to soluble IgE binding to Fc&#949;RII/CD23 expressed on the surface of activated B cells. Here we describe a unique procedure for accurate measurement of IgE-producing mouse B cells that have undergone CSR in culture. The method is based on trypsin-mediated cleavage of IgE-CD23 complexes on cell surfaces, allowing for detection of IgE-producing B lineage cells by cytoplasmic staining. This procedure offers a convenient solution for flow cytometric analysis of CSR to IgE.

In vitro analysis of class switch recombination in mice is challenging due to cytophilic IgE molecules bound to Fc receptors on the surface of B cells. We describe a method for IgE detection using trypsin-mediated cleavage of surface-bound IgE prior to fixation and permeabilization for cytoplasmic fluorescence staining.

B lymphocyte immunoglobulin heavy chain (IgH) class switch recombination (CSR) is a process wherein initially expressed IgM switches to other IgH ...

A Simple and Rapid Protocol to Non-enzymatically Dissociate Fresh Human Tissues for the Analysis of Infiltrating Lymphocytes

The ability of malignant cells to evade the immune system, characterized by tumor escape from both innate and adaptive immune responses, is now accepted as an important hallmark of cancer. Our research on breast cancer focuses on the active role that tumor infiltrating lymphocytes play in tumor progression and patient outcome. Toward this goal, we developed a methodology for the rapid isolation of intact lymphoid cells from normal and abnormal tissues in an effort to evaluate them proximate to their native state. Homogenates prepared using a mechanical dissociator show both increased viability and cell recovery while preserving surface receptor expression compared to enzyme-digested tissues. Furthermore, enzymatic digestion of the remaining insoluble material did not recover additional CD45+ cells indicating that quantitative and qualitative measurements in the primary homogenate likely genuinely reflect infiltrating subpopulations in the tissue fragment. The lymphoid cells in these homogenates can be easily characterized using immunological (phenotype, proliferation, etc.) or molecular (DNA, RNA and/or protein) approaches. CD45+ cells can also be used for subpopulation purification, in vitro expansion or cryopreservation. An additional benefit of this approach is that the primary tissue supernatant from the homogenates can be used to characterize and compare cytokines, chemokines, immunoglobulins and antigens present in normal and malignant tissues. This protocol functions extremely well for human breast tissues and should be applicable to a wide variety of normal and abnormal tissues.

This protocol describes the rapid non-enzymatic dissociation of fresh human tissue fragments for qualitative and quantitative assessment of CD45+ cells (lymphocytes/leukocytes) present in various normal and malignant human tissues. Additionally, the supernatant obtained from the primary tissue homogenate can be collected and stored for further analysis or experimentation.

The ability of malignant cells to evade the immune system, characterized by tumor escape from both innate and adaptive immune responses, is now accepted ...

Efficient Isolation Protocol for B and T Lymphocytes from Human Palatine Tonsils

Tonsils form a part of the immune system providing the first line of defense against inhaled pathogens. Usually the term &#8220;tonsils&#8221; refers to the palatine tonsils situated at the lateral walls of the oral part of the pharynx. Surgically removed palatine tonsils provide a convenient accessible source of B and T lymphocytes to study the interplay between foreign pathogens and the host immune system. This video protocol describes the dissection and processing of surgically removed human palatine tonsils, followed by the isolation of the individual B and T cell populations from the same tissue sample. We present a method, which efficiently separates tonsillar B and T lymphocytes using an antibody-dependent affinity protocol. Further, we use the method to demonstrate that human adenovirus infects specifically the tonsillar T cell fraction. The established protocol is generally applicable to efficiently and rapidly isolate tonsillar B and T cell populations to study the role of different types of pathogens in tonsillar immune responses.

Palatine tonsils are a rich source of B and T lymphocytes. Here we provide an easy, efficient and rapid protocol to isolate B and T lymphocytes from human palatine tonsils. The method described has been specifically adapted for studies of the viral etiology of tonsil inflammation known as tonsillitis.

Tonsils form a part of the immune system providing the first line of defense against inhaled pathogens. Usually the term &#8220;tonsils&#8221; refers to ...

Rapid Molecular Detection and Differentiation of Influenza Viruses A and B

Influenza is a contagious respiratory illness caused by influenza viruses A and B in humans and causes a significant amount of morbidity and mortality every year. The Influenza A and B assay was the first CLIA-waived molecular rapid flu test available. The Influenza A and B test works by employing isothermal amplification with influenza-specific primers followed by target detection with molecular beacon probes. Here, the performance of the Influenza A and B assay on frozen, archived nasopharyngeal swab (NPS) specimens stored in viral transport medium (VTM) were compared to a respiratory panel assay.
The performance of the Influenza A and B assay was evaluated by comparing the results to the respiratory panel reference method. The sensitivity for total influenza virus A was 67.5% (95% CI (CI), 56.6-78.5) and the specificity was 86.9% (CI, 71.0-100). For influenza virus B testing, the sensitivity and specificity were 90.2% (CI, 68.5-100) and 98.8% (CI, 68.5-100), respectively.
This system has the advantage of a significantly shorter test time than any other currently available molecular assay and the simple, pipette-free procedure runs on a fully integrated, closed, small-footprint system. Overall, the Influenza A and B assay evaluated in this study has the potential to serve as a point-of-care rapid influenza diagnostic test.

We describe a rapid, molecular-based Influenza A and B assay. The Influenza assay detects each target within 15 min by employing isothermal amplification with influenza-specific primers followed by target detection with molecular beacon probes. The Influenza A and B assay is user-friendly and required minimal hands-on time to perform.

Influenza is a contagious respiratory illness caused by influenza viruses A and B in humans and causes a significant amount of morbidity and mortality ...

Molecular Diffusion in Plasma Membranes of Primary Lymphocytes Measured by Fluorescence Correlation Spectroscopy

Fluorescence correlation spectroscopy (FCS) is a powerful technique for studying the diffusion of molecules within biological membranes with high spatial and temporal resolution. FCS can quantify the molecular concentration and diffusion coefficient of fluorescently labeled molecules in the cell membrane. This technique has the ability to explore the molecular diffusion characteristics of molecules in the plasma membrane of immune cells in steady state (i.e., without processes affecting the result during the actual measurement time). FCS is suitable for studying the diffusion of proteins that are expressed at levels typical for most endogenous proteins. Here, a straightforward and robust method to determine the diffusion rate of cell membrane proteins on primary lymphocytes is demonstrated. An effective way to perform measurements on antibody-stained live cells and commonly occurring observations after acquisition are described. The recent advancements in the development of photo-stable fluorescent dyes can be utilized by conjugating the antibodies of interest to appropriate dyes that do not bleach extensively during the measurements. Additionally, this allows for the detection of slowly diffusing entities, which is a common feature of proteins expressed in cell membranes. The analysis procedure to extract molecular concentration and diffusion parameters from the generated autocorrelation curves is highlighted. In summary, a basic protocol for FCS measurements is provided; it can be followed by immunologists with an understanding of confocal microscopy but with no other previous experience of techniques for measuring dynamic parameters, such as molecular diffusion rates.

A method to measure protein diffusion in membranes of primary immune cells using fluorescence correlation spectroscopy (FCS) is described. In this paper, the use of antibodies for fluorescent labeling is illustrated.

Fluorescence correlation spectroscopy (FCS) is a powerful technique for studying the diffusion of molecules within biological membranes with high spatial ...

Rapid Quantification of Mitogen-induced Blastogenesis in T Lymphocytes for Identifying Immunomodulatory Drugs

Lymphocyte proliferation in response to antigenic or mitogenic stimulation is a readily quantifiable phenomenon useful for testing immunomodulatory (i.e., immunosuppressive or immunostimulatory) chemical compounds and biologics. One of the earliest steps during mitogenesis is cell enlargement or blastogenic transformation, whereupon the cell volume increases before division. It is usually detectable in the first several hours of T-lymphocyte stimulation. Here, we describe a rapid method to quantify blastogenesis in T lymphocytes isolated from mouse spleens and human peripheral blood mononuclear cells (PBMCs) using an automated cell counter. Various commonly used proliferation assays for the most part are laborious and only reflect the overall population effect rather than individual cellular effects within a population. In contrast, the presented automated cell counter assay provides rapid, direct, and precise measurements of cell diameters that can be used for assessing the effectiveness of various mitogens and immunomodulatory drugs in vitro.

T-lymphocyte mitogenesis is accompanied by blastogenic transformation, whereupon the cell volume enlarges before cell division. Here, we describe a method to quantify blastogenesis in T lymphocytes using an automated cell counter with the capability of measuring cell diameters.

Lymphocyte proliferation in response to antigenic or mitogenic stimulation is a readily quantifiable phenomenon useful for testing immunomodulatory (i.e., ...