Mutant worm strains were kindly provided by the Caenorhabditis Genetics Center. This research was supported by a grant of the Korea Health Technology R&amp;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &amp; Welfare, Republic of Korea (grant number: HI14C1277).

1. Labeling Probes with Digoxigenin-dUTP by PCR
<ol>
	<li>Perform PCR labeling with 10x dNTP mix containing digoxigenin-dUTP as previously described13.</li>
	<li>Purify PCR product with spin-column purification according to manufacturer&#39;s instruction.
	<ol>
		<li>If the probe is shorter than 200 bp, remove free digoxigenin-dUTP with spin-column chromatography from the reaction mixture rather than spin-column purification.</li>
	</ol>
	</li>
</ol>
2. Preparing Polylysine Coated Slide...

<ol>
	<li>Reddel, R. R., Bryan, T. M., Murnane, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immortalized+cells+with+no+detectable+telomerase+activity.+A+review.">Immortalized cells with no detectable telomerase activity. A review.</a> Biochemistry-Moscow. 62, 1254-1262 (1997).</li><li>Seo, 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=Telomere+maintenance+through+recruitment+of+internal+genomic+regions.">Telomere maintenance through recruitment of internal genomic regions.</a> Nat Commun. 6, 8189 (2015).</li><li>Cesare, A. J., Reddel, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+lengthening+of+telomeres:+models,+mechanisms+and+implications.">Alternative lengthening of telomeres: models, mechanisms and implications.</a> Nat Rev Genet. 11, 319-330 (2010).</li><li>Meier, 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=trt-1+is+the+Caenorhabditis+elegans+catalytic+subunit+of+telomerase.">trt-1 is the Caenorhabditis elegans catalytic subunit of telomerase.</a> Plos Genetics. 2, 187-197 (2006).</li><li>Cawthon, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Telomere+measurement+by+quantitative+PCR.">Telomere measurement by quantitative PCR.</a> Nucleic Acids Res. 30, 47 (2002).</li><li>Raices, M., Maruyama, H., Dillin, A., Karlseder, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uncoupling+of+longevity+and+telomere+length+in+C.+elegans.">Uncoupling of longevity and telomere length in C. elegans.</a> PLoS Genet. 1, 30 (2005).</li><li>Southern, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+Specific+Sequences+among+DNA+Fragments+Separated+by+Gel-Electrophoresis.">Detection of Specific Sequences among DNA Fragments Separated by Gel-Electrophoresis.</a> Journal of Molecular Biology. 98, 503 (1975).</li><li>Lee, M., 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=Telomere+extension+by+telomerase+and+ALT+generates+variant+repeats+by+mechanistically+distinct+processes.">Telomere extension by telomerase and ALT generates variant repeats by mechanistically distinct processes.</a> Nucleic Acids Res. 42, 1733-1746 (2014).</li><li>Cheung, I., 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=Strain-specific+telomere+length+revealed+by+single+telomere+length+analysis+in+Caenorhabditis+elegans.">Strain-specific telomere length revealed by single telomere length analysis in Caenorhabditis elegans.</a> Nucleic Acids Res. 32, 3383-3391 (2004).</li><li>Shtessel, 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=Caenorhabditis+elegans+POT-1+and+POT-2+repress+telomere+maintenance+pathways.">Caenorhabditis elegans POT-1 and POT-2 repress telomere maintenance pathways.</a> G3. 3, 305-313 (2013).</li><li>Duerr, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunohistochemistry.">Immunohistochemistry.</a> WormBook (The C. elegans Research Community). , (2006).</li><li>Phillips, C. M., McDonald, K. L., Dernburg, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytological+analysis+of+meiosis+in+Caenorhabditis+elegans.">Cytological analysis of meiosis in Caenorhabditis elegans.</a> Meiosis: Volume 2, Cytological Methods. , 171-195 (2009).</li><li>Emanuel, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+and+efficient+system+for+synthesis+of+non-radioactive+nucleic+acid+hybridization+probes+using+PCR.">Simple and efficient system for synthesis of non-radioactive nucleic acid hybridization probes using PCR.</a> Nucleic acids research. 19, 2790 (1991).</li><li>Stiernagle, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maintenance+of+C.+elegans.">Maintenance of C. elegans.</a> WormBook. , 1-11 (2006).</li><li>Porta-de-la-Riva, M., Fontrodona, L., Villanueva, A., Ceron, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+Caenorhabditis+elegans+methods:+synchronization+and+observation.">Basic Caenorhabditis elegans methods: synchronization and observation.</a> J Vis Exp. , e4019 (2012).</li><li>Poon, S. S. S., Martens, U. M., Ward, R. K., 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=Telomere+length+measurements+using+digital+fluorescence+microscopy.">Telomere length measurements using digital fluorescence microscopy.</a> Cytometry. 36, 267-278 (1999).</li><li>Ferreira, H. C., Towbin, B. D., Jegou, T., Gasser, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+shelterin+protein+POT-1+anchors+Caenorhabditis+elegans+telomeres+through+SUN-1+at+the+nuclear+periphery.">The shelterin protein POT-1 anchors Caenorhabditis elegans telomeres through SUN-1 at the nuclear periphery.</a> J Cell Biol. 203, 727-735 (2013).</li><li>Lee, M. H., Schedl, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+in+situ+hybridization+of+dissected+gonads.">RNA in situ hybridization of dissected gonads.</a> WormBook. , 1-7 (2006).</li><li>Tabara, H., Motohashi, T., Kohara, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+multi-well+version+of+in+situ+hybridization+on+whole+mount+embryos+of+Caenorhabditis+elegans.">A multi-well version of in situ hybridization on whole mount embryos of Caenorhabditis elegans.</a> Nucleic Acids Res. 24, 2119-2124 (1996).</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=Quantitative+fluorescence+in+situ+hybridization+(Q-FISH).">Quantitative fluorescence in situ hybridization (Q-FISH).</a> Curr Protoc Cell Biol. 18, 14 (2001).</li></ol>

The main advantage of our protocol is the simplicity of the procedure without noticeable damage to the morphology of cellular structure. Several steps were optimized for C. elegans FISH in this protocol. The critical steps for successful FISH include labeling of probes, fixation of embryos and penetration. Digoxigenin-dUTP labeling method provides an easy-to-use labeling method by PCR or nick-translation. To label long target sequence, nick-translation is preferred. In this case, the probes should be digested wi...

Telomere protects chromosomal ends from aberrant fusion and degradation. Mammalian telomere is composed of G-rich hexameric repeats, TTAGGG, and shelterin complexes. The telomere repeat sequence of the nematode is similar to those of mammals (TTAGGC). Most eukaryotes utilize telomerase to add telomere repeats to their chromosomal ends. However, 10 - 15% of cancer cells utilize telomerase independent mechanism, known as Alternative Lengthening of Telomeres (ALT)3. Previously, we reported that telomere repeats and its associated sequences, named as TALT, were amplified in the telomeres of telomerase mutant lines that survived critical sterility2.
Telomere length was measured by quantitative PCR or by Southern blot, which provides average length of total telomeres4,5,6,7. Read count of telomere repeat in whole genome sequencing data is also an indicator of total telomere contents8. Although Single TElomere Length Analysis (STELA) could provide the length of a single telomere, it cannot provide spatial information of telomeres9. While POT-1::mCherry reporter protein provides the spatial information of telomeres in vivo, it cannot represent lengths of double-stranded telomeres, as POT-1 is a single-strand telomere binding protein10.
While aforementioned methods provide the averaged information of repetitive sequences, fluorescence in situ hybridization (FISH) allows to observe the amount and spatial pattern of individual sequences of interest on a chromosomal scale. Instead of purification of DNA, tissues or cells are fixed to preserve the native spatial information in FISH. Thus, FISH is a both quantitative and qualitative tool for observation of individual repeat sequences, such as telomere repeats.
This protocol provides an efficient method for simultaneous detection of both telomere and other repeats based on improvements from previously described methods 11,12. C. elegans larvae or adults are multicellular organism with highly differentiated cells. The heterogeneity of cells impedes on the quantitative analysis of a large number of telomere spots. To maximize the number of cells analyzed, embryos are isolated and spread on the polylysine-coated slides for FISH. In addition, this protocol can also be combined with immunofluorescence.
As a proof that the protocol works, we show that it is possible to observe and quantify two different repetitive sequences. DNA probe against TALT1 was generated with simple PCR incorporating digoxigenin-dUTP. Then this TALT1 probe and fluorescence-labeled telomere PNA probe were hybridized simultaneously. Subsequently, digoxigenin was detected by canonical immunofluorescence methods. We present here the representative images where TALT1 colocalized with the telomere in trt-1 survivors.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>PNA probe</td>
			<td>PANAGENE</td>
			<td>custom order</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Digoxigenin-Fluorescein, Fab fragments</td>
			<td>Roche</td>
			<td>11207741910</td>
			<td>use 1:200 diluted in PBST</td>
		</tr>
		<tr>
			<td>Digoxigenin-dUTP</td>
			<td>Roche</td>
			<td>11573152910</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>SIGMA-ALDRICH</td>
			<td>A-7906</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>SIGMA-ALDRICH</td>
			<td>P-6148</td>
			<td>prepare 4% paraformaldehyde by heating in DW with few drops of NaOH. add 0.1 volume of 10x PBS.</td>
		</tr>
		<tr>
			<td>Vectashield</td>
			<td>Vector Laboratories</td>
			<td>H-1200</td>
			<td></td>
		</tr>
		<tr>
			<td>Hybridizaiton solution</td>
			<td></td>
			<td></td>
			<td>3X SSC, 50% formamide, 10% (w/v) dextran sulfate, 50 ug/ml heparin, 100 ug/ml yeast tRNA , 100ug/ml sonicated salmon sperm DNA</td>
		</tr>
		<tr>
			<td>Hybridizaiton wash solution</td>
			<td></td>
			<td></td>
			<td>2X SSC, 50% formamide</td>
		</tr>
		<tr>
			<td>Formamide</td>
			<td>BIONEER</td>
			<td>C-9012</td>
			<td>toxic</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carlo Erba</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Carlo Erba</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>SIGMA-ALDRICH</td>
			<td>H3393</td>
			<td>make 10 mg/ml for stock solution</td>
		</tr>
		<tr>
			<td>Dextran sulfate</td>
			<td>SIGMA-ALDRICH</td>
			<td>67578</td>
			<td></td>
		</tr>
		<tr>
			<td>10X PBS</td>
			<td></td>
			<td></td>
			<td>For 1 Liter DW : 80 g NaCl, 2.0 g KCl, 27 g Na2HPO4:7H2O, 2.4 g KH2PO</td>
		</tr>
		<tr>
			<td>PBST</td>
			<td></td>
			<td></td>
			<td>1X PBS, 0.1% tween-20</td>
		</tr>
		<tr>
			<td>Polysorbate 20</td>
			<td>SIGMA-ALDRICH</td>
			<td>P-2287</td>
			<td>Commercial name is Tween-20</td>
		</tr>
		<tr>
			<td>Poly-L-Lysine solution (0.1 % w/v)</td>
			<td>SIGMA-ALDRICH</td>
			<td>P-8920</td>
			<td>prepare fresh 0.01 % w/v solution before use</td>
		</tr>
		<tr>
			<td>M9</td>
			<td></td>
			<td></td>
			<td>3 g KH2PO4, 6 g Na2HPO4, 5 g NaCl, 1 ml 1 M MgSO4, H2O to 1 L</td>
		</tr>
		<tr>
			<td>Bleaching solution</td>
			<td></td>
			<td></td>
			<td>20% sodium hypochlorite, 0.5 M KOH</td>
		</tr>
		<tr>
			<td>Antibody buffer</td>
			<td></td>
			<td></td>
			<td>1X PBST, 1mM EDTA, 0.1% BSA, 0.05% Sodium azide (toxic)</td>
		</tr>
		<tr>
			<td>Blocking solution</td>
			<td></td>
			<td></td>
			<td>Antibody buffer with 5% bovine serum albumin (BSA)</td>
		</tr>
		<tr>
			<td>illustra Microspin G-50</td>
			<td>GE healthcare</td>
			<td>27-53310-01</td>
			<td></td>
		</tr>
		<tr>
			<td>20X SSC</td>
			<td></td>
			<td></td>
			<td>To make 1L, 175.3 g of NaCl, 88.2 g of sodium citrate, H2O to 1 L, adjust pH to 7.0</td>
		</tr>
		<tr>
			<td>2X SSCT</td>
			<td></td>
			<td></td>
			<td>2X SSC, 0.1 % tween-20</td>
		</tr>
		<tr>
			<td>10x digoxigenin-dUTP mix</td>
			<td></td>
			<td></td>
			<td>1 mM dATP, 1 mM dGTP, 1 mM dCTP, 0.65mM dTTP, 0.35mM DIG-11-dUTP</td>
		</tr>
		<tr>
			<td>PCR purification columns</td>
			<td>Cosmo genetech</td>
			<td>CMR0112</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass cleaner / ULTRA CLEAN</td>
			<td>Dukssan pure chemicals</td>
			<td>8AV721</td>
			<td></td>
		</tr>
		<tr>
			<td>Multi-well glass slide</td>
			<td>MP biomedicals</td>
			<td>96041205</td>
			<td></td>
		</tr>
		<tr>
			<td>Nematode growth media</td>
			<td></td>
			<td></td>
			<td>to make 1 L, 3 g of NaCl, 17 g of agar, 2.5 g of peptone, H2O to 974 mL. Autoclave and cool the flask. Add 1 mL of 1M CaCl2, 1 ml of 4 mg/mL cholesterol in ethanol, 1 ml of 1 M MgSO4, 25 mL of 1 M KPO4.</td>
		</tr>
		<tr>
			<td>Levamisole</td>
			<td>SIGMA-ALDRICH</td>
			<td>196142</td>
			<td></td>
		</tr>
		<tr>
			<td>Razor</td>
			<td>Feather</td>
			<td>blade No. 11</td>
			<td></td>
		</tr>
		<tr>
			<td>Rnase A</td>
			<td>Enzynomics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>SIGMA-ALDRICH</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Equipments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microsope</td>
			<td>Zeiss</td>
			<td>LSM 510</td>
			<td>EC Plan-Neofluar 100x was used as objective lens.</td>
		</tr>
		<tr>
			<td>Dry block / aluminum block</td>
			<td>Labtech</td>
			<td>LBH-T03</td>
			<td>Set temperature to 80&#8451;</td>
		</tr>
		<tr>
			<td>Humid chamber</td>
			<td></td>
			<td></td>
			<td>Plastic box filled with paper towel soaked in DW</td>
		</tr>
		<tr>
			<td>Image Analysis Software&#160;</td>
			<td>Dr. Peter Landsdorp</td>
			<td>TFL-telo</td>
			<td><a href="http://www.flintbox.com/public/project/502">http://www.flintbox.com/public/project/502</a></td>
		</tr>
	</tbody>
</table>

observation and quantification of telomere and repetitive sequences using fluorescence in situ hybridization (fish) with pna probes in caenorhabditis elegans

Telomere is a ribonucleoprotein structure that protects chromosomal ends from aberrant fusion and degradation. Telomere length is maintained by telomerase or an alternative pathway, known as alternative lengthening of telomeres (ALT)1. Recently, C. elegans has emerged as a multicellular model organism for the study of telomere and ALT2. Visualization of repetitive sequences in the genome is critical in understanding the biology of telomeres. While telomere length can be measured by telomere restriction fragment assay or quantitative PCR, these methods only provide the averaged telomere length. On the contrary, fluorescence in situ hybridization (FISH) can provide the information of the individual telomeres in cells. Here, we provide protocols and representative results of the method to determine telomere length of C. elegans by fluorescent in situ hybridization. This method provides a simple, but powerful, in situ procedure that does not cause noticeable damage to morphology. By using fluorescently labeled peptide nucleic acid (PNA) and digoxigenin-dUTP-labeled probe, we were able to visualize two different repetitive sequences: telomere repeats and template of ALT (TALT) in C. elegans embryos and gonads.

It was previously reported that ALT survivor can emerge from telomerase-deficient mutant, trt-1(ok410), in low frequency by replicating internally localized &#39;Template of ALT&#39; (TALT) sequences for telomere maintenance2. Using PNA probe, we were able to visualize telomeres in the dissected gonads (Figure 2A). The faint telomere signal was detected both in trt-1(ok410) and ALT survivor. The fuzzy signal was overlapped only with DAPI, sugg...

Watch this Scientific Journal Video about Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization FISH with PNA Probes in Caenorhabditis elegans at

Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization FISH with PNA Probes in Caenorhabditis elegans

We report a concise procedure of fluorescence in situ hybridization (FISH) in the gonad and embryos of Caenorhabditis elegans for observing and quantifying repetitive sequences. We successfully observed and quantified two different repetitive sequences, telomere repeats and template of alternative lengthening of telomeres (TALT).

Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization (FISH) with PNA Probes in Caenorhabditis elegans

Telomere is a ribonucleoprotein structure that protects chromosomal ends from aberrant fusion and degradation. Telomere length is maintained by telomerase ...

The overall goal of this fluorescence in situ hybridization technique is to concisely analyze telomere number and length in C.Elegans. This method can help answer key questions about tumor regenesis, alternative lengthening of telomeres, and cellular senescence. The main advantage of this technique is that the procedures are concise and the telomeres can be visualized and quantified in less than 24 hours.Collect the gravid adult worms with a little liquid media without debris in a 15 milliliter tube. Now wash the worms three times as follows. Add M9 buffer for a total volume of 15 milliliters.Then spin the tube down at 300 G for three minutes, and discard the solution above the pellet of worms. Then repeat the process. If after the centrifugation the worms are floating, then lighten the brake on the centrifuge.After the third wash, leave the worms with 5 milliliters of M9.Then add 6.5 milliliters of distilled water, two milliliters of hyperchlorite, and one milliliter of five molar potassium-hydroxide. Let the worms incubate in this bleaching solution for three minutes with 50 RPM of agitation. Then vortex the worms to shear them open and free their eggs.Under a dissection microscope, look for the released eggs. If they are not released yet, continue the incubation or up to eight minutes. If the worms are mostly dissolved and the eggs are free, fill the tube to 15 milliliters with M9 and wash the eggs three times just as the worms were washed before.To the washed eggs, with most of the M9 removed, fill the volume to 500 microliters with PBST, and then add 500 microliters of 4%PFA. Now load 40 microliter aliquots of eggs in 2%PFA to the wells of polylysine coated slides. Then transfer the slides to a humidified chamber and let them incubate for 15 minutes at room temperature.For this protocol, have an aluminum block on dry ice stored at 80 degrees Celsius. Also, have methanol and acetone stored at 20 degrees Celsius. After the fixation step is completed, remove most of the PFA solution from the slides, leaving about five microliters.Then place second polylysine coated slides over each sample slide so that the two coated surfaces stick together, trapping the tissues in the well. If there is excessive fixative, mop it up with a tissue. Now freeze the slides by placing them on the cold aluminum block for at least 15 minutes.Meanwhile, prepare methanol and acetone baths on ice for the slides. Once the slides are frozen, twist one to freeze crack the sample. Discard the upper slide and soak the bottom slide in ice cold methanol for five minutes.Do this for all the samples. Freeze cracking allows for penetration of probes and antibody through the hard eggshell. If the eggs are successfully freeze cracked, you could see the eggs on both slides.After at least five minutes in methanol, move the slides to cold acetone for five minutes. In another five minutes, soak the samples in PBST three times for five minutes per bath. After the PBST washes, the slides may be stored in 100%ethanol at four degrees celsius for several days.To proceed, add 20 microliters of RNase solution to the sample wells and incubate them in a humidified chamber at 37 degrees celsius for an hour. Next wash the slides in 2x SSCT twice for 15 minutes per wash. After the two washes, add 20 microliters of hybridization solution to the samples and incubate them at 37 degrees Celsius for an hour in a humidified chamber.Meanwhile, prepare the probe for a double stranded DNA probe. Denature it at 95 degrees Celsius for five minutes and then chill it on ice briefly. After an hour, aspirate the hybridization solution and add the probe solution.From this step forward, protect the sample from the light. After adding the probe, cover the samples with glass cover slips. Then make a humidified chamber on an 80 degrees Celsius heat block.When the heat block has stabilized back to 80 degrees Celsius, place the sample slides in the warmed chamber and let then denature for three minutes. Then incubate all the processed slides in a humidified chamber at 37 degrees Celsius overnight. After the overnight incubation, wash the samples in PBST at room temperature for five minutes.In preparation, warm the hybridization solution to 37 degrees Celsius one hour before wash. Then load the slides into a jar of hybridization wash solution and incubate them at 37 degrees Celsius for 30 minutes. To remove the hybridization solution, wash the samples with PBST at room temperature for 15 minutes.Do this three times. After aspirating off the last PBST wash, add 20 microliters of blocking solution to each sample and incubate them in humidified chambers at room temperature for one hour in the dark. Then aspirate the blocking solution and replace it with FITC conjugated anti-digoxigenin antibody solution at one to 200.Cover the slides and incubate them at room temperature for three hours in the dark. After the antibody stain, wash the samples twice with PBST for 15 minutes per wash in the dark. Next aspirate the PBST and replace it with 10 microliters of mounting solution containing DAPI.Apply a cover glass and sop up any excess solution. Finally, seal the edges of the cover glass with nail polish and proceed with observing the samples under a fluorescent microscope. Using the PNA probe, the telomeres of animals surviving a telomere-sufficient mutation were observed.In the gonads, the number of telomeres per nucleus is quantifiable. The telomere signal co-localized with a TALT1 signal, supporting the notion that TALT1 is responsible for survivorship without telomeres. The intensity of telomere signal was compared using software.The signal was stronger in the ALT survivors than in the parental strains used to generate the telomeres-deficient mutants. Don't forget that working with paraformaldehyde and formamide can be extremely hazardous, and precautions, such as wearing gloves, should always be taken while performing this procedure.

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Research

JoVE Journal

Biology

10.2K Views.  Seoul National University. The overall goal of this fluorescence in situ hybridization technique is to concisely analyze telomere number and length in C.Elegans. This method can help answer key questions about tumor regenesis, alternative lengthening of telomeres, and cellular senescence. The main advantage of this technique is that the procedures are concise and the telomeres can be visualized and quantified in less than 24 hours.Collect the gravid adult worms with a little liquid media without debris in a 15 m...

Video: Observation and Quantification of Telomere and Repetitive Sequences Using Fluorescence In Situ Hybridization FISH with PNA Probes in Caenorhabditis elegans