This work was supported by US National Institutes of Health grants HL082798 and HL111580.

1. Kidney Tissue Sections
<ol>
	<li>Formalin-fixed (10%) paraffin-embedded kidney sections are cut onto microscope slides at 5 mm thickness using a Microm HM 355 S. The slides can be stored for several months before analysis.</li>
</ol>
2. Solution Preparation
<ol>
	<li>Prepare 1 L of 1x PBS in ddH2O in an autoclavable screw top bottle. Fill another bottle with 1 L of ddH2O. Add 1 ml of DEPC to each bottle, cover and shake vigorously. Let the solutions sit overnight at room temperature to destroy RNAses and then autoclave. Add 400 ml Tween-20 to 1 L of 1x PBS to make PBS-T.</li>
	<li>Prepare proteinase K buffer (50 mMTris-HCl, pH 8.0 and 1 mM CaCl2 in DEPC treated water).</li>
	<li>Prepare a solution of 0.2% glycine in PBS-T.</li>
</ol>
3. Tissue Preparation
<ol>
	<li>Prepare a large volume of hybridization buffer (50-100 ml) composed of 50% Formamide, 5x SSC, 0.1% Tween, 9.2 mM citric acid for adjustment to pH 6, 50 &#181;g/ml heparin, and 500 &#181;g/ml yeast RNA in DEPC treated ddH2O. Divide into 1 ml aliquots and store at -80 &#186;C.</li>
	<li>Remove the paraffin from the tissue by washing 3x in fresh xylene for 5 min each.</li>
	<li>Rehydrate the tissue sections by 5 min incubations in decreasing concentrations of ethanol (100%, 75%, 50%, and 25%) in ddH2O.</li>
	<li>Treat the slides with enough DEPC to completely cover the tissue sections (approximately 0.4-0.5 ml) for 1 min. Make sure tissues do not dry out.</li>
	<li>Rinse the slides in DEPC treated PBS-T twice for 5 min, collecting the DEPC containing waste for proper disposal. All reagents should be DEPC treated to eliminate RNAses from this point on.</li>
	<li>Prewarm Proteinase K buffer and add proteinase K to a final concentration of 10 &#956;g/ml. Cover tissue sections with proteinase K solution and incubate at 37 &#186;C for 5 min.</li>
	<li>Quickly remove the proteinase K solution and add 0.2% glycine in PBS-T for 30 sec.</li>
	<li>Rinse slides in DEPC treated PBS-T twice for 30 sec each.</li>
	<li>Fix sections in freshly made 4% paraformaldehyde for 10 min.</li>
</ol>
4. Hybridization
<ol>
	<li>Add 50 &#181;l of hybridization buffer (50% Formamide, 5x SSC, 0.1% Tween, 9.2 mM citric acid for adjustment to pH 6, 50 &#181;g/ml heparin, 500 &#181;g/ml yeast RNA) per tissue section and cover with RNAse free HybriSlips cut just larger than the tissue sections.</li>
	<li>Prehybridize sections in humidity controlled hybridization oven for 2 hr at hybridization temperature determined for the 3&#8217; digoxigenin labeled probe (usually DNA Tm of the probe -21 &#176;C, ( i.e.&#160;54 &#176;C for miR-382, probe DNA Tm= 75 &#176;C), using tissue lab wipes soaked in 50% formamide/50% 5x SSC to keep the chamber humidified.</li>
	<li>Dilute the miRNA probe, positive control (U6, small nuclear RNA) and negative control (scrambled sequence) to 40 nM in hybridization buffer (75 &#181;l of buffer is needed per section).</li>
	<li>Heat the probe in hybridization buffer at 65&#160;&#186;C for 5 min.</li>
	<li>Remove slides from hybridization oven and remove coverslips and excess hybridization buffer from prehybridization.</li>
	<li>Add 75 &#181;l of probe containing buffer per tissue section, directly to tissue. Cover tissue with HybriSlips just large enough to cover the tissue sections.</li>
	<li>Keeping slide holder level, return to hybridization oven for overnight incubation at temperature from step 4.2 (approximately 16 hr).</li>
</ol>
5. Stringency Wash
<ol>
	<li>Add 200 &#181;l 2x SSC, heated to the hybridization temperature, just under one edge of the coverslips to help release the coverslip from the tissue. Remove the coverslip by tilting the slide.</li>
	<li>Wash the slides in 200 &#181;l of 50% formamide, 50% 2x SSC at hybridization temperature 3x for 30 min each.</li>
	<li>Rinse the slides 5x in PBS-T at room temperature for 5 min each on orbital shaker on low speed.</li>
</ol>
6. Detection
<ol>
	<li>Incubate slide in blocking buffer (2% goat or horse serum, 2 mg/ml BSA in PBS-T) for 1 hr at room temperature on orbital shaker on low speed.</li>
	<li>Dilute anti-DIG-AP Fab fragments in blocking buffer at 1:100. Add 100 &#181;l per tissue section and cover with HybriSlips cut just large enough to cover the section.</li>
	<li>Incubate antibody in a humidified chamber at 4 &#176;C overnight (approximately 16 hr).</li>
	<li>Wash the slides in PBS-T 7x, for 5 min each on orbital shaker at low speed.</li>
	<li>Wash the slides in AP buffer (100 mM TrisHCl pH 9.5, 50 mM MgCl2,100mM NaCl, 0.1% Tween 20) 3x, for 5 min each.</li>
	<li>Add NBT/BCIP solution to AP buffer (200 &#181;l/10 ml buffer)</li>
	<li>Add 400-500 ml of diluted NBT/BCIP solution to each slide to completely cover all tissue sections. Develop in a dark, level, humidified chamber for 4-5 hr.</li>
</ol>
7. Mounting Slides
<ol>
	<li>Dehydrate sections in increasing concentrations of ethanol (25%, 50%, 75%, 100%) for 5 min each.</li>
	<li>Incubate in xylene 5x in order to clear sections.</li>
	<li>Mount slides in Permount mounting medium and dry overnight.</li>
</ol>

<ol>
	<li>Nagalakshmi, V. K., Ren, Q., Pugh, M. M., Valerius, M. T., McMahon, A. P., Yu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dicer+regulates+thedevelopment+of+nephrogenic+and+ureteric+compartments+in+the+mammalian+kidney.">Dicer regulates thedevelopment of nephrogenic and ureteric compartments in the mammalian kidney.</a> Kidney Int. 79 (3), 317-330 (2011).</li><li>Ho, J., Pandey, P., Schatton, T., Sims-Lucas, S., Khalid, M., Frank, M. H., Hartwig, S., Kreidberg, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pro-apoptotic+protein+Bim+is+a+MicroRNA+target+in+kidney+progenitors.">The pro-apoptotic protein Bim is a MicroRNA target in kidney progenitors.</a> J. Am. Soc. Neph. 22 (6), 1053-1063 (2011).</li><li>Tian, Z., Greene, A. S., Pietrusz, J. L., Matus, I. R., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNA-target+pairs+in+the+rat+kidney+identified+by+microRNA+microarray,+proteomic,+and+bioinformaticanalysis.">MicroRNA-target pairs in the rat kidney identified by microRNA microarray, proteomic, and bioinformaticanalysis.</a> Genome Res. 18 (3), 404-411 (2008).</li><li>Mladinov, D., Liu, Y., Mattson, D. L., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs+contribute+to+the+maintenance+of+cell-type-specific+physiological+characteristics:+miR-192+targets+Na+/K+-ATPase+&#946;1.">MicroRNAs contribute to the maintenance of cell-type-specific physiological characteristics: miR-192 targets Na+/K+-ATPase &#946;1.</a> Nucleic Acids Res. 41 (2), 1273-1283 (2013).</li><li>Liu, Y., Taylor, N. E., Lu, L., Usa, K., Cowley, A. W., Ferreri, N. R., Yeo, N. C., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Renal+medullary+microRNAs+in+Dahl+salt-sensitive+rats:+miR-29b+regulates+several+collagens+and+related+genes.">Renal medullary microRNAs in Dahl salt-sensitive rats: miR-29b regulates several collagens and related genes.</a> Hypertension. 55 (4), 974-982 (2010).</li><li>Kato, M., Zhang, J., Wang, M., Lanting, L., Yuan, H., Rossi, J. J., Natarajan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNA-192+in+diabetic+kidney+glomeruliand+its+function+in+TGF-b-induced+collagen+expression+via+inhibition+of+E-box+repressors.">MicroRNA-192 in diabetic kidney glomeruliand its function in TGF-b-induced collagen expression via inhibition of E-box repressors.</a> Proc. Natl. Acad. Sci. U.S.A. 104 (4), 3432-3437 (2007).</li><li>Krupa, A., Jenkins, R., Luo, D. D., Lewis, A., Phillips, A., Fraser, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+microRNA-192+promotes+fibrogenesis+in+diabetic+nephropathy.">Loss of microRNA-192 promotes fibrogenesis in diabetic nephropathy.</a> J. Am. Soc. Neph. 21 (3), 438-447 (2010).</li><li>Wang, B., Herman-Edelstein, M., Koh, P., Burns, W., Jandeleit-Dahm, K., Watson, A., Saleem, M., Goodall, G. J., Twigg, S. M., Cooper, M. E., Kantharidis, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=E-cadherin+expression+is+regulated+by+miR-192/215+by+a+mechanism+that+is+independent+of+the+profibrotic+effects+of+transforming+growth+factor-&#946;.">E-cadherin expression is regulated by miR-192/215 by a mechanism that is independent of the profibrotic effects of transforming growth factor-&#946;.</a> Diabetes. 59 (7), 1794-1802 (2010).</li><li>Kato, M., Arce, L., Wang, M., Putta, S., Lanting, L., Natarajan, 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+microRNA+circuit+mediates+transforming+growth+factor-&#946;1+autoregulation+in+renal+glomerular+mesangial+cells.">A microRNA circuit mediates transforming growth factor-&#946;1 autoregulation in renal glomerular mesangial cells.</a> Kidney Int. 80 (4), 358-368 (2011).</li><li>Gottardo, F., Liu, C. G., Ferracin, M., Calin, G. A., Fassan, M., Bassi, P., Sevignani, C., Byrne, D., Negrini, M., Pagano, F., Gomella, L. G., Croce, C. M., Baffa, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro-RNA+profiling+in+kidney+and+bladder+cancers.">Micro-RNA profiling in kidney and bladder cancers.</a> Urol. Oncol. 25 (5), 387-392 (2007).</li><li>Juan, D., Alexe, G., Antes, T., Liu, H., Madabhushi, A., Delisi, C., Ganesan, S., Bhanot, G., Liou, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+microRNA+panel+for+clear-cell+kidney+cancer.">Identification of a microRNA panel for clear-cell kidney cancer.</a> Urol. 75 (4), 835-841 (2010).</li><li>Xu, X., Kriegel, A. J., Liu, Y., Usa, K., Mladinov, D., Liu, H., Fang, Y., Ding, X., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delayed+ischemic+preconditioning+contributes+to+renal+protection+by+upregulation+of+miR-21.">Delayed ischemic preconditioning contributes to renal protection by upregulation of miR-21.</a> Kidney Int. 82 (11), 1167-1175 (2012).</li><li>Kriegel, A. J., Mladinov, D., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+study+of+microRNAs+and+its+application+in+kidney+disease+and+hypertension.">Translational study of microRNAs and its application in kidney disease and hypertension.</a> 122 (10), 439-447 (2012).</li><li>Kloosterman, W. P., Wienholds, E., de Bruijn, E., Kauppinen, S., Plasterk, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+detection+of+miRNAs+in+animal+embryos+using+LNA-moidified+oligonucleotide+probes.">In situ detection of miRNAs in animal embryos using LNA-moidified oligonucleotide probes.</a> Nat. Methods. 3 (1), 27-29 (2006).</li><li>Nelson, P. T., Baldwin, D. A., Kloosterman, W. P., Kauppinen, S., Plasterk, R. H., Mourelatos, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RAKE+and+LNA-ISH+reveal+microRNA+expression+and+localization+in+archival+human+brain+tissue.">RAKE and LNA-ISH reveal microRNA expression and localization in archival human brain tissue.</a> RNA. 12 (2), 187-191 (2006).</li><li>Obernosterer, G., Martinez, J., Alenius, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Locked+nucleic+acid-based+in+situ+detection+of+microRNAs+in+mouse+tissue+sections.">Locked nucleic acid-based in situ detection of microRNAs in mouse tissue sections.</a> Nat. Protocols. 2 (6), 1508-1514 (2007).</li><li>Kriegel, A. J., Liu, Y., Cohen, B., Usa, K., Liu, Y., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MiR-382+targeting+of+kallikrein+5+contributes+to+renal+inner+medullary+interstitial+fibrosis.">MiR-382 targeting of kallikrein 5 contributes to renal inner medullary interstitial fibrosis.</a> Physiol. Genomics. 44 (4), 259-267 (2012).</li></ol>

There is nothing to disclose.

The goal of this article was to describe a protocol for miRNA in situ hybridization that works well in formalin fixed kidney tissues. While working out this protocol several important sources of staining artifact have been identified. Careful attention to these points can help avoid staining artifact and increase the likelihood of a successful ISH run.
One of the most avoidable causes of staining artifact can occur when tissue sections become dried out during long incubations. When this occurs the portion of the tissue that becomes dried will stain very darkly during the NBT/BCIP development (Figure 1). Throughout this protocol it is critical that the tissue sections remain completely covered by liquid throughout all incubations and that the slides are kept completely level. Additionally, the tissue sections should remain completely covered by HybriSlips during long incubations such as hybridization steps and the antibody incubation, to help prevent liquid loss. If partial or complete drying of a tissue section is observed it is unlikely that the samples will yield optimal staining, which will not allow miRNA expression to be interpreted in those samples.
Other steps in the protocol where liquid coverage is essential are during the proteinase K digestion and paraformaldehyde treatment. This digestion is needed to permit access of the miRNA probe into the cells. If the coverage of the tissue is incomplete during this short incubation, the areas that are not exposed to the enzyme digestion will not permit as much probe to enter and bind, and will ultimately not stain as darkly as other as other areas of the tissue. When applying this protocol to other tissue types, the duration of proteinase K digestion may need to be optimized. The subsequent paraformaldehyde fixation is also essential to prevent loss of miRNAs following permeabilization.
The duration of NBT/BCIP development is also an important variable to control. We found that NBT/BCIP incubations of longer than 4 or 5 hr significant background artifact begins to develop in the tissues probed with the scrambled-miR control probes (Figure 2A). Four hours of NBT/BCIP development is sufficient for detection of probe targets expressed in relatively high abundance, such as the U6 small RNA positive control (Figure 2B). Longer incubations do not appear to allow for additional low level expression to be detected, rather this may simply results in increased background artifact.
This leads to the important issue of the detectability of lower expressed miRNAs. Though we have found the 5&#8217; digoxigenin conjugated probes to provide us with sufficient detection sensitivity for our applications in kidney. The alkaline phosphatase based color development allows for multiple signal particles to be measured for each molecule of probe, however some low level miRNA still may not be detectable. Exiqon had developed miRNA probes that are labeled on both the 5&#8217; and 3&#8217; ends allowing for the potential for twice the colorimetric development per microRNA molecule. While our lab has not tested these probes, their use in kidney tissues with a similar protocol has been reported8.
This basic protocol can be adapted to other tissue types and miRNA probes by optimizing proteinase K digestion time, miRNA probe concentrations, hybridization temperatures, and NBT/BCIP development times. It is also possible to use the first portion of the protocol in combination with fluorescent antibodies in tissues where autofluorescence is appropriately low.

MicroRNA are small (approximately 22 nucleotides long) noncoding RNAs that are endogenously produced. They generally function to suppress protein expression through translational repression or mRNA degradation. miRNAs bind to mRNA targets with incomplete complementarity, making it possible for a single miRNA to suppress multiple targets.
Understanding which cell types and structures express miRNAs is an important part of understanding the mechanisms through which alterations in miRNA expression influence cell and tissue phenotypes. While methods such as miRNA sequencing, qPCR and Northern blotting can be used for detection of miRNAs in whole tissues, this approach does not allow one to determine which specific cell type they came from within a given tissue. Dissection of cellular and structural components prior to analysis using these methods can be very difficult and the conditions needed to achieve adequate isolations can lead to alterations in gene expression or degradation of RNAs. microRNA in situ hybridization is a method used to visualize microRNA location and expression levels in tissues. This technique is especially valuable in tissues composed of heterogeneous structures, such as the kidney.
MicroRNAs have been shown to play an regulatory role in kidney development2,3 and physiology4. microRNA expression alterations have also been shown to be involved with renal pathology such as fibrosis5-10, diabetic nephropathy7, renal carcinoma11,12, and acute kidney injury13. In our research, we have found that optimizing microRNA in situ hybridization for kidney tissues was valuable for determining the exact structural locations of miRNA expression in both health and disease14. Determination of the tubular and cellular expression of different microRNAs is important because their regulation of targets may be dependent on cellular functions. In diseased states it is also important to determine how alterations in miRNA expression may be impacting function.
The goal of the method described here was to build upon existing ISH methodologies developed by Kloosterman et al.15, other investigators16,17, and those suggested by Exiqon1 and optimize the method for formalin fixed kidney tissues. We have successfully used this method to identify distinct regional differences in renal microRNA miR-382 expression with unilateral ureteral obstruction18. This approach can be used with other tissues as well, with additional optimization.

<table border="0" cellpadding="0" cellspacing="0" width="481">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Paraformaldehyde</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">P6148</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">PBS</td>
			<td style="width:71px;">Gibco</td>
			<td style="width:137px;">70011044</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Diethyl Pyrocarbonate</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">D5758</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Tween-20</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">P1379</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Xylenes</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">534056</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Ethanol</td>
			<td style="width:71px;">Ultra Pure</td>
			<td style="width:137px;">200CSPTP</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">Tris-HCl</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">15506-017</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">CaCl2</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">C2536</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Glycine</td>
			<td style="width:71px;">J.T. Baker</td>
			<td style="width:137px;">4059-00</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Citric Acid</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">C2404</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Formamide</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">F9037</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">20x SSC Buffer</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">15557-044</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Heparin</td>
			<td style="width:71px;">SAGENT</td>
			<td style="width:137px;">25021-400-30</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">Yeast RNA</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">AM7118</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">MgCl2</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">M8266-1004</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">NaCl</td>
			<td style="width:71px;">J.T. Baker</td>
			<td style="width:137px;">4058-01</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Proteinase K</td>
			<td style="width:71px;">Fermentas</td>
			<td style="width:137px;">EO0491</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">3&#8217; DIG- miRNA probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">miR dependent-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">3&#8217; DIG- Scrambled miR probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">99004-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">3&#8217; DIG- U6 miR probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">99002-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Anti-Digoxigenin-Ab Fab</td>
			<td rowspan="2" style="width:71px;">Roche</td>
			<td rowspan="2" style="width:137px;">11093274910</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Fragments</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">NBT/BCIP</td>
			<td style="width:71px;">Roche</td>
			<td style="width:137px;">11681451001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Permount</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:137px;">SP15-500</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Coverslips</td>
			<td style="width:71px;">Fisher</td>
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			<td height="60" style="height:60px;width:195px;">Microtom HM 355 S</td>
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			<td style="width:137px;">23-900-672</td>
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			<td height="40" style="height:40px;width:195px;">In-slide Out Hybridization Oven</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">241000</td>
			<td style="width:79px;"></td>
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			<td height="21" style="height:21px;width:195px;">Aluminum Tray Assembly</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">C2403973</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Stainless Steel Rack Insert</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">C2403754</td>
			<td style="width:79px;"></td>
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microrna in situ hybridization for formalin fixed kidney tissues

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA probes. This protocol, originally developed by Kloosterman and colleagues for broad use with Exiqon miRNA probes1, has been modified to overcome challenges inherent in miRNA analysis in kidney tissues. These include issues such as structure identification and hard to remove residual probe and antibody. Use of relatively thin, 5 mm thick, tissue sections allowed for clear visualization of kidney structures, while a strong probe signal was retained in cells. Additionally, probe concentration and incubation conditions were optimized to facilitate visualization of microRNA expression with low background and nonspecific signal. Here, the optimized protocol is described, covering the initial tissue collection and preparation through the mounting of slides at the end of the procedure. The basic components of this protocol can be altered for application to other tissues and cell culture models.

The areas of a tissue section that become dried out during the hybridizations, incubations or wash steps generally end up staining more darkly during the NBT/BCIP development. Figure 1 shows a portion of a kidney section in which the HybriSlip slipped off of the edge of the tissue, allowing it to become partially dehydrated. Despite rehydration and coverage in the remaining steps, the signal in the dehydrated portion is artificially high.
The importance of controlling the time of NBT-BCIP development is demonstrated in Figures 2A and 2B. Development periods of longer than 4-5 hr result in pronounced nonspecific color development in scrambled-miR control probed tissues throughout the kidney (Figure 2A). Kidneys probed for high abundance targets, such as the U6 small nuclear RNA control, do not exhibit improved signals with incubations longer than 4-5 hours (Figure 2B).
The applicability of the ISH method described here to miRNA detection in kidney tissue is demonstrated in Figure 3, a figure reproduced from Kriegel et al.18&#160;In that study we found that unilateral ureteral obstruction (UUO) induced a nearly 3-fold increase in qPCR detected miR-382 expression in homogenized kidney tissue when compared to sham operated animals. This increase was blocked by intravenous deliver of anti-miR-382 (data not shown). The use of ISH on these kidney tissues indicated that the miR-382 detection provided by this probe was sensitive enough to provide quantifiable results that mirrored qPCR based expression analysis. Additionally, ISH allowed us to measure distinct regional differences in miRNA expression within the kidney.
<img alt="Figure 1" fo:content-width="5in" src="/files/ftp_upload/50785/50785fig1.jpg" width="600px" /> 
Figure 1. The effect of the partial dehydration of a rat kidney section during hybridization step. Calibration bar =100 mm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50785/50785fig1highres.jpg" target="_blank">Click here to view larger image</a>.
<img alt="Figure 2" fo:content-width="5in" src="/files/ftp_upload/50785/50785fig2.jpg" width="600px" /> 
Figure 2. Optimization of the duration of NBT/BCIP development. Allowing the NBT/BCIP development to continue for more than 4-5 hr results in significant background staining in scrambled-miR probed tissues (Figure 2A), while providing no further improvement in the signal in the positive control, U6 small nuclear RNA probed samples (Figure 2B). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50785/50785fig2highres.jpg" target="_blank">Click here to view larger image</a>.
<img alt="Figure 3" fo:content-width="5in" src="/files/ftp_upload/50785/50785fig3.jpg" width="600px" /> 
Figure 3. Representative images of miR-382 expression in mouse kidney sections obtained by in situ hybridization. Calibration bar = 50 &#181;m. (B) miR-382 expression as percent average IOD of sham + anti-scrambled treated mice. This figure has been modified from Kriegel et al., (Figure 5), which describes the details of treatment groups, methods, and results18. Anti-scrambled treated n= 10/group; anti-miR-382 n= 8/group; *significantly different from anti-scrambled treated mice with same surgery (P&#60;0.05), # significantly different from sham operated animals receiving the same anti-miR treatment. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50785/50785fig3highres.jpg" target="_blank">Click here to view larger image</a>.

Watch this Scientific Journal Video about MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues at JoVE.com

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA ...

microrna-in-situ-hybridization-for-formalin-fixed-kidney-tissues

Nanyang Technological University

Research

JoVE Journal

Biology

14.9K Views.  Medical College of Wisconsin. This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.

Video: MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

Double Whole Mount in situ Hybridization of Early Chick Embryos

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  gene expression in brain, neural tube, somite and heart primordia formation. This video demonstrates the different steps in 2-color whole mount in situ hybridization; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, the embryo is processed for prehybridization. The embryo is then hybridized with two different probes, one coupled to DIG, and one coupled to FITC.  Following overnight hybridization, the embryo is incubated with DIG coupled antibody. Color reaction for DIG substrate is performed, and the region of interest appears blue. The embryo is then incubated with FITC coupled antibody. The embryo is processed for color reaction with FITC, and the region of interest appears red. Finally, the embryo is fixed and processed for phtograph and sectioning. A troubleshooting guide is also presented.

This video demonstrates 2-color whole mount in situ hybridization, a method by which the spatial and temporal expression pattern of 2 different genes can be visualized in young chick embryos. This method was originally introduced by David Wilkinson, Domingos Henrique, Phil Ingham and David Ish -Horowicz.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Fluorescence in situ hybridization (FISH) Protocol in Human Sperm

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic process in the parents. In human males, these errors can lead to the production of spermatozoa with numerical chromosome abnormalities which represent an increased risk of transmitting these anomalies to the offspring.
For this reason, the technique of fluorescence in situ hybridization (FISH) on sperm nuclei has become a protocol widely incorporated in the context of clinical diagnosis. This practice provides an estimate of the frequencies of numerical chromosome abnormalities in the gametes of the patients that seek for genetic reproductive advice.
To date, the chromosomes most frequently included in sperm FISH analysis are chromosomes X, Y, 13, 18 and 21.
This video-article describes, step by step, how to process and fix a human semen sample, how to decondense and denature the sperm chromatin, how to proceed to obtain sperm FISH preparations, and how to visualize the results at the microscope. Special remarks of the most relevant steps are given to achieve the best results.

Fluorescence in situ hybridization FISH Protocol in Human Sperm

This video-article describes, step by step, how to process a semen sample to achieve good-quality fluorescence in situ hybridization on human spermatozoa. Preparations obtained can be used for aneuploidy screening in the context of clinical diagnosis.

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic ...

In Situ Hybridization for the Precise Localization of Transcripts in Plants

With the advances in genomics research of the past decade, plant biology has seen numerous studies presenting large-scale quantitative analyses of gene expression. Microarray and next generation sequencing approaches are being used to investigate developmental, physiological and stress response processes, dissect epigenetic and small RNA pathways, and build large gene regulatory networks1-3. While these techniques facilitate the simultaneous analysis of large gene sets, they typically provide a very limited spatiotemporal resolution of gene expression changes. This limitation can be partially overcome by using either profiling method in conjunction with lasermicrodissection or fluorescence-activated cell sorting4-7. However, to fully understand the biological role of a gene, knowledge of its spatiotemporal pattern of expression at a cellular resolution is essential. Particularly, when studying development or the effects of environmental stimuli and mutants can the detailed analysis of a gene's expression pattern become essential. For instance, subtle quantitative differences in the expression levels of key regulatory genes can lead to dramatic phenotypes when associated with the loss or gain of expression in specific cell types. 
Several methods are routinely used for the detailed examination of gene expression patterns. One is through analysis of transgenic reporter lines. Such analysis can, however, become time-consuming when analyzing multiple genes or working in plants recalcitrant to transformation. Moreover, an independent validation to ensure that the transgene expression pattern mimics that of the endogenous gene is typically required. Immunohistochemical protein localization or mRNA in situ hybridization present relatively fast alternatives for the direct visualization of gene expression within cells and tissues. The latter has the distinct advantage that it can be readily used on any gene of interest. In situ hybridization allows detection of target mRNAs in cells by hybridization with a labeled anti-sense RNA probe obtained by in vitro transcription of the gene of interest. 
Here we outline a protocol for the in situ localization of gene expression in plants that is highly sensitivity and specific. It is optimized for use with paraformaldehyde fixed, paraffin-embedded sections, which give excellent preservation of histology, and DIG-labeled probes that are visualized by immuno-detection and alkaline-phosphatase colorimetric reaction. This protocol has been successfully applied to a number of tissues from a wide range of plant species, and can be used to analyze expression of mRNAs as well as small RNAs8-14.

In Situ Hybridization for the Precise Localization of Transcripts in Plants

The in situ hybridization protocol described here allows a direct localization of mRNA and small RNA expression at the cellular level with high sensitivity and specificity. The procedure is optimized for paraffin-embedded plant tissue sections, is applicable to a wide range of plants and tissues, and can be completed within ten days.

With the advances in genomics research of the past decade, plant biology has seen numerous studies presenting large-scale quantitative analyses of gene ...

Radioactive in situ Hybridization for Detecting Diverse Gene Expression Patterns in Tissue

Knowing the timing, level, cellular localization, and cell type that a gene is expressed in contributes to our understanding of the function of the gene. Each of these features can be accomplished with in situ hybridization to mRNAs within cells. Here we present a radioactive in situ hybridization method modified from Clayton et al. (1988)1 that has been working successfully in our lab for many years, especially for adult vertebrate brains2-5. The long complementary RNA (cRNA) probes to the target sequence allows for detection of low abundance transcripts6,7. Incorporation of radioactive nucleotides into the cRNA probes allows for further detection sensitivity of low abundance transcripts and quantitative analyses, either by light sensitive x-ray film or emulsion coated over the tissue. These detection methods provide a long-term record of target gene expression. Compared with non-radioactive probe methods, such as DIG-labeling, the radioactive probe hybridization method does not require multiple amplification steps using HRP-antibodies and/or TSA kit to detect low abundance transcripts. Therefore, this method provides a linear relation between signal intensity and targeted mRNA amounts for quantitative analysis. It allows processing 100-200 slides simultaneously. It works well for different developmental stages of embryos. Most developmental studies of gene expression use whole embryos and non-radioactive approaches8,9, in part because embryonic tissue is more fragile than adult tissue, with less cohesion between cells, making it difficult to see boundaries between cell populations with tissue sections. In contrast, our radioactive approach, due to the larger range of sensitivity, is able to obtain higher contrast in resolution of gene expression between tissue regions, making it easier to see boundaries between populations. Using this method, researchers could reveal the possible significance of a newly identified gene, and further predict the function of the gene of interest.

Radioactive in situ Hybridization for Detecting Diverse Gene Expression Patterns in Tissue

This protocol is successfully used to quantitatively detect levels and spatial patterns of mRNA expression in multiple tissue types across vertebrate species. The method can detect low abundance transcripts and allows processing of hundreds of slides simultaneously. We present this protocol using expression profiling of avian embryonic brain formation as an example.

Knowing the timing, level, cellular localization, and cell type that a gene is expressed in contributes to our understanding of the function of the gene. ...

Detection of Viral RNA by Fluorescence in situ Hybridization (FISH)

Viruses that infect cells elicit specific changes to normal cell functions which serve to divert energy and resources for viral replication. Many aspects of host cell function are commandeered by viruses, usually by the expression of viral gene products that recruit host cell proteins and machineries. Moreover, viruses engineer specific membrane organelles or tag on to mobile vesicles and motor proteins to target regions of the cell (during de novo infection, viruses co-opt molecular motor proteins to target the nucleus; later, during virus assembly, they will hijack cellular machineries that will help in the assembly of viruses). Less is understood on how viruses, in particular those with RNA genomes, coordinate the intracellular trafficking of both protein and RNA components and how they achieve assembly of infectious particles at specific loci in the cell. The study of RNA localization began in earlier work. Developing lower eukaryotic embryos and neuronal cells provided important biological information, and also underscored the importance of RNA localization in the programming of gene expression cascades. The study in other organisms and cell systems has yielded similar important information. Viruses are obligate parasites and must utilise their host cells to replicate. Thus, it is critical to understand how RNA viruses direct their RNA genomes from the nucleus, through the nuclear pore, through the cytoplasm and on to one of its final destinations, into progeny virus particles 1.
FISH serves as a useful tool to identify changes in steady-state localization of viral RNA. When combined with immunofluorescence (IF) analysis 22, FISH/IF co-analyses will provide information on the co-localization of proteins with the viral RNA3. This analysis therefore provides a good starting point to test for RNA-protein interactions by other biochemical or biophysical tests 4,5, since co-localization by itself is not enough evidence to be certain of an interaction. In studying viral RNA localization using a method like this, abundant information has been gained on both viral and cellular RNA trafficking events 6. For instance, HIV-1 produces RNA in the nucleus of infected cells but the RNA is only translated in the cytoplasm. When one key viral protein is missing (Rev) 7, FISH of the viral RNA has revealed that the block to viral replication is due to the retention of the HIV-1 genomic RNA in the nucleus 8. 
Here, we present the method for visual analysis of viral genomic RNA in situ. The method makes use of a labelled RNA probe. This probe is designed to be complementary to the viral genomic RNA. During the in vitro synthesis of the antisense RNA probe, the ribonucleotide that is modified with digoxigenin (DIG) is included in an in vitro transcription reaction. Once the probe has hybridized to the target mRNA in cells, subsequent antibody labelling steps (Figure 1) will reveal the localization of the mRNA as well as proteins of interest when performing FISH/IF.

Detection of Viral RNA by Fluorescence in situ Hybridization FISH

A fluorescence in situ hybridization (FISH) method was developed to visually detect viral genomic RNA using fluorescence microscopy. A probe is made with specificity to the viral RNA that can then be identified using a combination of hybridization and immunofluorescence techniques. This technique offers the advantage of identifying the localization of the viral RNA or DNA at steady-state, providing information on the control of intracellular virus trafficking events.

Viruses  that infect cells elicit specific changes to normal cell functions which serve  to divert energy and resources for viral replication. Many ...

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The specification of replication timing is thought to be a dynamic process regulated by tissue-specific and developmental cues that are responsive to epigenetic modifications. However, the mechanisms regulating where and when DNA replication initiates along chromosomes remains poorly understood. Homologous chromosomes usually replicate synchronously, however there are notable exceptions to this rule. For example, in female mammalian cells one of the two X chromosomes becomes late replicating through a process known as X inactivation1. Along with this delay in replication timing, estimated to be 2-3 hr, the majority of genes become transcriptionally silenced on one X chromosome. In addition, a discrete cis-acting locus, known as the X inactivation center, regulates this X inactivation process, including the induction of delayed replication timing on the entire inactive X chromosome. In addition, certain chromosome rearrangements found in cancer cells and in cells exposed to ionizing radiation display a significant delay in replication timing of &gt;3 hours that affects the entire chromosome2,3. Recent work from our lab indicates that disruption of discrete cis-acting autosomal loci result in an extremely late replicating phenotype that affects the entire chromosome4. Additional 'chromosome engineering' studies indicate that certain chromosome rearrangements affecting many different chromosomes result in this abnormal replication-timing phenotype, suggesting that all mammalian chromosomes contain discrete cis-acting loci that control proper replication timing of individual chromosomes5.
Here, we present a method for the quantitative analysis of chromosome replication timing combined with fluorescent in situ hybridization. This method allows for a direct comparison of replication timing between homologous chromosomes within the same cell, and was adapted from6. In addition, this method allows for the unambiguous identification of chromosomal rearrangements that correlate with changes in replication timing that affect the entire chromosome. This method has advantages over recently developed high throughput micro-array or sequencing protocols that cannot distinguish between homologous alleles present on rearranged and un-rearranged chromosomes. In addition, because the method described here evaluates single cells, it can detect changes in chromosome replication timing on chromosomal rearrangements that are present in only a fraction of the cells in a population.

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

A quantitative method for the analysis of chromosome replication timing is described. The method utilizes BrdU incorporation in combination with fluorescent in situ hybridization (FISH) to assess replication timing of mammalian chromosomes. This technique allows for the direct comparison of rearranged and un-rearranged chromosomes within the same cell.

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The ...

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for using FISH to quantify the number of mRNAs in single yeast cells. Cells can be grown in any condition of interest and then fixed and made permeable. Subsequently, multiple single-stranded deoxyoligonucleotides conjugated to fluorescent dyes are used to label and visualize mRNAs. Diffraction-limited fluorescence from single mRNA molecules is quantified using a spot-detection algorithm to identify and count the number of mRNAs per cell. While the more standard quantification methods of northern blots, RT-PCR and gene expression microarrays provide information on average mRNAs in the bulk population, FISH facilitates both the counting and localization of these mRNAs in single cells at single-molecule resolution.

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

This protocol describes an experimental procedure for performing Fluorescence in situ Hybridization (FISH) for counting mRNAs in single cells at single-molecule resolution.

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for ...

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale quantitative analysis of formalin fixed and paraffin embedded (FFPE) tissue. The procedure comprises four distinct steps. The first one is the preparation of sections from the FFPE material and microdissection of cells of interest. In the second step the isolated cells are lysed and processed using 'filter aided sample preparation' (FASP) technique. In this step, proteins are depleted from reagents used for the sample lysis and are digested in two-steps using endoproteinase LysC and trypsin. 
After each digestion, the peptides are collected in separate fractions and their content is determined using a highly sensitive fluorescence measurement. Finally, the peptides are fractionated on 'pipette-tip' microcolumns. The LysC-peptides are separated into 4 fractions whereas the tryptic peptides are separated into 2 fractions. In this way prepared samples allow analysis of proteomes from minute amounts of material to a depth of 10,000 proteins. Thus, the described workflow is a powerful technique for studying diseases in a system-wide-fashion as well as for identification of potential biomarkers and drug targets.

Archival formalin fixed and paraffin embedded (FFPE) clinical samples are valuable material for investigation of diseases. Here we demonstrate a sample preparation workflow allowing in-depth proteomic analysis of microdissected FFPE tissue.

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale ...

qPCR Is a Sensitive and Rapid Method for Detection of Cytomegaloviral DNA in Formalin-fixed, Paraffin-embedded Biopsy Tissue

It is crucial to identify cytomegalovirus (CMV) infection in the gastrointestinal (GI) tract of immunosuppressed patients, given their greater risk for developing severe infection. Many laboratory methods for the detection of CMV infection have been developed, including serology, viral culture, and molecular methods. Often, these methods reflect systemic involvement with CMV and do not specifically identify local tissue involvement. Therefore, detection of CMV infection in the GI tract is frequently done by traditional histology of biopsy tissue. Hematoxylin and eosin (H&#38;E) staining in conjunction with immunohistochemistry (IHC) have remained the mainstays of examining these biopsies. H&#38;E and IHC sometimes result in atypical (equivocal) staining patterns, making interpretation difficult. It was shown that quantitative polymerase chain reaction (qPCR) for CMV can successfully be performed on formalin-fixed, paraffin-embedded (FFPE) biopsy tissue for very high sensitivity and specificity. The goal of this protocol is to demonstrate how to perform qPCR testing for the detection of CMV in FFPE biopsy tissue in a clinical laboratory setting. This method is likely to be of great benefit for patients in cases of equivocal staining for CMV in GI biopsies.

This protocol describes qPCR detection of cytomegalovirus in formalin-fixed, paraffin-embedded biopsy tissue, which is rapid, sensitive, specific, and useful for interpreting equivocal hematoxylin and eosin or immunohistochemical staining patterns.

It is crucial to identify cytomegalovirus (CMV) infection in the gastrointestinal (GI) tract of immunosuppressed patients, given their greater risk for ...

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly effective at mapping highly repetitive sequences to heterochromatic regions, where computational approaches face prohibitive challenges. Here we describe a streamlined protocol for DNA ISH that circumvents formamide washes that are standard steps in other DNA ISH protocols. Our protocol is optimized for hybridization with short single strand DNA probes that carry fluorescent dyes, which effectively mark repetitive DNA sequences within heterochromatic chromosomal regions across a number of different insect tissue types. However, applications may be extended to use with larger probes and visualization of single copy (non-repetitive) DNA sequences. We demonstrate this method by mapping several different repetitive sequences to squashed chromosomes from Drosophila melanogaster neural cells and Nasonia vitripennis spermatocytes. We show hybridization patterns for both small, commercially synthesized probes and for a larger probe for comparison. This procedure uses simple laboratory supplies and reagents, and is ideal for investigators who have little experience with performing DNA ISH.

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

Here, we present a simple method for performing fluorescence DNA in situ hybridization (DNA ISH) to visualize repetitive heterochromatic sequences on slide-mounted chromosomes. The method requires minimal reagents and it is versatile for use with short or long probes, different tissues, and detection with fluorescence or non-fluorescence-based signals.