We thank Dr. Thomas Tuschl, head of the laboratory for RNA molecular biology, as well as members of his laboratory for their support and for sharing the technology developed in his laboratory and providing access to the RNAworld pipeline. We also thank Dr. Markus Hafner for sharing his protocol and providing detailed descriptions on all biochemical and enzymatic steps used in his initial procedure.

<ol><li>Peiró-Chova, L., Peña-Chilet, M., López-, J. A., García-Gimenez, J. L., Alonso-Yuste, E., Burgues, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High+stability+of+microRNAs+in+tissue+samples+of+compromised+quality%5BTitle%5D)+AND+%22Virchows.+Arch%22%5BJournal%5D)">High stability of microRNAs in tissue samples of compromised quality.</a> Virchows. Arch. 463, 765-774 (2013).</li>
<li>Klopfleisch, R., Weiss, A. T., Gruber, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Excavation+of+a+buried+treasure--DNA%2C+mRNA%2C+miRNA+and+protein+analysis+in+formalin+fixed%2C+paraffin+embedded+tissues%5BTitle%5D)+AND+%22Histol.+Histopathol%22%5BJournal%5D)">Excavation of a buried treasure--DNA, mRNA, miRNA and protein analysis in formalin fixed, paraffin embedded tissues.</a> Histol. Histopathol. 26, 797-810 (2011).</li>
<li>Kakimoto, Y., Kamiguchi, H., Ochiai, E., Satoh, F., Osawa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNA+Stability+in+Postmortem+FFPE+Tissues%3A+Quantitative+Analysis+Using+Autoptic+Samples+from+Acute+Myocardial+Infarction+Patients%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">MicroRNA Stability in Postmortem FFPE Tissues: Quantitative Analysis Using Autoptic Samples from Acute Myocardial Infarction Patients.</a> PLoS One. 10 (6), e0129338(2015).</li>
<li>Giricz, O., Reynolds, P. A., Ramnauth, A., Liu, C., Wang, T., Stead, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hsa-miR-375+is+differentially+expressed+during+breast+lobular+neoplasia+and+promotes+loss+of+mammary+acinar+polarity%5BTitle%5D)+AND+%22J.+Pathol%22%5BJournal%5D)">Hsa-miR-375 is differentially expressed during breast lobular neoplasia and promotes loss of mammary acinar polarity.</a> J. Pathol. 226, 108-119 (2012).</li>
<li>Hui, A. B., Shi, W., Boutros, P. C., Miller, N., Pintilie, M., Fyles, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Robust+global+micro-RNA+profiling+with+formalin-fixed+paraffin-embedded+breast+cancer+tissues%5BTitle%5D)+AND+%22Lab.+Invest%22%5BJournal%5D)">Robust global micro-RNA profiling with formalin-fixed paraffin-embedded breast cancer tissues.</a> Lab. Invest. 89, 597-606 (2009).</li>
<li>Zhang, X., Chen, J., Radcliffe, T., Lebrun, D. P., Tron, V. A., Feilotter, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+array-based+analysis+of+microRNA+expression+comparing+matched+frozen+and+formalin-fixed+paraffin-embedded+human+tissue+samples%5BTitle%5D)+AND+%22J.+Mol.+Diagn%22%5BJournal%5D)">An array-based analysis of microRNA expression comparing matched frozen and formalin-fixed paraffin-embedded human tissue samples.</a> J. Mol. Diagn. 10, 513-519 (2008).</li>
<li>Kolbert, C. P., Feddersen, R. M., Rakhshan, F., Grill, D. E., Simon, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Multi-platform+analysis+of+microRNA+expression+measurements+in+RNA+from+fresh+frozen+and+FFPE+tissues%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">Multi-platform analysis of microRNA expression measurements in RNA from fresh frozen and FFPE tissues.</a> PLoS One. 8, e52517(2013).</li>
<li>Meng, W., McElroy, J. P., Volinia, S., Palatini, J., Warner, S., Ayers, L. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Comparison+of+microRNA+deep+sequencing+of+matched+formalin-fixed+paraffin-embedded+and+fresh+frozen+cancer+tissues%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">Comparison of microRNA deep sequencing of matched formalin-fixed paraffin-embedded and fresh frozen cancer tissues.</a> PLoS One. 8 (5), e64393(2013).</li>
<li>Liu, A., Tetzlaff, M. T., Vanbelle, P., Elder, D., Feldman, M., Tobias, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNA+expression+profiling+outperforms+mRNA+expression+profiling+in+formalin-fixed+paraffin-embedded+tissues%5BTitle%5D)+AND+%22Int.+J.+Clin.+Exp.+Pathol%22%5BJournal%5D)">MicroRNA expression profiling outperforms mRNA expression profiling in formalin-fixed paraffin-embedded tissues.</a> Int. J. Clin. Exp. Pathol. 2, 519-527 (2009).</li>
<li>Dijkstra, J. R., Mekenkamp, L. J., Teerenstra, S., De Krijger, I., Nagtegaal, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNA+expression+in+formalin-fixed+paraffin+embedded+tissue+using+real+time+quantitative+PCR%3A+the+strengths+and+pitfalls%5BTitle%5D)+AND+%22J+Cell+Mol+Med%22%5BJournal%5D)">MicroRNA expression in formalin-fixed paraffin embedded tissue using real time quantitative PCR: the strengths and pitfalls.</a> J Cell Mol Med. 16, 683-690 (2012).</li>
<li>Siebolts, U., Varnholt, H., Drebber, U., Dienes, H. P., Wickenhauser, C., Odenthal, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissues+from+routine+pathology+archives+are+suitable+for+microRNA+analyses+by+quantitative+PCR%5BTitle%5D)+AND+%22J.+Clin.+Pathol%22%5BJournal%5D)">Tissues from routine pathology archives are suitable for microRNA analyses by quantitative PCR.</a> J. Clin. Pathol. 62, 84-88 (2009).</li>
<li>Jang, J. S., Simon, V. A., Feddersen, R. M., Rakhshan, F., Schultz, D. A., Zschunke, M. A., Lingle, W. L., Kolbert, C. P., Jen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Quantitative+miRNA+expression+analysis+using+fluidigm+microfluidics+dynamic+arrays%5BTitle%5D)+AND+%22BMC+Genomics%22%5BJournal%5D)">Quantitative miRNA expression analysis using fluidigm microfluidics dynamic arrays.</a> BMC Genomics. 12, 144(2011).</li>
<li>Andreasen, D., Fog, J. U., Biggs, W., Salomon, J., Dahslveen, I. K., Baker, A., Mouritzen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Improved+microRNA+quantification+in+total+RNA+from+clinical+samples%5BTitle%5D)+AND+%22Methods%22%5BJournal%5D)">Improved microRNA quantification in total RNA from clinical samples.</a> Methods. 50 (4), S6-S9 (2010).</li>
<li>Kelly, A. D., Hill, K. E., Correll, M., Wang, Y. E., Rubio, R., Duan, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Next-generation+sequencing+and+microarray-based+interrogation+of+microRNAs+from+formalin-fixed%2C+paraffin-embedded+tissue%3A+preliminary+assessment+of+cross-platform+concordance%5BTitle%5D)+AND+%22Genomics%22%5BJournal%5D)">Next-generation sequencing and microarray-based interrogation of microRNAs from formalin-fixed, paraffin-embedded tissue: preliminary assessment of cross-platform concordance.</a> Genomics. 102, 8-14 (2013).</li>
<li>Visone, R., Croce, C. M. <a target="_blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671346/">MiRNAs and cancer.</a> Am. J. Pathol. 174, 1131-1138 (2009).</li>
<li>Lu, J., Getz, G., Miska, E. A., Alvarez-Saavedra, E., Lamb, J., Peck, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNA+expression+profiles+classify+human+cancers%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">MicroRNA expression profiles classify human cancers.</a> Nature. 435, 834-838 (2005).</li>
<li>Cho, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNAs%3A+potential+biomarkers+for+cancer+diagnosis%2C+prognosis+and+targets+for+therapy%5BTitle%5D)+AND+%22Int.+J.+Biochem.+Cell.+Biol%22%5BJournal%5D)">MicroRNAs: potential biomarkers for cancer diagnosis, prognosis and targets for therapy.</a> Int. J. Biochem. Cell. Biol. 42, 1273-1281 (2010).</li>
<li>Hui, A., How, C., Ito, E., Liu, F. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Micro-RNAs+as+diagnostic+or+prognostic+markers+in+human+epithelial+malignancies%5BTitle%5D)+AND+%22BMC+Cancer%22%5BJournal%5D)">Micro-RNAs as diagnostic or prognostic markers in human epithelial malignancies.</a> BMC Cancer. 11, 500(2011).</li>
<li>Tam, S., de Borja, R., Tsao, M. S., McPherson, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Robust+global+microRNA+expression+profiling+using+next-generation+sequencing+technologies%5BTitle%5D)+AND+%22Lab.+Invest%22%5BJournal%5D)">Robust global microRNA expression profiling using next-generation sequencing technologies.</a> Lab. Invest. 94, 350-358 (2014).</li>
<li>Loudig, O., Wan, T., Ye, K., Lin, J., Wang, Y., Ramnauth, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evaluation+and+Adaptation+of+a+Laboratory+Based+cDNA+Library+Preparation+Protocol+for+Retrospective+Sequencing+of+Archived+MicroRNAs+from+up+to+35-Year-Old+Clinical+FFPE+Specimens%5BTitle%5D)+AND+%22Int+J+Mol+Sci%22%5BJournal%5D)">Evaluation and Adaptation of a Laboratory Based cDNA Library Preparation Protocol for Retrospective Sequencing of Archived MicroRNAs from up to 35-Year-Old Clinical FFPE Specimens.</a> Int J Mol Sci. 18, e627(2017).</li>
<li>Kotorashvili, A., Ramnauth, A., Liu, C., Lin, J., Ye, K., Kim, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effective+DNA%2FRNA+co-extraction+for+analysis+of+microRNAs%2C+mRNAs%2C+and+genomic+DNA+from+formalin-fixed+paraffin-embedded+specimens%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">Effective DNA/RNA co-extraction for analysis of microRNAs, mRNAs, and genomic DNA from formalin-fixed paraffin-embedded specimens.</a> PLoS One. 7 (4), e34683(2012).</li>
<li>Hafner, M., Renwick, N., Farazi, T. A., Mihailović, A., Pena, J. T., Tuschl, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Barcoded+cDNA+library+preparation+for+small+RNA+profiling+by+next-generation+sequencing%5BTitle%5D)+AND+%22Methods%22%5BJournal%5D)">Barcoded cDNA library preparation for small RNA profiling by next-generation sequencing.</a> Methods. 58 (2), 164-170 (2012).</li>
<li>Loudig, O., Brandwein-Gensler, M., Kim, R. S., Lin, J., Isayeva, T., Liu, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Illumina+whole-genome+complementary+DNA-mediated+annealing%2C+selection%2C+extension+and+ligation+platform%3A+assessing+its+performance+in+formalin-fixed%2C+paraffin-embedded+samples+and+identifying+invasion+pattern-related+genes+in+oral+squamous+cell+carcinoma%5BTitle%5D)+AND+%22Hum.+Pathol%22%5BJournal%5D)">Illumina whole-genome complementary DNA-mediated annealing, selection, extension and ligation platform: assessing its performance in formalin-fixed, paraffin-embedded samples and identifying invasion pattern-related genes in oral squamous cell carcinoma.</a> Hum. Pathol. 42 (12), 1911-1922 (2011).</li>
</ol>

The authors wish to disclose that a publication containing some of the data presented in this manuscript was published in the International Journal of Molecular Sciences by Loudig et al.21.

A highly reproducible and robust cDNA library preparation protocol for NGS of small RNAs archived in FFPE RNA specimens is presented in this protocol, which is a modified and optimized version of the procedure described by Hafner et al.22
All steps of this protocol have been optimized for use with older archived and compromised total RNA recovered from FFPE specimens. The key step of this protocol, for processing small amounts of FFPE RNA, resides in the poolin...

miRNAs are remarkably well conserved in formalin-fixed paraffin-embedded (FFPE) specimens1,2,3. Previous work has demonstrated that the expression of these short regulatory non-coding single stranded RNA molecules can be successfully evaluated using total RNA from FFPE samples and provide relevant gene expression data when compared to the original fresh tissues4,5,6,7,8. When compared to large-size messenger RNAs, which have been shown to be critically affected by FFPE tissue processing (formaldehyde, heat, desiccation, etc.), endogenous RNases, and the age of the specimens, the small size of miRNAs (~18&#8211;24 nucleotides) appears to make them resistant to degradation and resilient to long-term storage, also demonstrated through miRNA expression studies that outperform high-throughput mRNA studies in archived specimens9. miRNA expression studies using archived clinical specimens, which have mostly been performed in small-scale analyses, have demonstrated that single or multiplexed quantitative PCR assays, different types of microarray technologies, and most recently NGS can be used to assess the expression of preserved miRNAs after optimization of these assays10,11,12,13,14.
Given that dysregulation of miRNA expression has been associated with the development of a variety of human malignancies and that there is potentially an enormous supply of clinically annotated archived specimens, it has become apparent that these small RNA molecules represent a promising source of potential cancer biomarkers15,16,17,18. The use of a high-throughput gene expression technology such as NGS has the advantage of providing a global evaluation of all miRNA transcripts when compared to targeted technologies such as PCR and/or microarrays19. For this reason, an optimized, affordable, and easily applicable protocol for cDNA library preparation of small RNAs from older archived specimens for NGS was optimized to enable large-scale retrospective studies20.
We previously established a simultaneous RNA/DNA extraction protocol for separate recovery of RNA and DNA from older archived specimens, which we found to outperform contemporary commercial kits21. Using this extraction protocol, to obtain total RNA from FFPE tissues archived for extended period of times, we optimized the preparation of cDNA libraries for NGS of miRNAs preserved in clinical specimens for up to 35 years. Furthermore, in a recently published study where we prepared cDNA libraries from clinically classified ductal carcinoma in situ (DCIS) specimens, we identified differentially expressed miRNAs that were validated by quantitative PCR, which indicated that specific miRNA expression changes may be detectable in DCIS lesions from patients who develop breast cancer when compared to DCIS lesions from patients who do not develop breast cancer.
Considering the cost of commercial kits for preparation of small RNA cDNA libraries, the potential for their discontinuation, as well as the use of copyright/patent-protected reagents that cannot be optimized, we decided to adapt a previously published laboratory-based and kit-free 3&#39; barcoded cDNA library preparation protocol for NGS of small RNAs archived in FFPE specimens, allowing simultaneous analysis of 18 samples22. This protocol provides an ideal and robust step-by-step procedure with visual and technical evaluation checkpoints, which were critical for adaptation to FFPE RNA specimens, and has a strong potential for application to other sources of compromised or difficult to use RNA material. The original protocol&#39;s applicability was improved by replacing radioactively labeled size markers with fluorescent (e.g., SYBR Gold) detectable RNA size markers used during selection of ligated libraries on large polyacrylamide gels. This optimized protocol relies on the ligation of 3&#39; barcoded adapters to 18 individual FFPE RNA specimens, which are then pooled together to undergo 5&#39; adapter ligation, reverse-transcription, and a pilot PCR analysis for tailored amplification of the final cDNA library prior to large-scale PCR amplification, purification, and NGS on a high throughput sequencer.

<table><tbody><tr><td>1% Triton x-100</td><td>Invitrogen</td><td>HFH10</td><td></td></tr><tr><td>10mM ATP</td><td>Ambion</td><td>AM8110G</td><td></td></tr><tr><td>10X dNTPs</td><td>Ambion</td><td>AM8110G</td><td></td></tr><tr><td>10x TBE</td><td>Thermofisher Scientific</td><td>15581044</td><td></td></tr><tr><td>14M Mercaptoethanol</td><td>Sigma</td><td>O3445I-100</td><td></td></tr><tr><td>20 nt ladder</td><td>Jena Bioscience</td><td>M-232S</td><td></td></tr><tr><td>20mg/ml Bovine Serum Albumine</td><td>Sigma</td><td>B8894-5ML</td><td></td></tr><tr><td>50X Titanium Taq</td><td>Clontech Laboratories</td><td>639208</td><td></td></tr><tr><td>Ammonium Persulfate</td><td>Fisher Scientific</td><td>7727-54-0</td><td></td></tr><tr><td>BRL Vertical Gel Electrophoresis System with glass plates and combs</td><td>GIBCO</td><td>V16</td><td></td></tr><tr><td>Dimethyl sulfoxide (DMSO)</td><td>Sigma</td><td>D9170-5VL</td><td></td></tr><tr><td>Eppendorf microcentrifuge 5424R</td><td>USA scientific</td><td>4054-4537Q</td><td></td></tr><tr><td>Eppndorf Thermomixer</td><td>USA scientific</td><td>4053-8223Q</td><td></td></tr><tr><td>Fisherbrand&amp;trade; Siliconized Low-Retention Microcentrifuge Tubes 1.5ml</td><td>Fisher Scientific</td><td>02-681-320</td><td></td></tr><tr><td>Gel Breaker Tube 0.5 ml</td><td>IST Engineering Inc,</td><td>3388-100</td><td></td></tr><tr><td>Gel electrophoresis apparatus 7cm x10cm- Mini-sub Cell GT with gel trays and combs</td><td>Biorad</td><td>1704446</td><td></td></tr><tr><td>Glycoblue</td><td>Ambion</td><td>AM9516</td><td></td></tr><tr><td>Jersey-Cote</td><td>LabScientific, Inc</td><td>1188</td><td></td></tr><tr><td>KcL 2M</td><td>Ambion</td><td>AM9640G</td><td></td></tr><tr><td>MgCl2 1M</td><td>Ambion</td><td>AM9530G</td><td></td></tr><tr><td>Minifuge dual rotor personal centrifuge</td><td>USA scientific</td><td>2641-0016</td><td></td></tr><tr><td>Model V16 polyacrylamide gel electrophoresis apparatus, glasses, combs, and spacers</td><td>Ciore Life Science</td><td>21070010</td><td></td></tr><tr><td>Oligonucleotides</td><td>IDT</td><td>Defined during order</td><td></td></tr><tr><td>Owl EasyCast B2 mini electrophoresis system- with gel trays and combs</td><td>Thermofisher Scientific</td><td>B2</td><td></td></tr><tr><td>Qiaquick Gel Extraction kit</td><td>Qiagen</td><td>28704</td><td></td></tr><tr><td>Restriction enzyme PmeI</td><td>NEB</td><td>R0560S</td><td></td></tr><tr><td>RNase-free water</td><td>Ambion</td><td>AM9932</td><td></td></tr><tr><td>Safe Imager 2.0</td><td>Life Technologies</td><td>G6600</td><td></td></tr><tr><td>Safe Imager 2.0 blue light transilluminator</td><td>Thermofisher</td><td>G6600</td><td></td></tr><tr><td>SeaKem LE agarose</td><td>Lonza</td><td>50002</td><td></td></tr><tr><td>Superscript III reverse transcription kit</td><td>Invitrogen</td><td>18080-044</td><td></td></tr><tr><td>SybrGold</td><td>Life Technologies</td><td>S11494</td><td></td></tr><tr><td>T4 RNA Ligase 1</td><td>NEB</td><td>M0204S</td><td></td></tr><tr><td>T4 RNA Ligase 2 Truncated K227Q</td><td>NEB</td><td>0351L</td><td></td></tr><tr><td>TEMED</td><td>Fisher Scientific</td><td>O3446I-100</td><td></td></tr><tr><td>Themocycler with heated lid</td><td>Applied Biosystem</td><td>4359659</td><td></td></tr><tr><td>Tris 1M pH 7.5</td><td>Invitrogen</td><td>15567027</td><td></td></tr><tr><td>Tris 1M pH8.0</td><td>Ambion</td><td>AM9855G</td><td></td></tr><tr><td>UltraPure Sequagel system concentrate, diluent, and buffer</td><td>National Diagnostics</td><td>EC-833</td><td></td></tr></tbody></table>

retrospective microrna sequencing: complementary dna library preparation protocol using formalin-fixed paraffin-embedded rna specimens

&#8211;Archived, clinically classified formalin-fixed paraffin-embedded (FFPE) tissues can provide nucleic acids for retrospective molecular studies of cancer development. By using non-invasive or pre-malignant lesions from patients who later develop invasive disease, gene expression analyses may help identify early molecular alterations that predispose to cancer risk. It has been well described that nucleic acids recovered from FFPE tissues have undergone severe physical damage and chemical modifications, which make their analysis difficult and generally requires adapted assays. MicroRNAs (miRNAs), however, which represent a small class of RNA molecules spanning only up to ~18&#8211;24 nucleotides, have been shown to withstand long-term storage and have been successfully analyzed in FFPE samples. Here we present a 3&#39; barcoded complementary DNA (cDNA) library preparation protocol specifically optimized for the analysis of small RNAs extracted from archived tissues, which was recently demonstrated to be robust and highly reproducible when using archived clinical specimens stored for up to 35 years. This library preparation is well adapted to the multiplex analysis of compromised/degraded material where RNA samples (up to 18) are ligated with individual 3&#39; barcoded adapters and then pooled together for subsequent enzymatic and biochemical preparations prior to analysis. All purifications are performed by polyacrylamide gel electrophoresis (PAGE), which allows size-specific selections and enrichments of barcoded small RNA species. This cDNA library preparation is well adapted to minute RNA inputs, as a pilot polymerase chain reaction (PCR) allows determination of a specific amplification cycle to produce optimal amounts of material for next-generation sequencing (NGS). This approach was optimized for the use of degraded FFPE RNA from specimens archived for up to 35 years and provides highly reproducible NGS data.

As described in the method here, a total of 18 individual FFPE RNA samples (100 ng each) are set up in separate tubes to undergo 3&#39; adenylated barcoded oligonucleotide T4 ligation overnight. The next day, the enzymatic reactions are heat-deactivated, combined, and precipitated in a single tube. The RNA pellet is resuspended and the ligated RNA molecules are separated on a 15% denaturing polyacrylamide gel (PAGE), where RNA oligonucleotide size markers that migrated in adjacent wells o...

Watch this Scientific Journal Video about Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed Paraffin-embedded RNA Specimens at JoVE.com

Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed Paraffin-embedded RNA Specimens

Formalin-fixed paraffin-embedded specimens represent a valuable source of molecular biomarkers of human diseases. Here we present a laboratory-based cDNA library preparation protocol, initially designed with fresh frozen RNA, and optimized for the analysis of archived microRNAs from tissues stored up to 35 years.

&#8211;Archived, clinically classified formalin-fixed paraffin-embedded (FFPE) tissues can provide nucleic acids for retrospective molecular studies of ...

retrospective-microrna-sequencing-complementary-dna-library

Research

JoVE Journal

Genetics

9.3K Views.  Hackensack University Medical Center. Formalin-fixed paraffin-embedded specimens represent a valuable source of molecular biomarkers of human diseases. Here we present a laboratory-based cDNA library preparation protocol, initially designed with fresh frozen RNA, and optimized for the analysis of archived microRNAs from tissues stored up to 35 years.

Video: Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed Paraffin-embedded RNA Specimens

A Complete Pipeline for Isolating and Sequencing MicroRNAs, and Analyzing Them Using Open Source Tools

Half of all human transcripts are thought to be regulated by microRNAs. Therefore, quantifying microRNA expression can reveal underlying mechanisms in disease states and provide therapeutic targets and biomarkers. Here, we detail how to accurately quantify microRNAs. Briefly, this method describes isolating microRNAs, ligating them to adaptors suitable for high-throughput sequencing, amplifying the final products, and preparing a sample library. Then, we explain how to align the obtained sequencing reads to microRNA hairpins, and quantify, normalize, and calculate their differential expression. Versatile and robust, this combined experimental workflow and bioinformatic analysis enables users to begin with tissue extraction and finish with microRNA quantification.

Here, we describe a step-by-step strategy for isolating small RNAs, enriching for microRNAs, and preparing samples for high-throughput sequencing. We then describe how to process sequence reads and align them to microRNAs, using open source tools.

Half of all human transcripts are thought to be regulated by microRNAs. Therefore, quantifying microRNA expression can reveal underlying mechanisms in ...

Cerebrospinal Fluid MicroRNA Profiling Using Quantitative Real Time PCR

MicroRNAs (miRNAs) constitute a potent layer of gene regulation by guiding RISC to target sites located on mRNAs and, consequently, by modulating their translational repression. Changes in miRNA expression have been shown to be involved in the development of all major complex diseases. Furthermore, recent findings showed that miRNAs can be secreted to the extracellular environment and enter the bloodstream and other body fluids where they can circulate with high stability. The function of such circulating miRNAs remains largely elusive, but systematic high throughput approaches, such as miRNA profiling arrays, have lead to the identification of miRNA signatures in several pathological conditions, including neurodegenerative disorders and several types of cancers. In this context, the identification of miRNA expression profile in the cerebrospinal fluid, as reported in our recent study, makes miRNAs attractive candidates for biomarker analysis.
There are several tools available for profiling microRNAs, such as microarrays, quantitative real-time PCR (qPCR), and deep sequencing. Here, we describe a sensitive method to profile microRNAs in cerebrospinal fluids by quantitative real-time PCR. We used the Exiqon microRNA ready-to-use PCR human panels I and II V2.R, which allows detection of 742 unique human microRNAs. We performed the arrays in triplicate runs and we processed and analyzed data using the GenEx Professional 5 software.
Using this protocol, we have successfully profiled microRNAs in various types of cell lines and primary cells, CSF, plasma, and formalin-fixed paraffin-embedded tissues.

We describe a protocol of real time PCR to profile microRNAs in the cerebrospinal fluid (CSF). With the exception of RNA extraction protocols, the procedure can be extended to RNA extracted from other body fluids, cultured cells, or tissue specimens.

MicroRNAs (miRNAs) constitute a potent layer of gene regulation by guiding RISC to target sites located on mRNAs and, consequently, by modulating their ...

Medicine

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

Sequencing RNAs that co-immunoprecipitate (co-IP) with RNA binding proteins has increased our understanding of splicing by demonstrating that binding location often influences function of a splicing factor.  However, as with any sampling strategy the chance of identifying an RNA bound to a splicing factor is proportional to its cellular abundance.  We have developed a novel in vitro approach for surveying binding specificity on otherwise transient pre-mRNA. This approach utilizes a specifically designed oligonucleotide pool that tiles across introns, exons, splice junctions, or other pre-mRNA.  The pool is subjected to some kind of molecular selection. Here, we demonstrate the method by separating the oligonucleotide into a bound and unbound fraction and utilize a two color array strategy to record the enrichment of each oligonucleotide in the bound fraction. The array data generates high-resolution maps with the ability to identify sequence-specific and structural determinates of ribonucleoprotein (RNP) binding on pre-mRNA.  A unique advantage to this method is its ability to avoid the sampling bias towards mRNA associated with current IP and SELEX techniques, as the pool is specifically designed and synthesized from pre-mRNA sequence. The flexibility of the oligonucleotide pool is another advantage since the experimenter chooses which regions to study and tile across, tailoring the pool to their individual needs.  Using this technique, one can assay the effects of polymorphisms or mutations on binding on a large scale or clone the library into a functional splicing reporter and identify oligonucleotides that are enriched in the included fraction.  This novel in vitro high-resolution mapping scheme provides a unique way to study RNP interactions with transient pre-mRNA species, whose low abundance makes them difficult to study with current in vivo techniques.  



A Rapid High-throughput Method for Mapping Ribonucleoproteins RNPs on Human pre-mRNA

Due to the transient nature of pre-mRNA, it can be difficult to isolate and study in vivo. Here, we present a novel in vitro approach to investigate RNA-protein interactions using a synthetic oligo pool that tiles across selected regions of pre-mRNA.

Sequencing RNAs that co-immunoprecipitate (co-IP) with RNA binding proteins has increased our understanding of splicing by demonstrating that binding ...

Biology

miRNA Expression Analyses in Prostate Cancer Clinical Tissues

A critical challenge in prostate cancer (PCa) clinical management is posed by the inadequacy of currently used biomarkers for disease screening, diagnosis, prognosis and treatment. In recent years, microRNAs (miRNAs) have emerged as promising alternate biomarkers for prostate cancer diagnosis and prognosis. However, the development of miRNAs as effective biomarkers for prostate cancer heavily relies on their accurate detection in clinical tissues. miRNA analyses in prostate cancer clinical specimens is often challenging owing to tumor heterogeneity, sampling errors, stromal contamination etc. The goal of this article is to describe a simplified workflow for miRNA analyses in archived FFPE or fresh frozen prostate cancer clinical specimens using a combination of quantitative real-time PCR (RT-PCR) and in situ hybridization (ISH). Within this workflow, we optimize the existing methodologies for miRNA extraction from FFPE and frozen prostate tissues and expression analyses by Taqman-probe based miRNA RT-PCR. In addition, we describe an optimized method for ISH analyses formiRNA detection in prostate tissues using locked nucleic acid (LNA)- based probes. Our optimized miRNA ISH protocol can be applied to prostate cancer tissue slides or prostate cancer tissue microarrays (TMA).

Here we describe a simplified protocol for microRNA (miRNA) expression analyses in archived Formalin-Fixed, Paraffin-Embedded (FFPE) or fresh frozen prostate cancer (PCa) clinical tissues employing quantitative real-time PCR (RT-PCR) and in situ hybridization (ISH).

A critical challenge in prostate cancer (PCa) clinical management is posed by the inadequacy of currently used biomarkers for disease screening, ...

Collection and Processing of Lymph Nodes from Large Animals for RNA Analysis: Preparing for Lymph Node Transcriptomic Studies of Large Animal Species

Large animals (both livestock and wildlife) serve as important reservoirs of zoonotic pathogens, including Brucella, Mycobacterium bovis, Salmonella, and E. coli, and are useful for the study of pathogenesis and/or spread of the bacteria in natural hosts. With the key function of lymph nodes in the host immune response, lymph node tissues serve as a potential source of RNA for downstream transcriptomic analyses, in order to assess the temporal changes in gene expression in cells over the course of an infection. This article presents an overview of the process of lymph node collection, tissue sampling, and downstream RNA processing in livestock, using cattle (Bos taurus) as a model, with additional examples provided from the American bison (Bison bison). The protocol includes information about the location, identification, and removal of lymph nodes from multiple key sites in the body. Additionally, a biopsy sampling methodology is presented that allows for a consistency of sampling across multiple animals. Several considerations for sample preservation are discussed, including the generation of RNA suitable for downstream methodologies like RNA-sequencing and RT-PCR. Due to the long delays inherent in large animal vs. mouse time course studies, representative results from bison and bovine lymph node tissues are presented to describe the time course of the degradation in this tissue type, in the context of a review of previous methodological work on RNA degradation in other tissues. Overall, this protocol will be useful to both veterinary researchers beginning transcriptome projects on large animal samples and to molecular biologists interested in learning techniques for in vivo tissue sampling and in vitro processing.

This protocol provides an overview of procedures for the isolation of RNA for the transcriptomic profiling of lymph node tissues from large animals, including steps in the identification and excision of lymph nodes from livestock and wildlife, sampling approaches to provide consistency across multiple animals, and considerations plus representative results for the post-collection preservation and processing for RNA analysis.

Large animals (both livestock and wildlife) serve as important reservoirs of zoonotic pathogens, including Brucella, Mycobacterium bovis, Salmonella, and ...

Immunology and Infection

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.

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.

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

Highly Efficient Ligation of Small RNA Molecules for MicroRNA Quantitation by High-Throughput Sequencing

MiRNA cloning and high-throughput sequencing, termed miR-Seq, stands alone as a transcriptome-wide approach to quantify miRNAs with single nucleotide resolution. This technique captures miRNAs by attaching 3&#8217; and 5&#8217; oligonucleotide adapters to miRNA molecules and allows de novo miRNA discovery. Coupling with powerful next-generation sequencing platforms, miR-Seq has been instrumental in the study of miRNA biology. However, significant biases introduced by oligonucleotide ligation steps have prevented miR-Seq from being employed as an accurate quantitation tool. Previous studies demonstrate that biases in current miR-Seq methods often lead to inaccurate miRNA quantification with errors up to 1,000-fold for some miRNAs1,2. To resolve these biases imparted by RNA ligation, we have developed a small RNA ligation method that results in ligation efficiencies of over 95% for both 3&#8217; and 5&#8242; ligation steps. Benchmarking this improved library construction method using equimolar or differentially mixed synthetic miRNAs, consistently yields reads numbers with less than two-fold deviation from the expected value. Furthermore, this high-efficiency miR-Seq method permits accurate genome-wide miRNA profiling from in vivo total RNA samples2.

MicroRNAs (miRNAs) are a widely conserved class of regulatory molecules. Here we describe a miRNA cloning method that relies upon two potent ligation steps followed by high-throughput sequencing. Our method permits accurate genome-wide quantitation of miRNAs.

MiRNA cloning and high-throughput sequencing, termed miR-Seq, stands alone as a transcriptome-wide approach to quantify miRNAs with single nucleotide ...

Targeted RNA Sequencing Assay to Characterize Gene Expression and Genomic Alterations

RNA sequencing (RNAseq) is a versatile method that can be utilized to detect and characterize gene expression, mutations, gene fusions, and noncoding RNAs. Standard RNAseq requires 30 - 100 million sequencing reads and can include multiple RNA products such as mRNA and noncoding RNAs. We demonstrate how targeted RNAseq (capture) permits a focused study on selected RNA products using a desktop sequencer. RNAseq capture can characterize unannotated, low, or transiently expressed transcripts that may otherwise be missed using traditional RNAseq methods. Here we describe the extraction of RNA from cell lines, ribosomal RNA depletion, cDNA synthesis, preparation of barcoded libraries, hybridization and capture of targeted transcripts and multiplex sequencing on a desktop sequencer. We also outline the computational analysis pipeline, which includes quality control assessment, alignment, fusion detection, gene expression quantification and identification of single nucleotide variants. This assay allows for targeted transcript sequencing to characterize gene expression, gene fusions, and mutations.

We describe a targeted RNA sequencing-based method that includes preparation of indexed cDNA libraries, hybridization and capture with custom probes and data analysis to interrogate selected transcripts for gene expression, mutations, and gene fusions. Targeted RNAseq permits cost-effective, rapid evaluation of selected transcripts on a desktop sequencer.

RNA sequencing (RNAseq) is a versatile method that can be utilized to detect and characterize gene expression, mutations, gene fusions, and noncoding ...

Preparation of Formalin-fixed Paraffin-embedded Tissue Cores for both RNA and DNA Extraction

Formalin-fixed paraffin embedded tissue (FFPET) represents a valuable, well-annotated substrate for molecular investigations. The utility of FFPET in molecular analysis is complicated both by heterogeneous tissue composition and low yields when extracting nucleic acids. A literature search revealed a paucity of protocols addressing these issues, and none that showed a validated method for simultaneous extraction of RNA and DNA from regions of interest in FFPET. This method addresses both issues. Tissue specificity was achieved by mapping cancer areas of interest on microscope slides and transferring annotations onto FFPET blocks. Tissue cores were harvested from areas of interest using 0.6 mm microarray punches. Nucleic acid extraction was performed using a commercial FFPET extraction system, with modifications to homogenization, deparaffinization, and Proteinase K digestion steps to improve tissue digestion and increase nucleic acid yields. The modified protocol yields sufficient quantity and quality of nucleic acids for use in a number of downstream analyses, including a multi-analyte gene expression platform, as well as reverse transcriptase coupled real time PCR analysis of mRNA expression, and methylation-specific PCR (MSP) analysis of DNA methylation.

This modified extraction protocol improves RNA and DNA yields from more precisely targeted regions of interest in histopathologic tissue blocks.

Formalin-fixed paraffin embedded tissue (FFPET) represents a valuable, well-annotated substrate for molecular investigations. The utility of FFPET in ...

FFPE Tissue Pretreatment for RNA CISH: A Procedure to Process Formalin-Fixed Paraffin-Embedded Tissue Sections for RNA Chromogenic In Situ Hybridization

Source: Outh-Gauer, S. et al. <a href="https://www.jove.com/video/59422" target="_blank">Chromogenic In Situ Hybridization as a Tool for HPV-Related Head and Neck Cancer Diagnosis.</a> J. Vis. Exp. (2019)
This video demonstrates the steps involved in the pretreatment of FFPE tissue specimens for RNA chromogenic in situ hybridization. The pretreatment process helps maintain nucleic acid integrity within the cells and overall tissue morphology.

Source: Outh-Gauer, S. et al. Chromogenic In Situ Hybridization as a Tool for HPV-Related Head and Neck Cancer Diagnosis. J. Vis. Exp. (2019)
This video ...

Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed Paraffin-embedded RNA Specimens

Summary

Explore More Videos

A Complete Pipeline for Isolating and Sequencing MicroRNAs, and Analyzing Them Using Open Source Tools

Cerebrospinal Fluid MicroRNA Profiling Using Quantitative Real Time PCR

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

miRNA Expression Analyses in Prostate Cancer Clinical Tissues

Collection and Processing of Lymph Nodes from Large Animals for RNA Analysis: Preparing for Lymph Node Transcriptomic Studies of Large Animal Species

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

Highly Efficient Ligation of Small RNA Molecules for MicroRNA Quantitation by High-Throughput Sequencing

Targeted RNA Sequencing Assay to Characterize Gene Expression and Genomic Alterations

Preparation of Formalin-fixed Paraffin-embedded Tissue Cores for both RNA and DNA Extraction

FFPE Tissue Pretreatment for RNA CISH: A Procedure to Process Formalin-Fixed Paraffin-Embedded Tissue Sections for RNA Chromogenic In Situ Hybridization