We thank Eric L Van Nostrand and Gene W Yeo for helpful guidance with the original protocol. K.Z. was supported by National Key R&#38;D Program of China (2016YFA0500902, 2018YFC1003500), and National Natural Science Foundation of China (31771653). L.Y. was supported by National Natural Science Foundation of China (81471502, 31871503) and Innovative and Entrepreneurial Program of Jiangsu Province.

<ol>
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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Argonaute+HITS-CLIP+decodes+microRNA-mRNA+interaction+maps.">Argonaute HITS-CLIP decodes microRNA-mRNA interaction maps.</a> Nature. 460 (7254), 479-486 (2009).</li><li>Zheng, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+MOV10L1+associates+with+Piwi+proteins+and+is+an+essential+component+of+the+Piwi-interacting+RNA+(piRNA)+pathway.">Mouse MOV10L1 associates with Piwi proteins and is an essential component of the Piwi-interacting RNA (piRNA) pathway.</a> Proceedings of National Acadamy of Sciences U S A. 107 (26), 11841-11846 (2010).</li><li>Gregersen, L. 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The authors have nothing to disclose.

With increasing understanding of the universal role of RBPs under both biological and pathological contexts, the CLIP methods have been widely utilized to reveal the molecular function of RBPs20,32,33,34,35. The protocol described here represents an adapted application of the eCLIP method to mouse testis.
One challenge in performing...

Mammalian testis represents an excellent developmental model wherein an intricate cell differentiation program runs cyclically to yield numerous spermatozoa. An unique value of this model lies in the emergence of transcriptional inactivation at certain stages of spermatogenesis, typically when meiotic sex chromosome inactivation (MSCI) occurs1,2 and when round spermatids undergo drastic nuclear compaction during spermiogenesis3. These inconsecutive transcriptional events necessitate post-transcriptional gene regulation, in which RNA-binding proteins (RBPs) play a crucial role, shaping transcriptome and maintaining male fertility.
To identify the bona fide RNA targets of an individual RBP in vivo, the crosslinking immunoprecipitation (CLIP) method was developed4,5, based on but beyond the regular RNA immunoprecipitation (RIP)6,7, by incorporation of key steps including ultraviolet (UV) crosslinking, stringent wash and gel transfer to improve signal specificity. The advanced application of the CLIP combined with high-throughput sequencing has provoked large interest in profiling protein-RNA interaction at genome-wide levels8. In addition to genetic studies on RBP function, such biochemical methods that identify the direct interplay of endogenous protein and RNA have been indispensable to accurately elucidate the RNA regulatory roles of RBPs. For example, MOV10L1 is a testis-specific RNA helicase required for male fertility and the Piwi-interacting RNA (piRNA) biogenesis9. Its paralogue MOV10 is known as a ubiquitously expressed and multifunctional RNA helicase with roles in multiple aspects of RNA biology10,11,12,13,14,15,16,17,18. By employing the conventional CLIP-seq, we found that MOV10L1 binds and regulates primary piRNA precursors to initiate early piRNA processing19,20, and that MOV10 binds mRNA 3&#39; UTRs and as well as noncoding RNA species in testicular germ cells (data not shown).
Nevertheless, CLIP is originally a laborious, radioactive procedure followed by sequencing library preparation with a remarkable loss of CLIP tags. In the conventional CLIP, a cDNA library is prepared using adapters ligated at both RNA extremities. After protein digestion, crosslinked short polypeptides remain attached to RNA fragments. This crosslinking mark partially blocks reverse transcriptase (RTase) progression during cDNA synthesis, resulting in truncated cDNAs which represent about 80% of the cDNA library21,22. Thus, only cDNA fragments resulting from RTase bypassing the crosslinking site (read-through) are sequenced. Recently, various CLIP approaches, such as PAR-CLIP, iCLIP, eCLIP and uvCLAP, have been employed to identify crosslink sites of RBPs in living cells. PAR-CLIP involves the application of 365 nm UV radiation and photoactivatable nucleotide analogs and is therefore exclusive to in-culturing living cells, and incorporation of nucleoside analogs into newly synthesized transcripts is prone to producing bias where RNA physically interacts with protein23,24. In iCLIP, only a single adapter is ligated to the 3&#39; extremity of crosslinked RNA fragments. After reverse transcription (RT), both truncated and read-through cDNAs are obtained by intramolecularly circularization and re-linearization followed by polymerase chain reaction (PCR) amplification25,26. However, the efficiency of intramolecular circularization is relatively low. Although older CLIP protocols need labeling of crosslinked RNA with a radioisotope, ultraviolet crosslinking and affinity purification (uvCLAP), with a process of stringent tandem affinity purification, does not rely on radioactivity27. Nevertheless, uvCLAP is limited to cultured cells that must be transfected with the expression vector carrying the 3x FLAG-HBH tag for tandem affinity purification.
In eCLIP, adapters were ligated first at the 3&#39; extremity of RNA followed by RT, and next at the 3&#39; extremity of cDNAs in an intermolecular mode. Hence, eCLIP is able to capture all truncated and read-through cDNA28. Also, it is neither restricted to radioactive labeling, nor to using cell lines based on its principle, while maintaining single-nucleotide resolution.
Here, we provide a step-by-step description of an eCLIP protocol adapted for mouse testis. Briefly, this eCLIP protocol starts with UV crosslinking of testicular tubules, followed by partial RNase digestion and immunoprecipitation using a protein-specific antibody. Next, the protein-bound RNA is dephosphorylated, and adapter is ligated to its 3&#39; end.&#160;After protein gel electrophoresis and gel-to-membrane transfer, RNA is isolated by cutting the membrane area of an expected size range. After RT, DNA adapter is ligated to the 3&#39; end of cDNA followed by PCR amplification. Screening of subclones prior to high-throughput sequencing is taken as a library quality control. This protocol is efficient at identifying major species of protein-bound RNA of RBPs, exemplified by the two testis-expressing RNA helicases MOV10L1 and MOV10.

<table border="0" cellpadding="0" cellspacing="0" style="width:804px;" width="804">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Antibodies</td>
			<td style="width:180px;"></td>
			<td style="width:171px;"></td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:229px;">Anti-mouse MOV10&#160; antibody</td>
			<td style="width:180px;">Proteintech, China</td>
			<td style="width:171px;">10370-1-AP</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:229px;">Anti-mouse MOV10L1 antibody</td>
			<td style="width:180px;">Zheng et al.20109</td>
			<td style="width:171px;">polyclonal antisera UP2175</td>
			<td style="width:224px;">provided by P. Jeremy Wang lab&#65288;University of Pennsylvania&#65289;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">HRP Goat Anti-Rabbit IgG&#160;</td>
			<td style="width:180px;">ABclonal</td>
			<td style="width:171px;">AS014</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Rabbit IgG</td>
			<td style="width:180px;">Beyotime, China</td>
			<td style="width:171px;">A7016</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Equipment</td>
			<td style="width:180px;"></td>
			<td style="width:171px;"></td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">Centrifuge</td>
			<td style="width:180px;">Eppendorf, Hamburg, Germany</td>
			<td style="width:171px;">5242R</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Digital sonifier</td>
			<td style="width:180px;">BRANSON,USA</td>
			<td style="width:171px;">BBV12081048A</td>
			<td style="width:224px;">450 Watts; 50/60 HZ</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">DynaMag-2 Magnet</td>
			<td style="width:180px;">Invitrogen,USA</td>
			<td style="width:171px;">12321D</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Mini Blot Module</td>
			<td style="width:180px;">Invitrogen,USA</td>
			<td style="width:171px;">B1000</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Mini Gel Tank</td>
			<td style="width:180px;">Invitrogen,USA</td>
			<td style="width:171px;">A25977</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Shaking incubator</td>
			<td>Eppendorf, Hamburg, Germany</td>
			<td>Thermomixer comfort&#160;</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="38">
			<td height="38" style="height:39px;">Tissue Grinder, Dounce</td>
			<td>PYREX, USA</td>
			<td>1234F35</td>
			<td style="width:224px;">only&#160; the &#34;loose&#34; pestle is used in this protocol</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">TProfessional standard 96 Gradient</td>
			<td style="width:180px;">Biometra, Germany</td>
			<td style="width:171px;">serial no.: 2604323</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Tube Revolver&#160;</td>
			<td style="width:180px;">Crystal, USA</td>
			<td style="width:171px;">serial no.: 3406051</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">UV-light cross-linker</td>
			<td>UVP, USA</td>
			<td style="width:171px;">CL-1000</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Materials</td>
			<td></td>
			<td style="width:171px;"></td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">TC-treated Culture Dish</td>
			<td>Corning, USA</td>
			<td style="width:171px;">430167</td>
			<td style="width:224px;">100 mm&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Tubes</td>
			<td style="width:180px;">Corning, USA</td>
			<td style="width:171px;">430791</td>
			<td style="width:224px;">15 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Microtubes tubes</td>
			<td style="width:180px;">AXYGEN , USA</td>
			<td style="width:171px;">MCT-150-C</td>
			<td style="width:224px;">1.5 mL&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Reagents&#160;</td>
			<td style="width:180px;"></td>
			<td style="width:171px;"></td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:229px;">Acid phenol/chloroform/isoamyl alcohol&#160;</td>
			<td style="width:180px;">Solarbio, China</td>
			<td style="width:171px;">P1011</td>
			<td style="width:224px;">25:24:01</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">AffinityScript Enzyme</td>
			<td style="width:180px;">Agilent, USA</td>
			<td style="width:171px;">600107</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Antioxidant</td>
			<td style="width:180px;">Invitrogen,USA</td>
			<td style="width:171px;">NP0005</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:229px;">DH5&#945; competent bacteria</td>
			<td style="width:180px;">Thermo Scientific, USA</td>
			<td>18265017</td>
			<td style="width:224px;">these economical cells yield &#62;1 x 106 transformants/&#181;g control DNA per 50 &#181;L reaction.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">DMSO</td>
			<td style="width:180px;">Sigma-Aldrich, USA</td>
			<td style="width:171px;">D8418</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">DNA Ladder</td>
			<td style="width:180px;">Invitrogen, USA</td>
			<td style="width:171px;">10416014</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">dNTP</td>
			<td style="width:180px;">Sigma-Aldrich, USA</td>
			<td style="width:171px;">DNTP100-1KT</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dynabeads Protein A&#160;</td>
			<td>Invitrogen, USA</td>
			<td>10002D</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ECL reagent</td>
			<td>Vazyme, China</td>
			<td>E411-04</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">EDTA</td>
			<td>Invitrogen, USA</td>
			<td style="width:171px;">AM9260G</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">EDTA free protease inhibitor cocktail</td>
			<td style="width:180px;">Roche, USA</td>
			<td style="width:171px;">04693132001</td>
			<td style="width:224px;">add fresh</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Exo-SAP-IT</td>
			<td style="width:180px;">Affymetrix, USA</td>
			<td style="width:171px;">78201</td>
			<td style="width:224px;">PCR Product Cleanup Reagent&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">FastAP enzyme</td>
			<td style="width:180px;">Thermo Scientific, USA</td>
			<td style="width:171px;">EF0652</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">LDS Sample Buffer</td>
			<td style="width:180px;">Thermo Scientific, USA</td>
			<td style="width:171px;">NP0007</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">MetaPhor Agarose&#160;</td>
			<td style="width:180px;">lonza, Switzerland</td>
			<td style="width:171px;">50180</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:229px;">MgCl2</td>
			<td>Invitrogen, USA</td>
			<td style="width:171px;">AM9530G</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:229px;">MiniElute gel Extraction</td>
			<td style="width:180px;">QIAGEN, Germany</td>
			<td style="width:171px;">28604</td>
			<td style="width:224px;">column store at 4 &#8451;; buffer QG=gel dissolving buffer; buffer PE= wash buffer(for step 14)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">MyONE Silane beads</td>
			<td style="width:180px;">Thermo Scientific, USA</td>
			<td>37002D</td>
			<td style="width:224px;">nucleic acids extraction magnetic beads</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NaCl</td>
			<td>Invitrogen,USA</td>
			<td>AM9759 
			&#160;</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">NP-40</td>
			<td style="width:180px;">Amresco, USA</td>
			<td style="width:171px;">M158-500ML</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">NuPAGE Bis-Tris Protein Gels</td>
			<td style="width:180px;">Invitrogen, USA</td>
			<td style="width:171px;">NP0336BOX</td>
			<td style="width:224px;">4%&#8211;12%,1.5 mm, 15-well</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">NuPAGE MOPS SDS Buffer Kit&#160;</td>
			<td style="width:180px;">Invitrogen, USA</td>
			<td style="width:171px;">NP0050</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS</td>
			<td>Gibco, USA</td>
			<td>10010023</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">Phase-Locked Gel (PLG) heavy tube&#160;&#160;</td>
			<td style="width:180px;">TIANGEN, China</td>
			<td style="width:171px;">WM5-2302831</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">PowerUp SYBR Green Master Mix</td>
			<td style="width:180px;">Applied Biosystems, USA</td>
			<td style="width:171px;">A25742</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">proteinase K</td>
			<td style="width:180px;">NEB, New England&#160;</td>
			<td style="width:171px;">P8107S</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Q5 PCR master mix&#160;</td>
			<td style="width:180px;">NEB, New England&#160;</td>
			<td style="width:171px;">M0492L</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">RLT buffer</td>
			<td style="width:180px;">QIAGEN, Germany</td>
			<td style="width:171px;">79216</td>
			<td style="width:224px;">RNA purification lysis buffer&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">RNA Clean &#38; Concentrator-5 columns&#160;</td>
			<td style="width:180px;">ZYMO RESEARCH, USA</td>
			<td style="width:171px;">R1016</td>
			<td style="width:224px;">RNA purification and concentration columns</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">RNase I&#160;</td>
			<td>Invitrogen, USA</td>
			<td style="width:171px;">AM2295</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">RNase Inhibitor</td>
			<td style="width:180px;">Promega, USA</td>
			<td style="width:171px;">N251B</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">RQ1 DNase</td>
			<td style="width:180px;">Promega,USA</td>
			<td style="width:171px;">M610A</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Sample Reducing Agent</td>
			<td>Invitrogen,USA</td>
			<td style="width:171px;">NP0009</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">SDS Solution</td>
			<td>Invitrogen, USA</td>
			<td style="width:171px;">15553027</td>
			<td style="width:224px;">10%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Sodium deoxycholate</td>
			<td style="width:180px;">Sigma-Aldrich, USA</td>
			<td style="width:171px;">30970</td>
			<td style="width:224px;">protect from light</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">T4 PNK enzyme</td>
			<td style="width:180px;">NEB, New England&#160;</td>
			<td style="width:171px;">M0201L</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">T4 RNA ligase 1 high conc</td>
			<td style="width:180px;">NEB, New England&#160;</td>
			<td style="width:171px;">M0437M</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">TA/Blunt-Zero Cloning Mix</td>
			<td style="width:180px;">Vazyme, China</td>
			<td style="width:171px;">C601-01</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">TBE</td>
			<td>Invitrogen,USA</td>
			<td style="width:171px;">AM9863</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris-HCI Buffer</td>
			<td>Invitrogen, USA</td>
			<td>15567027</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Triton X-100</td>
			<td style="width:180px;">Sangon Biotech, China</td>
			<td style="width:171px;">A600198&#160;</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Tween-20</td>
			<td style="width:180px;">Sangon Biotech, China</td>
			<td style="width:171px;">A600560</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Urea</td>
			<td style="width:180px;">Sigma-Aldrich, USA</td>
			<td style="width:171px;">U5378</td>
			<td style="width:224px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">X-ray Films</td>
			<td style="width:180px;">Caresteam, Canada</td>
			<td style="width:171px;">6535876</td>
			<td style="width:224px;"></td>
		</tr>
	</tbody>
</table>

enhanced crosslinking immunoprecipitation (eclip) method for efficient identification of protein-bound rna in mouse testis

Spermatogenesis defines a highly ordered process of male germ cell differentiation in mammals. In testis, transcription and translation are uncoupled, underlining the importance of post-transcriptional regulation of gene expression orchestrated by RBPs. To elucidate mechanistic roles of an RBP, crosslinking immunoprecipitation (CLIP) methodology can be used to capture its endogenous direct RNA targets and define the actual interaction sites. The enhanced CLIP (eCLIP) is a newly-developed method that offers several advantages over the conventional CLIPs. However, the use of eCLIP has so far been limited to cell lines, calling for expanded applications. Here, we employed eCLIP to study MOV10 and MOV10L1, two known RNA-binding helicases, in mouse testis. As expected, we find that MOV10 predominantly binds to 3' untranslated regions (UTRs) of mRNA and MOV10L1 selectively binds to Piwi-interacting RNA (piRNA) precursor transcripts. Our eCLIP method allows fast determination of major RNA species bound by various RBPs via small-scale sequencing of subclones and thus availability of qualified libraries, as a warrant for proceeding with deep sequencing. This study establishes an applicable basis for eCLIP in mammalian testis.

The eCLIP procedure and results are illustrated in Figure 1, Figure 2, Figure 3, Figure 4. Mice were euthanized with carbon dioxide and a small incision was made in the lower abdomen using surgical scissors (Figure 2A,B). Mo...

Watch this Scientific Journal Video about Enhanced Crosslinking Immunoprecipitation eCLIP Method for Efficient Identification of Protein-bound RNA in Mouse Testis at JoVE.com

Enhanced Crosslinking Immunoprecipitation eCLIP Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Here, we present an eCLIP protocol to determine major RNA targets of RBP candidates in testis.

Enhanced Crosslinking Immunoprecipitation (eCLIP) Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Spermatogenesis defines a highly ordered process of male germ cell differentiation in mammals. In testis, transcription and translation are uncoupled, ...

enhanced-crosslinking-immunoprecipitation-eclip-method-for-efficient

Universidad de Cartagena UDEC

Research

JoVE Journal

Biology

19.8K Views.  Nanjing Medical University. Here, we present an eCLIP protocol to determine major RNA targets of RBP candidates in testis.

Video: Enhanced Crosslinking Immunoprecipitation eCLIP Method for Efficient Identification of Protein-bound RNA in Mouse Testis

In vitro Transcription and Capping of Gaussia Luciferase mRNA Followed by HeLa Cell Transfection

In vitro transcription is the synthesis of RNA transcripts by RNA polymerase from a linear DNA template containing the corresponding promoter sequence (T7, T3, SP6) and the gene to be transcribed (Figure 1A). A typical transcription reaction consists of the template DNA, RNA polymerase, ribonucleotide triphosphates, RNase inhibitor and buffer containing Mg2+ ions.
Large amounts of high quality RNA are often required for a variety of applications. Use of in vitro transcription has been reported for RNA structure and function studies such as splicing1, RNAi experiments in mammalian cells2, antisense RNA amplification by the "Eberwine method"3, microarray analysis4 and for RNA vaccine studies5. The technique can also be used for producing radiolabeled and dye labeled probes6. Warren, et al. recently reported reprogramming of human cells by transfection with in vitro transcribed capped RNA7. The T7 High Yield RNA Synthesis Kit from New England Biolabs has been designed to synthesize up to 180 &mu;g RNA per 20 &mu;l reaction. RNA of length up to 10kb has been successfully transcribed using this kit. Linearized plasmid DNA, PCR products and synthetic DNA oligonucleotides can be used as templates for transcription as long as they have the T7 promoter sequence upstream of the gene to be transcribed.
Addition of a 5' end cap structure to the RNA is an important process in eukaryotes. It is essential for RNA stability8, efficient translation9, nuclear transport10 and splicing11. The process involves addition of a 7-methylguanosine cap at the 5' triphosphate end of the RNA. RNA capping can be carried out post-transcriptionally using capping enzymes or co-transcriptionally using cap analogs. In the enzymatic method, the mRNA is capped using the Vaccinia virus capping enzyme12,13. The enzyme adds on a 7-methylguanosine cap at the 5' end of the RNA using GTP and S-adenosyl methionine as donors (cap 0 structure). Both methods yield functionally active capped RNA suitable for transfection or other applications14 such as generating viral genomic RNA for reverse-genetic systems15 and crystallographic studies of cap binding proteins such as eIF4E16.
In the method described below, the T7 High Yield RNA Synthesis Kit from NEB is used to synthesize capped and uncapped RNA transcripts of Gaussia luciferase (GLuc) and Cypridina luciferase (CLuc). A portion of the uncapped GLuc RNA is capped using the Vaccinia Capping System (NEB). A linearized plasmid containing the GLuc or CLuc gene and T7 promoter is used as the template DNA. The transcribed RNA is transfected into HeLa cells and cell culture supernatants are assayed for luciferase activity. Capped CLuc RNA is used as the internal control to normalize GLuc expression.

In vitro Transcription and Capping of Gaussia Luciferase mRNA Followed by HeLa Cell Transfection

This method describes high yield in vitro synthesis of both capped and uncapped mRNA from a linearized plasmid containing the Gaussia luciferase (GLuc) gene. The RNA is purified and a fraction of the uncapped RNA is enzymatically capped using the Vaccinia virus capping enzyme. In the final step, the mRNA is transfected into HeLa cells and cell culture supernatants are assayed for luciferase activity.

In vitro transcription is the synthesis of RNA transcripts by RNA polymerase from a linear DNA template containing the corresponding promoter sequence ...

Efficient Differentiation of Mouse Embryonic Stem Cells into Motor Neurons

Direct differentiation of embryonic stem (ES) cells into functional motor neurons represents a promising resource to study disease mechanisms, to screen new drug compounds, and to develop new therapies for motor neuron diseases such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). Many current protocols use a combination of retinoic acid (RA) and sonic hedgehog (Shh) to differentiate mouse embryonic stem (mES) cells into motor neurons1-4. However, the differentiation efficiency of mES cells into motor neurons has only met with moderate success. We have developed a two-step differentiation protocol5 that significantly improves the differentiation efficiency compared with currently established protocols. The first step is to enhance the neuralization process by adding Noggin and fibroblast growth factors (FGFs). Noggin is a bone morphogenetic protein (BMP) antagonist and is implicated in neural induction according to the default model of neurogenesis and results in the formation of anterior neural patterning6. FGF signaling acts synergistically with Noggin in inducing neural tissue formation by promoting a posterior neural identity7-9. In this step, mES cells were primed with Noggin, bFGF, and FGF-8 for two days to promote differentiation towards neural lineages. The second step is to induce motor neuron specification. Noggin/FGFs exposed mES cells were incubated with RA and a Shh agonist, Smoothened agonist (SAG), for another 5 days to facilitate motor neuron generation. To monitor the differentiation of mESs into motor neurons, we used an ES cell line derived from a transgenic mouse expressing eGFP under the control of the motor neuron specific promoter Hb91. Using this robust protocol, we achieved 51&plusmn;0.8% of differentiation efficiency (n = 3; p &lt; 0.01, Student's t-test)5. Results from immunofluorescent staining showed that GFP+ cells express the motor neuron specific markers, Islet-1 and choline acetyltransferase (ChAT). Our two-step differentiation protocol provides an efficient way to differentiate mES cells into spinal motor neurons.

We developed a new protocol to improve efficiency of in vitro differentiation of mouse embryonic stem cells into motor neurons. The differentiated ES cells acquired motor neurons features as evidenced by expression of neuronal and motor neuron markers using immunohistochemical techniques.

Direct differentiation of embryonic stem (ES) cells into functional  motor neurons represents a promising resource to study disease mechanisms, to  screen ...

Performing Vaginal Lavage, Crystal Violet Staining, and Vaginal Cytological Evaluation for Mouse Estrous Cycle Staging Identification

A rapid means of assessing reproductive status in rodents is useful not only in the study of reproductive dysfunction but is also required for the production of new mouse models of disease and investigations into the hormonal regulation of tissue degeneration (or regeneration) following pathological challenge. The murine reproductive (or estrous) cycle is divided into 4 stages: proestrus, estrus, metestrus, and diestrus. Defined fluctuations in circulating levels of the ovarian steroids 17-&beta;-estradiol and progesterone, the gonadotropins luteinizing and follicle stimulating hormones, and the luteotropic hormone prolactin signal transition through these reproductive stages. Changes in cell typology within the murine vaginal canal reflect these underlying endocrine events. Daily assessment of the relative ratio of nucleated epithelial cells, cornified squamous epithelial cells, and leukocytes present in vaginal smears can be used to identify murine estrous stages. The degree of invasiveness, however, employed in collecting these samples can alter reproductive status and elicit an inflammatory response that can confound cytological assessment of smears. Here, we describe a simple, non-invasive protocol that can be used to determine the stage of the estrous cycle of a female mouse without altering her reproductive cycle. We detail how to differentiate between the four stages of the estrous cycle by collection and analysis of predominant cell typology in vaginal smears and we show how these changes can be interpreted with respect to endocrine status.

Here, we describe how to identify the stage of the murine reproductive (proestrus, estrus, metestrus, or diestrus) by simple, non-invasive collection and cytological assessment of vaginal smear samples. We further describe how vaginal cytology reflects circulating hormonal levels underlying transition through the murine reproductive cycle.

A rapid means of assessing reproductive status in rodents is useful not only in the study of reproductive dysfunction but is also required for the ...

Efficient Chromatin Immunoprecipitation using Limiting Amounts of Biomass

Chromatin immunoprecipitation (ChIP) is a widely-used method for determining the interactions of different proteins with DNA in chromatin of living cells. Examples include sequence-specific DNA binding transcription factors, histones and their different modification states, enzymes such as RNA polymerases and ancillary factors, and DNA repair components. Despite its ubiquity, there is a lack of up-to-date, detailed methodologies for both bench preparation of material and for accurate analysis allowing quantitative metrics of interaction. Due to this lack of information, and also because, like any immunoprecipitation, conditions must be re-optimized for new sets of experimental conditions, the ChIP assay is susceptible to inaccurate or poorly quantitative results.
Our protocol is ultimately derived from seminal work on transcription factor:DNA interactions1,2 , but incorporates a number of improvements to sensitivity and reproducibility for difficult-to-obtain cell types. The protocol has been used successfully3,4 , both using qPCR to quantify DNA enrichment, or using a semi-quantitative variant of the below protocol.
This quantitative analysis of PCR-amplified material is performed computationally, and represents a limiting factor in the assay. Important controls and other considerations include the use of an isotype-matched antibody, as well as evaluation of a control region of genomic DNA, such as an intergenic region predicted not to be bound by the protein under study (or anticipated not to show changes under the experimental conditions). In addition, a standard curve of input material for every ChIP sample is used to derive absolute levels of enrichment in the experimental material. Use of standard curves helps to take into account differences between primer sets, regardless of how carefully they are designed, and also efficiency differences throughout the range of template concentrations for a single primer set. Our protocol is different from others that are available5-8 in that we extensively cover the later, analysis phase.

We describe a robust method for chromatin immunoprecipitation using primary T cells. The method is founded on standard approaches, but uses a specific set of conditions and reagents that improve efficiency for limited a quantities of cells. Importantly, a detailed description of the data analysis phase is presented.

Chromatin immunoprecipitation (ChIP) is a  widely-used method for determining the interactions of different proteins with  DNA in chromatin of living ...

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants. Low affinity interactions can be preserved through the use of less-stringent buffer conditions and remain readily identifiable. This protocol discusses the labeling of tissue culture cells with stable isotope labeled amino acids, transfection and immunoprecipitation of an affinity tagged protein of interest, followed by the preparation for submission to a mass spectrometry facility. This protocol then discusses how to analyze and interpret the data returned from the mass spectrometer in order to identify cellular partners interacting with a protein of interest. As an example this technique is applied to identify proteins binding to the eukaryotic translation initiation factors: eIF4AI and eIF4AII.

SILAC immunoprecipitation experiments represent a powerful means for discovering novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants, and low affinity interactions preserved through use of less-stringent buffer conditions.

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel ...

In Vivo Microinjection and Electroporation of Mouse Testis

This video and article contribution gives a comprehensive description of microinjection and electroporation of mouse testis in vivo. This particular transfection technique for testicular mouse cells allows the study of unique processes in spermatogenesis.
The following protocol focuses on transfection of testicular mouse cells with plasmid constructs. Specifically, we used the reporter vector pEGFP-C1, which expresses enhanced green fluorescent protein (eGFP) and also the pDsRed2-N1 vector expressing red fluorescent protein (DsRed2). Both encoded reporter genes were under the control of the human cytomegalovirus immediate-early promoter (CMV).
For performing gene transfer into mouse testes, the reporter plasmid constructs are injected into testes of living mice. To that end, the testis of an anaesthetized animal is exposed and the site of microinjection is prepared. Our preferred place of injection is the efferent duct, with the ultimately connected rete testis as the anatomical transport route of the spermatozoa between the testis and the epididymis. In this way, the filling of the seminiferous tubules after microinjection is excellently managed and controlled due to the use of stained DNA solutions. After observing a sufficient filling of the testis by its colored tubule structure, the organ is electroporated. This enables the transfer of the DNA solution into the testicular&#160;cells. Following 3 days of incubation, the testis is removed and investigated under the microscope for green or red&#160;fluorescence, illustrating transfection success.
Generally, this protocol can be employed for delivering DNA- or RNA- constructs into living mouse testis in order to (over)express or knock down genes, facilitating in vivo gene function analysis. Furthermore, it is suitable for studying reporter constructs or putative gene regulatory elements. Thus, the main advantages of the electroporation technique are fast performance in combination with low effort as well as the moderate technical equipment and skills required compared to alternative techniques.

In Vivo Microinjection and Electroporation of Mouse Testis

This article describes microinjection and electroporation of mouse testis in&#160;vivo as a&#160;transfection technique for testicular mouse cells to study unique processes of spermatogenesis. The presented protocol involves steps of glass capillary preparation, microinjection via the efferent duct, and transfection by electroporation.

This video and article contribution gives a comprehensive description of microinjection and electroporation of mouse testis in vivo. This particular ...

Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster

The last decades have witnessed the explosion of scientific interest around gene expression control mechanisms at the RNA level. This branch of molecular biology has been greatly fueled by the discovery of noncoding RNAs as major players in post-transcriptional regulation. Such a revolutionary perspective has been accompanied and triggered by the development of powerful technologies for profiling short RNAs expression, both at the high-throughput level (genome-wide identification) or as single-candidate analysis (steady state accumulation of specific species). Although several state-of-art strategies are currently available for dosing or visualizing such fleeing molecules, Northern Blot assay remains the eligible approach in molecular biology for immediate and accurate evaluation of RNA expression. It represents a first step toward the application of more sophisticated, costly technologies and, in many cases, remains a preferential method to easily gain insights into RNA biology. Here we overview an efficient protocol (Enhanced Northern Blot) for detecting weakly expressed microRNAs (or other small regulatory RNA species) from Drosophila melanogaster whole embryos, manually dissected larval/adult tissues or in vitro cultured cells. A very limited amount of RNA is required and the use of material from flow cytometry-isolated cells can be also envisaged.

Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster

The aim of this publication is to visualize and discuss the operative steps of an Enhanced Northern Blot protocol on RNA extracted from Drosophila melanogaster embryos, cells, and tissues. This protocol is particularly useful for the efficient detection of small RNA species.

The last decades have witnessed the explosion of scientific interest around gene expression control mechanisms at the RNA level. This branch of molecular ...

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 ...

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and silencing of genes mediate the response of plants to environmental signals and developmental cues. Therefore, insights into the mechanisms that control plant gene expression are essential to gain a deep understanding of how biological processes are regulated in plants. The chromatin immunoprecipitation (ChIP) technique described here is a procedure to identify the DNA-binding sites of proteins in genes or genomic regions of the model species Arabidopsis thaliana. The interactions with DNA of proteins of interest such as transcription factors, chromatin proteins or posttranslationally modified versions of histones can be efficiently analyzed with the ChIP protocol. This method is based on the fixation of protein-DNA interactions in vivo, random fragmentation of chromatin, immunoprecipitation of protein-DNA complexes with specific antibodies, and quantification of the DNA associated with the protein of interest by PCR techniques. The use of this methodology in Arabidopsis has contributed significantly to unveil transcriptional regulatory mechanisms that control a variety of plant biological processes. This approach allowed the identification of the binding sites of the Arabidopsis chromatin protein EBS to regulatory regions of the master gene of flowering FT. The impact of this protein in the accumulation of particular histone marks in the genomic region of FT was also revealed through ChIP analysis.

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Chromatin immunoprecipitation is a powerful technique for the identification of DNA binding sites of Arabidopsis proteins in vivo. This procedure includes chromatin cross-linking and fragmentation, immunoprecipitation with selective antibodies against the protein of interest, and qPCR analysis of bound DNA. We describe a simple ChIP assay optimized for Arabidopsis plants.

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and ...

TChIP-Seq: Cell-Type-Specific Epigenome Profiling

Epigenetic regulation plays central roles in gene expression. Since histone modification was discovered in the 1960s, its physiological and pathological functions have been extensively studied. Indeed, the advent of next-generation deep sequencing and chromatin immunoprecipitation (ChIP) via specific histone modification antibodies has revolutionized our view of epigenetic regulation across the genome. Conversely, tissues typically consist of diverse cell types, and their complex mixture poses analytic challenges to investigating the epigenome in a particular cell type. To address the cell type-specific chromatin state in a genome-wide manner, we recently developed tandem chromatin immunoprecipitation sequencing (tChIP-Seq), which is based on the selective purification of chromatin by tagged core histone proteins from cell types of interest, followed by ChIP-Seq. The goal of this protocol is the introduction of best practices of tChIP-Seq. This technique provides a versatile tool for tissue-specific epigenome investigation in diverse histone modifications and model organisms.

We describe a step-by-step protocol for tandem chromatin immunoprecipitation sequencing (tChIP-Seq) that enables the analysis of cell-type-specific genome-wide histone modification.

Epigenetic regulation plays central roles in gene expression. Since histone modification was discovered in the 1960s, its physiological and pathological ...

Enhanced Crosslinking Immunoprecipitation (eCLIP) Method for Efficient Identification of Protein-bound RNA in Mouse Testis

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Chapters in this video

In vitro Transcription and Capping of Gaussia Luciferase mRNA Followed by HeLa Cell Transfection

Efficient Differentiation of Mouse Embryonic Stem Cells into Motor Neurons

Performing Vaginal Lavage, Crystal Violet Staining, and Vaginal Cytological Evaluation for Mouse Estrous Cycle Staging Identification

Efficient Chromatin Immunoprecipitation using Limiting Amounts of Biomass

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

In Vivo Microinjection and Electroporation of Mouse Testis

Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster

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

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

TChIP-Seq: Cell-Type-Specific Epigenome Profiling