This work was supported by NIH grant R01-CA158283 and NSFC grant 31400726 to Z.W. Y.W. is funded by the Young Thousand Talents Program and the National Natural Science Foundation of China (grants 31471235 and 81422038). X.Y. is funded by the postdoctoral science foundation of China (2015M571612).

<ol>
	<li>Wang, E. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+isoform+regulation+in+human+tissue+transcriptomes.">Alternative isoform regulation in human tissue transcriptomes.</a> Nature. 456 (7221), 470-476 (2008).</li><li>Pan, Q., Shai, O., Lee, L. J., Frey, B. J., Blencowe, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep+surveying+of+alternative+splicing+complexity+in+the+human+transcriptome+by+high-throughput+sequencing.">Deep surveying of alternative splicing complexity in the human transcriptome by high-throughput sequencing.</a> Nat Genet. 40 (12), 1413-1415 (2008).</li><li>Wang, Z., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Splicing+regulation:+from+a+parts+list+of+regulatory+elements+to+an+integrated+splicing+code.">Splicing regulation: from a parts list of regulatory elements to an integrated splicing code.</a> Rna. 14 (5), 802-813 (2008).</li><li>Matera, A. G., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+day+in+the+life+of+the+spliceosome.">A day in the life of the spliceosome.</a> Nat Rev Mol Cell Biol. 15 (2), 108-121 (2014).</li><li>Singh, R. K., Cooper, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pre-mRNA+splicing+in+disease+and+therapeutics.">Pre-mRNA splicing in disease and therapeutics.</a> Trends Mol Med. 18 (8), 472-482 (2012).</li><li>Wang, G. -. S., Cooper, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Splicing+in+disease:+disruption+of+the+splicing+code+and+the+decoding+machinery.">Splicing in disease: disruption of the splicing code and the decoding machinery.</a> Nat Rev Genet. 8 (10), 749-761 (2007).</li><li>Li, Y. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+splicing+is+a+primary+link+between+genetic+variation+and+disease.">RNA splicing is a primary link between genetic variation and disease.</a> Science. 352 (6285), 600-604 (2016).</li><li>Scotti, M. M., Swanson, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+mis-splicing+in+disease.">RNA mis-splicing in disease.</a> Nat Rev Genet. 17 (1), 19-32 (2016).</li><li>Black, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+alternative+pre-messenger+RNA+splicing.">Mechanisms of alternative pre-messenger RNA splicing.</a> Annu Rev Biochem. 72 (1), 291-336 (2003).</li><li>Graveley, B. R., Maniatis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arginine/serine-rich+domains+of+SR+proteins+can+function+as+activators+of+pre-mRNA+splicing.">Arginine/serine-rich domains of SR proteins can function as activators of pre-mRNA splicing.</a> Mol cell. 1 (5), 765-771 (1998).</li><li>Del Gatto-Konczak, F., Olive, M., Gesnel, M. -. C., Breathnach, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=hnRNP+A1+recruited+to+an+exon+in+vivo+can+function+as+an+exon+splicing+silencer.">hnRNP A1 recruited to an exon in vivo can function as an exon splicing silencer.</a> Mol Cell Biol. 19 (1), 251-260 (1999).</li><li>Auweter, S. D., Oberstrass, F. C., Allain, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequence-specific+binding+of+single-stranded+RNA:+is+there+a+code+for+recognition.">Sequence-specific binding of single-stranded RNA: is there a code for recognition.</a> Nucleic Acids Res. 34 (17), 4943-4959 (2006).</li><li>Dong, S., 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=Specific+and+modular+binding+code+for+cytosine+recognition+in+Pumilio/FBF+(PUF)+RNA-binding+domains.">Specific and modular binding code for cytosine recognition in Pumilio/FBF (PUF) RNA-binding domains.</a> J Biol Chem. 286 (30), 26732-26742 (2011).</li><li>Filipovska, A., Razif, M. F., Nyg&#229;rd, K. K., Rackham, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+universal+code+for+RNA+recognition+by+PUF+proteins.">A universal code for RNA recognition by PUF proteins.</a> Nat Chem Biol. 7 (7), 425-427 (2011).</li><li>Wei, H., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+RNA-binding+proteins+with+diverse+activities.">Engineering RNA-binding proteins with diverse activities.</a> Wiley Interdiscip Rev RNA. 6 (6), 597-613 (2015).</li><li>Wang, Y., Cheong, C. -. G., Hall, T. M. T., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+splicing+factors+with+designed+specificities.">Engineering splicing factors with designed specificities.</a> Nat Methods. 6 (11), 825-830 (2009).</li><li>Choudhury, R., Tsai, Y. S., Dominguez, D., Wang, Y., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+RNA+endonucleases+with+customized+sequence+specificities.">Engineering RNA endonucleases with customized sequence specificities.</a> Nat Commun. 3, 1147 (2012).</li><li>Wang, Y., 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=A+complex+network+of+factors+with+overlapping+affinities+represses+splicing+through+intronic+elements.">A complex network of factors with overlapping affinities represses splicing through intronic elements.</a> Nat Struct Mol Biol. 20 (1), 36-45 (2013).</li><li>McCabe, B. C., Gollnick, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+levels+of+trp+RNA-binding+attenuation+protein+in+Bacillus+subtilis.">Cellular levels of trp RNA-binding attenuation protein in Bacillus subtilis.</a> J Bacteriol. 186 (15), 5157-5159 (2004).</li><li>Wang, Y., Ma, M., Xiao, X., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intronic+splicing+enhancers,+cognate+splicing+factors+and+context-dependent+regulation+rules.">Intronic splicing enhancers, cognate splicing factors and context-dependent regulation rules.</a> Nat Struct Mol Biol. 19 (10), 1044-1052 (2012).</li><li>Choudhury, R., 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=The+splicing+activator+DAZAP1+integrates+splicing+control+into+MEK/Erk-regulated+cell+proliferation+and+migration.">The splicing activator DAZAP1 integrates splicing control into MEK/Erk-regulated cell proliferation and migration.</a> Nat Commun. 5, (2014).</li><li>Xiao, X., Wang, Z., Jang, M., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coevolutionary+networks+of+splicing+cis-regulatory+elements.">Coevolutionary networks of splicing cis-regulatory elements.</a> Proc Natl Acad Sci U S A. 104 (47), 18583-18588 (2007).</li><li>Wang, Z., Xiao, X., Van Nostrand, E., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+and+specific+functions+of+exonic+splicing+silencers+in+splicing+control.">General and specific functions of exonic splicing silencers in splicing control.</a> Mol Cell. 23 (1), 61-70 (2006).</li><li>Li, M., Husic, N., Lin, Y., Snider, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+lentiviral+vectors+for+transducing+cells+from+the+central+nervous+system.">Production of lentiviral vectors for transducing cells from the central nervous system.</a> J Vis Exp. (63), e4031 (2012).</li><li>Tiscornia, G., Singer, O., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+purification+of+lentiviral+vectors.">Production and purification of lentiviral vectors.</a> Nat Protoc. 1 (1), 241-245 (2006).</li><li>Venables, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aberrant+and+alternative+splicing+in+cancer.">Aberrant and alternative splicing in cancer.</a> Cancer Res. 64 (21), 7647-7654 (2004).</li><li>Cooke, A., Prigge, A., Opperman, L., Wickens, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+translational+regulation+using+the+PUF+protein+family+scaffold.">Targeted translational regulation using the PUF protein family scaffold.</a> Proc Natl Acad Sci U S A. 108 (38), 15870-15875 (2011).</li><li>He, C., Zhou, F., Zuo, Z., Cheng, H., Zhou, 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+global+view+of+cancer-specific+transcript+variants+by+subtractive+transcriptome-wide+analysis.">A global view of cancer-specific transcript variants by subtractive transcriptome-wide analysis.</a> PloS one. 4 (3), 4732 (2009).</li><li>Venables, J. P., 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=Identification+of+alternative+splicing+markers+for+breast+cancer.">Identification of alternative splicing markers for breast cancer.</a> Cancer Res. 68 (22), 9525-9531 (2008).</li><li>Shapiro, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+EMT-Driven+Alternative+Splicing+Program+Occurs+in+Human+Breast+Cancer.">An EMT-Driven Alternative Splicing Program Occurs in Human Breast Cancer.</a> PLoS Genet. 7 (8), 1002218 (2011).</li><li>David, C. J., Manley, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+pre-mRNA+splicing+regulation+in+cancer:+pathways+and+programs+unhinged.">Alternative pre-mRNA splicing regulation in cancer: pathways and programs unhinged.</a> Genes Dev. 24 (21), 2343-2364 (2010).</li><li>Ladomery, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aberrant+alternative+splicing+is+another+hallmark+of+cancer.">Aberrant alternative splicing is another hallmark of cancer.</a> Int J Cell biol. 2013, (2013).</li><li>Karni, R., 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=The+gene+encoding+the+splicing+factor+SF2/ASF+is+a+proto-oncogene.">The gene encoding the splicing factor SF2/ASF is a proto-oncogene.</a> Nat Struct Mol Biol. 14 (3), 185-193 (2007).</li><li>Anczuk&#242;w, O., 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=SRSF1-regulated+alternative+splicing+in+breast+cancer.">SRSF1-regulated alternative splicing in breast cancer.</a> Mol cell. 60 (1), 105-117 (2015).</li></ol>

The authors have nothing to disclose.

This report provides a detailed description for the design and construction of artificial splicing factors that can specifically manipulate the alternative splicing of a target gene. This method takes advantage of the unique RNA binding mode of PUF repeats to produce an RNA-binding scaffold with customized specificity. It can be used to either activate or repress splicing.
The critical step in this protocol is the generation of the reprogramed PUF domain that defines the specificity of ESFs. A PCR stitching protocol has been developed and optimized for the rapid generation of the PUF scaffold. The key for its success is to adjust the ratio of different overlapping templates to 1:1:1. The purification of the PCR products after each round is also critical, because unpurified products may have primer contamination from the last round. Another important step is to assay the splicing ratio using semi-quantitative RT-PCR. Generally, too many amplification cycles should be avoided, as they may saturate the PCR reaction. In our experiments with the co-expression of a splicing reporter, 20 - 25 cycles were routinely used, but this may vary depending on the abundance of the mRNA when measuring the splicing of endogenous genes. When quantifying the splicing isoforms using a new pair of primers, we suggest calibrating the PCR experiment each time, as previously described16.
A potential limitation with designer ESFs is their off-target effects, because the specificity is determined by the number of repeats in the PUF scaffold. Wildtype PUF recognizes an 8-nt site, which is comparable to the specificity of an siRNA that recognizes its target through &#34;seed match.&#34; However, since any 8-nt sequence could occur once by chance in a transcript 65,000 nt long (48 = 65,536), there will be other off-target transcripts recognized by the designer PUF. The off-target effect can be reduced by using PUFs with additional repeats; however, it is still useful to evaluate the specificity and off-target effects of ESFs. To minimize potential off-target effects, the expression of a combination of multiple designer ESFs at a lower level may also be carried out. In such a case, the off-targeted genes may not be affected by the low amount of ESFs, whereas the splicing of the real target will be affected by the multiple ESFs that function synergistically. This solution is similar to what researchers used in gene silencing with RNAi, where the pooled siRNAs (each at a reduced concentration) that target multiple sites of a single mRNA can decrease the off-target effects.
The other main method to manipulate AS is to use antisense oligonucleotides that pair with certain regions of the pre-mRNA. Compared to this existing method, the ESFs can cause prolonged effects in stably transfected cells. In addition, the in vivo delivery of ESF can take advantage of the increasing arsenal of gene therapy vectors, whereas the in vivo delivery of antisense oligonucleotides is very hard to control. In addition, this method can avoid complicated and costly modifications of oligonucleotides. Using various inducible promoters, a more precise control of the ESF expression in the correct cell types and at the correct times may also be achieved. The main disadvantage of this method is the relatively low specificity (an 8-nt recognition site versus a 16- to 20-nt recognition site in typical antisense oligonucleotides).
The dysregulation of alternative splicing causes many diseases, including cancer26,27. Genome-wide studies have revealed more than 15,000 tumor-associated splice variants in various types of cancers28,29,30. For instance, intronic splice-site mutations of tumor-suppressor genes often cause exon-skipping events and produce aberrant proteins that may contribute to tumor genesis26,31,32. Moreover, some splicing factors are found to be overexpressed in many cancer types, which contributes to cell transformation33,34, indicating that splicing factors can also play important roles in cancer biogenesis. Therefore, in addition to providing a useful tool to modulate gene function, manipulation of splicing with designer ESFs may restore misregulated splicing events in cancer, thus providing a potential therapeutic tool. In addition, by fusing a designer PUF domain with different functional domains, multiple artificial factors that manipulate various RNA metabolism processes can be designed. For example, the fusion of a translational activator (GLD2) or a translational repressor (CAF1) with the PUF domain produced novel factors that can activate or inhibit mRNA translation27. Using the same design principal, we combined a non-specific RNA endonuclease domain (PIN) with a series of designer PUF domains to generate artificial site-specific RNA endonucleases (ASREs) that function analogously to DNA restriction enzymes17.

Most human genes undergo Alternative Splicing (AS) to produce multiple isoforms with distinct activities, which has greatly increased the coding complexity of the genome1,2. AS provides a major mechanism to regulate gene function, and it is tightly regulated through diverse pathways in different cellular and developmental stages3,4. Because splicing misregulation is a common cause of human disease5,6,7,8, targeting splicing regulation is becoming an attractive therapeutic route.
According to a simplified model of splicing regulation, AS is mainly controlled by Splicing Regulatory cis-Elements (SREs) in pre-mRNA that function as splicing enhancers or silencers of alternative exons. These SREs specifically recruit various trans-acting protein factors (i.e.&#160;splicing factors) that promote or suppress the splicing reaction3,9. Most trans-acting splicing factors have separate sequence-specific RNA binding domains to recognize their targets and effector domains to control splicing. The best-known examples are the members of the serine/arginine-rich (SR) protein family that contain N-terminal RNA Recognition Motifs (RRMs), which bind exonic splicing enhancers, and C-terminal RS domains, which promote exon inclusion10. Conversely, hnRNP A1 binds to exonic splicing silencers through the RRM domains and inhibits exon inclusion through a C-terminal glycine-rich domain11. Using such modular configurations, researchers should be able to engineer artificial splicing factors by combining a specific RNA-Binding Domain (RBD) with different effector domains that activate or inhibit splicing.
The key of such a design is to use an RBD that recognizes given targets with programmable RNA binding specificity, which is analogous to the DNA-binding mode of the TALE domain. However, most native splicing factors contain RRM or K Homology (KH) domains, which recognize short RNA elements with weak affinity and thus lack a predictive RNA-protein recognition &#34;code&#34;12. The RBD of PUF repeat proteins (i.e.&#160;the PUF domain) has a unique RNA recognition mode, allowing for the redesign of PUF domains to specifically recognize different RNA targets13,14. The canonical PUF domain contains eight repeats of three &#945;-helices, each recognizing a single base in an 8-nt RNA target. The side chains of amino acids at certain positions of the second &#945;-helix form specific hydrogen bonds with the Watson-Crick edge of the RNA base, which determines the RNA binding specificity of each repeat (Figure 1A). The code for RNA base recognition of the PUF repeat is surprisingly simple (Figure 1A), allowing for the generation of PUF domains that recognize any possible 8-base combination (reviewed by Wei and Wang15).
This modular design principle allows for the generation of an Engineered Splicing Factor (ESF) that consists of a customized PUF domain and a splicing modulation domain (i.e.&#160;an SR domain or a Gly-rich domain). These ESFs can function as either splicing activators or as inhibitors to control various types of splicing events, and they have proven useful as tools to manipulate the splicing of endogenous genes related to human disease16,17. As an example, we have constructed PUF-Gly-type ESFs to specifically alter the splicing of the Bcl-x gene, converting the anti-apoptotic long isoform (Bcl-xL) to the pro-apoptotic short isoform (Bcl-xS). Shifting the ratio of the Bcl-x isoform was sufficient to sensitize several cancer cells to multiple anti-cancer chemotherapy drugs16, suggesting that these artificial factors may be useful as potential therapeutic reagents.
In addition to controlling splicing with known splicing effector domains (e.g., an RS or Gly-rich domain), the engineered PUF factors can also be used to examine the activities of new splicing factors. For example, using this approach, we have demonstrated that the C-terminal domain of several SR proteins can activate or inhibit splicing when binding to different pre-mRNA regions18, that the alanine-rich motif of RBM4 can inhibit splicing19, and that the proline-rich motif of DAZAP1 can enhance splicing20,21. These new functional domains can be used to construct additional types of artificial factors to fine-tune splicing.

<table border="0" cellpadding="0" cellspacing="0" width="1166">
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		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:420px;">High-fidelity DNA polymerase (Phusion High-Fidelity) with PCR buffer</td>
			<td style="width:155px;">New England Biolabs</td>
			<td style="width:103px;">M0530L</td>
			<td style="width:491px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNA ligase (T4 DNA ligase)</td>
			<td>New England Biolabs</td>
			<td>M0202L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Liposomal transfection reagent (Lipofectamine 2000)</td>
			<td>Invitrogen</td>
			<td>11668-019</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reduced serum medium (Opti-MEM)</td>
			<td>Gibco</td>
			<td>31985-062</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNA extraction buffer (TRIzol Reagent)</td>
			<td>ambion</td>
			<td>15596018</td>
			<td>TRIzol reagent includes phenol, which can cause burns. Wear gloves when handling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BSA (Bovine Serum Albumin)</td>
			<td>Sigma-Aldrich</td>
			<td>A7638-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS (1X)</td>
			<td>Life Technologies</td>
			<td>10010-031</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SuperScript III reverse transcriptase</td>
			<td>Invitrogen</td>
			<td>18080044</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Caspase-3 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>9668</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PARP&#160;antibody</td>
			<td>Cell Signaling Technology</td>
			<td>9542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bcl-x antibody</td>
			<td>BD Bioscience</td>
			<td>610211</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">beta-actin antibody</td>
			<td>Sigma-Aldrich</td>
			<td>A5441</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">alpha-tubulin antibody</td>
			<td>Sigma-Aldrich</td>
			<td>T5168</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FLAG antibody</td>
			<td>Sigma-Aldrich</td>
			<td>F4042</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nitrocellulose membrane</td>
			<td>Amersham-Pharmacia</td>
			<td>RPN203D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ECL Western Blotting detection reagents</td>
			<td>Invitrogen</td>
			<td>WP20005</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cy5-dCTP</td>
			<td>GE Healthcare</td>
			<td>PA55021</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fluorescence-activated cell sorter</td>
			<td>BD Bioscience</td>
			<td>FACSCalibur&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s Modified Eagle&#8217;s Medium (DMEM)</td>
			<td>GE Healthcare</td>
			<td>SH30243.01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine serum</td>
			<td>Invitrogen</td>
			<td>26140079</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propidium iodide (PI)</td>
			<td>Sigma</td>
			<td>P4170</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bovine Serum Albumin (BSA)</td>
			<td>Sigma</td>
			<td>A7638-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton-X100</td>
			<td>Promega</td>
			<td>H5142</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly-lysine&#160;</td>
			<td>Sigma</td>
			<td>P-4832</td>
			<td>Filter sterilize and store at 4 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector&#160; pWPXLd</td>
			<td>Addgene</td>
			<td>12258</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector pMD2.G</td>
			<td>Addgene</td>
			<td>12259</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector psPAX2</td>
			<td>Addgene</td>
			<td>12260</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase I (RNase-free)</td>
			<td>New England Biolabs</td>
			<td>M0303S</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Oligo(dT)18 Primer</td>
			<td>Thermo Scientific</td>
			<td>SO131&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-mouse secondary antibody (Anti-mouse IgG, HRP-linked Antibody)</td>
			<td>Cell Signaling Technology</td>
			<td>7076S</td>
			<td></td>
		</tr>
	</tbody>
</table>

engineering artificial factors to specifically manipulate alternative splicing in human cells

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which specifically binds the pre-mRNA target and an effector domain. Previously, we have taken advantage of the unique RNA binding mode of the PUF domain in human Pumilio 1 to generate a programmable RNA binding scaffold, which was used to engineer various artificial RBPs to manipulate RNA metabolism. Here, a detailed protocol is described to construct Engineered Splicing Factors (ESFs) that are specifically designed to modulate the alternative splicing of target genes. The protocol includes how to design and construct a customized PUF scaffold for a specific RNA target, how to construct an ESF expression plasmid by fusing a designer PUF domain and an effector domain, and how to use ESFs to manipulate the splicing of target genes. In the representative results of this method, we have also described the common assays of ESF activities using splicing reporters, the application of ESF in cultured human cells, and the subsequent effect of splicing changes. By following the detailed protocols in this report, it is possible to design and generate ESFs for the regulation of different types of Alternative Splicing (AS), providing a new strategy to study splicing regulation and the function of different splicing isoforms. Moreover, by fusing different functional domains with a designed PUF domain, researchers can engineer artificial factors that target specific RNAs to manipulate various steps of RNA processing.

This report describes the complete protocol for the design and construction of ESFs and splicing reporters. It also outlines the further application of ESFs in manipulating the AS of endogenous genes16. To illustrate typical results of ESF-mediated splicing changes, we use the data from our previous work as an example. The ESFs with different functional domains can be used to promote or inhibit the inclusion of the target cassette exon (Figure 1D &#38; E). ESFs can also affect the usage of alternative 5&#39; and 3&#39; splice sites in the reporter system (Figure 1F &#38; G).
The alternative splicing of the endogenous gene can also be specifically regulated with designer ESFs. We have demonstrated this application by specifically targeting Bcl-x, which can be spliced into two antagonistic isoforms with alternative 5&#39; splice sites. We designed an ESF, Gly-PUF(531), that recognizes an 8-nt RNA element between the alternative 5&#39; splice sites. This Gly-PUF(531) specifically shifted the splicing towards the production of Bcl-xS (Figure 2A). After transfecting the Gly-PUF(531) into HeLa cells, the level of Bcl-xS isoforms and Bcl-xS proteins increased in a dose-dependent manner, whereas the control ESF, Gly-PUF(WT), did not affect the ratio of Bcl-xS to Bcl-xL (Figure 2B &#38; C). In addition, the designer ESF can induce the cleavage of caspase 3 and poly (ADP-ribose) polymerase (PARP), two well-known molecular markers of apoptosis (Figure 2D). As expected, the designer ESFs are predominantly localized in the nuclei of transfected cells, as demonstrated by immunofluorescence microscopy (Figure 2E). Consistently, the splicing shift by Gly-PUF(531) caused the fragmentation of nuclear DNA, indicating that these cells are undergoing apoptosis (Figure 2E). The increase of apoptotic cells was further confirmed by examining more than 200 cells from randomly selected fields and by quantifying the percent of cells with fragmented nuclear DNA (Figure 2F).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/54967/54967fig1.jpg" /> 
Figure 1: Design of ESFs and Their Activity in Modulating Exon Skipping. (A) Specific binding between the PUF domain and RNA targets is illustrated with the RNA-PUF structure and a schematic diagram. The PUF binding code for each of the four RNA bases, shown on the right with different colors, is used to design PUF mutations. (B) Flow chart to obtain a customized PUF domain. The PUF that recognizes &#34;UGUAUAUA&#34; was used as an example. A 4-round PCR strategy is used to assemble a PUF scaffold with customized RNA-binding specificity (color coded similarly to panel A). In the first round, a series of PCR primers that incorporate the desired RNA-recognition codes for two adjacent PUF repeats are used to generate four fragments that include the eight RNA-recognition codes of a full PUF protein (R1/R2, R3/R4, R5/R6, and R7/R8). Cap fragments encoding an N-terminal nuclear localization signal, a C-terminal stop codon, and bridge fragments are also produced separately (5&#39;-end and 3&#39;-end cap, bridge 2/3, bridge 4/5, and bridge 6/7). In the second round, new templates are generated by mixing overlapping fragments encoding adjacent repeats with the appropriate bridge (e.g., mixing R1/R2, R3/R4, and bridge 2/3 generates the template for R1 - 4) and then extending with DNA polymerase to fill the gaps. Similarly, the third round joins R1-4, R5-8, and bridge 4/5. Finally, the fourth round adds the 5&#39;-end and 3&#39;-end caps of the PUF domain together with the cloning sites for subsequent cloning to expression vectors. (C) Modular domain organization of ESFs. ESFs are driven by CMV promoters (arrow) and encode, from the N- to the C-terminal: a FLAG epitope (for the detection of ESFs), a functional module (a Gly-rich domain or an RS domain), an NLS (facilitating the nuclear localization of ESFs), and an RNA-recognition domain (a PUF domain). NheI and BamHI are designed to insert a functional module, while XbaI and SalI are designed to insert an RNA-recognition domain. (D) Gly-PUF ESFs are co-expressed with exon skipping reporters, and the splicing pattern is assayed by RT-PCR. The modified PUFa and PUFb specifically bind to 8-mer targets A and B, respectively (in the same colors). All combinations are used, so the PUF-target pairs of different color serve as the controls. The effects of RS-PUF on exon skipping (E), the competing 5&#39; splice site (F), or the competing 3&#39; splice site reporter (G) were assayed by methods similar to panel D. The data of the RT-PCR are from Wang et al.16. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54967/54967fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/54967/54967fig2.jpg" /> 
Figure 2: Regulation of Endogenous Bcl-x pre-mRNA Splicing with ESFs. (A) Schematic of the alternative splicing of endogenous Bcl-x pre-mRNA. Two alternative 5&#39; splice site in exon 2 of Bcl-x are used to generate two isoforms of different sizes, Bcl-xL and Bcl-xS. The sequence UGUGCGUG between the two 5&#39; splice sites is selected as the ESF target, and WT PUF repeats 1, 3, and 5 (Q867E/Q939E/C935S/Q1011E/C1007S) are reprogrammed (asterisks) to recognize this target sequence. The resulting ESF containing a Gly-rich domain inhibits the use of the downstream 5&#39; ss (indicated by the red arrow). (B) Modulation of Bcl-x 5&#39; ss usage. Different amounts of the Gly-PUF(531) expression construct are transfected into HeLa cells. Gly-PUF(WT) is used as a control. Two isoforms of Bcl-x are detected with RT-PCR using primers corresponding to exons 1 and 3 of the Bcl-x gene. The percentage of the Bcl-xS isoform is quantified and shown at the bottom. (C) ESFs affect the expression levels of Bcl-xL and Bcl-xS. Samples are loaded in the same order as in panel B, and all proteins are detected by Western blots. The expression of ESFs is detected by the anti-FLAG antibody, and the tubulin level is used as a control. (D) Different amounts of ESF expression constructs are transfected into HeLa cells, resulting in the cleavage of PARP and caspase 3. Samples are detected by Western blot 24 h after transfection. The actin level is detected as a control. (E) The subcellular localization of ESFs in transfected HeLa cells is detected by immunofluorescence microscopy with the anti-FLAG antibody. The cells are co-stained with DAPI to show the nuclei. Some nuclei, especially in cells transfected with Gly-PUF(531), are fragmented due to apoptosis. Scale bar: 5 &#181;m. (F) Percentage of apoptotic cells (i.e.&#160;cells with fragmented nuclear DNA) are measured from randomly chosen fields of fluorescence microscopy images. The bars indicate the mean, while the dots indicate the data from the two experiments. The figures are modified from our earlier report by Wang et al.16 in accordance with the policy of Nature Publishing Group. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54967/54967fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells at JoVE.com

Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

This report describes a bioengineering method to design and construct novel Artificial Splicing Factors (ASFs) that specifically modulate the splicing of target genes in mammalian cells. This method can be further expanded to engineer various artificial factors to manipulate other aspects of RNA metabolism.

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which ...

engineering-artificial-factors-to-specifically-manipulate-alternative

Nanyang Technological University

Research

JoVE Journal

Genetics

8.9K Views.  Shanghai Institutes for Biological Sciences (SIBS). This report describes a bioengineering method to design and construct novel Artificial Splicing Factors (ASFs) that specifically modulate the splicing of target genes in mammalian cells. This method can be further expanded to engineer various artificial factors to manipulate other aspects of RNA metabolism.

Video: Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

siRNA Transfection and EMSA Analyses on Freshly Isolated Human Villous Cytotrophoblasts

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend diseases related to pregnancy. In this protocol, human primary villous cytotrophoblasts freshly isolated from placentas through a standard DNase/trypsin protocol are microporated with small interfering RNA (siRNA). This approach provided greater efficiency for siRNA transfection when compared to a lipofection-based method. Transfected cells can subsequently be analyzed by standard Western blot within a time frame of 3-4 days post-transfection. In addition, using cultured primary villous cytotrophoblasts, Electrophoretic Mobility Shift Assay (EMSA) analysis was optimized and performed on extracts from days 1 to 4. The use of these cultured primary cells and the protocol described allow for an evaluation of the implication of specific genes and transcription factors in the process of villous cytotrophoblast differentiation into a syncytiotrophoblast-like cell layer. However, the limited time span allowable in culture precludes the use of methods requiring more time, such as generation of a stable cell population. Therefore testing of this cell population requires highly optimized gene transfer protocols.

This protocol describes a method for efficiently transfecting siRNA in freshly isolated human villous cytotrophoblasts using microporation and identifying DNA-protein complexes in these cells. Transfected cells can be monitored by Western blot and EMSA analyses during the 4-day culture time.

Human primary villous cytotrophoblasts are a very useful source of primary cells to study placental functions and regulatory mechanisms, and to comprehend ...

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex is by far the most common pathway to initiate protein synthesis in eukaryotic cells, but stress-specific variations of this complex are now emerging. Purifying cap-binding proteins with an affinity resin composed of Agarose-linked m7GTP (a 5' mRNA cap analog) is a useful tool to identify factors involved in the regulation of translation initiation. Hypoxia (low oxygen) is a cellular stress encountered during fetal development and tumor progression, and is highly dependent on translation regulation. Furthermore, it was recently reported that human adult organs have a lower oxygen content (physioxia 1-9% oxygen) that is closer to hypoxia than the ambient air where cells are routinely cultured. With the ongoing characterization of a hypoxic eIF4F complex (eIF4FH), there is increasing interest in understanding oxygen-dependent translation initiation through the 5' mRNA cap. We have recently developed a human cell culture method to analyze cap-binding proteins that are regulated by oxygen availability. This protocol emphasizes that cell culture and lysis be performed in a hypoxia workstation to eliminate exposure to oxygen. Cells must be incubated for at least 24 hr for the liquid media to equilibrate with the atmosphere within the workstation. To avoid this limitation, pre-conditioned media (de-oxygenated) can be added to cells if shorter time points are required. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. This method allows the user to identify novel oxygen-regulated translation factors involved in cap-dependent translation.

Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex ...

Highly Efficient Gene Disruption of Murine and Human Hematopoietic Progenitor Cells by CRISPR/Cas9

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. Complete gene ablation in HSCs required the generation of knockout mice from which HSCs could be isolated, and gene ablation in primary human HSCs was not possible. Viral transduction could be used for knock-down approaches, but these suffered from variable efficacy. In general, genetic manipulation of human and mouse hematopoietic cells was hampered by low efficiencies and extensive time and cost commitments. Recently, CRISPR/Cas9 has dramatically expanded the ability to engineer the DNA of mammalian cells. However, the application of CRISPR/Cas9 to hematopoietic cells has been challenging, mainly due to their low transfection efficiencies, the toxicity of plasmid-based approaches and the slow turnaround time of virus-based protocols.
A rapid method to perform CRISPR/Cas9-mediated gene editing in murine and human hematopoietic stem and progenitor cells with knockout efficiencies of up to 90% is provided in this article. This approach utilizes a ribonucleoprotein (RNP) delivery strategy with a streamlined three-day workflow. The use of Cas9-sgRNA RNP allows for a hit-and-run approach, introducing no exogenous DNA sequences in the genome of edited cells and reducing off-target effects. The RNP-based method is fast and straightforward: it does not require cloning of sgRNAs, virus preparation or specific sgRNA chemical modification. With this protocol, scientists should be able to successfully generate knockouts of a gene of interest in primary hematopoietic cells within a week, including downtimes for oligonucleotide synthesis. This approach will allow a much broader group of users to adapt this protocol for their needs.

A protocol for fast CRISPR/Cas9-mediated gene disruption in mouse and human primary hematopoietic cells is described in this article. Cas9-sgRNA ribonucleoproteins are introduced via electroporation with sgRNAs generated through in vitro transcription and commercial Cas9. High editing efficiencies are achieved with limited time and financial cost.

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. ...

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell type-specific fashion. AS expression patterns are typically analyzed by RT-PCR and RNA-seq using RNA samples isolated from a population of cells. In situ examination of AS expression patterns for a particular biological structure can be carried out by RNA in situ hybridization (ISH) using exon-specific probes. However, this particular use of ISH has been limited because alternative exons are generally too short to design exon-specific probes. In this report, the use of BaseScope, a recently developed technology that employs short antisense oligonucleotides in RNA ISH, is described to analyze AS expression patterns in mouse brain sections. Exon 23a of neurofibromatosis type 1 (Nf1) is used as an example to illustrate that short exon-exon junction probes exhibit robust hybridization signals with high specificity in RNA ISH analysis on mouse brain sections. More importantly, signals detected with exon inclusion- and skipping-specific probes can be used to reliably calculate the percent spliced in values of Nf1 exon 23a expression in different anatomical areas of a mouse brain. The experimental protocol and calculation method for AS analysis are presented. The results indicate that BaseScope provides a powerful new tool to assess AS expression patterns in situ.

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

An in situ hybridization (ISH) protocol that uses short antisense oligonucleotides to detect alternative pre-mRNA splicing patterns in mouse brain sections is described.

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell ...

Endogenous Protein Tagging in Human Induced Pluripotent Stem Cells Using CRISPR/Cas9

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame&#160;N- or C-terminal fluorescent tags. The prokaryotic CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeats/CRISPR-associated 9) may be used to introduce large exogenous sequences into genomic loci via homology directed repair (HDR). To achieve the desired knock-in, this protocol employs the ribonucleoprotein (RNP)-based approach where wild type Streptococcus pyogenes Cas9 protein, synthetic 2-part guide RNA (gRNA), and a donor template plasmid are delivered to the cells via electroporation. Putatively edited cells expressing the fluorescently tagged proteins are enriched by fluorescence activated cell sorting (FACS). Clonal lines are then generated and can be analyzed for precise editing outcomes. By introducing the fluorescent tag at the genomic locus of the gene of interest, the resulting subcellular localization and dynamics of the fusion protein can be studied under endogenous regulatory control, a key improvement over conventional overexpression systems. The use of hiPSCs as a model system for gene tagging provides the opportunity to study the tagged proteins in diploid, nontransformed cells. Since hiPSCs can be differentiated into multiple cell types, this approach provides the opportunity to create and study tagged proteins in a variety of isogenic cellular contexts.

Described here is a protocol for tagging endogenously expressed proteins with fluorescent tags in human induced pluripotent stem cells using CRISPR/Cas9. Putatively edited cells are enriched by fluorescence activated cell sorting and clonal cell lines are generated.

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame&#160;N- or ...

Cell Based Assays of SINEUP Non-coding RNAs That Can Specifically Enhance mRNA Translation

Targeted-protein enhancement is of importance not only for the study of biological processes but also for therapeutic and biotechnological applications. Here, we present a method to selectively up-regulate protein expression of desired genes in cultured cells by means of synthetic antisense non-coding RNAs known as SINEUPs. This positive control of gene expression is at the post-transcriptional level and exerted by an inverted short interspersed nuclear element (SINE) repeat at the 3&#697; end of SINEUPs that comprises its effector domain (ED). SINEUPs can specifically bind to any protein-coding mRNA of choice through its binding domain (BD), a region designed to complement the sequence within the 5&#697; untranslated region (5&#697; UTR) and around the start codon of the mRNA. Target-specific SINEUPs designed in this manner are transfected to cultured cells, and protein and RNA are extracted for downstream analyses, generally 24-48 h post-transfection. SINEUP-induced protein up-regulation is detected by Western-blot analysis and RNA expression is measured using real-time quantitative reverse transcription PCR. We have observed that BD design is critical for achieving optimum SINEUP activity and that testing different BD sizes and positions with respect to the start codon of the target mRNA is recommended. Therefore, we describe here a semi-automated high-throughput imaging method based on fluorescence detection that can be implemented to target mRNA fused with green fluorescent protein (GFP). SINEUPs specifically enhance translation within normal physiological range of the cell, without altering the target transcript level. This method has been successfully employed against a range of endogenous and exogenous targets, in a wide variety of human, mouse, and insect cell lines along with in vivo systems. Moreover, SINEUPs have been reported to increase antibody production and work as an RNA therapeutic against haploinsufficient genes. The versatile and modular nature of SINEUPs makes them a suitable tool for gene-specific translational control.

SINEUPs are synthetic antisense non-coding RNAs, which contain a binding domain (BD) and an effector domain (ED) and up-regulate translation of target mRNA. Here, we describe detection methods for SINEUPs in cultured cell lines, analysis of their translation-promoting activity by Western-blot and a semi-automated high throughput imaging system.

Targeted-protein enhancement is of importance not only for the study of biological processes but also for therapeutic and biotechnological applications. ...

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other important cellular biology questions. The technologies available to genetically manipulate Dictyostelium cells are well-developed. Transfections can be performed using different selectable markers and marker re-cycling, including homologous recombination and insertional mutagenesis. This is supported by a well-annotated genome. However, these approaches are optimized for axenic cell lines growing in liquid cultures and are difficult to apply to non-axenic wild-type cells, which feed only on bacteria. The mutations that are present in axenic strains disturb Ras signaling, causing excessive macropinocytosis required for feeding, and impair cell migration, which confounds the interpretation of signal transduction and chemotaxis experiments in those strains. Earlier attempts to genetically manipulate non-axenic cells have lacked efficiency and required complex experimental procedures. We have developed a simple transfection protocol that, for the first time, overcomes these limitations. Those series of large improvements to Dictyostelium molecular genetics allow wild-type cells to be manipulated as easily as standard laboratory strains. In addition to the advantages for studying uncorrupted signaling and motility processes, mutants that disrupt macropinocytosis-based growth can now be readily isolated. Furthermore, the entire transfection workflow is greatly accelerated, with recombinant cells that can be generated in days rather than weeks. Another advantage is that molecular genetics can further be performed with freshly isolated wild-type Dictyostelium samples from the environment. This can help to extend the scope of approaches used in these research areas.

Genetic Engineering of Dictyostelium discoideum Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is a popular model organism to study complex cellular processes such as cell migration, endocytosis, and development. The utility of the organism is dependent on the feasibility of genetic manipulation. Here, we present methods to transfect Dictyostelium discoideum cells that overcome existing limitations of culturing cells in liquid media.

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other ...

Lentiviral Mediated Gene Silencing in Human Pseudoislet Prepared in Low Attachment Plates

Various genetic tools are available to modulate genes in pancreatic islets of rodents to dissect function of islet genes for diabetes research. However, the data obtained from rodent islets are often not fully reproduced in or applicable to human islets due to well-known differences in islet structure and function between the species. Currently, techniques that are available to manipulate gene expression of human islets are very limited. Introduction of transgene into intact islets by adenovirus, plasmid, and oligonucleotides often suffers from low efficiency and high toxicity. Low efficiency is especially problematic in gene downregulation studies in intact islets, which require high efficiency. It has been known that enzymatically-dispersed islet cells reaggregate in culture forming spheroids termed pseudoislets. Size-controlled reaggregation of human islet cells creates pseudoislets that maintain dynamic first phase insulin secretion after prolonged culture and provide a window to efficiently introduce lentiviral short hairpin RNA (shRNA) with low toxicity. Here, a detailed protocol for the creation of human pseudoislets after lentiviral transduction using two commercially available multiwell plates is described. The protocol can be easily performed and allows for efficient downregulation of genes and assessment of dynamism of insulin secretion using human islet cells. Thus, human pseudoislets with lentiviral mediated gene modulation provide a powerful and versatile model to assess gene function within human islet cells.

A protocol to create gene modified human pseudoislets from dispersed human islet cells that are transduced by lentivirus carrying short hairpin RNA (shRNA) is presented. This protocol utilizes readily available enzyme and culture vessels, can be performed easily, and produces genetically modified human pseudoislets suitable for functional and morphological studies.

Various genetic tools are available to modulate genes in pancreatic islets of rodents to dissect function of islet genes for diabetes research. However, ...

Pooled CRISPR-Based Genetic Screens in Mammalian Cells

Genome editing using the CRISPR-Cas system has vastly advanced the ability to precisely edit the genomes of various organisms. In the context of mammalian cells, this technology represents a novel means to perform genome-wide genetic screens for functional genomics studies. Libraries of guide RNAs (sgRNA) targeting all open reading frames permit the facile generation of thousands of genetic perturbations in a single pool of cells that can be screened for specific phenotypes to implicate gene function and cellular processes in an unbiased and systematic way. CRISPR-Cas screens provide researchers with a simple, efficient, and inexpensive method to uncover the genetic blueprints for cellular phenotypes. Furthermore, differential analysis of screens performed in various cell lines and from different cancer types can identify genes that are contextually essential in tumor cells, revealing potential targets for specific anticancer therapies. Performing genome-wide screens in human cells can be daunting, as this involves the handling of tens of millions of cells and requires analysis of large sets of data. The details of these screens, such as cell line characterization, CRISPR library considerations, and understanding the limitations and capabilities of CRISPR technology during analysis, are often overlooked. Provided here is a detailed protocol for the successful performance of pooled genome-wide CRISPR-Cas9 based screens.

CRISPR-Cas9 technology provides an efficient method to precisely edit the mammalian genome in any cell type and represents a novel means to perform genome-wide genetic screens. A detailed protocol discussing the steps required for the successful performance of pooled genome-wide CRISPR-Cas9 screens is provided here.

Genome editing using the CRISPR-Cas system has vastly advanced the ability to precisely edit the genomes of various organisms. In the context of mammalian ...

Generation of Defined Genomic Modifications Using CRISPR-CAS9 in Human Pluripotent Stem Cells

Human pluripotent stem cells offer a powerful system to study gene function and model specific mutations relevant to disease. The generation of precise heterozygous genetic modifications is challenging due to CRISPR-CAS9 mediated indel formation in the second allele. Here, we demonstrate a protocol to help overcome this difficulty by using two repair templates in which only one expresses the desired sequence change, while both templates contain silent mutations to prevent re-cutting and indel formation. This methodology is most advantageous for gene editing coding regions of DNA to generate isogenic control and mutant human stem cell lines for studying human disease and biology. In addition, optimization of transfection and screening methodologies have been performed to reduce labor and cost of a gene editing experiment. Overall, this protocol is widely applicable to many genome editing projects utilizing the human pluripotent stem cell model.

This protocol provides a method to facilitate the generation of defined heterozygous or homozygous nucleotide changes using CRISPR-CAS9 in human pluripotent stem cells.

Human pluripotent stem cells offer a powerful system to study gene function and model specific mutations relevant to disease. The generation of precise ...