We thank all members of our laboratory for helpful discussions. We thank Joanna Lisztwan and Christina Gewinner for critical reading of the manuscript. This work was supported by the BBSRC grant BB/I021248/1 and the Wellcome Trust grant 090090/Z/09/Z.A.H. is a Wellcome Trust Research Career Development fellow at the UCL Cancer Institute.

1. Cloning of pcDNA6_TetR_IRES_blast
<ol>
	<li>As illustrated in Figure 3, perform a partial digest of the pcDNA6/TR plasmid (V1025-20, Invitrogen) with the restriction enzymes XbaI and NcoI to remove the TetR gene and the promoter of the blasticidin resistance (BlastR) gene. Isolate the 4.6 kb vector fragment.</li>
	<li>To remove the polyadenylation sequence from the TetR gene, introduce by PCR an XhoI site immediately after the Stop codon of the TetR cDNA while conserving the XbaI site at the 5'end of the cDNA. Subclone the resulting fragment into pMigR117 using restriction enzymes XbaI and XhoI to generate the pMigR1_TetR plasmid.</li>
	<li>Digest the pMigR1_TetR vector with the restriction enzymes XbaI and NcoI to release the TetR_IRES fragment. Isolate the 1.25 kb insert fragment.</li>
	<li>Ligate the 4.6 kb pcDNA6/TR and the 1.25 kb TetR_IRES fragments. Transform the ligation product into competent E.coli and identify the desired pcDNA6_TetR_IRES_blast construct using standard molecular biology techniques.</li>
</ol>
2. Generation of Cell Lines Stably Expressing TetR
<ol>
	<li>On day 1, Seed 1x106 cells per 10-cm tissue culture plate using your standard growth medium (e.g. DMEM supplemented with 10% FCS). Seed two plates, one for transfection with pcDNA6_TetR_IRES_blast, and the other as a negative control for blasticidin selection. Ensure to use the lowest passage possible and the recommended growth medium.</li>
	<li>On day 2, transfect one plate with 2 &mu;g of pcDNA6_TetR_IRES_blast using Fugene 6 (E2691, Promega) following the manufacturer's instructions. Do not transfect the second plate.</li>
	<li>On day 3, add standard growth medium containing 5 &mu;g/ml blasticidin to both plates. Please note that the optimal selection concentration may vary for a given cell line and might need to be determined beforehand.</li>
	<li>On day 4, split the cells at 1/5, 1/25, 1/50 and 1/100 using 10-cm plates and standard growth medium containing 5 mg/ml blasticidin. Make sure to properly label plates containing untransfected or transfected cells. Prepare two plates per dilution step.</li>
	<li>Check cells daily, ensuring that all cells on the untransfected plates have died within the first week. Change selection media every 2-3 days.</li>
	<li>After 1-2 weeks, blasticidin-resistant colonies should begin to appear. Select plates containing 5 to 50 colonies to ensure that single colonies can be picked.</li>
	<li>When colonies have reached a diameter of approximately 5 mm (or bigger), isolate at least 12 independent clones using cloning cylinders to pick single colonies. Transfer each clone into a separate well of a 24-well tissue culture plate. When confluent, split the cells from each well into one single well of a 6-well tissue culture plate.</li>
	<li>Continue to culture clones in selection media. When confluent, split cells from each well into two single wells of a 6-well tissue culture plate.</li>
	<li>For each clone to be tested, freeze one well of confluent cells and harvest cells in the other well for subsequent testing by immunoblotting.</li>
	<li>Detect TetR by Western blotting using the mouse monoclonal anti-TET02 antibody (MoBiTec GmbH). Remember to include a lysate of the parental cell line as a negative control.</li>
	<li>Select 3 clones with the highest TetR expression and expand each clonal culture. Freeze stocks of each promising clone as soon as possible. Finally, examine the molecular and cell biological parameters of interest by comparing the parental cell lines with the TetR-expressing clones. Select the 'best' clone with the highest TetR expression that does not display any alterations in the molecular and cell biological parameters of interest.</li>
</ol>
3. Pilot Testing of pTER and pT-Rex DEST30 Vectors Expressing shRNA or cDNAs, Respectively
<ol>
	<li>Generate pTER plasmid with shRNA inserts as described12. Construct pT-Rex DEST30 vector (12301-016, Invitrogen) containing the cDNA of interest using Gateway technology (Invitrogen). In case of cDNA expression, addition of a tag to the cDNA will later facilitate detection of exogenously expressed protein.</li>
	<li>Transiently transfect the parental target cell line with pTER or pT-Rex DEST30 plasmids (expressing either shRNAs or cDNAs of interest) using the transfection reagent of choice. For testing of shRNA expression plasmids, ensure high transfection efficiencies can be achieved.</li>
	<li>Harvest transfected cells and process for immunoblotting using the appropriate antibodies, expecting to detect a depletion or overexpression of your gene of interest.</li>
</ol>
4. Generation of Stable Cell Lines with Tetracycline-inducible (Tet-on) Expression of shRNAs or cDNAs Using pTER or pT-Rex DEST30 Vectors
<ol>
	<li>On day 1, seed 1x106 cells of the 'best' TetR-expressing clone per 10-cm plate using your standard growth medium supplemented with certified Tetracycline-free serum (for example FBS from Invitrogen; 16000-014). Seed one plate for transfection with pTER (or pT-Rex DEST30), and one plate as negative control for double selection. Make sure to use the lowest passage possible.</li>
	<li>On day 2, transfect one plate with 2 &mu;g of pTER (or pT-Rex DEST30) using Fugene 6. Do not transfect the second plate.</li>
	<li>On day 3, add standard growth medium containing 5 &mu;g/ml blasticidin and 500 &mu;g/ml zeocin (or 1 mg/ml G418).</li>
	<li>On day 4, split the cells at 1/5, 1/25, 1/50 and 1/100 using 10-cm plates and standard growth medium containing 5 &mu;g/ml blasticidin and 500 &mu;g/ml zeocin (or 1 mg/ml G418). Prepare two plates per dilution step.</li>
	<li>Check the cells daily, making sure that within the first week all cells on the untransfected plates have died. Change the standard growth medium containing blasticidin and zeocin (or G418) every 3-4 days.</li>
	<li>After 2-3 weeks, blasticidin/zeocin (or blasticidin/G418) double-resistant colonies should begin to appear. Select plates containing 5 to 50 colonies to pick single colonies.</li>
	<li>When colonies have reached a diameter of approximately 5 mm (or bigger), use cloning cylinders to pick single colonies. Isolate at least 24 individual clones. Transfer each clone into a separate well of a 24-well tissue culture plate.</li>
	<li>Culture clones in medium containing maintenance concentrations of blasticidin (5 &mu;g/ml) and zeocin (250 &mu;g/ml) [or G418 (0.5 mg/ml)]. When confluent, split the cells from each well into one single well of a 6-well tissue culture plate.</li>
	<li>For each clone to be tested, split one confluent well of a 6-well plate into three single wells of a 6-well plate. When confluent, freeze cells from one well. Use the remaining two wells for testing the tetracycline-inducible expression. Add tetracycline at a concentration of 1 &mu;g/ml to one well, while leaving the second well tetracycline free.</li>
	<li>After 24 to 96 hr of incubation with Tetracycline, harvest cells and process for immunoblotting using appropriate antibodies. Shorter tetracycline incubation times are recommended when screening for the induction of cDNA expression, while longer tetracycline treatments will be necessary to determine shRNA-mediated depletion of endogenous proteins.</li>
	<li>Select at least two clones with the desired depletion/overexpression and expand each culture. Freeze stocks of each promising clone as soon as possible. When growing Tet-on clones for experiments always make sure to use media supplemented with Tetracycline-free serum and the respective selection antibiotics at maintenance concentrations.</li>
</ol>

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U.S.A. 89, 5547-5551 (1992).</li><li>Gossen, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+activation+by+tetracyclines+in+mammalian+cells.">Transcriptional activation by tetracyclines in mammalian cells.</a> Science. 268, 1766-1769 (1995).</li><li>Elbashir, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duplexes+of+21-nucleotide+RNAs+mediate+RNA+interference+in+cultured+mammalian+cells.">Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells.</a> Nature. 411, 494-498 (2001).</li><li>Brummelkamp, T. 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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+silencing+using+micro-RNA+designed+hairpins.">Gene silencing using micro-RNA designed hairpins.</a> RNA. 8, 842-850 (2002).</li><li>Miyagishi, M., Taira, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=U6+promoter-driven+siRNAs+with+four+uridine+3'+overhangs+efficiently+suppress+targeted+gene+expression+in+mammalian+cells.">U6 promoter-driven siRNAs with four uridine 3' overhangs efficiently suppress targeted gene expression in mammalian cells.</a> Nat. Biotechnol. 20, 497-500 (2002).</li><li>Paddison, P. J., Caudy, A. A., Bernstein, E., Hannon, G. J., Conklin, D. 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No conflicts of interest declared.

We believe that Tet-on systems greatly facilitate the analysis of gene function, particularly in cell systems that are difficult to manipulate and/or when the manipulated gene is essential for cell survival. Furthermore, the ability to control gene expression by highly specific Tet-on systems offers the opportunity to study gene functions at different stages (for example during cell cycle progression or well-defined differentiation processes). The method presented here will enable researchers to generate the desir...

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>Fetal Bovine Serum(FBS)</td>
 <td>Invitrogen</td>
 <td>16000-044</td>
 <td>Tested Tet-free</td>
 </tr>
 <tr>
 <td>Blasticidin</td>
 <td>Invivogen</td>
 <td>ant-bl-1</td>
 <td></td>
 </tr>
 <tr>
 <td>Zeocin</td>
 <td>Invivogen</td>
 <td>ant-zn-5</td>
 <td></td>
 </tr>
 <tr>
 <td>G418</td>
 <td>PAA laboratories</td>
 <td>P31-011</td>
 <td>100 mg/ml in media</td>
 </tr>
 <tr>
 <td>anti-TET02</td>
 <td>MoBiTec GmbH</td>
 <td>TET02</td>
 <td>Use at 1/1000 to 1/2000 for WB</td>
 </tr>
 <tr>
 <td>pcDNA6/TR</td>
 <td>Invitrogen</td>
 <td>V1025-20 </td>
 <td></td>
 </tr>
 <tr>
 <td>pT-Rex DEST30</td>
 <td>Invitrogen</td>
 <td>12301-016 </td>
 <td></td>
 </tr>
 <tr>
 <td>Tetracycline</td>
 <td>Sigma</td>
 <td>87128</td>
 <td>2 mg/ml in ethanol</td>
 </tr>
 <tr>
 <td>Doxycycline</td>
 <td>Sigma</td>
 <td>D9891</td>
 <td>2 mg/ml in water</td>
 </tr>
 <tr>
 <td>Cloning cylinders</td>
 <td>Bellco Glass Inc.</td>
 <td>2090-00808</td>
 <td>re-useable</td>
 </tr>
 </tbody>
</table>

generation of stable human cell lines with tetracycline-inducible (tet-on) shrna or cdna expression

A major approach in the field of mammalian cell biology is the manipulation of the expression of genes of interest in selected cell lines, with the aim to reveal one or several of the gene's function(s) using transient/stable overexpression or knockdown of the gene of interest. Unfortunately, for various cell biological investigations this approach is unsuitable when manipulations of gene expression result in cell growth/proliferation defects or unwanted cell differentiation. Therefore, researchers have adapted the Tetracycline repressor protein (TetR), taken from the E. coli tetracycline resistance operon1, to generate very efficient and tight regulatory systems to express cDNAs in mammalian cells2,3. In short, TetR has been modified to either (1) block initiation of transcription by binding to the Tet-operator (TO) in the promoter region upon addition of tetracycline (termed Tet-off system) or (2) bind to the TO in the absence of tetracycline (termed Tet-on system) (Figure 1). Given the inconvenience that the Tet-off system requires the continuous presence of tetracycline (which has a half-life of about 24 hr in tissue cell culture medium) the Tet-on system has been more extensively optimized, resulting in the development of very tight and efficient vector systems for cDNA expression as used here.
Shortly after establishment of RNA interference (RNAi) for gene knockdown in mammalian cells4, vectors expressing short-hairpin RNAs (shRNAs) were described that function very similar to siRNAs5-11. However, these shRNA-mediated knockdown approaches have the same limitation as conventional knockout strategies, since stable depletion is not feasible when gene targets are essential for cellular survival. To overcome this limitation, van de Wetering et al.12 modified the shRNA expression vector pSUPER5 by inserting a TO in the promoter region, which enabled them to generate stable cell lines with tetracycline-inducible depletion of their target genes of interest.
Here, we describe a method to efficiently generate stable human Tet-on cell lines that reliably drive either inducible overexpression or depletion of the gene of interest. Using this method, we have successfully generated Tet-on cell lines which significantly facilitated the analysis of the MST/hMOB/NDR cascade in centrosome13,14 and apoptosis signaling15,16. In this report, we describe our vectors of choice, in addition to describing the two consecutive manipulation steps that are necessary to efficiently generate human Tet-on cell lines (Figure 2). Moreover, besides outlining a protocol for the generation of human Tet-on cell lines, we will discuss critical aspects regarding the technical procedures and the characterization of Tet-on cells.

An example for the initial characterization of RPE-1 cell lines stably expressing TetR is shown in Figure 4. Note that all RPE-1 clones express varying levels of TetR (compare lanes 2 and 5), while the parental cell line (which serves as negative control) does not express the exogenous TetR protein (Figure 4, lane 1). This variation in TetR expression among RPE-1 Tet-on cell clones is expected, since the expression of the TetR expressing plasmids is highly dependent on the plasmid...

Watch this Scientific Journal Video about Generation of Stable Human Cell Lines with Tetracycline-inducible Tet-on shRNA or cDNA Expression at JoVE.com

Generation of Stable Human Cell Lines with Tetracycline-inducible Tet-on shRNA or cDNA Expression

A rapid and simple way to generate human cell lines with inducible and reversible cDNA overexpression or shRNA-mediated knock-down of the gene of interest. This method enables researchers to reliably and highly reproducibly manipulate cell lines that are difficult to alter by transient transfection methods or conventional knockdown/knockout strategies.

Generation of Stable Human Cell Lines with Tetracycline-inducible (Tet-on) shRNA or cDNA Expression

A major approach in  the field of mammalian cell biology is the manipulation of the expression of  genes of interest in selected cell lines, with the aim ...

generation-stable-human-cell-lines-with-tetracycline-inducible-tet-on

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35.0K Views.  UCL Cancer Institute. A rapid and simple way to generate human cell lines with inducible and reversible cDNA overexpression or shRNA-mediated knock-down of the gene of interest. This method enables researchers to reliably and highly reproducibly manipulate cell lines that are difficult to alter by transient transfection methods or conventional knockdown/knockout strategies.

Video: Generation of Stable Human Cell Lines with Tetracycline-inducible Tet-on shRNA or cDNA Expression

Passaging HuES Human Embryonic Stem Cell-lines with Trypsin.

In this video we demonstrate how our lab routinely passages HuES human embryonic stem cell lines with trypsin.  Human embryonic stem cells are artifacts of cell culture, and tend to acquire karyotypic abnormalities with high population doublings.  Proper passaging is essential for maintaining a healthy, undifferentiated, karyotypically normal HuES human embryonic stem cell culture.  First, an expanding culture is washed in PBS to remove residual media and cell debris, then cells are overlaid with a minimal volume of warm 0.05% Trypsin-EDTA.  Trypsin is left on the cells for up to five minutes, then cells are gently dislodged with a 2mL serological pipette.  The cell suspension is collected and mixed with a large volume of HuES media, then cells are collected by gentle centrifugation.  The inactivated trypsin media mixture is removed, and cells resuspended in pre-warmed HuES media.  An appropriate split ratio is calculated (generally 1:10 to 1:20), and cells re-plated onto a 1-2 day old plate containing a monolayer of irradiated mouse embryonic fibroblast feeder cells.  The newly seeded HuES culture plate is left undisturbed for 48 hrs, then media is changed every day thereafter.  It is important not to trpsinize down to a single cell suspension, as this increases the risk of introducing karyotypic abnormalities.

In this video we demonstrate how our lab routinely passages HuES human embryonic stem cell lines with trypsin. Brought to you by JoVE.

In this video we demonstrate how our lab routinely passages HuES human embryonic stem cell lines with trypsin.  Human embryonic stem cells are artifacts ...

Generation of Stable Transgenic C. elegans Using Microinjection

Transgenic Caenorhabditis elegans can be readily created via microinjection of a DNA plasmid solution into the gonad 1. The plasmid DNA rearranges to form extrachromosomal concatamers that are stably inherited, though not with the same efficiency as actual chromosomes 2. A gene of interest is co-injected with an obvious phenotypic marker, such as rol-6 or GFP, to allow selection of transgenic animals under a dissecting microscope. The exogenous gene may be expressed from its native promoter for cellular localization studies. Alternatively, the transgene can be driven by a different tissue-specific promoter to assess the role of the gene product in that particular cell or tissue. This technique efficiently drives gene expression in all tissues of C. elegans except for the germline or early embryo 3. Creation of transgenic animals is widely utilized for a range of experimental paradigms. This video demonstrates the microinjection procedure to generate transgenic worms. Furthermore, selection and maintenance of stable transgenic C. elegans lines is described.

This video demonstrates the technique of microinjection into the gonad of C. elegans to create transgenic animals.

Transgenic Caenorhabditis elegans can be readily created via microinjection of a DNA plasmid solution into the gonad 1.  The plasmid DNA rearranges to ...

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Generation of Human CD40-activated B cells

CD40-activated B cells (CD40-B cells) have been identified as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cancer immunotherapy 1-3. Compared to Dendritic cells (DCs), the best characterized APC, CD40-B cells have several distinct biological and technical properties. Similar to DCs, B cells show an increased expression of MHC and co-stimulatory molecules (Fig.1b), exhibit a strong migratory capacity and present antigen presentation efficiently to T cells, after stimulation with interleukin-4 and CD40 ligand (CD40L). However, in contrast to immature or mature DCs, CD40-B cells express the full lymph node homing triad consisting of CD62L, CCR7/CXCR4, and leukocyte function antigen-1 (LFA1, CD11a/CD18), necessary for homing to secondary lymphoid organs (Fig.1a) 3. CD40-B cells can be generated without difficulties from very small amounts of peripheral blood which can be further expanded in vitro to very large amounts of highly-pure CD40-B cells (&gt;109 cells per patient) from healthy donors as well as cancer patients (Fig.1c,d) 1,4. 
In this protocol we demonstrate how to obtain fully activated CD40-B cells from human PBMC. Key molecules for the cell culture are CD40 ligand, interleukin-4 (IL-4) and cyclosporin A (CsA), which are replenished in a 3-4 day culture cycle. For laboratory purposes CD40-stimulation is provided by NIH/3T3 cells expressing recombinant human CD40 ligand (tCD40L NIH/3T3) 5. To avoid contamination with non-transfected cells, expression of the human CD40 ligand on the transfectants has to be checked regularly (Fig.2). 
After 14 days CD40-B cell cultures consist of more than 95% pure B cells and an expansion of CD40-B cells over 65 days is frequently possible without any loss of function 1, 4. CD40-B cells efficiently take up, process and present antigens to T cells 6. They do not only prime na&#970;ve, but also expand memory T cells 7,8. CD40-activated B cells can be used to study B-cell activation, differentiation and function. Moreover, they represent a promising tool for therapeutic or preventive vaccination against tumors 9.

In this video we present the ex vivo generation and expansion of human CD40-activated B cells (CD40-B) from peripheral blood mononuclear cells (PBMC) by stimulation with CD40 ligand and interleukin-4.

CD40-activated B cells (CD40-B cells) have been identified as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cancer ...

RNA Isolation from Embryonic Zebrafish and cDNA Synthesis for Gene Expression Analysis

Many important and complex laboratory procedures require an input of high quality, intact RNA.  A degraded sample or the presence of impurities can lead to disastrous results in downstream experimental applications.  It is therefore, of utmost importance to use solid techniques with numerous safeguards and quality control checks to ensure a superior sample.  Herein, we detail a protocol to isolate total RNA from whole zebrafish embryos using a commercially available chemical denaturant and subsequent cleanup to remove traces of DNA and impurities using a commercial RNA isolation kit. As RNA is relatively unstable and easily prone to cleavage by RNAses, most protocols assay gene expression using a cDNA product that is directly synthesized from an RNA template. We detail a procedure to convert RNA into the more stable cDNA product using a commercially available kit. Throughout these procedures there are numerous quality control checks to ensure that the sample is not degraded or contaminated.  The end product of these protocols is cDNA that is suitable for microarray analysis, RT-PCR or long-term storage.    

The isolation of high quality, intact RNA is an essential step in many laboratory protocols. Here, we demonstrate RNA extraction from whole zebrafish embryos and cDNA synthesis for subsequent application in various experimental procedures including gene expression microarray analysis.

Many important and complex laboratory procedures require an input of high quality, intact RNA.  A degraded sample or the presence of impurities can lead ...

Using the Gene Pulser MXcell Electroporation System to Transfect Primary Cells with High Efficiency

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell electroporation system and Gene Pulser electroporation buffer (Bio-Rad) were specifically developed to easily transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells. We will demonstrate how to perform a simple experiment to quickly identify the best electroporation conditions. We will demonstrate how to run several samples through a range of electroporation conditions so that an experiment can be conducted at the same time as optimization is performed. We will also show how optimal conditions identified using 96-well electroporation plates can be used with standard electroporation cuvettes, facilitating the switch from electroporation plates to electroporation cuvettes while maintaining the same electroporation efficiency. In the video, we will also discuss some of the key factors that can lead to the success or failure of electroporation experiments.

This procedure shows how to use the Gene Pulser MXcell electroporation system to rapidly and easily identify the best electroporation conditions for mouse embryonic fibroblasts (MEFs) or other primary cells. Considerations for troubleshooting are also discussed in the associated video.

Using an Automated Cell Counter to Simplify Gene Expression Studies: siRNA Knockdown of IL-4 Dependent Gene Expression in Namalwa Cells

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only to study the effects of downregulating single genes, but also to interrogate signaling pathways and other complex interaction networks.  These pathway analyses require both the use of relevant cellular models and methods that cause less perturbation to the cellular physiology.  Electroporation is increasingly being used as an effective way to introduce siRNA and other nucleic acids into difficult to transfect cell lines and primary cells without altering the signaling pathway under investigation. There are multiple critical steps to a successful siRNA experiment, and there are ways to simplify the work while improving the data quality at several experimental stages.  To help you get started with your siRNA mediated gene knockdown project, we will demonstrate how to perform a pathway study complete from collecting and counting the cells prior to electroporation through post transfection real-time PCR gene expression analysis.  The following study investigates the role of the transcriptional activator STAT6 in IL-4 dependent gene expression of CCL17 in a Burkitt lymphoma cell line (Namalwa).  The techniques demonstrated are useful for a wide range of siRNA-based experiments on both adherent and suspension cells.  We will also show how to streamline cell counting with the TC10 automated cell counter, how to electroporate multiple samples simultaneously using the MXcell electroporation system, and how to simultaneously assess RNA quality and quantity with the Experion automated electrophoresis system.

This procedure describes a quick and easy workflow to introduce siRNA into difficult to transfect cell lines and follow gene expression by real-time PCR. Use of an automated cell counter, multi-well electroporation plate, and automated electrophoresis station provide quick and reliable results without the need for expensive robotic handling.

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only ...

Transduction of Human Cells with Polymer-complexed Ecotropic Lentivirus for Enhanced Biosafety

Stem and tumor cell biology studies often require viral transduction of human cells with known or suspected oncogenes, raising major safety issues for laboratory personnel. Pantropic lentiviruses, such as the commonly used VSV-G pseudotype, are a valuable tool for studying gene function because they can transduce many cell types, including non-dividing cells. However, researchers may wish to avoid production and centrifugation of pantropic viruses encoding oncogenes due to higher biosafety level handling requirements and safety issues. Several potent oncogenes, including c-Myc and SV40 large T antigen, are known to enhance production of induced pluripotent stem cells (iPSC). All other known iPSC-inducing genetic changes (OCT4, SOX2, KLF4, NANOG, LIN28, and p53 loss of function) also have links to cancer, making them of relatively high safety concern as well. 
While these cancer-related viruses are useful in studying cellular reprogramming and pluripotency, they must be used safely. To address these biosafety issues, we demonstrate a method for transduction of human cells with ecotropic lentivirus, with additional emphasis on reduced cost and convenient handling. We have produced ecotropic lentivirus with sufficiently high titer to transduce greater than 90% of receptor-expressing human cells exposed to the virus, validating the efficacy of this approach. 
Lentivirus is often concentrated by ultracentrifugation; however, this process takes several hours and can produce aerosols infectious to human biomedical researchers. As an alternative, viral particles can be more safely sedimented onto cells by complexation with chondroitin sulfate and polybrene (CS/PB). This technique increases the functional viral titer up to 3-fold in cells stably expressing murine retrovirus receptor, with negligible added time and cost. Transduction of human dermal fibroblasts (HDFs) is maximally enhanced using CS/PB concentrations approximately 4-fold lower than the optimal value previously reported for cancer cell lines, suggesting that polymer concentration should be titrated for the target cell type of interest. We therefore describe the use of methylthiazolyldiphenyl-tetrazolium bromide (MTT) to assay for polymer toxicity in a new cell type. We observe equivalent viability of HDFs after viral transduction using either polymer complexation or the standard dose of polybrene (PB, 6 &mu;g/ml), indicating minimal acute toxicity.
In this protocol, we describe the use of ecotropic lentivirus for overexpression of oncogenes in human cells, reducing biosafety risks and increasing the transduction rate. We also demonstrate the use of polymer complexation to enhance transduction while avoiding aerosol-forming centrifugation of viral particles.

Lentiviruses are a valuable research tool for exploring gene function; however, researchers may wish to avoid production of pantropic lentivirus encoding known or suspected oncogenes. As an alternative, we present a safer protocol for use of ecotropic lentivirus on human cells modified to express the ecotropic receptor mSlc7a1.

Stem and tumor cell biology studies often require viral transduction of human cells with known or suspected oncogenes, raising major safety issues for ...

Preparation of Cell-lines for Conditional Knockdown of Gene Expression and Measurement of the Knockdown Effects on E4orf4-Induced Cell Death

Functional inactivation of gene expression in mammalian cells is crucial for the study of the contribution of a protein of interest to various pathways1,2. However, conditional knockdown of gene expression is required in cases when constitutive knockdown is not tolerated by cells for a long period of time3-5. Here we describe a protocol for preparation of cell lines allowing conditional knockdown of subunits of the ACF chromatin remodeling factor. These cell lines facilitate the determination of the contribution of ACF to induction of cell death by the adenovirus E4orf4 protein6. Sequences encoding short hairpin RNAs for the Acf1 and SNF2h subunits of the ACF chromatin remodeling factor were cloned next to a doxycycline-inducible promoter in a plasmid also containing a gene for the neomycin resistance gene. Neomycin-resistant cell clones were selected in the presence of G418 and isolated. The resulting cell lines were induced by doxycycline treatment, and once Acf1 or SNF2h expression levels were reduced, the cells were transfected with a plasmid encoding E4orf4 or an empty vector. To confirm the specific effect of the shRNA constructs, Acf1 or SNF2h protein levels were restored to WT levels by cotransfection with a plasmid expressing Acf1 or SNF2h which were rendered resistant to the shRNA by introduction of silent mutations. The ability of E4orf4 to induce cell death in the various samples was determined by a DAPI assay, in which the frequency of appearance of nuclei with apoptotic morphologies in the transfected cell population was measured7-9.
The protocol described here can be utilized for determination of the functional contribution of various proteins to induction of cell death by their protein partners in cases when constitutive knockdown may be cell lethal.

Contribution of the ACF chromatin remodeling factor to E4orf4-induced cell death was measured. The protocol includes selection of cell clones in which doxycycline treatment induces conditional knockdown of the ACF subunits Acf1 and SNF2h, and use of the DAPI assay to measure E4orf4-induced cell death in the inducible cell lines.