<ol>
<li>The evening before transformation, plate 293T cells at 3-5x106 cells/6 cm tissue cultureplate. Note: We use 293T cells for their ease of transfection and efficacyas virus producing cells. These cells are deficient in packaging the virus unless a helper plasmid is introduced. </li>
<li>The first morning, gently remove medium and replace with 4 ml 293T cell med containing 25 mM Chloroquine. Put in incubator for 1 hr. Note: the plate should be about 80% confluent. </li>
<li>Meanwhile, prepare virus-making mixture for 2 plates at a time, in 5 ml tubes:<ol>
<li>2 x 10 mg retroviral plasmid construct</li>
<li>2 x 5 mg packaging construct (EcoPak), </li>
<li>2 x 62 ml CaCl</li>
<li>complete to 1 ml with sterile ddH2O Note: While the retroviral plasmid encodes the oncogene of interest and a marker, EcoPak encodes gag-pol-env. Together with the 293T cells, they will produce an ecotropic retrovirus(RV) specific for mouse cells, but not infective for human cells. Both Chloroquine and CaCl2 have been shown to increase transfection efficiency. </li>
</ol></li>
<li>Add 1ml of 2x sterileHBS drop-wise to the mixture, while gently vortexing the tube.</li>
<li>Immediately add this solution to 2 plates, 1 ml each, gently, drop by drop. </li>
<li>Put in incubator for 7 to 11 hrs.</li>
<li>In the evening (7 to 11 hrs. later), gently remove medium, and very gently replace with 5 ml fresh 293T medium. Put in incubator until noon, the next day. Note: this step is important, as you need to take off the chloroquine from the cells. If kept for extended periods of time, chloroquine is toxic. The solution in the plates looks fuzzy, due to a very fine, dust-like precipitation of the transfection mixture. Note: It is important to do all media changes with extreme gentleness, as the cells have been sensitized by the chloroquine, and can easily detach from the plate. </li>
<li>Next day, 18 to 24 hrs. before retrieving the virus (around noon), gently remove medium, and very gently replace with 3 ml fresh 293T medium. Replace in incubator O/N.</li>
<li>The third morning (18 to 24 hrs. later), gently suck up the medium form the plates with a 10 ml syringe fitted with an 18 G needle. This supernatant contains the retrovirus.</li>
<li>Change the needle to a 45 mm syringe filter, invert syringe several times to mix the solution well, pass supernatant through filter, and aliquot in cryotubes Note: Alternatively, if you are making 3+ plates of virus, pool all supernatants of the same virus into a 50 ml conical tube. Mix well, then aliquot supernatants containing the retrovirus in cryotubes by filtering. </li>
<li>The tubes containing the virus-full supernatants are kept in -80&deg;C until used.</li>
</ol>

<ol>
	<li>DuBridge, R. B., Tang, P., Hsia, H. C., Leong, P. M., Miller, J. H., Calos, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+mutation+in+human+cells+by+using+an+Epstein-Barr+virus+shuttle+system.">Analysis of mutation in human cells by using an Epstein-Barr virus shuttle system.</a> Mol Cell Biol. 7, 379-387 (1987).</li><li>Cherry, S. R., Biniszkiewicz, D., van Parijs, L., Baltimore, D., Jaenisch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retroviral+expression+in+embryonic+stem+cells+and+hematopoietic+stem+cells.">Retroviral expression in embryonic stem cells and hematopoietic stem cells.</a> Mol Cell Biol. 20, 7419-7426 (2000).</li><li>Finer, M. H., Dull, T. J., Qin, L., Farson, D., Roberts, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=kat:+A+high-efficiency+retroviral+transduction+system+for+primary+human+T+lymphocytes.">kat: A high-efficiency retroviral transduction system for primary human T lymphocytes.</a> Blood. 83, 43-50 (1994).</li><li>Naviaux, R. K., Costanzi, E., Haas, M., 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=The+pCL+vector+system:+rapid+production+of+helper-free,+high-titer,+recombinant+retroviruses.">The pCL vector system: rapid production of helper-free, high-titer, recombinant retroviruses.</a> J Virol. 70, 5701-5705 (1996).</li><li>Pear, W. S., Miller, J. P., Xu, L., Pui, J. C., Soffer, B., Quackenbush, R. C., Pendergast, A. M., Bronson, R., Aster, J. C., Scott, M. L., Baltimore, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+and+rapid+induction+of+a+chronic+myelogenous+leukemia-like+myeloproliferative+disease+in+mice+receiving+P210+bcr/abl-transduced+bone+marrow.">Efficient and rapid induction of a chronic myelogenous leukemia-like myeloproliferative disease in mice receiving P210 bcr/abl-transduced bone marrow.</a> Blood. 92, 3780-3792 (1998).</li><li>Pear, W. S., Nolan, G. P., Scott, M. L., Baltimore, D. <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+high-titer+helper-free+retroviruses+by+transient+transfection.">Production of high-titer helper-free retroviruses by transient transfection.</a> Proc Natl Acad Sci USA. 90, 8392-8396 (1993).</li><li>Stocking, C., Kollek, R., Bergholz, U., Ostertag, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long+terminal+repeat+sequences+impart+hematopoietic+transformation+properties+to+the+myeloproliferative+sarcoma+virus.">Long terminal repeat sequences impart hematopoietic transformation properties to the myeloproliferative sarcoma virus.</a> Proc Natl Acad Sci USA. 82, 5746-5750 (1985).</li><li>Van Etten, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+chronic+myeloid+leukemia.">Models of chronic myeloid leukemia.</a> Curr Oncol Rep. 3, 228-237 (2001).</li><li>Van Etten, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studying+the+pathogenesis+of+BCR-ABL++leukemia+in+mice.">Studying the pathogenesis of BCR-ABL+ leukemia in mice.</a> Oncogene. 21, 8643-8651 (2002).</li></ol>

Four critical points will assure the success of a good viral stock: &nbsp;&nbsp;&nbsp;
<ol>
<li>The 293T producing cells have to be very healthy, meaning they have been split on a very regular schedule, were never overgrown, and are plated at the optimized density of 3.5-5 million per 6 cm tissue culture plate, so that they reach a density of 80% of the plate on the morning of the transfection.&nbsp; </li>
<li>Addition of chloroquine improves transfection efficiency and subsequent virus titer, about 3- ...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>293T cells</td>
<td>cell-line</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Split 1:3 to 1:4 every 3 days, otherwise they will tend to clump with replating and will not transfect as well. </td>
</tr>
<tr>
<td>293T cell medium</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>DMEM/hi-glu + 10 % FBS + 1% Pen/Strep + 1% L-Glutamine (1% NEAA, optional). We obtain our tissue culture slutions from CellGro.</td>
</tr>
<tr>
<td>coding DNA plasmid</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Twice purified by CsCl. MSCV backbone, encoding oncogene and marker of choice (Neo, GFP, etc.)</td>
</tr>
<tr>
<td>EcoPak</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>also called pMCV-Ecopac: ecotropic packaging plasmid, encoding gag-pol-env</td>
</tr>
<tr>
<td>2x HBS</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>For 500 ml: 8.0 g NaCl	+ 0.37 g KCl + 106.5 mg Na2HPO4 (anhydrous; 201.1 mg if 7xH2O) + 1.0 g dextrose (D-glucose) + 5.0 g HEPES powder. Dissolve in 450 ml dH2O (milli-Q), adjust pH to 7.05 with NaOH, then complete to 500 ml with dH2O. Sterile filter thru 0.45 &#181; filter. Store at room temperature, with the cap on tight.
</td>
</tr>
<tr>
<td>2M CaCl2</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>miliQ H2O</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>sterile-filtered</td>
</tr>
<tr>
<td>Chloroquine</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>1000x stock is 25 mM in PBS- (w/o Ca2+/Mg2+), stored at -20C. Add fresh to the medium when needed.</td>
</tr>
<tr>
<td>6 cm plates</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>for tissue culture</td>
</tr>
<tr>
<td>Incubator</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>for tissue culture. Set at 37C, 10% CO2.</td>
</tr>
<tr>
<td>10 cc sterile syringes</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Sterile. One per virus type.</td>
</tr>
<tr>
<td>18G needles</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>single use, one per virus type.</td>
</tr>
<tr>
<td>45 um syringe filters</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>5 ml plastic tubes</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Sterile, to mix transfection solution, for up to 2 plates at a time (2 ml). We use Falcon tubes.</td>
</tr>
<tr>
<td>50 ml conical tubes</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>cryovials</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>2 and 4 ml, for virus aliquots.</td>
</tr>		</tbody>
		</table>
		</div>
			<div>
			All reagents used in the transfection must be sterile-filtered (CaCl2, 2x HBS, miliQ H2O) and kept sterile.		</div>

production of replication-defective retrovirus by transient transfection of 293t cells

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, Bcr-PDGFR&#945;, etc.). We are able to model and study a human-like disease in our mouse model, by transplanting bone marrow cells previously infected with a retrovirus expressing the oncogene of interest. Replication-defective retrovirus encoding a human oncogene and a marker (GFP, RFP, antibiotic resistance gene, etc.) is produced by a transient transfection protocol using 293T cells, a human renal epithelial cell line transformed by the adenovirus E1A gene product. 293 cells have the unusual property of being highly transfectable by calcium phosphate (CaPO4), with up to 50-80% transfection efficiency readily attainable. Here, we co-transfect 293 cells with a retroviral vector expressing the oncogene of interest and a plasmid that expresses the gag-pol-env packaging functions, such as the single-genome packaging constructs kat or pCL, in this case the EcoPak plasmid. The initial transfection is further improved by use of chloroquine. Stocks of ecotropic virus, collected as culture supernatant 48 hrs. post-transfection, can be stored at -80&deg;C and used for infection of cell-lines in view of transformation and in vitro studies, or primary cells such as mouse bone marrow cells, that can then be used for transplant in our mouse model.

Watch this Scientific Journal Video about Production of Replication-Defective Retrovirus by Transient Transfection of 293T cells at JoVE.com

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Production of Replication-Defective Retrovirus by Transient Transfection of 293T cells

This technique demonstrates an efficient way to prepare replication-defective retroviral stocks encoding a human oncogene, and subsequently used for induction of myeloproliferative disease in the mouse model.

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, ...

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19.5K Views.  Tufts University. This technique demonstrates an efficient way to prepare replication-defective retroviral stocks encoding a human oncogene, and subsequently used for induction of myeloproliferative disease in the mouse model.

Video: Production of Replication-Defective Retrovirus by Transient Transfection of 293T cells

Optimized Transfection Strategy for Expression and Electrophysiological Recording of Recombinant Voltage-Gated Ion Channels in HEK-293T Cells

The in vitro expression and electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T) is a ubiquitous research strategy. HEK-293T cells must be plated onto glass coverslips at low enough density so that they are not in contact with each other in order to allow for electrophysiological recording without confounding effects due to contact with adjacent cells. Transfected channels must also express with high efficiency at the plasma membrane for whole-cell patch clamp recording of detectable currents above noise levels. Heterologous ion channels often require long incubation periods at 28&deg;C after transfection in order to achieve adequate membrane expression, but there are increasing losses of cell-coverslip adhesion and membrane stability at this temperature. To circumvent this problem, we developed an optimized strategy to transfect and plate HEK-293T cells. This method requires that cells be transfected at a relatively high confluency, and incubated at 28&deg;C for varying incubation periods post-transfection to allow for adequate ion channel protein expression. Transfected cells are then plated onto glass coverslips and incubated at 37&deg;C for several hours, which allows for rigid cell attachment to the coverslips and membrane restabilization. Cells can be recorded shortly after plating, or can be transferred to 28&deg;C for further incubation. We find that the initial incubation at 28&deg;C, after transfection but before plating, is key for the efficient expression of heterologous ion channels that normally do not express well at the plasma membrane. Positively transfected, cultured cells are identified by co-expressed eGFP or eGFP expressed from a bicistronic vector (e.g. pIRES2-EGFP) containing the recombinant ion channel cDNA just upstream of an internal ribosome entry site and an eGFP coding sequence. Whole-cell patch clamp recording requires specialized equipment, plus the crafting of polished recording electrodes and L-shaped ground electrodes from borosilicate glass. Drug delivery to study the pharmacology of ion channels can be achieved by directly micropipetting drugs into the recording dish, or by using microperfusion or gravity flow systems that produce uninterrupted streams of drug solution over recorded cells.

Reliable method for highly efficient in vitro expression and subsequent electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T).

The in vitro expression and electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T) ...

Optimization and Utilization of Agrobacterium-mediated Transient Protein Production in Nicotiana

Agrobacterium-mediated transient protein production in plants is a promising approach to produce vaccine antigens and therapeutic proteins within a short period of time. However, this technology is only just beginning to be applied to large-scale production as many technological obstacles to scale up are now being overcome. Here, we demonstrate a simple and reproducible method for industrial-scale transient protein production based on vacuum infiltration of Nicotiana plants with Agrobacteria carrying launch vectors. Optimization of Agrobacterium cultivation in AB medium allows direct dilution of the bacterial culture in Milli-Q water, simplifying the infiltration process. Among three tested species of Nicotiana, N. excelsiana (N. benthamiana &#215; N. excelsior) was selected as the most promising host due to the ease of infiltration, high level of reporter protein production, and about two-fold higher biomass production under controlled environmental conditions. Induction of Agrobacterium harboring pBID4-GFP (Tobacco mosaic virus-based) using chemicals such as acetosyringone and monosaccharide had no effect on the protein production level. Infiltrating plant under 50 to 100 mbar for 30 or 60 sec resulted in about 95% infiltration of plant leaf tissues. Infiltration with Agrobacterium laboratory strain GV3101 showed the highest protein production compared to Agrobacteria laboratory strains LBA4404 and C58C1 and wild-type Agrobacteria strains at6, at10, at77 and A4. Co-expression of a viral RNA silencing suppressor, p23 or p19, in N. benthamiana resulted in earlier accumulation and increased production (15-25%) of target protein (influenza virus hemagglutinin).

Optimization and Utilization of Agrobacterium-mediated Transient Protein Production in Nicotiana

Transient protein production in Nicotiana plants based on vacuum infiltration with Agrobacteria carrying launch vectors (Tobacco mosaic virus-based) is a rapid and economic approach to produce vaccine antigens and therapeutic proteins. We simplified the procedure and improved target accumulation by optimizing conditions of bacteria cultivation, selecting host species, and co-introducing RNA silencing suppressors.

Agrobacterium-mediated transient protein production in plants is a promising approach to produce vaccine antigens and therapeutic proteins within a short ...

Transient Expression of Proteins by Hydrodynamic Gene Delivery in Mice

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past years, hydrodynamic gene delivery (HGD) has emerged as a simple, fast, safe and effective method for delivering transgenes into rodents. This technique relies on the force generated by the rapid injection of a large volume of physiological solution to increase the permeability of cell membranes of perfused organs and thus deliver DNA into cells. One of the main advantages of HGD is the ability to introduce transgenes into mammalian cells using naked plasmid DNA (pDNA). Introducing an exogenous gene using a plasmid is minimally laborious, highly efficient and, contrary to viral carriers, remarkably safe. HGD was initially used to deliver genes into mice, it is now used to deliver a wide range of substances, including oligonucleotides, artificial chromosomes, RNA, proteins and small molecules into mice, rats and, to a limited degree, other animals. This protocol describes HGD in mice and focuses on three key aspects of the method that are critical to performing the procedure successfully: correct insertion of the needle into the vein, the volume of injection and the speed of delivery. Examples are given to show the application of this method to the transient expression of two genes that encode secreted, primate-specific proteins, apolipoprotein L-I (APOL-I) and haptoglobin-related protein (HPR).

In vivo transfection of naked DNA by hydrodynamic gene delivery introduces genes into the tissue of an animal with minimal inflammatory response. Sufficient amounts of gene product are generated such that gene function and regulation as well as protein structure and function can be analyzed.

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Production of Haploid Zebrafish Embryos by In Vitro Fertilization

The zebrafish has become a mainstream vertebrate model that is relevant for many disciplines of scientific study. Zebrafish are especially well suited for forward genetic analysis of developmental processes due to their external fertilization, embryonic size, rapid ontogeny, and optical clarity &#8211; a constellation of traits that enable the direct observation of events ranging from gastrulation to organogenesis with a basic stereomicroscope. Further, zebrafish embryos can survive for several days in the haploid state. The production of haploid embryos in vitro is a powerful tool for mutational analysis, as it enables the identification of recessive mutant alleles present in first generation (F1) female carriers following mutagenesis in the parental (P) generation. This approach eliminates the necessity to raise multiple generations (F2, F3, etc.) which involves breeding of mutant families, thus saving the researcher time along with reducing the needs for zebrafish colony space, labor, and the husbandry costs. Although zebrafish have been used to conduct forward screens for the past several decades, there has been a steady expansion of transgenic and genome editing tools. These tools now offer a plethora of ways to create nuanced assays for next generation screens that can be used to further dissect the gene regulatory networks that drive vertebrate ontogeny. Here, we describe how to prepare haploid zebrafish embryos. This protocol can be implemented for novel future haploid screens, such as in enhancer and suppressor screens, to address the mechanisms of development for a broad number of processes and tissues that form during early embryonic stages.

Production of Haploid Zebrafish Embryos by In Vitro Fertilization

The zebrafish is a powerful model system for developmental biology and human disease research due to their genetic similarity with higher vertebrates. This protocol describes a methodology to create haploid zebrafish embryos that can be utilized for forward screen strategies to identify recessive mutations in genes essential for early embryogenesis.

The zebrafish has become a mainstream vertebrate model that is relevant for many disciplines of scientific study. Zebrafish are especially well suited for ...

High Yield Expression of Recombinant Human Proteins with the Transient Transfection of HEK293 Cells in Suspension

The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and function. The rapid establishment and high recovery from transiently-transfected mammalian cell lines addresses this barrier and is an effective means of expressing proteins that are naturally channeled through the ER and Golgi-mediated secretory pathway. Here is one protocol for protein expression using the human HEK293F and HEK293S cell lines transfected with a mammalian expression vector designed for high protein yields. The applicability of this system is demonstrated using three representative glycoproteins that expressed with yields between 95-120 mg of purified protein recovered per liter of culture. These proteins are the human Fc&#947;RIIIa and the rat &#945;2-6 sialyltransferase, ST6GalI, both expressed with an N-terminal GFP fusion, as well as the unmodified human immunoglobulin G1 Fc. This robust system utilizes a serum-free medium that is adaptable for expression of isotopically enriched proteins and carbohydrates for structural studies using mass spectrometry and nuclear magnetic resonance spectroscopy. Furthermore, the composition of the N-glycan can be tuned by adding a small molecule to prevent certain glycan modifications in a manner that does not reduce yield.

Laboratory-scale production of eukaryotic proteins with appropriate post-translational modification represents a significant barrier. Here is a robust protocol with rapid establishment and turnaround for protein expression using a mammalian expression system. This system supports selective amino acid, selective labeling of proteins and small molecule modulators of glycan composition.

The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and ...

Transient Expression and Cellular Localization of Recombinant Proteins in Cultured Insect Cells

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and the determination of the biochemical function of proteins at the sub-organismal level. Although baculovirus expression systems are increasingly used for protein production in numerous biotechnological, pharmaceutical, and industrial applications, nonlytic systems that do not involve viral infection have clear benefits but are often overlooked and underutilized. Here, we describe a method for generating nonlytic expression vectors and transient recombinant protein expression. This protocol allows for the efficient cellular localization of recombinant proteins and can be used to rapidly discern protein trafficking within the cell. We show the expression of four&#160;recombinant proteins in a commercially available insect cell line, including two aquaporin proteins from the insect Bemisia tabaci, as well as subcellular marker proteins specific for the cell plasma membrane and for intracellular lysosomes. All recombinant proteins were produced as chimeras with fluorescent protein markers at their carboxyl termini, which allows for the direct detection of the recombinant proteins. The double transfection of cells with plasmids harboring constructs for the genes of interest and a known subcellular marker allows for live cell imaging and improved validation of cellular protein localization.

Nonlytic insect cell expression systems are underutilized for production, cellular trafficking/localization, and recombinant protein functional analysis. Here, we describe methods to generate expression vectors and subsequent transient protein expression in commercially available lepidopteran cell lines. The co-localization of Bemisia tabaci aquaporins with subcellular fluorescent marker proteins is also presented.

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and ...

Studying Protein Expression During Chicken Lens Development

Microinjection of Recombinant RCAS(A) Retrovirus into Embryonic Chicken Lens

Embryonic chicken (Gallus domesticus) is a well-established animal model for the study of lens development and physiology, given its high degree of similarity with the human lens. RCAS(A) is a replication-competent chicken retrovirus that infects dividing cells, which serves as a powerful tool to study the in situ expression and function of wild-type and mutant proteins during lens development by microinjection into the empty lumen of lens vesicle at early developmental stages, restricting its action to surrounding proliferating lens cells. Compared to other approaches, such as transgenic models and ex vivo cultures, the use of an RCAS(A) replication-competent avian retrovirus provides a highly effective, rapid, and customizable system to express exogenous proteins in chick embryos. Specifically, targeted gene transfer can be confined to proliferative lens fiber cells without the need for tissue-specific promoters. In this article, we will briefly overview the steps needed for recombinant retrovirus RCAS(A) preparation, provide a detailed, comprehensive overview of the microinjection procedure, and provide sample results of the technique.

Author Spotlight: Investigating Lens Development and Function Through Microinjection of RCAS(A) Retrovirus in Embryonic Chicken Lens 

This protocol paper describes the methodology of embryonic chicken lens microinjection of an RCAS(A) retrovirus as a tool for studying in situ function and expression of proteins during lens development.

Embryonic chicken (Gallus domesticus) is a well-established animal model for the study of lens development and physiology, given its high degree of ...

FACS Analysis of GFP and mCherry Reporter Cells to Evaluate NHEJ & HR Efficiency

Analysis of Nonhomologous End Joining and Homologous Recombination Efficiency in HEK-293T Cells Using GFP-Based Reporter Systems

DNA double-strand breaks (DSBs) represent the most perilous DNA lesions, capable of inducing substantial genetic information loss and cellular demise. In response, cells employ two primary mechanisms for DSB repair: nonhomologous end joining (NHEJ) and homologous recombination (HR). Quantifying the efficiency of NHEJ and HR separately is crucial for exploring the relevant mechanisms and factors associated with each. The NHEJ assay and HR assay are established methods used to measure the efficiency of their respective repair pathways. These methods rely on meticulously designed plasmids containing a disrupted green fluorescent protein (GFP) gene with recognition sites for endonuclease I-SceI, which induces DSBs. Here, we describe the extrachromosomal NHEJ assay and HR assay, which involve co-transfecting HEK-293T cells with EJ5-GFP/DR-GFP plasmids, an I-SceI expressing plasmid, and an mCherry expressing plasmid. Quantitative results of NHEJ and HR efficiency are obtained by calculating the ratio of GFP-positive cells to mCherry-positive cells, as counted by flow cytometry. In contrast to chromosomally integrated assays, these extrachromosomal assays are more suitable for conducting comparative investigations involving multiple established stable cell lines.

Author Spotlight: Decoding DNA Repair by Extrachromosomal NHEJ Assay and HR Assays

This protocol describes an extrachromosomal nonhomologous end joining (NHEJ) assay and homologous recombination (HR) assay to quantify the efficiency of NHEJ and HR in HEK-293T cells.

DNA double-strand breaks (DSBs) represent the most perilous DNA lesions, capable of inducing substantial genetic information loss and cellular demise. In ...