Efficient gene transfer by sequential treatment of mammalian cells with DEAE-dextran and deoxyribonucleic acid

DEAE-Dextran Transfection

Biochemical methods of transfection, including calcium phosphate-mediated and diethylaminoethyl (DEAE)-dextran-mediated transfection, have been used for many years to deliver nucleic acids into cultured eukaryotic cells. Here, we briefly review the use of DEAE-dextran in transfection.

Electric field-induced molecular vibration for noninvasive, high-efficiency DNA transfection

Gene delivery is an essential research tool for elucidating gene structure, regulation, and function in biomedical research and is the technological basis for gene therapy. However, the application of nonviral vectors in mammalian cell transfection and gene therapy is limited in that current methods require large amounts of exogenous DNA and/or exhibit high cytotoxicity and low transfection efficiency in primary cells. Here we describe the development of a novel, noninvasive gene delivery protocol using plasmid DNA vectors, based on the principle of electric field-induced molecular vibration. This method enables foreign DNA molecules to penetrate the plasma membrane and enter the cytoplasm of both primary mesenchymal progenitor cells and established cell lines of various species, at high efficiency and with low cell mortality. This procedure requires no special reagents, allows stable expression of transduced DNA, and does not interfere with the normal cellular differentiation activities of human and chick mesenchymal progenitors.

Pharmaceutical perspectives of nonviral gene therapy

The use of nonviral plasmid-based gene medicines represents an attractive in vivo gene transfer strategy that is simple and lacks many risks that are inherent to viral systems. Commercialization of gene medicines requires a thorough analysis of business opportunities, unmet clinical needs, competitive products under development, and issues related to intellectual property. Synthetic gene delivery systems are designed to control the location of a gene within the body by affecting distribution and access of a gene expression system to the target cell, and/or recognition by a cell surface receptor and uptake followed by intracellular and nuclear translocation. Plasmid-based gene expression systems are designed to control the level, fidelity, and duration of in vivo production of a therapeutic gene product. This review will provide insights into the potentials of plasmid-based gene therapy and critical evaluation of gene delivery sciences and clinical applications of gene medicines.

Comparison of sequence and function of the Oct-6 genes in zebrafish, chicken and mouse

To examine the role of the Oct-6 gene in Schwann cell differentiation we have cloned and characterized the chicken and zebrafish homologues of the mouse Oct-6 gene. While highly homologous in the Pit1-Oct1/2-Unc86 (POU) domain, sequence similarities are limited outside this domain. Both genes are intronless and both proteins lack the amino acid repeats that are a characteristic feature of the mammalian Oct-6 proteins. However as in mammals, the aminoterminal parts of the chicken and zebrafish Oct-6 proteins are essential for transactivation of octamer containing promoters. By immunohistochemistry we have found that the chicken Oct-6 protein is expressed in late embryonic ensheathing Schwann cells of the sciatic nerve and is rapidly downregulated when myelination proceeds. This expression profile in glial cells is identical to that in the mouse and rat. Furthermore the zebrafish Oct-6 homolog is expressed in the posterior lateral nerve at a time when it contains actively myelinating Schwann cells. Thus despite extensive primary sequence divergence among the vertebrate Oct-6 proteins, the expression of the chicken and zebrafish Oct-6 proteins is consistent with the notion that Oct-6 functions as a 'competence factor' in promyelin cells to execute the myelination program.

Folding and aggregation of DNA chains induced by complexation with lipospermine: formation of a nucleosome-like structure and network assembly

Dioctadecylamidoglycylspermine (DOGS) is a cationic lipid vector capable of efficiently introducing DNA into various eukaryotic cells. We investigated the higher-order structure of the DNA/DOGS complex using fluorescence and electron microscopy. Our results show that the DNA/DOGS complex exhibits a nucleosome-like structure in which DNA wraps around an aggregate of DOGS molecules. In addition, DNA/DOGS complexes tend to associate with each other to form network structures. The resulting network assembly may play a role in effective gene transfection.

Bead transfection of adherent cells. Gene transfer into adherent mammalian cells using glass beads

Bead transfection is a simple, rapid, efficient, and cost-effective method of gene transfer into adherent mammalian cells. It involves a brief incubation of the cells with glass beads in a solution containing the DNA to be transferred. We have optimized this technique using COS-7 (an SV40 transformed monkey kidney cell line) and a transient expression assay for chloramphenicol acetyl transferase (CAT). Stable transfection efficiency assessed using the selectable marker gene neomycin phosphotransferase (NEOR) was 27% in COS-7 cells. As this technique delivers high transfection efficiency with little manipulation of the exogenous DNA and does not require the use of any viral sequences, it may be a useful alternative method of gene delivery in the development of gene therapy protocols.

Optimization of retroviral vector-mediated gene transfer into endothelial cells in vitro

Retroviral vector-mediated gene transfer into endothelial cells is relatively inefficient with transduction rates as low as 1-2% in vitro and even lower in vivo. To increase the efficiency of gene transfer into endothelial cells, we used retroviral vectors expressing beta-galactosidase and urokinase and measured endothelial cell transduction efficiencies with quantitative assays for beta-galactosidase and urokinase protein. We evaluated several techniques reported to improve the efficiency of retroviral transduction in vitro, including 1) extended periods of exposure to vector, 2) repeated exposures to vector, 3) maximization of the ratio of vector particles to endothelial cells by increasing the volume and concentration of vector particles or by decreasing the number of endothelial cells exposed, 4) cocultivation of endothelial cells with vector-producing cells, and 5) variation of the type and concentration of polycation used with the retroviral vector. Only the use of more concentrated (higher titer) vector-containing supernatant and the use of the polycation DEAE-dextran improved the efficiency of gene transfer into endothelial cells in vitro. In an optimized transduction protocol, a 60-second exposure to 1 mg/ml DEAE-dextran followed by a single 6-hour exposure to supernatant of a titer of 10(5)-10(6) colony-forming units/ml resulted in transduction efficiencies of 50-90% with both vectors. Decreasing the time of the supernatant exposure to 15 minutes permitted transduction efficiencies of 15-20% while significantly minimizing the duration of the transduction. Therefore, the optimized protocol allows high efficiency in vitro gene transfer into endothelial cells within several hours. The briefer protocol may prove useful for in vivo gene transfer in which the time of exposure to the supernatant is limited.

Transient analysis for antiproliferative gene activity

A subset of tumor suppressor genes presumably functions by the inhibition of cellular proliferation; however, antiproliferative activity after transfection with putative suppressor genes has been difficult to demonstrate and often requires lengthy selection either in nude mice or in vitro. A rapid alternative is presented here that utilizes a gene encoding a surface marker protein to identify transfectants in a transient expression assay. In this assay the labeling index, rate of DNA synthesis, cell-cycle distribution, and surface receptor display are measured by flow cytometry. Human beta-interferon, a gene with proven antiproliferative activity, was studied using the transient analysis system. The beta-interferon gene was introduced into human tumor cells along with the marker gene encoding the 55-kDa subunit of the human interleukin 2 receptor. Within a few days of transfection, analysis of transfectants by flow cytometry revealed a decrease in the fraction of cells in G2/M and an increase in the fraction of cells in G1/G0 and S phases. The distortion of the cell cycle was accompanied by as much as a 69% reduction in the rate of DNA synthesis and, in some experiments, an unanticipated increase in the labeling index. Therefore, cells accumulating in S phase were not blocked but continued to synthesize DNA although at a reduced rate. These studies on DNA synthetic rates revealed the caveat that screening for antiproliferative candidate genes with a labeling index alone could, in certain circumstances, exclude potentially interesting sequences from further consideration. Although this transient analysis system was developed for studies on cellular proliferation, it may prove suitable for phenotypic assays on other genes as well.