Ongoing scientific interest in simian virus 40 (SV40), which was accidentally introduced to a significant proportion of the human population through contaminated polio vaccines, has led to the development of a large number of mutants of the virus. The COS-7 cell line is a line that was developed from the standard CV-1 African green monkey kidney line by transforming the normal cells with an origin defective mutant of simian virus 40 that codes for the wild-type large tumor antigen (T antigen).

COS-7 cells exhibit typical fibroblast morphology and are often used in transfection experiments and in research focusing on SV40, which has been connected in some studies with the development of certain types of cancer and features a genome that can be manipulated with relative ease. COS-7 kidney fibroblast cells fully permit the lytic growth of SV40 and the replication of pure populations of SV40 mutants with deletions in the early region.

The SV40 genome is comprised of 5243 nucleotides organized in a closed circular superhelical arrangement. The genome is encased in a small capsid that only allows enough space for the DNA to encode a few functions, and necessitates overlapping reading frames for some of the proteins that are encoded. One of the proteins encoded by the SV40 genome is the viral oncogene called T antigen. In simian cells, T antigen typically moderates SV40 replication and packaging. In some other cell types, however, the protein binds certain proteins (p53 and Rb) involved in growth regulation and interferes with their customary functions so that tumor growth is initiated.

The culture of transformed monkey kidney cells (COS-7 line) that is presented in the digital image above was labeled with SYTOX Orange and Alexa Fluor 488 conjugated to phalloidin, which target DNA and F-actin, respectively. In addition, the mitochondria were stained with MitoTracker Deep Red 633. Images were recorded in grayscale with a 12-bit digital camera coupled to either a Nikon E-600 or Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles with the exception of MitoTracker Deep Red 633, which was pseudocolored blue.

Targeting Tubulin in Transformed Monkey Kidney Cell Cultures with Immunofluorescence - The microtubule network was visualized in the culture of transformed African green monkey kidney fibroblast cells (COS-7) displayed in this section via immunofluorescent labeling with primary anti-tubulin mouse monoclonal antibodies followed by goat anti-mouse Fab fragments conjugated to Cy3. In addition, F-actin and cell nuclei were targeted with Alexa Fluor 488 conjugated to phalloidin and DAPI, respectively.

COS-7 Kidney Cells Labeled with Soybean Agglutinin - An adherent monolayer culture of COS-7 fibroblasts that was labeled with Oregon Green 488 conjugated to soybean agglutinin, which has saccharide binding sites that recognize and bind terminal alpha- and beta-N-acetylgalactosamine and galactopyranosyl oligosaccharides. The cells were also labeled with Alexa Fluor 568 conjugated to phalloidin and DAPI, targeting the cytoskeletal F-actin network and nuclear DNA, respectively.

Localization of Actin, Mitochondria, and Nuclei by Fluorescent Proteins in Monkey Kidney Fibroblasts - The culture of COS-7 fibroblasts illustrated in this section was transfected with chimeric EGFP and ECFP plasmid vectors that express fluorescent fusion proteins targeted at cytoplasmic actin and cell nuclei, respectively. The specimen was also transfected with a pDsRed-Mitochondria plasmid subcellular localization vector, thus localizing a red fluorescent protein tag to the intracellular mitochondrial network.

Triple Labeling of COS-7 Monolayer Cultures with Alexa Fluor 546, MitoTracker Deep Red 633, and SYTOX Green - An adherent COS-1 transformed fibroblast cell culture was fluorescently labeled for the cytoskeletal filamentous actin and intracellular mitochondrial networks with Alexa Fluor 546 conjugated to phalloidin and MitoTracker Deep Red 633, respectively. Nuclei present in the cells were counterstained with SYTOX Green.

Targeting Sialic Acid Residues in COS-7 Cells with Wheat Germ Agglutinin - The culture of transformed African green monkey kidney cells (COS-7 line) featured in this section was labeled with Alexa Fluor 350 conjugated to wheat germ agglutinin, a fluorescent lectin that selectively binds to sialic acid residues found in both mucoproteins and glycoproteins. The cells were also stained with Alexa Fluor 488 conjugated to phalloidin and the intercalating dye propidium iodide, which target the cytoskeletal filamentous actin network and nuclear DNA, respectively.

Visualizing Tubulin with Immunofluorescence in Transformed Monkey Kidney Cells - The technique of immunofluorescence was utilized to target the intracellular microtubule network in the culture of COS-7 cells displayed in this section. The cells were treated with primary anti-tubulin mouse monoclonal antibodies followed by goat anti-mouse Fab fragments conjugated to Cy3. The specimen was also stained for nuclear DNA with the ultraviolet-absorbing probe DAPI and for filamentous actin with Alexa Fluor 488 conjugated to phalloidin.

Filamentous Actin, Mitochondria, and DNA Distribution in Cultured COS-7 Fibroblasts - The COS-7 fibroblast cells presented in this section were resident in an adherent culture stained for F-actin with Alexa Fluor 546 conjugated to phalloidin, and for DNA with SYTOX Green. The mitochondrial network was simultaneously visualized using MitoTracker Deep Red 633.

Triple Fluorescence in Viral-Transformed African Green Monkey Kidney Cells - An adherent culture of COS-7 cells was first treated with MitoTracker Red CMXRos, and then fixed, permeabilized, and blocked with 1-percent bovine serum albumen before staining for filamentous actin with phalloidin conjugated to Alexa Fluor 488. The nuclei were counterstained with DAPI.