Nature Methods

Researchers have shown that by labeling pools of cells with different combinations of dyes, they can generate fluorescent ‘barcodes’ that can be used to determine which cell belongs to which group. As demonstrated in the May issue of Nature Methods, this approach could prove a boon to researchers interested in performing large-scale cell-based studies for drug discovery and other applications.

Protein phosphorylation has a major role in a wide variety of essential cellular functions, and a few years ago Garry Nolan and his colleagues developed ‘phospho flow’, an approach for simultaneously characterizing the phosphorylation status of multiple proteins in different groups of cells. However, phospho flow can become impractical when scaled up for the analysis of multiple protein targets in response to a large variety of different compounds.

Nolan and coauthor Peter Krutzik now present a solution. They show that cells labeled with different concentrations of a fluorophore can be readily distinguished, and that combinations of fluorophores - each present at a different concentration - can generate cell-specific ‘barcodes’. Thanks to these barcodes, researchers can subject large numbers of cell populations to different treatments, then pool the cells for simultaneous phospho flow sorting and analysis, resulting in a considerable savings in efficiency and reagent consumption.

The authors show that with just three barcoding fluorophores, one can easily sort out the phospho flow data for differentially treated cells from a 96-well assay plate - and larger assays should prove equally feasible. In an accompanying ‘News and Views’ feature, James Jacobberger looks at the potential implications of this technology for the rapidly growing field of high-content screening.

CONTACT
Garry Nolan (Stanford University, Stanford, CA, USA)
Tel: +1 650 725 7002; Email: gnolan@stanford.edu


James Jacobberger (Case Western Reserve University, Cleveland, OH, USA)
Tel: +1 216 368 4645; Email: jwj@case.edu




A new way to spotlight cells in live animals

Nature Methods

A technique described in the May issue of Nature Methods helps cell culture make the leap into the third dimension, allowing scientists to more closely replicate naturally occurring arrangements of cells in the laboratory.

Cells are generally cultured on hard, flat surfaces - typically glass or plastic - which may be conducive to cell growth and division, but can also result in unwanted effects. Many cell types are exquisitely sensitive to such factors as relative position and proximity to each other within a tissue, and cells grown under unnatural conditions may be prone to deviations in their signaling and gene expression profiles - changes that could seriously impact experimental data.

Sangeeta Bhatia and her colleagues tested an alternative culture substrate: a polymer solution that switches from liquid to gel form after exposure to ultraviolet light (UV). Cells are introduced into a thin layer of this solution sandwiched between two electrodes, and are then arranged into three-dimensional patterns with the help of an electric field. A brief treatment with UV gels the solution, locking the cells into their new positions.

Bhatia’s group demonstrates the safety and efficacy of this technique with bovine chondrocytes, arranging the cells into various complex patterns and showing how their spatial arrangement of can markedly influence their behavior. Multiple slabs of cells arranged in this way can easily be stacked for coculture, and this technique should be a promising tool for researchers interested in working with organized cellular assemblies that more closely mirror naturally occurring, physiological environments.

CONTACT
Sangeeta Bhatia (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 617 324 0221; Email: sbhatia@mit.edu

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