Addressing variability in a Xenopus laevis melanophore cell line

Xenopus laevis melanophores can be used in high-throughput screens for guanine nucleotide binding protein coupled receptor ligands and have potential as biosensors. Inherent in this immortal cell line is a substantial variability, which macroscopic evaluations disregard. Here we demonstrate a systematic way to incorporate this natural variability in the evaluations. Clusters of similar cells from a sparsely seeded cell culture are examined by imaging changes in cell appearance, pigment motility, and cumulative displacements. The time evolution of the image intensity distributions of clusters upon a pigment-dispersing stimulus is used as a signature of the cell clusters, and their behaviors are classified by multivariate analysis. Conventional image subtraction procedures are used to highlight cumulative and transitory changes in the pigment dynamics, enabling characterization of multiple aspects of the cell response from a single experiment. Additionally, a simple way to accomplish standard optical density changes at the single-cell group level is shown. The present results also provide evidence that natural cell variability arising from a cell culture can enrich the diversity of responses from pigment-containing cells assays and underscore that in conventional macroscopic evaluations these aspects are overlooked and can lead to spurious results.