Imaging-Based Analysis of Cell-Cell Contact-Dependent Migration in Dictyostelium.

Cell-cell interaction mediated by secreted and adhesive signaling molecules forms the basis of the coordinated cell movements (i.e., collective cell migration) observed in developing embryos, regenerating tissues, immune cells, and metastatic cancer. Decoding the underlying input/output rules at the single-cell level, however, remains a challenge due to the vast complexity in the extracellular environments that support such cellular behaviors. The amoebozoa Dictyostelium discoideum uses GPCR-mediated chemotaxis and cell-cell contact signals mediated by adhesion proteins with immunoglobulin-like folds to form a collectively migrating slug. Coordinated migration and repositioning of the cells in this relatively simple morphogenetic system are driven strictly by regulation of actin cytoskeleton by these signaling factors. Its unique position in the eukaryotic tree of life outside metazoa points to basic logics of tissue self-organization that are common across taxa. Here, we describe a method to reconstitute intercellular contact signals and the resulting cell polarization using purified adhesion proteins. In addition, a protocol using a microfluidic chamber is laid out where one can study how the cell-cell contact signal and chemoattractant signals, when simultaneously presented, are interpreted. Quantitative image analysis for obtaining cell morphology features is also provided. A similar approach should be applicable to study other collectively migrating cells.