A Cre-based double fluorescence indicator system for monitoring cell fusion events and selection of fused cells.

We have established an in vitro Cre/loxP-based assay for monitoring cell fusion events that specifically traces the transport of cytoplasm from one cell to its fusion partner. Cells with a double fluorescence vector indicate fusion with cells expressing Cre recombinase by switching expression from red to green fluorescent protein through a Cre-mediated recombination event that simultaneously activates puromycin-acetyltransferase expression. This strategy allows for both the observation and puromycin selection of indicator cells that have undergone fusion with a Cre recombinase-expressing partner.