A simple and robust fluorescent labeling method to quantify trophoblast fusion.

Trophoblast fusion into syncytiotrophoblasts is a specialized yet enigmatic cellular process, which is essential for placental development and function. To facilitate mechanistic understanding of this critical process, here we re-purposed a widely used fluorescent membrane potential dye, Di-8-ANEPPS, to stably label the plasma membrane of live BeWo trophoblast cells. Compared to the methods currently available to quantify trophoblast fusion, our new fluorescent labeling method is simple, economical, robust and versatile, enabling quick and accurate quantification of fusion index in living cells.