Using Mosaic Cell Labeling to Visualize Polyploid Cells in the Drosophila Brain.

Traditional methods used to study endoreplication have limitations when used to identify rare events of polyploidization in complex, densely-packed tissues. Here, we describe a method to identify and visualize polyploid cells in situ using an existing mosaic, multicolor labeling technique named "CoinFLP" (Bosch et al., Development 142(3):597-606, 2015). CoinFLP allows easy visualization of polyploid cells in situ and can be combined with other techniques such as immunofluorescence for cell-type-specific labeling and flow cytometry to perform quantifications and can also be used for genetic manipulations. Further, by modifying the time of labeling, this technique can also be used to distinguish events of cell fusion from endocycle (Nandakumar et al., eLife 25:9, 2020)-allowing one to infer the method of polyploidization.