Transwell Cell Migration Assay

Transwell cell migration assay was performed as described previously [14 (link), 16 (link)]. HEK293T cells were transfected with YFP alone, or together with the indicated plasmids and incubated for 24 h. The cells were detached and then resuspended in serum free DMEM. The cells were replated onto the upper chamber of a Transwell filter (Costar, 8 μm pore size). DMEM supplemented with 10% FBS was added to the lower chamber. At 6 h after plating, cells were fixed with 4% paraformaldehyde in phosphate buffered saline. Non-migrated cells on the upper side of the filter were removed with a cotton swab. In parallel, cells were separately plated to culture wells without the Transwell filters for estimating the total number of attached cells. Cell migration was calculated by the number of YFP-positive cells underside of the filter normalized to the total number of the YFP-positive attached cells. For each experiment, the number of cells in at least 8 random fields on the underside of the filter was counted, and four or five independent filters were analyzed.