E-cadherin-mediated cell–cell adhesion is essential for collective electrotaxis. a–c MDCK I cells in a monolayer culture migrated directionally to the anode. d–f After pretreatment with 4 mM EGTA for 10 min, directedness values decreased significantly in an EF in the continuous presence of 1 mM EGTA in calcium-free medium. g–i Restoration of the extracellular Ca2+ level completely restored the electrotaxis response. The extracellular Ca2+ level was restored by replacing Ca2+ free medium with normal growth medium containing calcium for 2 h following pretreatment in 4 mM EGTA for 10 min. j–l Blocking the E-cadherin with DECMA-1 (E-cadherin antibody; 50 μg/ml) completed blocked the recovery of the directedness. m, n Migratory directedness and speed of MDCK I cells in monolayer culture under different treatments as indicated. EF = 200 mV/mm for 6 h. The data are shown as mean ± SEM. *p < 0.01 compared with control group; †
p < 0.05, ‡
p < 0.01, compared with restoration group, respectively. Scale bars 50 μm. See Supplementary Video S4