Coculture with WT- but not DM-oocytes promotes EGFR signaling in WT OOX cumulus cells. A, Levels of Egfr mRNA expressed in WT, COCs, OOX cumulus cells (OOX), OOX cumulus cell cocultured with WT Oocytes (OOX+WT), or DM oocytes (OOX+DM), 20 h after culture. B, Western blot analysis of EGFR, p-SMAD2, and β-actin (ACTB) in the same experimental groups as stated in panel A 20 h after culture. C, Changes of the levels of p-MAPK3/1 in the same experimental groups as stated in panel A after the initial 20-h culture and then treated with or without (control) AREG for 30 min. Groups indicated with different letters are significantly different, P < 0.05.