a-d, Electron micrographs of etoposide-treated Atg5-/- MEFs. a, AVs were observed near the Golgi apparatus (G). Inset, the isolation membrane (I) was extended from the Golgi stack. b, Developing autophagosome. rER, rough endoplasmic reticulum. c, d, Isolation membrane fusing with vesicles containing thick membrane (d) and a complete autophagosome (c) is generated. 