The blockade of ER-Golgi complex transport and tunicamycin treatment do not cause ER vesiculation. (A) Overexpression of a dominant negative form of Sar1 (Sar1[T39N]) in wild-type MEFs showed no effect on ER structure, suggesting that ER vesiculation was not due to impaired ER-to-Golgi complex transport. Wild-type MEFs were electroporated with FLAG-Sar1[T39N], and after 24 h, they were fixed and double stained with antibodies against FLAG (green) and BiP (red). (B) Tunicamycin treatment showed no effect on ER structure in wild-type MEFs, suggesting that ER vesiculation was not due to ER stress. Wild-type MEFs were treated with 10 μg/ml tunicamycin for 12 h, and they were fixed and double stained with antibodies against CHOP (green) and PDI (red). (A and B) Bars, 10 μm.