**Figure 2.** **Immortalized MEF Zmpste24 KO cells present an increase in ER-stress.** (**A**) Immunoblot analysis of BIP, P-PERK, PERK, eiF2α and P- eiF2α using both, β actin and Tubulin as loading control, in the cell extracts in basal state (*n* = 5). The plot indicates the quantification data of eiF2α/β-actin ratio, P-eiF2α 62/eiF2α ratio, BIP/Tubulin ratio and P-PERK/PERK ratio in the basal state. Data represent the mean ± standard error of the mean (SEM). Differences were determined by unpaired Student *t*-test analysis. ^{*}*p* < 0,05; ^{**}*p* < 0,01; ^{***}*p* < 0,005 (*n* = 5). (**B**) Electron microscopy of ER of MEF Zmpste24 WT and KO cells in basal state. The plot indicates the quantification data of ER dilation using image J. ^{*}*p* < 0,05.