ATF4 and cardiac hypertrophy: Moreover, western blot analysis revealed that Thbs1 overexpression in the heart induced a profile of ER stress markers like those observed during cardiac hypertrophy mediated by 2 weeks of TAC, including changes in nuclear ATF6α, phosphorylated and total PERK, phosphorylated and total IRE1α, ATF4 and calreticulin, and to a lesser extent Armet and BiP (Supplementary Fig. 4).