ATF4 and heart failure: To further identify the mechanism by which Aggf1 haploinsufficiency augments cardiac hypertrophy and heart failure, we analyzed CHOP and other ER stress signaling markers BiP, ERO1α, Puma, DR5, ATF4, cATF6, p-eIF2α, phosphorylated PERK (p-PERK), and sXBP1 using western blot analysis.