UPR activation in G193X Elane granulocytic precursors. (A) Real-time RT-PCR for the indicated genes was performed on RNA isolated from cultured wild-type (WT) or G193X Elane granulocytic precursors. Shown is the mRNA expression relative to β-actin mRNA. Data represent the means ± SEM of 4-9 samples. (B) Elastolytic activity in human or mouse bone marrow was measured using the chromogenic NE-specific substrate N-methoxysuccinyl Ala-Ala-Pro-Val p-nitroanilide. Shown is the change in optical density at 405nm (OD₄₀₅) per minute after normalizing for input protein. Data represent the means ± SEM of 2-4 samples. *P < .05; **P < .001.