Reduced Apoptosis and Cytochrome c–Mediated Caspase Activation in Mice Lacking Caspase 9

TLDR

Caspases are essential components of the mammalian cell death machinery. We generated Casp9 knockout mice to test whether Caspase 9 is a critical upstream activator of caspases. Casp9-deficient mice die perinatally with enlarged, malformed cerebrum due to reduced apoptosis, fail to activate Casp3 in embryonic brains, and show resistance to apoptotic stimuli, indicating that Casp9 is a critical upstream activator of the caspase cascade in vivo.

Abstract

Caspases are essential components of the mammalian cell death machinery. Here we test the hypothesis that Caspase 9 (Casp9) is a critical upstream activator of caspases through gene targeting in mice. The majority of Casp9 knockout mice die perinatally with a markedly enlarged and malformed cerebrum caused by reduced apoptosis during brain development. Casp9 deletion prevents activation of Casp3 in embryonic brains in vivo, and Casp9-deficient thymocytes show resistance to a subset of apoptotic stimuli, including absence of Casp3-like cleavage and delayed DNA fragmentation. Moreover, the cytochrome c-mediated cleavage of Casp3 is absent in the cytosolic extracts of Casp9-deficient cells but is restored after addition of in vitro-translated Casp9. Together, these results indicate that Casp9 is a critical upstream activator of the caspase cascade in vivo.