An alternative, nonapoptotic form of programmed cell death

The term apoptosis often has been used interchangeably with the term progra mmed cell death. Here we describe a form of programmed cell death that is d istinct from apoptosis by the criteria of morphology, biochemistry, and res ponse to apoptosis inhibitors. Morphologically, this alternative form of pr ogrammed cell death appears during development and in same cases of neurode generation. Despite its lack of response to caspase inhibitors and Bcl-x(L) , we show that this form of cell death is driven by an alternative caspase- 9 activity that is Apaf-1-independent. Characterization of this alternative farm of programmed cell death should lead to new insight into cell death p rograms and their roles in development and degeneration.