Mechanisms and control of programmed cell death in invertebrates

Apoptosis is a morphologically distinct form of programmed cell death that plays important roles in development, tissue homeostasis and a wide variety of diseases, including cancer, AIDS, stroke, myopathies and various neurod egenerative disorders (see Thompson (1995) for review). It is now clear tha t apoptosis occurs by activating an intrinsic cell suicide program which is constitutively expressed in most animal cells, and that key components of this program have been conserved in evolution from worms to insects to man. Genetic studies of programmed cell death in experimentally highly accessib le invertebrate model systems have provided important clues about the molec ular nature of the death program, and the intracellular mechanisms that con trol its activation. This review summarizes some of the key findings in thi s area, but also touches on some of the many unresolved questions and chall enges that remain.