Programmed cell death (apoptosis): the regulating mechanisms of cellular proliferation

the process of cell death under physiologic conditions has been recognized as an important phenomenon in normal embryonic development and in maintenance of tissue and organ homeostasis in the adult. this type of death is genetically controlled in a similar manner to the processes of cellular proliferation and differentiation and, similarly, the appearance of this type of cell death is predictable during development. the fact that a specific genetic program controls cell death implies that cells play an active role in their own destruction. given the morphologic and biochemical characteristics of this type of death, the term apoptosis was coined to differentiate this process from necrosis. the genes that control programmed cell death show a high rate of conservation among various animals, beginning with nematodes all the way to higher vertebrates, suggesting that this process first appeared with the most primitive multicellular animals. here we review some of the most relevant characteristics of this type of cell death nearly 25 years after it was first defined.