title: Signal antonymy: a mechanism for apoptosis induction.
abstract: The unfolding of the developmental programme and the organization of multicellular organisms require that cell numbers in differentiating and differentiated tissues are regulated. This is done by two distinct processes : control of cell proliferation and differentiation to a post-mitotic stage; and control of survival in post-mitotic cells. It is argued that elimination of cells by programmed cell death (PCD), which operates in both cases, is regulated by distinct mechanisms: PCD in post-mitotic cells corresponds to 'death-by-default' of (counter apoptotic) survival signals (Raff, 1992), while apoptosis in cycling cells, or in resting cells submitted to proliferative signals, results from antonymy in signalling pathways, i.e. a situation where a cell simultaneously engages into incompatible pathways of proliferation and cell cycle arrest. Antonymy arises in cells irreversibly committed to either proliferation or arrest and responding to a contradictory signal. In turn, the irreversible commitment arises by uncoupling of signal transduction from co-ordinated pathways (as in transformed cells with constitutive expression of growth-associated genes or in terminally differentiated post-mitotic cells).
authors.affiliation: Unite d'lmmunobiologie, Institut Pasteur, Paris, France.
authors.forename: U
authors.initials: U
authors.lastname: Hibner
authors.forename: A
authors.initials: A
authors.lastname: Coutinho