The Regulation of Neuronal Death during Insect Metamorphosis

Abstract

occurs during normal development, as tissues form: for example, in the dorsal root ganglion of the chick spinal cord, only 60% of the nerve cells present before hatching survive to become part of the mature nervous system (Hamburger and LeviMontalcini 1949). Some nerve cells most likely die during development because they fail to find a synaptic target (Hollyday and Hamburger 1976). Cell death also maintains tissue mass in slowly proliferating adult tissues such as the liver, in which the production of new hepatic cells is balanced with cell loss (Beneditti et al. 1988). And without mechanisms for cell suicide, the striking morphological changes that accompany metamorphosis (of caterpillars or tadpoles, for example) would not be possible. Exciting new data indicate that this cell suicide pathway is evolutionarily ancient and highly conserved, because homologous molecules have the same suicide-