The long term objective here is to understand the molecular mechanisms by which neurons die during normal development and in response to injury and disease. Such information will not only provide deep insight about a fundamental event in nervous system formation, but also potentially lead to discovery of therapeutic approaches to block neuron death in circumstances such as brain and spinal cord injuries, stroke and neurodegenerative disorders. The specific aims of this project are based on the finding that neuronal cell death generally requires transcription-dependent synthesis of death-associated proteins. The proposed studies will focus on two transcriptional pathways that are causally involved in neuronal death evoked by a wide range of apoptotic stimuli and that have been the subject of study and substantial progress during the present period of support. These are: 1) The neuronal apoptotic cell cycle pathway which is characterized by inappropriate activation of cyclin-dependent kinases that in turn leads to de-repression of death-associated genes that are normally repressed by the transcription factor E2F. Cell culture studies will evaluate the mechanisms by which this pathway is triggered by apoptotic stimuli, with emphasis on regulation of cyclin-dependent kinase 4 and cyclin D1. In addition, experiments will define the specific roles of the E2F-regulated transcription factors B- and c-myb in death as well as the mechanism by which the death-associated protein BIM is regulated by the cell cycle pathway. Finally, gene profiling methods (SAGE and gene microarrays) will be used to identify specific death-associated genes regulated by this pathway 2) The neuronal apoptotic JNK/cJun pathway which is characterized by activation of a chain of protein kinases that culminates in phosphorylation and activation of the transcription factor c-Jun. Studies will focus on characterizing the role of the scaffold protein POSH in this pathway and on using gene profiling technology to identify those death associated genes that this pathway regulates.