Rest-Activated Program of Gene Expression in Ischemia

DESCRIPTION (provided by applicant): REST/NRSF is a gene silencing transcription factor that is widely expressed during embryogenesis and plays a strategic role in terminal neuronal differentiation. In neural progenitors and non-neural cells, REST actively represses a large array of neural-specific genes important to synaptic plasticity and synaptic remodeling including those encoding synaptic vesicle proteins, structural proteins, voltage-sensitive ion channels, and the AMPAR subunit GluR2. As neurons differentiate, REST downregulation is essential for induction and maintenance of the neural phenotype. Perturbation of REST expression during embryogenesis results in cellular apoptosis, aberrant differentiation and patterning, and lethality. Dysregulation of REST and its target genes is implicated in the pathogenesis of Down's syndrome, Alzheimer's disease and some medulloblastomas. Global ischemia is a neurological disorder in which a brief neuronal insult induces selective, delayed death of hippocampal CA1 neurons. The substantial delay between insult and cell death is consistent with a role for transcriptional changes. Recent findings from this laboratory show that ischemic insults activate REST in neurons destined to die and implicate REST in global ischemia-induced neuronal death. The proposed research aims to study the role of the REST-initiated program of transcriptional changes in ischemia. The AMPAR subunit GluR2, brain-derived neurotrophic factor (BDNF) and the u opioid receptor are known targets of REST and are implicated in the excitotoxic death associated with global ischemia. A focus will be REST-dependent silencing of GluR2 and p receptor gene expression and upregulation of BDNF expression. The underlying hypothesis is that global ischemia triggers de-repression of the gene silencing transcription factor REST, which initiates a program of gene transcriptional changes and that one or more REST target genes are critical players in global ischemia-induced neuronal death. Specific Aims are 1) Examine activation of the REST repressor complex in post-ischemic CA1 neurons and determine whether REST is causally related to neuronal death. 2) Examine mechanisms by which REST alters target genes in post-ischemic neurons and determine whether REST-dependent chromatin remodeling is causally related to neuronal death; and 3) Identify novel REST target genes and determine whether they are causally related to neuronal death. Our findings are consistent with observations of transcriptional dysregulation in injured neurons and suggest that disruption of REST silencing has a critical role in the pathogenesis of global ischemia. The proposed research will impact on the development of new treatment strategies for intervention in global ischemia, a dehabilitating trauma that affects 200,000 Americans each year. This study has implications for research on other disorders including epilepsy, stroke, traumatic brain injury, spinal cord injury and Alzheimer's disease.