Molecular Characterization of Neural Stem Cell Apoptosis

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DESCRIPTION (provided by applicant): Neural stem cells play a critical role in normal nervous system development and dysregulated neural stem cell death contributes to brain and spinal cord malformations, brain tumor formation, and possibly, neurodegenerative and neuropsychiatric diseases. Cell death pathways are remarkably cell- and stimulus- specific and are dependent on interactions between an array of molecules including p53, Bcl-2 family members, caspases, and a variety of autophagy-associated proteins. In a series of studies supported by this grant, we have defined several stimulus-specific neural stem cell death pathways involving p53 and/or Puma, a pro-apoptotic member of the Bcl-2 family. In this revised competitive renewal application, we propose a series of novel studies focused on p53 and Puma regulation of physiological and pathological neural stem cell death. In addition to the well known role of apoptotic cell death (Type I Programmed Cell Death), autophagic cell death (Type II Programmed Cell Death) has been increasingly recognized to occur under neuropathological conditions. Studies supported by our grant have demonstrated a role for p53 and Bcl-2 family members in regulating both apoptotic and autophagic cell death in neural stem cells. Our recent data indicate that neural stem cell death is triggered in vivo by a variety of pathological stimuli including genotoxic stress, hypoxic- ischemic injury, and glucocorticoid exposure. These stimuli have been implicated in the pathogenesis of several human neonatal and pediatric neurological disorders. In this application, we focus on the molecular mechanisms regulating apoptotic and autophagic neural stem cell death, with a particular emphasis on the in vivo relevance of these overlapping death pathways in two important neonatal mouse models of human neuropathology. To accomplish our goals, we will pursue three specific aims. In aim one, we will test the hypothesis that p53 is a potent regulator of autophagic stress-induced neural stem cell death through its ability to engage both Puma-dependent and -independent death pathways. Aim two will characterize the molecular pathways involved in hypoxia-ischemia-induced neural stem cell death in the neonatal mouse brain in vivo, a model of human cerebral palsy, and test the hypothesis that p53 regulates neural stem cell death, at least in part, through a transcription-independent action. Aim three will extend our preliminary studies indicating that Puma, in a p53-independent fashion, regulates glucocorticoid-induced neural stem cell death in the neonatal mouse brain, and is a likely contributor to the neurological deficits associated with human premature birth. In total, these proposed studies of novel p53- and/or Puma-dependent neural stem cell death pathways represent an important extension of our highly productive investigations of apoptotic and autophagic cell death pathways and will yield new insights into the molecular mechanisms regulating neural stem cell death under physiological and pathological conditions. PUBLIC HEALTH RELEVANCE: Neural stem cells control nervous system development and too much, or too little, neural stem cell death is implicated in developmental brain malformations, brain tumor formation, and neuropsychiatric diseases. Defining the molecular pathways regulating neural stem cell death is important for understanding how the nervous system normally develops and identifying molecular targets for therapeutic interventions in a variety of human neuropathological disease states, including cerebral palsy, neurodevelopmental disorders, epilepsy, autism, brain tumors, and neurodegenerative diseases.