Regulation of Neural Stem Cells and Neurogenesis by Autophagy Genes

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In adult brains, neural progenitor/stem cells (NSCs) are responsible for the generation of new neurons for the maintenance of the existing circuitry and after injuries. Deficiency in NSC maintenance and/or neurogenesis contributes to both developmental defects and neurodegenerative diseases for which aging is a major risk factor. The long-term goal of the proposed studies is to determine the molecular and cellular mechanisms of NSC regulation in both young and aged animals, which can lead to the development of effective therapies for neurodegenerative diseases. Autophagy is a highly conserved cellular process for degradation of bulk cytoplasmic materials for maintenance of cellular homeostasis, and dysfunctions in autophagy have been implicated in various diseases, including neurodegeneration and other age-related disorders. FIP200 (FAK-family Interacting Protein of 200 kDa) was initially identified in our laboratory and subsequently shown as one component of the ULK1/Atg13/FIP200 complex essential for the induction of autophagy. In the previous funding period, we found that, deletion of Fip200, but not other autophagy genes Atg5, Atg7 and Atg16L1, led to defective NSC maintenance and neurogenesis, suggesting a potential role for the non-canonical function of FIP200 in NSC regulation through controlling p62 aggregate formation. In additional prelim studies, we obtained rigorous genetic evidence that non-canonical function of FIP200 is required for NSC maintenance and neurogenesis by generation and analyses of another unique mouse model with FIP200-4A mutation in NSCs that blocks autophagy function of FIP200 specifically. Additionally, we found that the FIP200 C-terminal region (FIP200-CT) could interact with p62, consistent with recent studies showing its importance in degrading p62 aggregates. Moreover, we found that FIP200 can regulate TBK1 activation, which can phosphorylate p62 to regulate its degradation, and that FIP200 also interacts with the TBK1 adaptor, AZI2. In a second set of prelim studies, we analyzed the role of another autophagy gene Beclin1 in NSCs employing new Becn1 KI mice and found that increased autophagy protected NSC pool and their neurogenesis in aged Becn1 KI mice without affecting NSC in young mice. Lastly, we obtained additional prelim data suggesting that oxidative stress may synergize with autophagy-deficiency to promote p62 aggregate formation. Building upon these preliminary and prior studies, we propose to 1). investigate the mechanisms of non-canonical functions of FIP200 and potential synergy with its autophagy function in the regulation of NSCs, 2). analyze the role and mechanisms of enhanced autophagy to prevent NSC pool decline and promote neurogenesis in Becn1 KI mice, and 3). explore the role and mechanisms of NSC maintenance and neurogenesis in autophagy-deficiency mice after oxidative insult and during aging. Together, these studies will significantly advance our understanding of the regulation of NSC and neurogenesis by autophagy genes that may contribute to future design of effective therapies for neurodegenerative and other related diseases.