Revealing the role of vimentin in adult mouse hippocampal neurogenesis

About This Grant

Project Summary Neural stem cells (NSCs) in the brain generate newborn neurons throughout life, providing an endogenous stem cell pool that can be harnessed to improve cognitive function during aging and neurodegenerative disease. Thus, understanding how adult neurogenesis is regulated may provide new targets and opportunities for therapeutic upregulation in these conditions. Intermediate filament (IF) proteins such as nestin and glial fibrillary acidic protein (GFAP) have been invaluable as markers for NSCs, increasing our understanding of the different cell states and cell types of the neurogenic niche. The IF protein vimentin is also expressed in NSCs, but due to variability in antibody quality and the lack of reporter mouse lines, very little is known about when and where it is expressed in the neurogenesis cascade. Recently, my lab has demonstrated many unique aspects of vimentin’s function and regulation in adult hippocampal NSCs in vitro. We found that vimentin mRNA is stabilized during quiescence, yet translationally repressed through an RNA-binding protein interaction with vimentin mRNA’s 3’UTR. As qNSCs activate, repression is removed, resulting in a rapid increase in vimentin protein. Additionally, as qNSCs activate, they traffic accumulated proteins that need to be degraded to the centrosome to form an aggresome. Vimentin collapses around the aggresome, forming a vimentin cage, bringing with it interacting proteins such as proteasomes. During cell division, the aggresome, vimentin cage, and associated proteins are asymmetrically segregated into one daughter cell. The daughter which inherits these cargoes has a decreased proliferation rate, whereas the non-inheriting daughter has a normal proliferation rate, resulting in a rejuvenative asymmetry between daughter cells. Vimentin is also required for efficient quiescence exit both in vitro and in vivo, further suggesting that vimentin’s role in NSCs is not only as a potential marker, but also as a key component to intrinsic mechanisms of quiescence exit. However, most of these findings were largely performed in vitro, thus we do not know if this process is conserved in the adult brain, nor how this asymmetric inheritance would affect the outcome of daughter cells in the neurogenic niche itself. To address these open questions, we created a novel transgenic mouse with endogenous vimentin fused to linker-mScarlet. We will characterize vimentin-mScarlet expression at the mRNA and protein level in cells of the hippocampus, and through prospective sorting followed by cell behavior analyses, we will reveal when and where vimentin mRNA and protein are expressed in the hippocampus. Importantly, we will also perform chronic in vivo imaging in cranial windows in these mice to visualize vimentin-mScarlet protein during quiescence exit and its asymmetric segregation during divisions, following the consequence of this inheritance in vivo. These studies will not only provide an important novel tool to the scientific community, but also reveal new knowledge on NSC subpopulation dynamics, answering critical questions about how NSCs rejuvenate their niche.