Fiona Doetsch - US grants

[unreadable] DESCRIPTION (provided by applicant): Neural stem cells residing in specialized niches in the adult mammalian brain may represent a large pool of cells that can be stimulated for brain repair. Adult neural stem cells continuously generate new neurons that functionally integrate into neural circuits. Defining the molecular events that underly stem cell self-renewal and differentiation are essential steps towards harnessing the endogenous stem cells and progenitors for brain repair. While recent progress has been made in identifying transcriptional pathways regulating these processes, post-transcriptional regulatory mechanisms are almost completely unknown. MicroRNAs are a novel class of small non-coding RNAs that largely act by repressing translation. We hypothesize that miRNAs are key mediators of stem cell biology and cell fate decisions and act in concert with transcriptional regulators to control adult neural stem cell self-renewal and differentiation. We propose here to 1) characterize the functional role of 3 miRNAs we have identified in the adult neural stem cell lineage. We will use retroviruses to ectopically over-express and knock down these miRNAs in cultured neural stem cells to examine their functional role in stem cell self-renewal and differentiation. We will determine the functional consequences for adult neurogenesis in vivo by retroviral over-expression and knock down of these miRNAs. 2) We will identify the physiological targets of these miRNAs, which will yield important insight into the networks regulated by miRNAs. 3) We will clone and characterize specific libraries of miRNAs for each cell stage in the lineage of adult neurogenesis. These studies will yield key insights into the function of miRNAs in stem cells for adult neurogenesis. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Stem cells reside in specialized niches, which provide extrinsic signals that regulate their life-long self-renewal and differentiation. Adult neural stem cells continuously generate neurons in restricted parts of the brain that functionally integrate into neural circuits. These stem cells may represent an important source of endogenous cells that can be stimulated for brain repair. Defining the components of the niche that regulate adult neural stem cell behavior is essential to eventually harnessing these cells for brain repair, as well as illuminating the contribution of the niche to the decline in stem cell function that occurs with aging and disease. The subventricular zone (SVZ) is the largest germinal region in the adult brain. SVZ stem cells and their progeny reside in a specialized vascular niche. While diffusible endothelial signals are known to promote stem cell self- renewal, little is known about the contribution of other perivascular cells to the niche. We propose here to: 1) co-culture purified SVZ stem cells and their progeny with primary perivascular cells purified from the SVZ and a non-neurogenic region of the brain. In addition we will seed purified SVZ cells onto an extracellular matrix scaffold. These experiments will define the functional contribution of diffusible signals, contact-mediated signals and the extracellular matrix to adult neural stem cell proliferation and lineage progression. 2) We will perform transcriptional profiling of acutely isolated perivascular cells to identify molecular signals from the niceh. This will provide a tremendous resource for future functional in vivo and in vitro studies of niche candidates from perivascular cells. PUBLIC HEALTH RELEVANCE: This project will define the functional role of diverse aspects of the vascular niche in regulating adult neural stem cells. It will provide information about the microenvironment that supports the formation of new neurons in the adult mammalian brain and how neural stem cells are maintained throughout life. Understanding these cues will yield insight into the possibility of stimulating endogenous stem cells or activating cells elsewhere in the brain for repair.

DESCRIPTION (provided by applicant): Stem cells continuously generate new neurons in restricted regions of the adult mammalian brain. The subventricular zone (SVZ) is the largest germinal region in the adult gives rise to neurons that migrate to the olfactory bulb as well as some oligodendrocytes. The in vivo stem cells are a subset of astrocytes, glial cells classically associated with support functions. These endogenous stem cells potentially represent a pool of cells that can be harnessed for brain repair. A balance between intrinsic and extrinsic signals mediates the activation of quiescent stem cells. However, the ability to distinguish between quiescent and activated stem cells has been hampered by a lack of markers. Here we identify a combination of markers that allow us to identify and isolate four populations of astrocytes from the SVZ directly from the in vivo niche. Based on cell cycle analysis, in vitro stem cell behavior and gene expression profiling, we hypothesize that they correspond to quiescent stem cell astrocytes, activated stem cell astrocytes and niche astrocytes. We propose to: 1) Define the cell cycle kinetics of the purified astrocyte populations, and their ability to act as stem cells in vitro, as well as how their numbers and functional properties change with aging, 2) perform lineage tracing of quiescent and activated stem cells under homeostasis and during regeneration and 3) define the role of PDGFRb in regulating adult neural stem cell quiescence. Together these studies will yield key insights into the regulation of stem cell quiescence in the adult brain. PUBLIC HEALTH RELEVANCE: Stem cells in the adult brain are a specialized kind of glial cell. Here we propose to define the progeny and molecular regulation of quiescent adult neural stems cells. These findings will inform strategies for brain repair.

DESCRIPTION (provided by applicant): Stem cells reside in specialized niches that support their life-long self-renewal and differentiation. Adult neural stem cells continuously generate neurons in restricted parts of the brain that functionally integrate into neural circuits. These stm cells may represent an important source of endogenous cells that can be stimulated for brain repair. Defining the source and identity of signals from the niche that regulate adult neural stem cell behavior is essential to eventually harnessing these cells for brain repair, as well as understanding how changes in niche contribute to the decline in stem cell function that occurs with aging and disease. The subventricular zone (SVZ) is the largest germinal region in the adult brain and is located adjacent to the cerebrospinal fluid (CSF)-filled lateral ventricles. Although stem cells in this niche contact the CSF, the role of the CSF is largely unexplored. We propose here to: 1) determine the functional role of the CSF in the SVZ adult neural stem cell niche and how it is altered during aging, 2) define the role of candidate factors in the CSF compartment that change that mediate age-related changes in adult neural stem cell behavior and 3) perform comprehensive lipid profiling of young and aged mouse CSF.