Biology subjects

Denninger, J. K.

Publications and source records attributed to Denninger, J. K..

4 recordsLinked to original sources

bioRxiv2023

Neural stem and progenitor cells support and protect adult hippocampal function via vascular endothelial growth factor secretion.

Adult neural stem and progenitor cells (NSPCs) reside in the dentate gyrus (DG) of the hippocampus throughout the lifespan of most mammalian species. In addition to generating new neurons, NSPCs may alter their niche via secretion of growth factors and cytokines. We recently showed that adult DG NSPCs secrete vascular endothelial growth factor (VEGF), which is critical for maintaining adult neurogenesis. Here, we asked whether NSPC-derived VEGF alters hippocampal function independent of adult neurogenesis. We found that loss of NSPC-derived VEGF acutely impaired hippocampal memory, caused neuronal hyperexcitability and exacerbated excitotoxic injury. We also found that NSPCs generate substantial proportions of total DG VEGF and VEGF disperses broadly throughout the DG, both of which help explain how this anatomically-restricted cell population could modulate function broadly. These findings suggest that NSPCs actively support and protect DG function via secreted VEGF, thereby providing a non-neurogenic functional dimension to endogenous NSPCs.

neuroscience↗

bioRxiv2021

Robust transcriptional profiling and identification of differentially expressed genes with low input RNA sequencing of adult hippocampal neural stem and progenitor populations

Multipotent neural stem cells (NSCs) are found in several isolated niches of the adult mammalian brain where they have unique potential to assist in tissue repair. Modern transcriptomics offer high-throughput methods for identifying disease or injury associated gene expression signatures in endogenous adult NSCs, but they require adaptation to accommodate the rarity of NSCs. Bulk RNA sequencing (RNAseq) of NSCs requires pooling several mice, which impedes application to labor-intensive injury models. Alternatively, single cell RNAseq can profile hundreds to thousands of cells from a single mouse and is increasingly used to study NSCs. The consequences of the low RNA input from a single NSC on downstream identification of differentially expressed genes (DEGs) remains largely unexplored. Here, to clarify the role that low RNA input plays in NSC DEG identification, we directly compared DEGs in an oxidative stress model of cultured NSCs by bulk and single cell sequencing. While both methods yielded DEGs that were replicable, single cell sequencing DEGs derived from genes with higher relative transcript counts compared to all detected genes and exhibited smaller fold changes than DEGs identified by bulk RNAseq. The loss of high fold-change DEGs in the single cell platform presents an important limitation for identifying disease-relevant genes. To facilitate identification of such genes, we determined an RNA-input threshold that enables transcriptional profiling of NSCs comparable to standard bulk sequencing and used it to establish a workflow for in vivo profiling of endogenous NSCs. We then applied this workflow to identify DEGs after lateral fluid percussion injury, a labor-intensive animal model of traumatic brain injury. Our work suggests that single cell RNA sequencing may underestimate the diversity of pathologic DEGs but population level transcriptomic analysis can be adapted to capture more of these DEGs with similar efficacy and diversity as standard bulk sequencing. Together, our data and workflow will be useful for investigators interested in understanding and manipulating adult hippocampal NSC responses to various stimuli.

neuroscience↗

bioRxiv2021

Intracrine Vascular Endothelial Growth Factor Maintains Hippocampal Neural Stem Cell Quiescence

The vasculature is a key component of adult brain neural stem cell (NSC) niches. In the adult mammalian hippocampus, NSCs reside in close contact with a dense capillary network. How this niche is maintained is unclear. We recently found that adult hippocampal NSCs express vascular endothelial growth factor (VEGF), a soluble factor with chemoattractive properties for vascular endothelia. Here, we show that NSC-specific VEGF loss led to dissociation of NSCs from local vasculature but surprisingly found no changes in vascular density. Instead, we found that NSC-derived VEGF supports the motility of NSCs themselves via a cell internal signaling loop. We further found that this internal autocrine loop also independently maintained NSC quiescence cell autonomously. Combined, our findings suggest that NSCs maintain their populations via 2 mechanisms that are dependent on cell internal VEGF signaling: self-stimulated motility towards vasculature and cell autonomous maintenance of quiescence programs.

neuroscience↗

bioRxiv2019

Defining the adult hippocampal neural stem cell secretome: in vivo versus in vitro transcriptomic differences and their correlation to secreted protein levels

Recent evidence shows that adult hippocampal neural stem and progenitor cells (NSPCs) secrete a variety of proteins that affect tissue function. Though several individual NSPC-derived proteins have been shown to impact cellular processes like neuronal maturation and stem cell maintenance, a broad characterization of NSPC-secreted factors is lacking. Secretome profiling of low abundance stem cell populations is typically achieved via proteomic characterization of in vitro, isolated cells. Here, we analyzed the in vitro NSPC secretome using conditioned media from cultured adult mouse hippocampal NSPCs and detected over 200 different bioactive proteins with an antibody array. We next assessed the NSPC secretome on a transcriptional level with RNA sequencing (RNAseq) of cultured NSPCs. This comparison revealed that quantification of gene expression did not accurately predict relative protein abundance for several factors. Furthermore, comparing our transcriptional data with previously published single cell RNA sequencing datasets of freshly isolated hippocampal NSPCs, we found key differences in gene expression of secreted proteins between cultured and acutely isolated NSPCs. Understanding the components and functions of the NSPC secretome is essential to understanding how these cells may modulate the hippocampal neurogenic niche, as well as how they can be applied therapeutically. Cumulatively, our data emphasize the importance of using proteomic analysis in conjunction with transcriptomic studies and highlights the need for better methods of global unbiased secretome profiling.

neuroscience↗