Single-Cell Transcriptomics and Fate Mapping of Ependymal Cells Reveals an Absence of Neural Stem Cell Function

Abstract

Ependymal cells are multi-ciliated cells that form the brain's ventricular epithelium and a niche for neural stem cells (NSCs) in the ventricular-subventricular zone (V-SVZ). In addition, ependymal cells are suggested to be latent NSCs with a capacity to acquire neurogenic function. This remains highly controversial due to a lack of prospective in vivo labeling techniques that can effectively distinguish ependymal cells from neighboring V-SVZ NSCs. We describe a transgenic system that allows for targeted labeling of ependymal cells within the V-SVZ. Single-cell RNA-seq revealed that ependymal cells are enriched for cilia-related genes and share several stem-cell-associated genes with neural stem or progenitors. Under in vivo and in vitro neural-stem- or progenitor-stimulating environments, ependymal cells failed to demonstrate any suggestion of latent neural-stem-cell function. These findings suggest remarkable stability of ependymal cell function and provide fundamental insights into the molecular signature of the V-SVZ niche.

A tale of two cousins: Ependymal cells, quiescent neural stem cells and potential mechanisms driving their functional divergence

“…A) or in neuroblasts (not shown) . Because we have demonstrated the presence of Sox2 protein in ependymal cells, qNSCs, aNSCs, and neuroblasts , as well as the expression of Sox2 mRNA in these populations (Fig. A), it may be that TF activity is regulated post‐translationally perhaps at the level of chromatin remodeling.…”

“…Although expression of most transcription factors (Sox2, Sox9, Klf9, Hes1 etc.) was similar across ependymal cells and qNSCs [17], there were several highly discrepant GRNs between these cell types ( Fig. 1B-D).…”

“…Recently, we identified a novel transgenic fate mapping model for ependymal cells, based on the unique expression of aSMA within ependymal cells in the subventricular zone (SVZ) niche, and its absence in neural lineages [17] which has now been independently replicated [18]. We were able to directly test the response of ependymal cells to injury, independent of NSCs, and assemble the first true molecular profile of ependymal cells and the neural stem cell lineage from the adult SVZ [17]. Indeed, this work confirmed a lack of overt stem cell function for ependymal cells and provided a compelling comparison to uncover fundamental insights into the molecular signatures underlying NSCs at various stages of activation.…”

Developmental dynamics of neurogenesis and gliogenesis in the postnatal mammalian brain in health and disease: Historical and future perspectives

“…B. Johansson et al, 1999). Since then, there have been a number of studies that support both ideas (Kaur, Rathnasamy, & Ling, 2016;Luo et al, 2015;Mirzadeh et al, 2008;Shah et al, 2018). At the end, it has turned out that the soma and/or apical processes of NSCs actually reside in both the ependymal and subependymal regions, and, thus, cells with a NSCs capacity and typical ependymal cells with motile multi cilia coexist in the ependymal layer (Abdelhamed et al, 2018;Coletti et al, 2018;Del Bigio, 2010;Guo et al, 2010;S.…”

GemC1 is a critical switch for neural stem cell generation in the postnatal brain

“…Although adult NSCs retain key epithelial properties of their progenitors, radial glial cells (Mirzadeh, Merkle, Soriano‐Navarro, Garcia‐Verdugo, & Alvarez‐Buylla, ), the ventricular surface in the adult brain displays a completely different pattern, as the small apical domains of NSCs are surrounded by the large apical surfaces of multiciliated ependymal cells (Mirzadeh et al, ). In contrast to NSCs, ependymal cells remain post‐mitotic and do not possess progenitor properties under physiological conditions (Shah et al, ; Spassky et al, ).…”