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Neural stem cells (NSCs) are progenitor cell populations generating glial cells and neurons and endowed with long-lasting self-renewal and differentiation potential. While some neural progenitors (NPs) in the embryonic nervous system are also long-lived and match this definition, the term NSC classically refers to such progenitor types in the adult. With the discovery of extensive NSC populations in the adult brain of Danio rerio (zebrafish) and of their high neurogenic activity, including for neuronal regeneration, this model organism has become a powerful tool to characterize and mechanistically dissect NSC properties. On these bases, this article will consider NSCs in the adult zebrafish brain, with a focus on its most extensively characterized domain, the telencephalon (notably its dorsal part, the pallium). Whenever necessary, we will also refer to other brain subdivisions, embryonic processes, and the mouse adult brain, whether for comparative purposes or because more information is available in these other systems.

In most vertebrates, adult neural stem cells (NSCs) continuously give rise to neurons in discrete brain regions. A critical process for maintaining NSC pools over long periods of time in the adult brain is NSC quiescence, a reversible and tightly regulated state of cell-cycle arrest. Recently, lysosomes were identified to regulate the NSC quiescence-proliferation balance. However, it remains controversial whether lysosomal activity promotes NSC proliferation or quiescence, and a finer influence of lysosomal activity on NSC quiescence duration or depth remains unexplored. Using RNA sequencing and pharmacological manipulations, we show that lysosomes are necessary for NSC quiescence maintenance. In addition, we reveal that expression of psap, encoding the lysosomal regulator Prosaposin, is enriched in quiescent NSCs (qNSCs) that reside upstream in the NSC lineage and display a deep/long quiescence phase in the adult zebrafish telencephalon. We show that shRNA-mediated psap knockdown increases the proportion of activated NSCs (aNSCs) as well as NSCs that reside in shallower quiescence states (signed by ascl1a and deltaA expression). Collectively, our results identify the lysosomal protein Psap as a (direct or indirect) quiescence regulator and unfold the interplay between lysosomal function and NSC quiescence heterogeneities., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

In vertebrates, fast saltatory conduction along myelinated axons relies on the node of Ranvier. How nodes assemble on CNS neurons is not yet fully understood. We previously described that node-like clusters can form prior to myelin deposition in hippocampal GABAergic neurons and are associated with increased conduction velocity. Here, we used a live imaging approach to characterize the intrinsic mechanisms underlying the assembly of these clusters prior to myelination. We first demonstrated that their components can partially preassemble prior to membrane targeting and determined the molecular motors involved in their trafficking. We then demonstrated the key role of the protein β2Na v for node-like clustering initiation. We further assessed the fate of these clusters when myelination proceeds. Our results shed light on the intrinsic mechanisms involved in node-like clustering prior to myelination and unravel a potential role of these clusters in node of Ranvier formation and in guiding myelination onset., (© 2020 Wiley Periodicals, Inc.)

The plasticity of the central nervous system (CNS) in response to neuronal activity has been suggested as early as 1894 by Cajal (1894). CNS plasticity has first been studied with a focus on neuronal structures. However, in the last decade, myelin plasticity has been unraveled as an adaptive mechanism of importance, in addition to the previously described processes of myelin repair. Indeed, it is now clear that myelin remodeling occurs along with life and adapts to the activity of neuronal networks. Until now, it has been considered as a two-part dialog between the neuron and the oligodendroglial lineage. However, other glial cell types might be at play in myelin plasticity. In the present review, we first summarize the key structural parameters for myelination, we then describe how neuronal activity modulates myelination and finally discuss how other glial cells could participate in myelinic adaptivity., (Copyright © 2020 Ronzano, Thetiot, Lubetzki and Desmazieres.)

In the nervous system, myelin is a complex membrane structure generated by myelinating glial cells, which ensheathes axons and facilitates fast electrical conduction. Myelin alteration has been shown to occur in various neurological diseases, where it is associated with functional deficits. Here, we provide a detailed description of an ex vivo model consisting of mouse organotypic cerebellar slices, which can be maintained in culture for several weeks and further be labeled to visualize myelin.

Immunochemistry (immunocytochemistry for cells and immunohistochemistry for tissues) is a method used to label specific antigens, based on highly specific antibody-epitope interactions. The resulting labeling can be visualized and imaged through microscopy adapted to the type of detection system used (fluorophore, peroxidase, etc.). In the nervous system, myelin is a complex membrane structure, generated by myelinating glial cells, which ensheath axons and facilitate electrical conduction. Myelin alteration has been shown to occur in various neurological diseases, in which it is associated with functional deficits. Here, we focus on myelin detection by immunofluorescence using immunochemistry protocols based on antibodies directed against major myelin proteins.