Clonal analysis by distinct viral vectors identifies bona fide neural stem cells in the adult zebrafish telencephalon and characterizes their division properties and fate

Abstract

SUMMARYNeurogenesis is widespread in the zebrafish adult brain through the maintenance of active germinal niches. To characterize which progenitor properties correlate with this extensive neurogenic potential, we set up a method that allows progenitor cell transduction and tracing in the adult zebrafish brain using GFP-encoding retro-and lentiviruses. The telencephalic germinal zone of the zebrafish comprises quiescent radial glial progenitors and actively dividing neuroblasts. Making use of the power of clonal viral vector-based analysis, we demonstrate that these progenitors follow different division modes and fates: neuroblasts primarily undergo a limited amplification phase followed by symmetric neurogenic divisions; by contrast, radial glia are capable at the single cell level of both self-renewing and generating different cell types, and hence exhibit bona fide neural stem cell (NSC) properties in vivo. We also show that radial glial cells predominantly undergo symmetric gliogenic divisions, which amplify this NSC pool and may account for its long-lasting maintenance. We further demonstrate that blocking Notch signaling results in a significant increase in proliferating cells and in the numbers of clones, but does not affect clone composition, demonstrating that Notch primarily controls proliferation rather than cell fate. Finally, through long-term tracing, we illustrate the functional integration of newborn neurons in forebrain adult circuitries. These results characterize fundamental aspects of adult progenitor cells and neurogenesis, and open the way to using virus-based technologies for stable genetic manipulations and clonal analyses in the zebrafish adult brain.

Distinct roles of neuroepithelial-like and radial glia-like progenitor cells in cerebellar regeneration

“…In agreement, recent imaging and lineage tracing studies in the telencephalon of rodents and zebrafish suggest that the neural stem and progenitor cell pool is gradually exhausted over time and that this may impact neural regeneration (Encinas et al, 2011;Rothenaigner et al, 2011;Barbosa et al, 2015;Calzolari et al, 2015). In the adult zebrafish cerebellum, we detected several-fold activation of VZ progenitors after injury, suggesting that quiescent cells are activated.…”

Notch Signaling Controls Generation of Motor Neurons in the Lesioned Spinal Cord of Adult Zebrafish

“…This is similar to the role of Notch during constitutive neurogenesis in the forebrain of zebrafish (Chapouton et al, 2010;Rothenaigner et al, 2011) and is compatible with a role of Notch signaling in maintaining progenitor pools. Remarkably, the function of Notch in the regenerating spinal cord of zebrafish is similar to its proposed role in the lesioned spinal cord of rats, where Notch is strongly upregulated and acts as an anti-neurogenic factor in vitro (Yamamoto et al, 2001).…”

Zebrafish midbrain slow-amplifying progenitors exhibit high levels of transcripts for nucleotide and ribosome biogenesis

“…In the zebrafish telencephalon, radial glial cells predominantly undergo symmetric gliogenic divisions, which amplify the NSC pool (Rothenaigner et al, 2011). The reason why fish seem to preferentially use this growth mode remains unknown, but it has been shown that a planar orientation of mitoses in neuroepithelia is required for the maintenance of layered structures (Peyre et al, 2011).…”