Adult Neurogenesis and Neuronal Regeneration in the Central Nervous System of Teleost Fish

Abstract

In contrast to mammals, teleost fish exhibit an enormous potential to produce new neurons in the adult central nervous system and to replace damaged neurons by newly generated ones. In the gymnotiform fish Apteronotus leptorhynchus, on average, 100,000 cells, corresponding to roughly 0.2% of the total population of cells in the adult brain, are in S-phase within any 2-h period. As in all other teleosts examined thus far, many of these cells are produced in specific proliferation zones located at or near the surface of ventricular, paraventricular, and cisternal systems, or in areas that are likely derived from proliferation zones located at ventricular surfaces during embryonic development. The majority of cells born in such proliferation zones migrate within the first few weeks following their generation to specific target areas. In the cerebellum, where approximately 75% of all brain cells are born during adulthood, cells originate from the molecular layers of the corpus cerebelli and the valvula cerebelli partes lateralis and medialis, as well as from the eminentia granularis pars medialis. From these proliferation zones, the young cells migrate to the associated granule cell layers or to the eminentia granularis pars posterior, respectively. In the course of their migration, the young cells appear to be guided by radial glial fibers. Upon arrival at their target region, approximately 50% of the young cerebellar cells undergo apoptosis. The remaining cells survive for the rest of the fish’s life, thus contributing to permanent brain growth. At least some cells differentiate into granule cell neurons. The potential to produce new neurons, together with the ability to guide the young cells to their target areas by radial glial fibers and to eliminate damaged cells through apoptosis, also forms the basis for the enormous regenerative capability of the central nervous system of Apteronotus, as demonstrated in the cerebellum and spinal cord. A factor involved in the cerebellar regeneration appears to be somatostatin, as the expression of this neuropeptide is up-regulated in a specific spatio-temporal fashion following mechanical lesions. Besides its involvement in neuronal regeneration adult neurogenesis in Apteronotus, and possibly teleost fish in general, appears to play a role in providing central neurons to match the growing number of sensory and motor elements in the periphery, and to establish the neural substrate to accommodate behavioral plasticity.

Cellular response after crush injury in adult zebrafish spinal cord

“…Fish CNS is capable of neurogenesis in adult life after injury and shows a remarkable ability for neural regeneration (Zupanc, 1999(Zupanc, , 2001Zupanc et al, 2005;Reimer et al, 2008). Studies on neurogenesis in spinal cord are still scarce (Kaslin et al, 2008) and little is known about the origin, fate, and differentiation of the produced cells, their survival as well as functional integration.…”

Expression of the transcription factor Olig2 in proliferating cells in the adult zebrafish telencephalon

“…Zebrafish has recently emerged as an anamniote model in adult neural stem cell research due to its high proliferative and regenerative potential in the central nervous system (CNS) that exceeds by far mammalian capabilities (Zupanc, 2001(Zupanc, , 2006Adolf et al, 2006;Grandel et al, 2006;Chapouton et al, 2007). In the adult mammalian brain, two regions display neurogenic potential: The subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the dentate gyrus located in the hippocampus harbour neural stem cells with astrocytic features generating predominantly neurons (Doetsch et al, 1999;Gage, 2000;Seri et al, 2001;Alvarez-Buylla and Garcia-Verdugo, 2002;Kempermann, 2002;Garcia et al, 2004).…”

Desarrollo de la Médula Espinal de Salmón (Salmo salar) durante el Período Post-eclosional

“…El aumento del número de neuronas se puede explicar por neurogénesis post-eclosión, como ocurre en otros teleósteos (Birse et al, 1980;Zupanc, 2001). Este estudio indica que al momento de la eclosión, el sistema nervioso está muy indiferenciando, y que durante las primeras semanas de vida del alevín ocurre la diferenciación de las neuronas y neurogénesis.…”