In the adult vertebrate brain, new neurons can be generated lifelong, migrate to specific target sites and integrate into pre-existing circuits. This evolutionary conserved process of adult neurogenesis is driven by a small group of undifferentiated glial-like neural stem cells (NSCs), which persist in the fully mature brain. How physiological states dynamically control NSC behavior and what could be the functional relevance of stem cell heterogeneity for adaptive brain plasticity during adulthood remain to be fully elucidated. Recently, our lab has shown that pregnancy in mice triggers transient production of short-lived, yet behaviorally-relevant neurons in one of the two main niches of the adult rodent brain: the ventricular-subventricular zone lining the lateral ventricles. In contrast to mice, adult neurogenesis in teleost fish is widespread and continuous throughout life. Interestingly, Zebrafish displays highly homologous niche territories and common molecular pathways for stem cell maintenance, as well as the heterogeneous nature of adult NSCs. Therefore, Zebrafish is a powerful model to further characterize and mechanistically dissect physiologically-relevant NSC properties. However, whether mating behavior in Zebrafish - species with no obvious parental care need - leads to increased NSC proliferation in regionally and functionally distinct NSC niches has not been explored so far. We tackle this question using the GFAP:GFP transgenic line to label adult NSCs and compare stem cell proliferation in mated, non-mated, as well as “reproduction-learning” females (“pseudo-virgin” controls). Brains were stained for GFAP, Sox2 and PCNA to differentiate radial glial NSCs and dividing progenitors, at different anatomical levels.

Our preliminary observations reveal a regionally-restricted increase of NSC proliferation, within functionally-distinct niche domains in the female Zebrafish brain. This suggests the existence of a spatially - and temporally - controlled neurogenesis in the adult fish brain, in response to specific physiological needs, similarly to what has been recently described in adult mouse brain during pregnancy and motherhood. Altogether, our data point to a conserved neurogenic response in two evolutionary-distant vertebrate species occupying totally distinct ecosystems, with possibly convergent functions that are still to be discovered.