Prss56, a novel marker of adult neurogenesis in the mouse brain.

Adult neurogenesis in the mammalian brain is restricted to specific regions, such as the dentate gyrus (DG) in the hippocampus and the subventricular zone (SVZ) in the walls of the lateral ventricles. Here, we used a mouse line carrying a knock-in of Cre recombinase in the Prss56 gene, in combination with two Cre-inducible fluorescent reporters (Rosa26 mTmG and Rosa26 tdTom ), to perform genetic tracing of Prss56-expressing cells in the adult brain. We found reporter-positive cells in three neurogenic niches: the DG, the SVZ and the hypothalamus ventricular zone. In the prospective DG, Prss56 is expressed during embryogenesis in a subpopulation of radial glia. The pattern of migration and differentiation of reporter-positive cells during development recapitulates the successive steps of DG neurogenesis, including the formation of a subpopulation of adult neural stem cells (NSC). In the SVZ, Prss56 is expressed postnatally in a subpopulation of adult NSC mainly localized in the medial-ventral region of the lateral wall. This subpopulation preferentially gives rise to deep granule and Calbindin-positive periglomerular interneurons in the olfactory bulb. Finally, Prss56 is also expressed in a subpopulation of α2-tanycytes, which are potential adult NSCs of the hypothalamus ventricular zone. Our observations suggest that some α2-tanycytes translocate their soma into the parenchyma and may give rise to a novel cell type in this territory. Overall, this study establishes the Prss56 Cre line as an efficient and promising new tool to study multiple aspects of adult neurogenesis in the mouse.