Wnt5a promotes differentiation and development of adult-born neurons in the hippocampus by noncanonical Wnt signaling.

In the adult hippocampus, new neurons are generated in the dentate gyrus. The Wnt signaling pathway regulates this process, but little is known about the endogenous Wnt ligands involved. We investigated the role of Wnt5a on adult hippocampal neurogenesis. Wnt5a regulates neuronal morphogenesis during embryonic development, and maintains dendritic architecture of pyramidal neurons in the adult hippocampus. Here, we determined that Wnt5a knockdown in the mouse dentate gyrus by lentivirus-mediated shRNA impaired neuronal differentiation of progenitor cells, and reduced dendritic development of adult-born neurons. In cultured adult hippocampal progenitors (AHPs), Wnt5a knockdown reduced neuronal differentiation and morphological development of AHP-derived neurons, whereas treatment with Wnt5a had the opposite effect. Interestingly, no changes in astrocytic differentiation were observed in vivo or in vitro, suggesting that Wnt5a does not affect fate-commitment. By using specific inhibitors, we determined that Wnt5a signals through CaMKII to induce neurogenesis, and promotes dendritic development of newborn neurons through activating Wnt/JNK and Wnt/CaMKII signaling. Our results indicate Wnt5a as a niche factor in the adult hippocampus that promotes neuronal differentiation and development through activation of noncanonical Wnt signaling pathways.

Local Klotho Enhances Neuronal Progenitor Proliferation in the Adult Hippocampus.

Klotho is an aging-related protein associated with hippocampal cognitive performance in mammals. Klotho regulates progenitor cell proliferation in non-neuronal tissues, but its role in adult hippocampal neurogenesis (AHN) has not been explored. Klotho expression in the adult mouse hippocampus was examined by immunofluorescence and polymerase chain reaction. AHN was evaluated in the hippocampus of klotho knock-out mice (KO), klotho KO/vitamin D-receptor mutant mice, and in a model of local klotho hippocampal knockdown. The recombinant Klotho effect on proliferation was measured in mouse-derived hippocampal neural progenitor cells. Hippocampal-dependent memory was assessed by a dry-land version of the Morris water maze. Klotho was expressed in the granular cell layer of the adult Dentate Gyrus. AHN was increased in klotho KO mice, but not in klotho KO/vitamin D-receptor mutant mice. Inversely, local downregulation of hippocampal Klotho diminished AHN. Recombinant Klotho increased the proliferation rate of neural progenitors. Downregulation of hippocampal Klotho correlated with a decreased performance in hippocampal-dependent memory. These results suggest that Klotho directly participates in regulating AHN. Our observations indicate that Klotho promotes proliferation, AHN and hippocampal-dependent cognition. Increased neurogenesis in klotho KO mice may be secondary to the activation of other pathways altered in the model, such as vitamin D.