Wnt and Shh signals regulate neural stem cell proliferation and differentiation in the optic tectum of adult zebrafish.

Adult neurogenesis occurs more commonly in teleosts, represented by zebrafish, than in mammals. Zebrafish is therefore considered a suitable model to study adult neurogenesis, for which the regulatory molecular mechanisms remain little known. Our previous study revealed that neuroepithelial-like neural stem cells (NSCs) are located at the edge of the dorsomedial region. We also showed that Notch signaling inhibits NSC proliferation in this region. In the present study, we reported the expression of Wnt and Shh signaling components in this region of the optic tectum. Moreover, inhibitors of Wnt and Shh signaling suppressed NSC proliferation, suggesting that these pathways promote NSC proliferation. Shh is particularly required for maintaining Sox2-positive NSCs. Our experimental data also indicate the involvement of these signaling pathways in neural differentiation from NSCs.