S07-03 Asymmetric division in zebrafish neural tube is a non-stochastic event and the neuron results from the daughter that inherits the apical domain

Emerging evidence suggests that neurogenesis may occur within the adult hypothalamus but the character and location of hypothalamic neural stem cells is unknown. We have identified a stem cell niche, confined to the central/posterior hypothalamus. Niche-derived cells require FGF signalling to maintain their proliferation exvivo, and proliferate, but do not differentiate, in response to exogenous FGF2 invivo. Enhanced proliferation of hypothalamic neural stem cells occurs concommitant with a reduction in proliferating progenitors. We define two distinct FGF2-dependent cell types, whose position correlates with particular tanycyte populations. Cells that map to GFAP+ive tanycytes show hallmarks of classical neural stem cells; cells that map to adjacent GFAPive ventral a2 tanycytes show characteristics intermediate beween stem and progenitor cells. Both cell types appear largely quiescent invivo, but endogenous FGFs may govern their proliferation: FGF ligands are expressed specifically within different tanycyte populations and FGF signalling elements are stochastically detected in tanycyte cells.