At E8.5 Wnt8b is expressed at the dorsal prosencephalic vesicle (A). At E10.5 expression is observed at the dorsal diencephalic-telencephalic boundary (DTB) (arrow in B), the dorsal-most part of the telencephalon (Tel), and the hypothalamus (Hy) (B). Wnt8b expression is seen in the E12.5 and E14.5 dorsomedial telencephalon (DmTel), with stronger levels of expression in the cortical hem (hem) (C-F). No expression is observed in the choroid plexus (ChP) (C,E,F). At E14.5 Wnt8b expression is also detected in the telencephalic roof plate (trp) (F). By E18.5, telencephalic expression of Wnt8b is restricted to the lateral margin of the hippocampal fimbria (fi) (G,G’). In the developing diencephalon, Wnt8b is strongly expressed in the E12.5 and E14.5 eminentia thalami (EmT) (C,E). Expression is also abundant in the ventricular zone of the E12.5 hypothalamus, (H). A similar, but more restricted hypothalamic expression domain is observed at E14.5 (I,I’). In addition, a small expression domain is observed between the dorsal and ventral thalamus (DT, VT) at the level of the zona limitans intrathalamica (ZLI) (I’). Panels G’ and I’ show higher magnifications of the boxed areas in G and I respectively. Scale bars: A, 500 μm; B, 50 μm; C-F, G’, H, I’, 200 μm; G, I, 400 μm. Abbreviations: Hy: hypothalamus; ET, epithalamus.