Fig. 1. Expression profile of Notch pathway genes during otic placode development. (A) Schematic views of embryos during otic placode development. The dotted line indicates the approximate level of sections in C. (B) Summary showing the onset of Notch1 (blue), jagged 1 (Jag1; brown), delta-like 1 (Dll1; green) and Hes1 (yellow-orange) expression with respect to Pax2 expression (pink-red) and Wnt signaling (purple). Preceding neurogenesis, Dll1 expression is high in the pre-otic field but progressively becomes weaker in the placode. During neurogenesis, Dll1 localizes to neuroblasts. (C) Sections comparing the expression of Wnt6, Notch1, Jag1, Dll1 and Hes1 with respect to Pax2 (red) and the Wnt reporter (blue). Arrowheads mark the pre-otic field. Brackets mark the extent of the otic placode. (D) Top row, Jag1 expression in the anterior and posterior pre-otic field; bottom row, consecutive serial sections through the pre-otic field immunostained with anti-Pax2 and anti-Jag1 antibodies, respectively. Scale bars: 50 µm.