ascl1b and neurod1 are both expressed in pancreatic endocrine precursors. (A-J) Double fluorescent WISH comparing the expression of ascl1b and neurod1 with the expression of the pancreatic factor sox4b (A, B, F, G), pdx1 (D, E) or with the insulin hormone (I, J) at early stages (12 to 16 hpf). The arrows point to a cell neurod1+/sox4b- (G) or neurod1+/ascl1b- (H). The arrowheads point to a cell neurod1+/ascl1b+ (H). Z-plane confocal images. All views are ventral with anterior part to the left. (K) Diagram illustrating the time windows for the expression of ascl1b, neurod1 and the pancreatic hormones. Scale bars : 50 µm hpf, hours post fertilization; WISH, whole-mount in situ hybridization.