Fig. 6

Expression of neural patterning genes is disrupted in zebrafish embryos with perturbed CREB function. 24 hpf zebrafish injected with 75–125 pg lacZ control (A–E), CREB-FY (F–J) or CREB-M1 (K–O) capped mRNA were stained by wholemount in-situ hybridization (WISH) for patterning markers of the midbrain (Otx2; A, F, K), midbrain–hindbrain boundary (Pax2.1; B–C, G–H, L–M), hindbrain rhombomeres (Krox20; D, I, N) and floor-plate (Shh; E, J, O). Otx2 expression in the midbrain (MB) is decreased in CREB-M1 injected embryos (compare K with A), but no increase is visible in the majority of CREB-FY injected embryos (compare F with A) relative to controls. The midbrain-specific localization of Otx2 is unchanged. Expression of Pax2.1 in isthmic organizer cells of the midbrain–hindbrain boundary (MHB) is unchanged, although a decrease in Pax2.1 is observed in the hindbrain neurons (HBN) of most CREB-FY (G, H) and CREB-M1 (L, M) injected fish relative to controls (B, C). Pax2.1 expression in the optic stalk (OS) and otic vesicle precursors (OV) is largely unchanged. Krox20 expression in rhombomeres 3 and 5 of both CREB-FY (I) and CREB-M1 (N) injected embryos is unchanged compared to controls (D). Shh mRNA (E, J, O) localizes to the floor plate neural organizer (FP) and the forebrain/midbrain boundary in the developing diencephalon (FMB). Both CREB-FY (J) and CREB-M1 (O) injected embryos show minor disruption of the floor plate, relative to lacZ injected controls (E), although the specific localization and distribution of cells along the anterior–posterior axis remains unaltered. The distribution of Shh demarcating the forebrain/midbrain boundary is largely unchanged in CREB-FY or CREB-M1 injected mutants relative to controls. Orientation is shown in either lateral (L) or dorsal (D) views; anterior in all pictures is to the left.