Expression patterns of regional brain markers in wild-type and GAK morphant embryos. (A-D) krox20 expression in (A, C) uninjected and (B, D) GAK morphant embryos at (A, B) 12- to 14-somite stage and (C, D) 24 hpf. At 12- to 14-somite stage, krox20 expression in the rhombomeres 3 (R3) and 5 (R5) of the control and injected embryos appears comparable. However, at 24 hpf, the spacing between R3 and R5 is dramatically reduced in GAK morphants (white arrowhead). (E, F) Lateral and (G, H) dorsal views of fgf8 expression in (E, G) wild-type and (F, H) GAK morphant embryos at 18- to 20-somite stage. The domains of fgf8 expression in the forebrain and mid-hindbrain boundary (MHB) are up-regulated in GAK morphants (black arrows). (I, J) shh expression in (I) wild-type and (J) GAK morphants at the 18-somite stage. In all the lateral views, anterior is to the left and dorsal is up. d, ventral diencephalon; f, floor plate; os, optic stalk; s, somite; t, telencephalon; dd, dorsal diencephalon; tb, tailbud. Scale Bar, 100 μm.