Fig. 7. Gli1 accounts for the differential sensitivity of the MIZ and LIZ to E(Spl) neurogenesis inhibitors. (A-H') Zebrafish embryos analyzed at the 3- to 5-somite stage for neurog1 and pax2.1 (color-coded) and flat-mounted, anterior up. Brackets, MIZ; blue arrows, ectopic neurog1 expression. In the absence of Gli1, which in itself has no effect on neurog1 expression (compare E with A), MIZ cells are unaffected by the loss of Her5 or Her11 (F,G, compare with B,C). MIZ and LIZ cells become concomitantly affected by a further downregulation of E(Spl) activity (loss of both Her5 and Her11), when they both upregulate neurog1, in an identical manner (H,H', compare with D).