Fig. 6

Fig. 6 Comparison of shh Expression in cyc Mutant Embryos and Wild-Type Embryos
The right-hand panels show cyc mutant embryos; the left-hand ones show wild-type embryos. Animal pole and lateral views are shown; rostral is to the left. Embryos were simultaneously hybridized with a probe for pax-2 that serves as a positional marker for the posterior midbrain (asterisk).
(A and B) Embryos at the end of gastrulation. Midline shh expression is marked by an arrowhead. Note the absence of the shh transcript in the head process rostral to the pax-2 expression in the mutant embryo (B).
(C and D) Embryos at the 5 somite stage. shh expression in the ventral neural keel is indicated by arrowheads (C); its absence in cyc embryos
(D) is indicated by arrowheads.
(E and F) shh expression in the tail bud at the end of somitogenesis. Note that shh is absent from the ventral CNS of cyc mutant embryos.
Abbreviations: fp, floor plate (in cyc, fp marks the region where the floor plate would normally form); and nc, notochord.