Fig. 2

Fig. 2 Localization of shh Transcripts in Wild-Type Zebrafish Embryos
Whole embryos were hybridized with digoxygenin-labeled shh riboprobe.
(A and B) Dorsal (A) and lateral (8) views of shh expression at 70% epiboly (the extent of spreading of the blastoderm over the yolk toward the vegetal pole is used as a staging index during epiboly) (Westerfield, 1989). Note the restriction of transcript to the inner cell layer (hypoblast).
(C) Lateral view of an embryo at the 100% epiboly bud stage; by this stage, shh expression extends to the animal pole.
(D) Embryo at 11.5 hr of development. The arrowhead denotes the row of floor plate cells in the neural keel and the underlying notochord cells that express shh.
(E) Embryo at 20 hr of development (22 somites). The arrowhead indicates the notochord that has now switched off shh expression; expression persists at high levels in the floor plate cells (shown in detail in [G]).
(F) Embryo at 26 hr of development (end of somitogenesis). The arrowhead marks shh expression in the telencephalon.
(G) Detail of the trunk region of a 20 hr embryo, similar to that shown in (E), showing shh expression exclusively in the floor plate.
(H and I) Lateral view (H) and top view (I) of an embryo at 33 hr of development, showing shh expression at the posterior end of the pectoral fin bud (arrowhead) and in the first gill (arrow).
(J) Pectoral fin bud of a 33 hr embryo; note that shh expression is confined to the mesoderm and that the superficial epithelial cell layer is devoid of shh expression.
Abbreviations: d, dorsal; eb, epiblast; fp, floor plate; hb, hypoblast; hp, head process; nc, notochord; nk, neural keel; and tb, tail bud.