Expression of shh and Alx-4 during chick limb bud outgrowth. (A) Right
side of a stage
17/18 chick stained with Alx-4. Arrows indicate lateral plate mesoderm
lacking detectable Alx-4 expression. (B) Contralateral side of the embryo
shown in A stained for shh expression. Arrows on the left mark the anterior
and posterior aspect of the limb field. Arrowheads on the right indicate
shh expression in the notochord/neural tube. Note that no expression is
detected in the presumptive limb region. (C) Higher magnification of the
wing region shown in A. Arrows mark the anterior and posterior margin of
the wing field. (D) Shh expression in a stage 19 wing bud. The arrows mark
the margins of the wing bud. (E) Contralateral wing of the embryo shown
in D stained for Alx-4 expression. Arrows again indicate wing margins.
(F,G) Contralateral wing buds at stage 20 stained for shh (F) or Alx-4
(G) expression. (H-J) Alx-4 expression in wing buds at stage 21 (H), 22
(I) and 25 (J).
![[Up]](../gifs/arrow-3.gif){kind=icon}