| |
Fig. 4. Induction of hindbrain by noggin and FGF.
Expression of Krox 20 (purple) and Muscle actin
(blue) in stage 24 control embryos (A) and in
stage 10.25 ectoderm treated with 1 mg/ml noggin
(B), 50 ng/ml FGF (C), and the mixture of noggin
and FGF (D) after culture to stage 24. Whole
embryos express Krox 20 in two stripes in the
developing hindbrain, while muscle actin is
expressed in the somites. Noggin does not induce
either gene. FGF can induce muscle actin (1/13 in
this experiment); induction of muscle is highly
stage-dependent and thus shows some variability
between experiments (compare to Fig. 1). FGF
may induce a low level of unlocalized Krox 20.
FGF + noggin explants show Krox 20 expression
localized to a stripe in the central region of the
elongated structure, and no muscle actin
expression. |
