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Fig. 5. Localization of HNF-3/3 mRNA in frog embryos. Xenopus embryos at the early gastrula stage (stage 10 (A)), late neurula/early tailbud
stage (stage ~ 24, (B)) and tadpole stage (stage 36, (C)) are shown after whole mount in situ hybridization with HNF-3/3 antisense RNA probes.
(A) View from the animal pole showing HNF-3/3 expression in the prospective endodermal region of the dorsal lip (Spemann's organizer). The
arrowhead depicts the dorsal lip. The animal cap cells of this embryo were removed to prevent background labelling accumulation in the
blastocoel. (B,C) Lateral views of the head region of early tailbud and tadpole stage showing HNF-3/3 expression in the pharyngeal endoderm
and ventral midbrain (B,C), hindbrain and spinal cord (C). Note the more dorsally located neural tube cells expressing this gene in the anterior
midbrain at tadpole stages (C). Anterior is to the left. Arrowheads indicate planes of section for E and F. (D) Lateral view of an exogastrula
embryo at stage ~ 30 showing HNF-3/3 expression only in the anterior endodermal region. No labelling was observed in the neural ectoderm.
The ectodermal portion of the exogastrula displays a typical cavity (top). (E,F) Cross sections of tadpole stage (stage 36) embryos after labelling
in whole mount as shown in (C). HNF-3/3 expression in the midbrain (E) occupies a wider region at the ventral midline of the neural tube than in
the hindbrain (F). Scale bars: (A) 120/zm; (B,C) = 100/zm; (D) = 200 tzm; (E,F) = 10/xm. |