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Fig. 2. WISH analysis of Wnt4 mRNA expression in the VBI and DLP in Xenopus embryos. (A–D) Wnt4 transcripts are observed in the neural plate and in the VBI and DLP mesoderm in stage-21 embryos. (B) Transverse section at site indicated by dashed line in A. (C) Closer view of dorsolateral and ventral regions (D). Wnt4 signal is clearly excluded from overlying ectoderm (C and D). Wnt4 transcripts in DLP are sustained in embryos at stage 25 (E) and restricted to pronephric region in embryos at stage 28 (F) and stage 34 (G). Wnt4 is clearly expressed in VBI (E–H) and specifically in the mesodermal layers (arrowhead in H), but not in overlying ectoderm (arrow in H). Wnt4 is also expressed in the brain, branchial arches, and lateral plate mesoderm (arrowhead in C). dlp, dorsal lateral plate, dlpm, dorsal lateral plate mesoderm; ecto, ectoderm; endo, endoderm; hb, hindbrain; hend, hepatic endoderm; mb, midbrain; mhb, midbrain–hindbrain boundary; meso, mesoderm; np, neural plate; nt, neural tube; pt, pronephric tubules; vbi, ventral blood island. |