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Fig. 4 Nodal-independent regulation of ntl. (A-F) Animal pole views of ntl RNA in situ hybridizations at 6 hpf. (A) A wild-type embryo. Embryos injected with lefty (B) (100% with displayed expression, n=61), lefty + wnt8 (C) (100% with displayed expression, n=42), lefty + Alk3* (D) (85% increased expression compared with B, n=40), lefty + wnt8 + Alk3* (E) (87% increased expression compared with B, n=79), lefty + dnBMPr (F) (80% no expression, n=40). (G) Luciferase assays performed at 6 hpf with the -2.1 kb ntl promoter fragment in wild-type embryos and embryos injected with RNA encoding Wnt8 and/or Alk3*. ΔE1 = -2.1 kb ntl promoter where E1 (40 bp) was present. ΔE1ΔE2 = -2.1 kb ntl promoter where E1 and E2 were removed.