Ntl and non-canonical Wnts synergistically regulate the expression of bmp4, but not Fgf genes. At 16 somites, fgf8 is expressed in the brain and somites, and posteriorly in ectoderm and mesoderm in the wild type (A) and in the ppt (B) and kny (C) mutants. Despite normal anterior fgf8 expression in ntl mutants (D), tail expression is extremely reduced but is not further reduced in ppt;ntl (E) or kny;ntl (F) double mutants. At 16 somites, sef expression in the brain, somites and tail is comparable in wild-type (G), ppt (H) and kny (I) embryos, but is reduced in ntl (J) mutants. Expression of sef is not further reduced in ppt;ntl (K) and kny;ntl (L) mutants. At five somites, bmp4 is expressed in the prechordal plate and tailbud of wild-type (M), ppt (N) and kny (O) embryos. In ntl mutants (P), tailbud expression of bmp4 is severely reduced and is absent in ppt;ntl (Q) and kny;ntl (R) double mutants. (A-L) Lateral views. (M-R) Dorsal flat mounts; arrowheads indicate tailbud. Scale bars=100 μm.