Fig. 4

Synergistic loss of the initiation of bmp2b/4 in rdr;alk8 double-morphants. WT embryos were injected with indicated MO(s) at subinhibitory concentrations and pictured live at 30 hpf (A–D) or were processed for in situ hybridization with bmp2b (E–H) or bmp4 (I–L) probes at sphere (4 hpf) and shield (6 hpf) stages, respectively. All views are lateral, anterior (A–D) or ventral (E–L) to the left. (A) Uninjected control. (B and C) A minority of low-dose single-morphants showed C1–C2 phenotypes (Table 1). Arrows in B and C show loss of ventral tail fin; arrowhead in C shows absence of ventral vein and yolk tube. (D) Double-morphants displayed a C4–C5 phenotype ventroposteriorally (arrow) and a Zrdr^MO phenotype anteriorally (arrowheads). (E–I) WT expression patterns of bmp2b and bmp4. (F and J) All low-dose alk8 morphants examined (n = 45) initiated bmps properly. (G and K) Only 4% (n = 50) of rdr^MO-injected embryos were slightly affected in the initiations of bmp2b and bmp4, correlating with the frequency of C2 phenotypes among rdr morphants observed at 30 hpf (C, Table 1). (H and L) All double-morphants examined (n = 50) failed to initiate bmp.