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Fig. 6 Rescue of ventral cell fates in sbn mutant cells by exogenous bmp4 mRNA or DNA (A-D) and wild-type environment (E-H); 36 hpf, lateral view. (A,B) Injection of 1 pg Xbmp4 mRNA into a sbn homozygous mutant embryo from a cross of two homozygous mutant parents. The injected embryo displays a normalization of the sbn mutant phenotype from C4 (A) to C1 (B, arrow indicates absence of ventral tail fin). (C,D) Injection of 50 pg pCSKA-bmp4 DNA into an embryo from a cross of two sbn heterozygous parents. The sbn mutant phenotype is converted from a strong dorsalization (C4, panel C) to a weak ventralization (V1, panel D; see slight duplication of the ventral tail fin (arrow) and the enlarged blood island (arrowhead). (E-H) Chimeric embryos with fluorescein-labeled cells from embryos of a sbn/+ x sbn/+ cross (E,G) or a sbn/sbn x sbn/sbn cross (F,H) transplanted into wild-type recipients. Donor cells give rise to blood (E,F) and ventral tail fin (G,H) (see also Table 2).