Fig. 5

lost-a-fin double mutant analysis. Embryonic phenotypes observed from crosses between laf; din double heterozygous fish (A–C). (A) A wild type embryo at 1 dpf. (B) A typical laf mutant embryo, which lacks the ventral tail fin (arrowheads). din mutant embryos were similar to the embryo in Fig. 3E. (C) A double mutant embryo displaying a sharp dorsal flexure of the tail, no ventral tail fin (arrowheads) and a mass at the posterior end of the yolk extension (arrow). (D) A laf;ogon double mutant exhibiting a sharp dorsal bend in the tail, no ventral tail fin (arrowheads) and a cell mass posterior to the yolk extension (arrowhead). The degree of dorsal flexure and the presence of the cell mass are variable compared to the laf; din embryos. Expression of myoD at the 20-somite stage in embryos from laf;din (E–H) and laf;ogon (I–L) intercrosses. Transverse sections of similar embryos approximately at the level of somite 16 (arrows) are shown as insets (E–H). (E and I) myoD expression in the somitic mesoderm of a wild type embryo. The somite staining does not extend toward the ventral side of the embryo. In contrast to the wild type (E and I), in laf mutant embryos (F) myoD expression in the tail somites extends ventrally beginning at approximately somite 17 (arrowhead). (G) din mutants also exhibited a ventral expansion of myoD expression, but in more posterior somites (arrowhead). (H) The double mutant embryos displayed a characteristic dorsal bend in the tail and ventral expansion of myoD expression at a more anterior somite than in either single mutant (somite 12, arrowhead). (J) laf embryos from laf; ogon crosses displayed a ventral expansion of myoD expression beginning at about somite 19. (K) ogon mutant embryos exhibit a less dramatic expansion of myoD expression in posterior somites at this stage. (L) As with din crosses the laf;ogon double mutants embryos exhibited a ventral expansion of somitic mesoderm at a more anterior position, beginning at about somite 15 (arrowhead).