sphk2 knockdown and rescue experiments.
A–F, whole-mount in situ hybridization of cmlc2. A–C, mating a homozygous sphk2 (−/−) mutant female with a wild-type male produced 100% Msphk2 mutants. Msphk2 one-cell stage embryos were injected with sphk2-morpholino oligomer (5 ng) into the yolk at one-cell stage embryos (B) or into the YSL around high stage embryos as confirmed by the distribution of co-injected rhodaminedextran (C). D–F, MZsphk2 embryos were injected with synthesized sphk2 mRNA (1 pg) into the yolk at one-cell stage embryos (E) or into the YSL around high stage embryos as confirmed by the distribution of co-injected rhodaminedextran (F). G, embryos exhibiting cardia bifida (red) or a normal single heart (blue) were quantified. Human SPHK1 or SPHK2 mRNA was injected into MZsphk2 embryos at the one-cell stage. The total number of embryos in each treatment is shown on the top of each column. Scale bar, 200 μm.