Figure 1. The sphk2^MZ embryos show developmental delay associated with enhanced levels of sphingosine.

(A,B) Compared to time-matched representative wildtype embryos observed at 7 or 8 hr post fertilization (hpf), the sphk2^MZ embryos (C,D) display a developmental delay during epiboly, denoted by arrows indicating the leading edge of the blastoderm. (E, F) Wildtype embryos treated at 2 hpf with 3 μM sphingosine (sph) were similarly developmentally delayed. Treatment of wildtype embryos with G) C8 ceramide (20 μM), (H) S1P (20 μM), or (I) N-acetyl-D-sphingosine (20 μM) had no adverse effects on epiboly. A-I show representative embryos, n at least 25 in each of 3 independent experiments. (J) Based on lipidomic profiling at 6 hpf, the sphk2^MZ embryos are depleted of S1P (Sph-1P) and have elevated levels of sphingosine and (K) total long-chain ceramides compared to time-matched wildtype embryos. For J and K, results are the average of three independent experiments pooling 50 embryos each; errors bars indicate the standard error of the mean.