Fig. 3. Morpholino-induced knockdown of psr results in the loss of the cell corpse-engulfment process and cell migration. (A,B) Control-MO-injected embryos. Lateral (A) and top (B) views of the normal somite (open square and arrow) reveal the clear furrow of somite at the 6-somites stage (12 hpf). (C) Lateral view of a PSR-MO-injected embryo reveals abnormal development of the somite. There is no evidence of the clear furrow and the somite is thinner. (D) In PSR-MO embryos, a substantial number of cell corpses accumulate in the somite region (arrows), and an apparent `hole' (long arrow) is formed on the surface of the somite. Scale bars: 100 µM. (E) In the control-MO group, complete epiboly and a normal brain (arrow) are observed; the clear bar of the eye can be seen. (F) In the PSR-MO group, incomplete epiboly (long arrow) and an abnormal brain (short arrow) are seen; the eye bar is not clearly evident. Scale bars: 250 µM. (G-J) The sequential pattern of cell corpse accumulation in whole embryos from 12-36 hpf. Embryonic cells were injected with control-MO and PSR-MO (40 ng per embryo) at the one-cell stage to block translation of the psr mRNA. (G,I) Control-MO groups at 12 hpf (G) and 36 hpf (I); embryos appear normal and no accumulation of cell corpses is evident. (H,J) PSR-MO groups at 12 hpf (H) and 36 hpf (J); embryos are abnormal and a gradual accumulation of corpse cells can be seen (arrows). Scale bars: 250 µM.