Fig. 4. Distribution and perdurance of injected mRNA. N teloblasts in stage 7 embryos were injected with nGFP mRNA. The embryos were fixed at times ranging from 1-120 hours post-injection, then processed in parallel for in situ hybridization. Arrowheads indicate the position of the first labeled clone, where visible. (A-D) Animal pole views of embryos fixed 1-72 hours after injection. The teloblast and relatively young blast cells (arrowhead in B) stained intensely, but a significant decline in staining was apparent in blast cell clones that had undergone their first mitosis (arrow in C,D). (E) Prospective posterior view of an embryo fixed 96 hours after injection. Although the teloblast still stained very intensely, the first labeled clone (not visible in this view) was barely visible. (F) By 120 hours after injection (side view), staining in the teloblast was clearly reduced, but still clear. By contrast, nGFP mRNA was no longer detectable in the first labeled clone under these conditions (arrowhead indicates the estimated position of the first labeled clone; compare with Fig. 2A,D). Scale bar: 100 µm.