Fig. 6. mRNA localization of 14-3-3 family during early development. A representative set of embryonic stages are shown for each mRNA. Maternal mRNA for 14-3-3 isoform T is localized to the animal pole of the unfertilized egg (data not shown), and to embryonic blastomeres at the two-cell stage (A; parallel to AV axis). (B) This pattern is observed in most blastomeres during the first few cleavages (perpendicular to the AV axis). The mRNA is located near the cell cortex. (C) 14-3-3T is later expressed throughout the nervous system, including very strong expression in the head and somites, and a thin border at the caudal end of the embryo, up to the developing anus. (D) 14-3-3 isoform Z is detected in the cortex of cleaving cells (four-cell stage embryo sectioned perpendicular to AV axis). During subsequent cleavages, transcripts are also detected in the animal half of vegetal cells (E) and in an unusual horseshoe pattern in cleavage-stage embryos (F). 14-3-3E mRNA is present throughout the animal pole of the unfertilized egg (data not shown). It becomes localized to one of the two blastomeres at the first cell division (G). This pattern is maintained at the four-cell stage (H). Sections of G and H, shown in I and J, respectively, confirm the pattern. Note that 14-3-3E mRNA at the two-cell stage is located in the central cytoplasm and not in the cell cortex (compare panel I with panels D and B). Red arrowheads indicate presence of mRNA; yellow arrowheads indicate lack of signal.