Fig. 4. Localization of 14-3-3 proteins during early development. Embryos were fixed, sectioned and processed for immunohistochemistry with 14-3-3 protein antibodies. (A-D) 14-3-3Z protein. (A) Unfertilized embryos sectioned parallel to the animal-vegetal (AV) axis display signal in the vegetal-most two-thirds of the embryo. (B) By the two-cell stage, the staining is much reduced in intensity. (C) By the four-cell stage, staining is almost completely absent. (D) At stage 10, weak staining is seen throughout the endodermal yolk mass of the gastrulating embryo. (E-J) 14-3-3E protein. (E) By contrast to 14-3-3Z, the 14-3-3E signal is seen in a coherent spot in the center of the unfertilized embryo. (F) By the two-cell stage, signal can be detected in only one of the two blastomeres. (G) At the four-cell stage, signal is seen in the right blastomeres. (H) During gastrulation, a strong signal is detected in the endodermal yolk mass. To check the mRNA construct as well as the antibody, embryos injected immediately after fertilization with 14-3-3E mRNA were processed for immunohistochemistry. A strong 14-3-3E signal can be detected throughout the embryo at the two- and four-cell stages (I,J). Red arrowheads indicate protein localization; yellow arrowheads indicate lack of signal.