Fig. 1. (A-C) Plan of the assays used in this study. Animal caps (B) were excised from embryos at the late blastula stage (A) and cultured for 10 minutes before fixation and staining for F-actin. The remainder of the embryos, the bases (C), were cultured for 1-2 hours to assay the degree of rigidity, the shape, and the ability to heal the wound left by animal cap excision. (D) Embryos from which the animal caps were removed 45 minutes previously: control embryos (upper row) and embryos injected at the two-cell stage with 5 ng mRNA from pool 12D (lower row). 12D-expressing embryos are more compact and rigid, and have an exaggerated wound-healing response. The margin of one of the wounds is indicated (arrow, D). (E) A control embryo (left), and an embryo injected with 1 ng mRNA from pool 12D, column 10 (right), treated identically to those embryos shown in D. The more rapidly healing wound of the 12D10-injected embryo is indicated (arrow). (F) Alexa-488 conjugated Phalloidin staining of animal caps from a control embryo (left) and an embryo injected with 100 pg mRNA from the single pool 12D10D (right). The animal cap expresses increased levels of cortical actin and has an exaggerated wound response. The purse-string that forms the boundary between the inside and outside surfaces of the cap is indicated in the 12D10D-injected cap (arrow). mRNA from this clone mimicked all of the effects of the whole pool 12D, and the column 12D10.