Fig. 3. LvAlx1 is required in macromere descendants for transfating. (A) Experimental protocol. (B-I) Embryos were immunostained with mAb 6a9 and the same embryos were photographed using both brightfield (left column) and epifluorescence (right column) optics. (B,C) Control late gastrula stage embryo, 20 hours postfertilization. (D,E) LvAlx1 MO-injected embryo, 48 hours postfertilization. Most morphogenetic processes are unaffected by LvAlx1 knockdown but the embryo lacks 6a9-positive cells and skeletal elements. (F,G) Micromere-deficient [micromere(-)] embryo, 24 hours postfertilization. Transfating has occurred, leading to the formation of many 6a9-positive cells (arrow) and two skeletal primordia. (H,I) LvAlx1 MO-injected, micromere-deficient embryo, 48 postfertilization. The embryo has undergone extensive morphogenetic changes but lacks 6a9-positive cells and a skeleton.