Fig. 9. Overexpression of LvAlx1 activates the PMC GRN in macromere descendants. (A) Experimental protocol. Fertilized eggs were injected with Lvalx1.WT mRNA. At the 16-cell stage, one macromere was injected with fluorescein dextran. After 12 hours, the embryos were fixed, immunostained with mAb 6a9 and a Cy5-conjugated secondary antibody, and examined by confocal microscopy. (B) A 2-D projection of a complete z-stack (16 images) of an experimental embryo. Fluorescent dextran is shown in green and 6a9 immunostaining in red. The macromere injected with dextran has contributed to a patch of cells outside the blastopore (arrowhead) as well as cells in the archenteron and a few migrating mesenchyme cells (arrows). This low M_r dextran is concentrated in cell nuclei (Hodor and Ettensohn, 1998). (C) A 2-D projection of a partial z-stack (4 images) from the same embryo. This projection shows more clearly that some 6a9-positive cells are also labeled with fluorescent dextran (arrows).