Fig. 3. Changes in gene expression become apparent during gastrulation of GPC4-depleted embryos. Dorso-vegetal view of embryos injected with CoMo (A,C,E,G,I) and Gpc4Mo (B,D,F,H,J). Arrowheads in panels A-D and G-J indicate the blastopore lip. Anterior is to the top. (A-D) Gsc expression during gastrulation (stage 10 to 10.5). (E,F) Xbra expression during late gastrulation (stage 12). (E) Expression in the developing notochord (No) in control embryos. Arrow in F indicates reduced length of notochord expression in GPC4-depleted embryos. (G,H) Noggin transcripts at stage 12. Asterisk indicates anterior-most expression. Bar indicates length of expression domain in the presumptive notochord. Noggin transcripts are normal in the anterior mesendoderm (asterisk), but the length of the presumptive notochord is reduced in GPC4-depleted embryos (compare G with H). (I,J) Sox2 expression in neuroectoderm (Ne) at stage 12. Sox2 is not expressed in the posterior midline of control embryos (asterisk in I), and Sox2 expression is not excluded from posterior midline in Gpc4Mo-injected embryos (asterisk in J). (K,L) Frontal view of Et expression (stage 21) to show that two retina fields form in CoMo-(K) and Gpc4Mo-injected embryos (L).