Fig. 5. Spatial expression of endomesoderm genes in foxa perturbed embryos. (A-O) S. purpuratus embryos at different time points injected with foxa (A-C,G-I) and control MASO (D-F,J-L) or mRNA (M-O) were hybridized with WMISH probes as indicated in the lower right corner of each panel; developmental time is indicated at lower left. Embryos are in lateral view with the vegetal pole towards the bottom of each panel, unless specified otherwise. AV, view from the apical plate; VV, view from the vegetal plate; OV, view from the oral ectoderm. An identical pattern of gcm expression is observed at mesenchyme blastula stage, in foxa MASO (A) and control (D) embryos. At 32 hours postfertilization, more cells stained positively for gcm are observed in the foxa MASO-injected embryo (B) than in control (E, see text for quantitation). The red arrowhead indicates a cell of the invaginating endoderm that is expressing gcm. (C,F) gatae expression at 48 hours in foxa MASO and control (late gastrula) embryos. At this stage, gatae is normally expressed in midgut, hindgut and coelomic pouches (Lee and Davidson, 2004); expression is nearly abolished in Foxa-depleted embryos (C). (G-L) Expression of foxa in foxa MASO and control embryos. At all three stages shown, the intensity of expression is increased by foxa MASO (G-I), compared with controls (J-L). The normal expression boundaries are maintained, however; although the remaining endoderm at 48 hours has failed to invaginate. (N,O) mRNA overexpression of Foxa. Complete repression of gcm relative to control embryos (M) is seen only at high concentrations (N) of injected mRNA.