Fig. 2

Ttrap knockdown with higher MO dose induces gastrulation defects. (A,B) Ttrap^MO embryos (B) with thickened germ ring at shield stage and a less distinct shield (arrowheads) than control (A). Animal views, dorsal on top (gr, germ ring; sh, shield). (C-F) ttrap is essential for CE movements. papc/myod-marked paraxial mesoderm cells fail to converge close to the midline in Ttrap^MO embryos (D,F). Dorsal-posterior views, tailbud stage. Double-headed arrows depict width between cells spanning the midline. (G-I) ttrap is required during epiboly. (G) Control embryo (3 ss) showing blastopore closure (red arrowhead) and normal head with polster (blue). (H,I) Ttrap^MO embryos (3 ss) showing varying degrees of severity with respect to epibolic movements. (H) Ttrap^MO embryo displaying mild epiboly defect (red arrowheads), which shows only slightly open blastopore and relatively normal head morphology with polster (blue). (I) Ttrap^MO embryo with more severe epiboly defect and larger open blastopore (red arrowheads). Downward spread of blastoderm cells only covers 80% of yolk cell; many of these embryos lyse shortly after; head region severely reduced in size with polster missing (blue arrowhead). The combination of CE and epiboly defects leads to severely truncated embryos. Blue dashed arrows and semi-circle depict embryo length and angle between anterior-posterior (AP) ends. Lateral views, dorsal to the right. (J,K) Live control^MO versus Ttrap^MO embryo, 24 hpf. The morphant embryo displays AP-axis truncation, microcephaly and micropthalmia.