Mesoderm specification is deficient in MZdchs1b embryos and WT embryos with impaired cytoskeleton. (A) ntl expression in MZdchs1b, Mdchs1b and MZdchs1bfh275/fh275;MZdchs2stl1/stl1stage-matched embryos at 30% epiboly; animal-pole view. (B) Quantification of gaps in ntl expression in WT, Mdchs1b and MZdchs1b embryos. (C) ntl expression in WT embryos treated with DMSO, 5 μM taxol, 3 μg/ml cytochalasin D and 0.01 μg/ml nocodazole at 30% epiboly; animal-pole view. (D) chd expression domain in WT, Mdchs1b and MZdchs1b embryos. Insets show embryos with gap in expression domain. (E) gsc expression in WT, MZdchs1b, MZdchs2stl1/stl1 and MZdchs1bfh275/fh275;MZdchs2stl1/stl1 stage-matched embryos at 30% epiboly; animal-pole view. Inset in MZdchs1b panel shows representative image of disrupted gsc domain. (F) Measurement of the chd expression domain in degrees for embryos shown in D. (G) Measurement of the gsc expression domain in degrees for embryos shown in E.