2-OST is necessary for epiboly in early zebrafish development. (A-L) Embryos (1- to 2-cell stage) were injected with 3 ng control MO (A-C), 3 ng of 2-OST MO1 (D-F), 3 ng of 2-OST MO2 (G-I), or mixture of 3 ng 2-OST MO1 and 0.2 ng 2-OST RNA (J-L), then incubated in embryo water at 28°C. They were examined at 2.5 hpf (A,D,G,J), 4 hpf (B,E,H,K) and 8 hpf (C,F,I,L). (M) Quantitative comparison of injections and rescue scored based on failure to initiate epiboly. The co-injection of 2-OST MO+2-OST RNA rescued the percentage of embryos that fail to initiate epiboly in the 2-OST MO alone or the 2-OST MO+control RNA by >50%. *P<0.05. Error bars represent s.d.