jak2a mediates the expanded ICM phenotypes in the chordin morphants. (A) Wild-type 24-hpf embryos. (B) chordin morphants at 24 hpf generated by injection of chordin MOs at the 1- to 4-cell stage. Bracket shows the extent of expanded ICM (arrowhead). (C) 24-hpf embryos coinjected with chordin and jak2a^UTR-MOs showing reduced expansion of ICM. Each image is a representative picture of 3 to 4 experiments using more than 20 embryos at each time. (D) Knock-down of jak2a by both UTR and splice-site MOs and AG490 reduced the width of ICM in 24-hpf chordin morphant embryos, expressed as the width of adjacent spanning somites (left panel) and percentage of embryos with an ICM of 5 somites or more (right panel). Each column represents mean value (± SEM) of 3 to 4 experiments using more than 20 embryos at each time. (E) Average results of flow cytometry showing means (± SEM) of 3 to 4 experiments. P values at the top of each column represent the results of statistical evaluation based on the paired Student t test when compared with chordin morphant.