Differential regulation of epiboly initiation and progression by zebrafish Eomesodermin A

► Zebrafish eomesa mutation was recovered by TILLING. ► Maternal Eomesa is required for the timely initiation of epiboly but is not required for epiboly progression. ► Yolk cell microtubules are defective in maternal-zygotic eomesa mutant embryos at dome stage but recover by 75% epiboly. ► Deep cell morphology is altered in maternal-zygotic mutant embryos. ► Expression the endoderm markers sox32, bon and og9x is abnormal in maternal-zygotic eomesa mutant embryos.