In situ hybridization analysis of tcf7 expression from four-cell to bud stage. A: Animal pole view. Ubiquitous maternal expression at four-cell stage. B: Animal pole view. Ubiquitous expression at dome stage. C: At 60% epiboly. Specific expression in shield and prechordal mesoderm (arrowhead) as well as ubiquitous expression in germ ring. Dorsal to left. D: Lateral view at 60% epiboly shows higher level of expression in the hypoblast (arrowhead). Dorsal to left. E,F: Bud stage. E: Expression in the prechordal plate (arrowhead). F: The arrow indicates expression in the tail bud, and the arrowhead indicates expression in notochord. Posterior view, dorsal to left. Scale bar = 300 μm in A (applies to A-F).
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