cdx4, but not cdx1a, is expressed in the prospective spinal cord territory before and during somitogenesis. Expression of cdx1a (A,A′,C,E) and cdx4 (B,B′,D,F) (purple) at the tailbud (A,A′,B,B′), 6-somite (C,D) and 10-somite (E,F) stages of development. Arrow indicates anterior limit of cdx4 expression, as compared with adjacent adaxial cells and somites (s) labeled for myod (red). Flat-mounted embryos, anterior to the left, except A′ and B′ which are lateral views of whole embryos, anterior to the top. Scale bars:100 μm. (G) Change in the anterior limit of cdx4 expression in the CNS as a function of time. Embryos at different developmental stages (hpf, hours post-fertilization, x-axis) were hybridized for cdx4 and myod and the anterior limit of cdx4 expression in the CNS analyzed with respect to adjacent somites (y-axis). Each point is the average of at least ten embryos; s.e. indicated with bars.
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