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Fig. 2. Xenopus Nkx2-5 transcripts in the abdomen become asymmetrical during development. In addition to the heart and pharyngeal region, Nkx2-5 transcripts are detectable by in situ hybridization, beginning at stage 37/38, in two bilaterally symmetric regions of mesoderm overlying the foregut. Within several hours, Nkx2-5 expression disappears from the right side, while it is maintained on the left side (A,B,E,F,I,J). While asymmetry is being generated, the right and left regions of expression, detected by in situ hybridization, remain disconnected (C,G,K) and no migration of Nkx2-5-expressing cells is detectable in cross-sections through the foregut region (D,H,L). (A-D) Stage 37 embryos; (E-H) stage 39 embryos; (I-L) stage 40 embryos. The embryos in A, E and I are photographed from the left side. B, F and J are right-side views of the embryos in A, E and I, respectively. C, G and K are ventral views and the left-side of the embryo is on the right side of the photographs. D, H and L are transverse sections through the foregut region. The left side of the embryo is on the right side of the photographs. The gut (g), heart (h) and melanocytes (m) are indicated. Arrows mark Nkx2-5 expression in the putative spleen precursors. |
