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Fig. 4. Shox2 overexpression downregulates Nkx2-5 expression. XNkx2-5 and XcTnI expression was analyzed by in situ hybridization in control embryos at stage 26 (A, E) and at stage 41 (C, G) and in GR-Shox2 mRNA injected induced embryos at same stages (B, F, D, H). XNkx2-5 expression is clearly reduced at the midline of injected induced embryos at stage 26 (B), as compared to control embryos (A). XcTnI expression is maintained in injected induced embryos laterally, but is absent at the midline at stage 26 (F), as compared to the controls (E). At stage 41, XNkx2-5 expression is absent in injected induced embryos (D) compared to control embryos (C). XcTnI expression in injected induced embryos (D) is comparable to that of control embryos (H). Altered gene expression is accompanied by the abnormal heart morphology when comparing control and injected induced embryos (C, D, G, H). Histological transverse sections of Xenopus embryos showing loss of mesodermal cardiac progenitor cells in the ventral midline in injected induced embryos (B’, D’, arrowheads), as evidenced by the loss of XNkx2-5 expression in the corresponding region when compared to control embryos (A’, C’, arrowheads). Scale bars represent 50 μm. |
