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FIG. 1. Single-sided expression of dominant inhibitory XNkx2-3 and XNkx2-5 inhibits myocardial gene expression. In all cases the arrowhead indicates the injected side of the embryo. All embryos were assayed for expression of the myocardial marker, TnIc, using whole-mount in situ hybridization. (A) Stage 28, water-injected control embryo, showing normal expression of TnIc. At this early stage, TnIc expression marks bilaterally symmetrical precardiac tissues, located on each side of the ventral midline. (B) Stage 28 embryo injected with 250 pg of wild-type Nkx2-5 mRNA showing increased expression of TnIc on the injected side. (C) Stage 28 embryo, after single-sided injection of 250 pg of Nkx2-3LP mRNA. Expression of TnIc is dramatically reduced on the injected side (indicated by the arrowhead). (D) Stage 29 embryo, after single-sided injection of 250 pg of Nkx2-5LP mRNA. Expression of TnIc is dramatically reduced on the injected side (arrowhead). (E) Lateral view of control and experimental stage 30 embryos. The water-injected control embryo is shown on top. The bottom embryo was injected with 250 pg of Nkx2-3LP mRNA and shows severe inhibition of TnIc expression in the cardiac region. Note that the overall morphology of the experimental embryo is indistinguishable from the water-injected control. (F) Histological section through the heart region of a stage 30, water-injected control embryo assayed for TnIc expression. Two regions of TnIc expression are visible on either side of the ventral midline. (G) Section through the heart region of a stage 30 embryo injected with 250 pg of Nkx2-3LP. Note the absence of TnIc expression on the injected side (arrowhead). |
