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FIG. 5. Overexpression of hermes inhibits heart and kidney development. Embryos injected with mRNA encoding hermes and lineage tracer GFP, or GFP alone. All embryos are at stage 28/29, unless otherwise specified. Whole-mount in situ hybridizations are photographed as lateral views except for (C), (F), and (I), which are ventral views of the same embryos pictured laterally. (A–C) GFP-injected control embryos showing normal expression of cardiac alpha-actin in the somites (A, B) and paired heart primordia (C). (D–F) Single-sided injections cause the ablation of the heart-forming region on the injected side (arrow) as assayed by cardiac alpha-actin. (G–I) Double-sided injections showing complete ablation of both heart primordia, while somite morphology (G, H) is unperturbed as assayed by cardiac alphaactin. (J, K) Transverse sections through stage 32 embryos (linear heart tube stage) injected with GFP mRNA only (J) or bilaterally injected with hermes mRNA (K) and assayed by cardiac alpha-actin. Note the absence of any cardiac alpha-actin staining as well as the absence of a morphologically detectable heart tube in (K), although the heart tube is easily detectable in (J). (L, M) GATA-4 expression in control embryos (L) is indistinguishable from hermes-injected embryos (M). (N, O) By contrast, a hermes-injected embryo (O) has reduced Nkx2–5 expression compared with a control GFP-injected embryo (N). (P, Q) A stage 25 hermes-injected embryo assayed with the kidney marker X-pax2. The uninjected side (P) shows normal kidney expression, while the injected side (Q) shows the absence of all kidney expression. |
