Effects of cypher gene-specific morpholinos on expression of heart development markers by in situ hybridization. Control injected embryos (a–c) and cypher-MO injected embryos (d–f) were fixed at the 15-somite stage and stained with probes for either ventricular myosin heavy chain (vmhc; a and d), cardiac myosin light chain 2 (cmlc2; b and e) or nkx2.5 (c and f). Hearts from control injected (g and k) or cypher-MO injected embryos (h and l) are shown at 24 hpf. Shown is the whole mount in situ staining for cmlc2. No significant differences in early heart development were observed in both the 15-somite embryos with the three different heart markers used and in the 24 hpf embryos stained with cmlc2. This is consistent with the late onset of cypher expression in the heart after 24 hpf. The earliest observation of a changed heart morphology was observed at 36 h of development, and cypher-MO injected embryos showed an elongated atrium (m and j) compared to the control (n and i). Shown in o–t are in situ hybridizations of 3 days post fertilization control injected embryos (o, q and s) and cypher-MO injected embryos (p, r, and t) for either cmlc2 (o–r) or vmhc (s and t) expression. Shown in q and r are longitudinal sections from 3 dpf embryos stained for cmlc2 and in s and t transversal sections of hearts from 3 dpf embryos stained for vmhc. Sections were counterstained with neutral red. The ventricle (v) and the atrium (at) are indicated in the figure. Similar results were found in all specimen investigated.
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