Fig. 1

The gata5 morpholinos can be used to phenocopy the faust mutant. (A, B) Shown are representative embryos following in situ hybridization using a gata5-specific probe at 24 hpf analyzing (A) wild-type embryos or (B) embryos injected with a gata5 morpholino that targets a splice site (ssG5 MO). Injection of ssG5 MO efficiently blocks accumulation of mature gata5 mRNA. While most embryos lack detectable message, the embryo shown in panel B represents an example of one that demonstrates a low level of remaining transcripts in a bifid pattern. (C–M) Shown are representative embryos following whole mount situ hybridization to detect transcripts for the cardiac marker nkx2.5 at 24 hpf. Samples represent results with (C) wild-type embryos (D, E) embryos injected with a translation-blocker morpholino specific to gata5 (tbG5), (F–I) ssG5 morphants, and (J–M) embryos derived from crossing two adult fish heterozygous for the fau^s26 allele. The ssG5 morphants display the same variable expressivity phenotype as the fau^s26 mutants, including embryos with a fused heart tube (F, J), a partially fused tube (G, K), cardia bifida (H, L) or a significant reduction of cardiac progenitors (I, M). The tbG5 morpholino more reproducibly generates cardia bifida. See Table 1 for all statistics. In panels A and B, embryos were flat mounted, views are dorsal, with anterior to the left. All other views are dorsal, with anterior to the top.