Fig. 3

Morpholino injection inhibits correct sid4 mRNA splicing and disrupts development of mesoderm and neuroectoderm. (A) RT-PCR demonstrates dose-response s-mo-specific deletion of sid4 exon 5. Treatments are given at the top of each lane. Arrows indicate amplification products that were cloned and sequenced. (B–G) Lateral views of live 24 hpf zebrafish embryos injected with 150 μM s-mo and s-co (B–F) and t-mo (G). (B) Tail mesoderm is unaffected by s-co. (C) Mildly affected morphant embryos exhibit expanded inner cell mass and defects in caudal somite morphology. Anterior somites appear normal. (D) Brain regionalization is normal in s-co and (E) mildly affected morphants. (F) In the majority of s-mo morphants, somites are rounded, tails severely truncated and brain structures indistinct. Magnification is the same in all panels. Anterior is to the left. hb, hindbrain; icm, inner cell mass; mhb, midbrain–hindbrain boundary.