Morpholino antisense knockdown of laminin α4 in bal mutants reveals redundant roles in notochord differentiation. Lateral views of 48 hpf control MO-injected embryos from a heterozygous bal cross showing a morphologically WT (A) and a bal mutant (B) (arrowhead; non-differentiated anterior notochord) embryo. From the same heterozygous bal cross, lama4 MO-injected embryos are also shown, ∼75% of embryos show a brain defect but no obvious notochord phenotype (C), whereas ∼25% of embryos have a severe notochord defect (D), with the entire anterior–posterior extent of the notochord disrupted. Whole mount laminin 1 antibody staining at 24 hpf shows expression of immunoreactivity in morphologically WT (E) and bal (F) mutant control MO-injected embryos. While ∼75% of lama4 MO-injected embryos have wild-type laminin 1 immunoreactivity (I), ∼25% (bal mutants) show severe loss of laminin 1 (J) (two independent experiments, total n = 136). Staining for expression of echidna hedgehog (ehh) at 24 hpf reveals the status of notochord differentiation in control MO-injected wild-type (G) and bal (H) mutant embryos. While lama4 MO-injected WT (K) embryos normally extinguish ehh expression, lama4 MO-injected bal mutant (L) embryos persistently express ehh.
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