Mrf4 has no role in trunk muscle differentiation. (A) Schematic illustrating the location of the mutation encoded by mrf4hu2041. (B) Proportion of mrf4hu2041/hu2041 (red), mrf4hu2041/+ (green) or mrf4+/+ (blue) in progeny from heterozygote crosses. The number of embryos of each genotype is shown. Homozygote mutants survive well and without obvious defects. (C) Whole-mount in situ mRNA hybridisation of myf5+myod morphants or myod MO-injected myf5hu2022 mutants reveal that residual medial fast fibres express myog (red) but not mrf4 (purple) at 22 ss, but accumulate mrf4 mRNA after terminal differentiation at 24 hpf. Lateral view, anterior to left. (D) In situ mRNA hybridisation for myhz1 (purple) in embryos from a mrf4+/hu2041 incross reveals that injection of myf5+myod MOs fails to ablate all muscle irrespective of mrf4 genotype.