(A) The schematic diagrams of plasmid constructs having a 1.1 kb fragment upstream of myf5 gene and having various deletions of exon 1 of myf5 which are proximal upstream regulatory segments of miR-3906. (B) Luciferase activity assay in zebrafish embryos at 24 hpf. Plasmids phRL-exon1-1, phRL-exon1-2, phRL-exon1-3, phRL-exon1-4 and phRL-exon1-5 were co-injected individually with pGL3-TK, an internal control, into one-cell embryos. The luc expression of embryos injected with plasmid phRL-exon1-1 served as 1. The relative luc expression level of each combination was examined. (C) Luciferase activity assay in zebrafish embryos at 16, 24 and 32 hpf. Plasmids phRL-myf5-promoter and phRL-exon1-1 were co-injected individually with pGL3-TK, an internal control, into one-cell embryos. The luc expression of each plasmid at 16 hpf served as 1. The relative luc expression levels of phRL-myf5-promoter and phRL-exon1-1 at 24 and 32 hpf were examined. Data were presented as means±SD from three independent experiments (n = 3). Student's t-test was used to calculate the differences among data. *: indicates significant difference at P<0.05. **: indicates significant difference at P<0.01.