Fig. S1

Overview of six1a, six1b, six4a, and six4b mRNA expression patterns. (A-P) RNA in situ hybridization for six1a, six1b, six4a, and six4b in embryos fixed at indicated times. (A-C) six1a trunk muscle expression peaks at 24 hpf and is lost by 52 hpf. (D) At 52 hpf, six1a is expressed in all MMP streams (arrowheads) and is most prominent in fin MMPs (brown and yellow arrowheads). (EH) six4a expression is very similar to six1a expression in trunk muscle and MMP streams. (I-L) six1b is expressed in trunk muscle, persisting at 52 hpf, and in all MMP streams. (M-P) six4b trunk muscle expression peaks at 24 hpf and is lost by 52 hpf; at 52 hpf, six4b is expressed in all MMP streams. six1/six4 genes are also expressed in other structures such as the ear (blue arrows) and the PrimI lateral line primordium (red arrows in six1a, six1b, and six4b panels). All supplemental figures use color-coded arrowheads, described also in Figure 1 legend, to indicate different MMP streams and the muscles they form. Red indicates the SHM and its precursors, brown indicates the AbFM and its precursors, yellow indicates the AdFM and its precursors, and light blue indicates the PHM and its precursors. Scale bars are 250 μm.