Fig. S7

Characterization of a previously unidentified subpopulation of MPCs and the failure to recover MPCs by fast muscle-specific expression of human mysterin.

(a) Co-staining of slow muscle nuclei (prox1: magenta) and MPC nuclei (engrailed: green) in control embryos at 1 and 2 dpf. Although MPCs are known as a subpopulation of slow muscle cells2, prox1-negative and engrailed-positive cells appear at 2 dpf. (b) Co-staining of MPC nuclei (engrailed: green) and all nuclei (Hoechst: blue) in control embryos at 2 dpf. The proper nuclear distribution of engrailed is confirmed by co-staining of total nuclei (Hoechst: blue). The number of engrailed-positive cells (MPCs) at 2 dpf was counted. (c) The MO targeting mysterin-α does not alter the number of prox1-positive slow muscle cells at 2 dpf. Quantification is shown in Fig. 5b. (d) MPCs are stained with an anti-engrailed antibody (green). The morphant has a significantly increased number of MPCs at 2 dpf, which is not affected by fast muscle-specific expression of human mysterin. RFP shows fast muscle-specific GAL4 activity.