Fig. 5

Satellite-like cells express Rbfox1l and Rbfox2 RNA-binding proteins after mechanical injury of adult zebrafish skeletal muscle. (A) Schematic of experimental procedure, which is identical to that described in Fig. 3A. (B) Rbfox1l (green) is robustly expressed beginning at 4 dpi, coinciding with the onset of new myofiber formation. Pax7 expression (overlaid in red) is the same as shown in Fig. 3C; the merge here shows overlap of Pax7 and Rbfox1l expression. The boxed region at 4 dpi is magnified in C-C''. (C-C'') Magnified view of boxed area in B, showing expression of Rbfox1l (C) and Pax7 (C'), and the overlay (C'') at 4 dpi. Examples of Pax7-positive, Rbfox1l-positive cells are indicated by purple arrowheads and of Pax7-negative, Rbfox1l-positive cells by blue arrowheads. Rbfox1l expression is observed in the cytoplasm of presumptive newly-forming myofibers (orange arrowheads indicate examples). Rbfox1l expression in uninjured areas surrounding the injury site appears less uniform in muscle fiber nuclei (compared to Fig. S6D-D'') as laser intensity was reduced to prevent over-saturation of signals within the injury site. (D) Ratio of Pax7-positive cells that are Rbfox1l-positive at post-injury time-points 2–7 dpi. (E) Rbfox2 expression (green) begins at 3 dpi and is more widespread than than Rbfox1l, closely resembling post-injury Pax7 expression (overlaid in red). The sections are alternating with those in B. The boxed region at 4 dpi is magnified in F-F''. (F-F'') Magnified view of boxed area in C, showing expression of Rbfox2 (F) and Pax7 (F'), and the overlay (F'') at 4 dpi. Examples of Pax7-positive, Rbfox2-positive cells are indicated by purple arrowheads, and of Pax7-negative, Rbfox2-positive cells by blue arrowheads. (G) Ratio of Pax7-positive cells that are Rbfox2-positive at post-injury time-points 2–7 dpi. Scale bar in B and E is 75 µm, and in C-C'' and F-F'' is 30 µm.