The actc1b:epNTR transgene can ablate muscle tissue in the presence of MTZ. (A, B) 3 dpf actc1b:epNTR embryos treated with DMSO vehicle (A) or 10 mM MTZ (B) at 1 day posttreatment. (C, D) 3 dpf actc1b:epNTR embryos treated with DMSO vehicle (C) or 10 mM MTZ (D) and stained with 10 ?M acridine orange at 1 day posttreatment. The mCherry and acridine orange channels are split to observe lack of acridine orange staining in the DMSO-treated embryo. Scale Bars = 50 ?M. NTR, nitroreductase; MTZ, metronidazole.

Ablated muscle tissue regenerates after MTZ is washed out. (A?D) Images of mCherry fluorescence in actc1b:epNTR embryos treated with DMSO vehicle at 1 dpf for 30 h followed by washout. (E?H) Images of mCherry fluorescence in actc1b:epNTR embryos treated with 10 mM MTZ at 1 dpf for 30 h followed by washout. The number of days following washout are indicated in the figure. (I?L) Cross-sections of embryos containing both the tg(ubi:mNG-lck) and tg(actc1b:epNTR-mcherry-caax) transgenes treated with DMSO (I) or MTZ (J) immediately after MTZ treatment (I, J) or 2 days after MTZ washout (K, L). Magenta indicates epNTR-mCherry-caax. Green indicates membrane localized mNeonGreen. Blue indicates DAPI. Yellow arrows (J) indicate an ablated cells with auto fluorescence, white arrows show regenerated muscle fibers, and the red arrow shows a cell-free gap that has formed. (J?, J??, K?L??) The green and magenta channels representing the different transgenes are shown separately. Scale Bars = 50 ?M. (M, N) In situ hybridization for myf5 in DMSO (M) or MTZ (N) treated actc1b:epNTR embryos. (O, P) In situ hybridization for ttn.2 in DMSO (O) or MTZ (P) treated actc1b:epNTR embryos.

Macrophages interacts with, and uptakes, apoptosing cells. (A) A representative image of a mpeg1:GFP host embryo with wild-type donor cells labeled in cascade blue. Individual fluorescent channels are shown for cascade blue donor cells (B) and GFP labeled macrophages (C). (D) A mpeg1:GFP host embryo containing transplanted wild-type cells that lack the actc1b:epNTR transgene shows macrophages (green) that do not linger within muscle tissue. (E) A mpeg1:GFP host embryo with transplanted actc1b:epNTR muscle cells (magenta) treated with MTZ and imaged 1 day after washout. Embryos show increased residence of macrophage cells in ablated area. (F) A mpeg1:GFP macrophage in an actc1b:epNTR embryo. mCherry puncta indicates uptake of ablated muscle debris from injured cells (white arrows). Scale Bars = 50 ?M