Fig. S10

MTZ specifically ablates pax7b:NTR-mCherry cells. A. Work flow of metronidazole (MTZ) mediated selective ablation of cells expressing nitroreductase (NTR) from pax7b-driven NTR-mCherry cells (hpT. hours post start of MTZ treatment; dpw. days post wound; dpf. days post fertilisation). B. Larve of the indicated genotype were treated with 10 mM MTZ or DMSO vehicle/control from 2.5 dpf to 3.5 dpf and not wounded. Lateral maximum intensity projection of stacks from the same (except righthand column) 24 hpT/3.5 dpf and 72 hpT/5.5 dpf embryos are shown. Bottom two rows show single channels of 5.5 dpf merge above. Controls lacking NTR (two lefthand columns) show that MTZ is not toxic without NTR. Marked fibres (white asterisks), xanthophores (yellow arrowheads) and MPCs (cyan arrowheads) survive treatment. In control DMSO-treated dual-labelled fish. GFP and mCherry largely overlap at 3.5 dpf in MPCs and xanthophores (right column). MTZ treatment of NTR-expressing larvae eliminated most of the mCherry MPCs and xanthophores. leaving dying cells (yellow arrows) that were eliminated by 72 hpT. Low numbers of GFP-only cells and fibres remained (magenta arrow and asterisks). By 3 days after MTZ treatment. almost all mCherry debris had been cleared and numerous motile phagocytes were present ventrally around major blood vessels (white arrows; GFP had been lost immediately upon engulfment). GFP shows reduction of pax7b-expressing cells. No re-appearance of mCherry was observed in MPCs or other cells. Bars = 50 µm.