The CHOPCHOP web tool was used to predict TALEN pairs targeting hmox1a. The selected TALEN information is listed in Supplementary Table 1. Constructs were assembled using Golden Gate assembly and cloned into pCS2TAL3DDD and pCS2TAL3RRR vectors [19] [20] [21] .
Genome editing was performed as described [21] . Briefly, TALENs, used to generate mutant zebrafish, were constructed using the Golden Gate assembly method [19, 20] . mRNAs were synthesized using the Transcription Kits (Invitrogen) and diluted to 50 ng/μL for microinjection.
Samples were prepared immediately before each injection. mRNAs were injected into zebrafish embryos at the early one-cell stage to 10% of the volume of the cell (~1 nL). Injected embryos were raised until they reached adulthood and then outcrossed to wild-type fish. Embryos from these crosses were used for screening to identify mutants. The resulting mutant line is hmox1a vcc42 .
After initial genotyping characterisation, experimental work was carried out on embryos derived from F3-F5+ generation adults.
Genome editing was performed as described [21] . Briefly, TALENs, used to generate mutant zebrafish, were constructed using the Golden Gate assembly method [19, 20] . mRNAs were synthesized using the Transcription Kits (Invitrogen) and diluted to 50 ng/μL for microinjection.
Samples were prepared immediately before each injection. mRNAs were injected into zebrafish embryos at the early one-cell stage to 10% of the volume of the cell (~1 nL). Injected embryos were raised until they reached adulthood and then outcrossed to wild-type fish. Embryos from these crosses were used for screening to identify mutants. The resulting mutant line is hmox1a vcc42 .
After initial genotyping characterisation, experimental work was carried out on embryos derived from F3-F5+ generation adults.