Fig. 5

Deletion and double mutant analyses suggest interactions of Mitfa with other bHLH-ZIP MiT subfamily members. (a) Mutants homozygous for a deletion (mitfadel) that prevents mitfa transcription developed abundant embryonic and adult xanthophores. (b) Double mutants for mitfaw2 and mitfb developed xanthophores, albeit fewer in the adult than mitfaw2 single mutants, with this deficit noticeable especially in fins. Double mutants for mitfaw2 and tfec completely lacked xanthophores in early larvae. tfec mutants were semi-viable through later larval stages owing to defects in swim bladder development and potentially other traits, but surviving mitfa; tfec mutant juveniles and adults lacked xanthophores, despite their presence in tfec single mutants (Petratou et al. 2021) (e.g., Figure S8b,c). (c) tfec homozygotes often recovered adult iridophores if wild-type or heterozygous mutant for mitfa. The left panel shows wild-type and three right panels show variable complements of iridophores in sibling tfec−/− fish with one or two mitfa+ alleles (individuals with iridophores: mitfaw2/+, 4 of 7 genotyped; mitfa+/+, 2 of 3 genotyped). Whole-fish images of adults are also shown in Figure S8a. Scale bars: For a and b, upper 200 μm, lower 500 μm; c, 250 μm.