Figure 6 figure supplement 4.

(A) At 5 dpf, scarb1 mutants had yellow larval xanthophores with wild-type levels of pteridines. (B) Carotenoids were not detectable in EL zebrafish (5 dpf, wild-type; compare to Figure 3D); csf1ra mutants, which lack xanthophores, had HPLC profiles indistinguishable from wild-type. (C) Carotenoid and pteridine pathway signature scores for xanthophores in euthyroid EL and euthyroid and hypothyroid adult scRNA-Seq data sets. Box plots as in Figure 3 with different letters above data indicating significant differences in post hoc comparisons (carotenoid, p<2e-16; pteridine, p=0.01; Tukey HSD). Pteridine signatures between EL, hypothyroid, and euthyroid xanthophores were more similar than carotenoid signatures. (D) Ammonia-induced pteridine fluorescence was present in adult xanthophores of both euthyroid and hypothyroid fish (red arrowheads).