Fig. 4

DrAlkals affect iridophore development via DrLtk. (A) Ectopic expression of DrAlkal2a does not rescue loss of iridophores in 4 dpf transheterozygous ltk knockout zebrafish larvae (2 bp insertion/22 bp insertion, n = 9/9), whereas in heterozygous or wild-type siblings and ltk^j9s1 larvae, it leads to overproduction of iridophores (n = 29/29 and 34/35). Overexpression of DrAlkal2a in ltk^mne mutant slightly enhances the phenotype. (B) Treatment with lorlatinib results in diminished iridophore numbers in 4 dpf larvae. (C) Mosaic overexpression of DrAlkal2a produces patches of supernumerary iridophores in wild-type and ltk^mne adults. Overexpression of DrAlkal2a in ltk^mne mutants enhances production of supernumerary iridophores compared with uninjected ltk^mne. (D) Zebrafish alkal mutants display defects in iridophore development. alkal1^ko mutants have reduced iridophores in eyes and operculum, and removal of both alkal1and alkal2b results in a complete loss of eye iridophores. alkal2a^ko mutants show the strongest phenotype, with reduced numbers of iridophores in the trunk, especially anteriorly. This phenotype displays increased penetrance in alkal2a;alkal2b double mutants. (E) Triple mutant for all alkal genes is embryonic lethal and displays total loss of iridophores, similar to ltk transheterozygous knockout.