Integration of transcriptomics and metabolomics reveals amelanism mechanism of Oscar Astronotus ocellatus (Agassiz, 1831)

Oscar Astronotus ocellatus (Agassiz, 1831), an Amazonian cichlid, has normal and amelanism varieties, but studies on its amelanism mechanism are scarce. Here, we investigated the ultrastructure, metabolome, and transcriptome profiles of skin from normal and amelanistic individuals. We found more stellate-shaped melanophores, mature melanosomes and melanin in normal, but less melanin, oval-shaped melanophores and immature melanosomes in amelanistic individuals. A significant separation in metabolome between normal and amelanism was observed. Pathways, e.g., biosynthesis of amino acids and unsaturated fatty acids, of differentially expressed metabolites (DEMs) involved in were significantly enriched. Transcriptome showed 323 differentially expressed genes (DEGs), of which stmn4, tyr, tyrp1, prkca, dusp8, hsp70, and wls were involved in melanin-related pathways especially tyrosine metabolism. Several classical melanin-related genes including slc24a5, acdy2, and acdy6 harbored non-synonymous SNPs in the functional domains. Integration of transcriptome and metabolome showed 18 strong correlations between DEMs and DEGs, e.g., between l-Proline and cds1, styk1, fam83b, and gimap7, between phosphorylcholine/N-alpha-Acetyl-l-lysine and myh, mical2b and mical3a, and between biopterin and dusp8. This study characterized the difference of skin melanophore, melanosome and melanin content between normal and amelanistic Oscar, and identified some candidate amelanism-related genes, metabolites and pathways, helping to understand its amelanism mechanisms.

Automated summary

This study compared the differences in melanophore, melanosome, and melanin content in the skin of normal and amelanistic Oscar Astronotus ocellatus. It identified candidate amelanism-related genes, metabolites, and pathways, providing insight into the mechanisms of amelanism in this species.