Transcriptome Profiling Towards Understanding of the Morphogenesis and Development of Scales in Blunt Snout Bream (Megalobrama amblycephala)

Skin appendages in vertebrates have individual morphological differences, but share the same evolutionary origin, which suggests that molecular regulation mechanism of their development may also be conserved. In the present study, we used Megalobrama amblycephala as a fish model to study the regulation mechanism of development skin appendages common in fish: scales. By combining in-toto live imaging method and transcriptomic analysis during the scale development, we elucidated core features of scale patterning and key regulatory genes in the fish scale development. The results revealed three distinct regions in the scales: the limiting layer (LL), external elasmodine (EE), and internal elasmodine (IE). We defined four stages of scale development: S (start), T (tail), 12R (12 rows), and B (beard) stages. Furthermore, differentially expressed genes in skin tissues at the initial site before and after scales development were also identified and analyzed by transcriptome and qPCR analyses. Among the annotated DEGs, we selected some genes (Wnt3, Wnt6, Fgf8, Fgf10, Fgf16, Fgfr1a, Ihhb and BMP6) that may be crucial for the formation of scales. This study provides a strong reference for further exploration of the function of genes related to the molecular regulation mechanism of scales development in M. amblycephala, as well as lays a foundation for future studies of the molecular mechanism of scale development in fish.