microRNA regulation of skin pigmentation in fish

MicroRNAs (miRNAs) are endogenous small non-coding RNAs that play crucial roles in numerous biological processes. However, the role of miRNAs in skin color determination in fish has not been completely determined. Here, we identified that 13 miRNAs are differentially expressed between red and white skin. The analysis of miRNA spatial and temporal expression patterns suggests that miR-429 is a potential regulator of skin pigmentation. miR-429 silencing results in an obvious change in skin pigmentation. Bioinformatics analysis and a luciferase reporter assay show that miR-429 directly regulates expression of Foxd3 by targeting its 3'-untranslated (3'-UTR) region. miR-429 silencing leads to a substantial increase in the expression of Foxd3 in vivo, thereby repressing the transcription of MITF and its downstream genes, such as TYR, TYRP1 or TYRP2. These findings would provide a novel insight into the determination of skin color in fish.