Effect of silencing microRNA-508 by STTM on melanogenesis in alpaca (Vicugna pacos)

Abstract

It has been demonstrated that microRNAs (miRNAs) play important roles in the regulation of melanogenesis and hair color in mammals. Short tandem target mimic (STTM) has been used to effectively block small RNA functions in plants and animals. We previously showed that miR508-3p plays a functional role in regulating melanogenesis in alpaca melanocytes by directly targeting microphthalmia (MITF). To verify the effect of miR-508-3p function on melanogenesis in alpaca melanocytes, miR-508-3p was blocked using STTM technology in the present research. miR508-3p was predicted to target the gene encoding SRY-box6 (SOX6) by bioinformatics. The luciferase reporter assay indicated that miR508-3p regulates SRY-box6 (SOX6) expression by targeting its 3′UTR. Here, STTM-miR508-3p overexpression in alpaca melanocytes blocked the expression of miR-508-3p and up-regulated SOX6 expression at both the mRNA and protein levels, resulting in increasing the expression of key melanogenic genes, including cAMP responsive element (CRE) binding protein (CREB), MITF, tyrosinase (TYR) and tyrosinase-related protein 1 and 2 (TYRP1 and TYRP2). STTM-miR508-3p overexpression in melanocytes also resulted in increased melanin production, including total alkali soluble melanogenesis (ASM), eumelanogenesis (EM) and pheomelanogenesis (PM). Additionally, we identified melanin granules in alpaca melanocytes transfected with STTM-miR508-3p under Fontana-Masson staining. These results suggest that STTM-miR508-3p could up-regulate melanogenesis by effectively blocking miR508-3p.