Quantitative variation of melanins in alpaca (Lama pacosL.)

miR-380-3p regulates melanogenesis by targeting SOX6 in melanocytes from alpacas (Vicugna pacos)

BACKGROUND

Melanocytes are derived from neural crest stem cells in the embryonic stage. In mature melanocytes, a series of complex enzyme-catalyzed reactions leads to the production of melanins, which determine the hair and skin colors of animals. The process of melanogenesis is complex and can be regulated by mRNA, microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) genes. MiRNAs are a type of endogenous noncoding RNA approximately 22 nt in size that predominantly regulate gene expression by inhibiting translation. miR-380-3p is a candidate miRNA potentially related to melanogenesis. To better understand the mechanism of miR-380-3p melanogenesis regulation, plasmids to overexpress or knockdown miR-380-3p were transfected into alpaca melanocytes, and their effects on melanogenesis were evaluated.

RESULTS

In situ hybridization identified a positive miR-380-3p signal in alpaca melanocyte cytoplasm. Luciferase activity assays confirmed that SOX6 is targeted by miR-380-3p. miR-380-3p overexpression and knockdown in alpaca melanocytes respectively downregulated and upregulated SOX6 expression at the mRNA and protein levels. Additionally, miR-380-3p overexpression and knockdown, respectively, in alpaca melanocytes decreased and increased the mRNA levels of melanin transfer-related genes, including microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosine-related protein-1 (TYRP1), and dopachrome tautomerase (DCT). In contrast, miR-380-3p overexpression and knockdown respectively increased and decreased the mRNA levels of β-catenin. Additionally, the effect of miR-380-3p on melanogenesis was assessed by Masson-Fontana melanin staining.

CONCLUSIONS

The results demonstrated that miR-380-3p targeted SOX6 to regulate melanogenesis by influencing β-catenin and MITF transcription and translation, which reduced the expression of downstream genes, including TYR, TYRP1, and DCT. These results provide insights into the mechanisms through which miR-380-3p controls melanogenesis.

Skin transcriptome profiles associated with black- and white-coated regions in Boer and Macheng black crossbred goats

To increase the current understanding of the gene-expression profiles in different skin regions associated with different coat colors and identify key genes for the regulation of color patterns in goats, we used the Illumina RNA-Seq method to compare the skin transcriptomes of the black- and white-coated regions containing hair follicles from the Boer and Macheng Black crossbred goat, which has a black head and a white body. Six cDNA libraries derived from skin samples of the white-coated region (n = 3) and black-coated region (n = 3) were constructed from three full-sib goats. On average, we obtained approximately 76.5 and 73.5 million reads for skin samples from black- and white-coated regions, respectively, of which 75.39% and 76.05% were covered in the genome database. A total of 165 differentially expressed genes (DEGs) were detected between these two color regions, among which 110 were upregulated and 55 were downregulated in the skin samples of white- vs. black-coated regions. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that some of these DEGs may play an important role in controlling the pigmentation of skin or hair follicles. We identified three key DEGs, i.e., Agouti, DCT, and TYRP1, in the pathway related to melanogenesis in the different skin regions of the crossbred goat. DCT and TYRP1 were downregulated and Agouti was upregulated in the skin of the white-coated region, suggesting a lack of mature melanocytes in this region and that Agouti might play a key developmental role in color-pattern formation. All data sets (Gene Expression Omnibus) are available via public repositories. In addition, MC1R was genotyped in 200 crossbred goats with a black head and neck. Loss-of-function mutations in MC1R as well as homozygosity for the mutant alleles were widely found in this population. The MC1R gene did not seem to play a major role in determining the black head and neck in our crossbred goats. Our study provides insights into the transcriptional regulation of two distinct coat colors, which might serve as a key resource for understanding coat color pigmentation in goats. The region-specific expression of Agouti may be associated with the distribution of pigments across the body in Boer and Macheng Black crossbred goats.

MicroRNA-5110 regulates pigmentation by cotargeting melanophilin and WNT family member 1

Mammalian pigmentation requires the production of melanin by melanocytes and its transfer to neighboring keratinocytes. These complex processes are regulated by several molecular pathways. Melanophilin ( MLPH) and WNT family member 1 ( WNT1), known to be involved in melanin transfer and melanin production, respectively, were predicted to be targets of microRNA-5110 using bioinformatics. In the current study, we investigated the effects of microRNA-5110 on pigmentation in alpaca ( Vicugna pacos) melanocytes. In situ hybridization identified high levels of microRNA-5110 in the cytoplasm of alpaca melanocytes. Luciferase activity assays confirmed that MLPH and WNT1 were targeted by microRNA-5110 in these cells. Overexpression and knockdown of microRNA-5110 in alpaca melanocytes downregulated and upregulated MLPH and WNT1 expression at the mRNA and protein levels, respectively. In addition, overexpression and knockdown of microRNA-5110 in alpaca melanocytes decreased and increased, respectively, the mRNA levels of the melanin transfer-related genes, rat sarcoma (RAS)-associated binding ( RAB27a) and myosin 5a ( MYO5a); the mRNA levels of microphthalmia-associated transcription factor ( MITF), tyrosinase ( TYR), and tyrosinase-related protein ( TYRP) 1; and the production of total alkali melanin and pheomelanin. In contrast, overexpression and knockdown of microRNA-5110 increased and decreased the mRNA levels of TYRP2, respectively. Overexpression of microRNA-5110 also increased eumelanin. These results indicate that microRNA-5110 regulates pigmentation in alpaca melanocytes by directly targeting MLPH and WNT1 to affect eumelanin production and transfer.-Yang, S., Liu, B., Ji, K., Fan, R., Dong, C. MicroRNA-5110 regulates pigmentation by cotargeting melanophilin and WNT family member 1.

The expression of KRT2 and its effect on melanogenesis in alpaca skins

In order to investigate the effects of the keratin 2 (KRT2) on alpaca melanocyte in vivo and vitro, the immunohistochemistry (IHC), quantitative real-time PCR (qPCR), Western blot, and alpaca melanocytes transfection methods were used. The results showed that mRNA and protein expression of KRT2 was highly expressed in brown skin in comparison with that in white skin. Moreover, we found that KRT2 was expressed in alpaca melanocytes in vitro by immunocytochemistry. After transfection with KRT2 in alpaca melanocytes, the relative mRNA and protein expression of KRT2, microphthalmia-associtated transcription factor (MITF), tyrosinase (TYR) and tyrosinase-related protein 1 (TYRP1) in alpaca skin melanocytes was increased with significant differences; a further result was the increase of melanin production. The results suggested that KRT2 functions in alpaca hair color formation, which offered an essential theoretical basis for further exploration of the role of melanogenesis.

Identification and characterization of microRNAs in white and brown alpaca skin

AB BACKGROUND: MicroRNAs (miRNAs) are small, non-coding 21-25 nt RNA molecules that play an important role in regulating gene expression. Little is known about the expression profiles and functions of miRNAs in skin and their role in pigmentation. Alpacas have more than 22 natural coat colors, more than any other fiber producing species. To better understand the role of miRNAs in control of coat color we performed a comprehensive analysis of miRNA expression profiles in skin of white versus brown alpacas.

RESULTS

Two small RNA libraries from white alpaca (WA) and brown alpaca (BA) skin were sequenced with the aid of Illumina sequencing technology. 272 and 267 conserved miRNAs were obtained from the WA and BA skin libraries, respectively. Of these conserved miRNAs, 35 and 13 were more abundant in WA and BA skin, respectively. The targets of these miRNAs were predicted and grouped based on Gene Ontology and KEGG pathway analysis. Many predicted target genes for these miRNAs are involved in the melanogenesis pathway controlling pigmentation. In addition to the conserved miRNAs, we also obtained 22 potentially novel miRNAs from the WA and BA skin libraries.

CONCLUSION

This study represents the first comprehensive survey of miRNAs expressed in skin of animals of different coat colors by deep sequencing analysis. We discovered a collection of miRNAs that are differentially expressed in WA and BA skin. The results suggest important potential functions of miRNAs in coat color regulation.