Morphological Characterization and Gene Expression Patterns for Melanin Pigmentation in Rex Rabbit

Animal melanin has an important role in the formation of animal fur and skin, which is determined by its quantities, character, and distribution. To identify the effect of melanin on the formation of multi-colored Rex rabbits (Black, Chinchilla, Beaver, Protein cyan, Protein yellow, White), the structure of hair follicles and melanin content in multi-colored Rex rabbit skins were observed by Hematoxylin and Eosin (H&E) staining and melanin staining, respectively. The melanin granules were primarily found in the epidermis and hair follicle roots. The melanin content of skin was measured by extracting melanin from skin tissue. The results demonstrated that the melanin content was the highest in the skin of black Rex rabbit. Additionally, we measured the mRNA and protein expression levels of melanin-related key genes (MITF and TYR) in the skin of different hair color by quantitative real-time PCR and Wes assay, respectively. The results revealed that the mRNA expression levels in the skin of black Rex rabbit was highly expressed when as compared with other Rex rabbit skin ( P < 0.01), and they were the lowest in the skin of white Rex rabbit. Finally, correlation analysis was conducted between melanin content and the expression levels of mRNA and protein. The results indicated a significant correlation between melanin content and the mRNA expression of MITF ( P < 0.05), but it was not correlated with the mRNA expression of TYR ( P > 0.05). In summary, melanin deposition has important economic value, and the coat color of fur-bearing animals is partly determined by the melanin-related genes.