Tyrosinase-related protein 2 (TYRP2) plays a pivotal role in the biosynthesis of eumelanin. Black-boned sheep have excessive melanin and eumelanin, resulting in dark (black) muscles and organs. This study was designed to investigate the effects of variants of the TYRP2 gene on black traits and coat colour of black-boned sheep. Melanin traits were measured in three populations of sheep (Nanping black-boned, Nanping normal, and Romney Marsh) and compared in this study. From the TYRP2 cDNA, all 8 exons and their flanking regions were amplified and characterized. Fifteen single nucleotide polymorphisms (SNPs) were identified in the exons and their flanking regions. Five exonic polymorphic sites, including two synonymous (c.93T>G and c.1140C>T) and three non-synonymous mutations (c.163C>T (p.R55W), c.605G>A (p.R202H), and c.1141A>G (p.T381A)), were retrieved. PCR-RFLP analysis of c.605G>A showed that the frequencies of allele G in the Nanping black-boned, Nanping normal, and Romney Marsh sheep were 0.632, 0.603, and 0.886, respectively. Sheep with the GG genotype had significantly (P < 0.05) lower tyrosinase activity, alkali-soluble melanin content, and ratio of eumelanin : total melanin than sheep with GA and AA genotypes when measured across all investigated samples but not when samples within each population of sheep were compared. However, there was no association of TYRP2 genotype at a single SNP position with coat colour across populations. Nonetheless, the two breeds with higher overall tyrosinase activity did produce darker and more varied coat colours than the breed with lower tyrosinase activity.

Melanin is distributed widely in many organisms including bacteria,fungi,plants and animals.Lighter variation soft pigmentation in humans is associated with diminished number,size,and density of melanosomes,the pigmented or ganelles of melanocytes.Here we reviewed that zebrafish golden mutants share these melanosomal changes and that golden encodes a putative cation exchanger SLC24A5 that localizes to an intracellular membrane,likely the melanosome or its precursor.The human ortholog is highly similar in sequence and functional in zebrafish.The evolutionarily conserved ancestral allele of a human coding polymorphism predominates in African and East Asian populations.In contrast,the variant allele is nearly fixed in European populations,is associated with a substantial reduction in regional heterozygosity,and correlates with lighter skin pigmentation in admixed populations,suggesting a key role for the SLC24A5 gene in human pigmentation.Finally,we reviewed research progress on melanin,SLC24A5 gene and Black-boned sheep.

It is well recognized that animal melanins can be classified into two major groups including eumelanin and phaeomelanin.Quantitative and qualitative analysis of melanin by using HPLC.The method is simple and rapid.We have explained the class of melanin pigment,quantitative and qualitative analysis and application of HPLC in this article.

Innate immunity recognizes invading micro-organisms and triggers a host defence response.However,the molecular mechanism for innate immune recognition was unclear.Recently,a family of Toll-like receptors(TLRs) was identified,and crucial roles of these receptors in the recognition of microbial components have been elucidated.The TLR family consists of 11 members and will be expanding.Each TLR distinguishes between specific patterns of microbial components to provoke innate immune responses.The activation of innate immunity then leads to the development of antigen-specific adaptive immunity.Thus,TLRs control both innate and adaptive immune responses.