Genetics and Breeding

Nitric oxide (NO) and α-melanocyte-stimulating hormone (α-MSH) have been correlated with the synthesis of melanin. The NO-dependent signaling of cellular response to activate the hypothalamopituitary proopiomelanocortin system, thereby enhances the hypophysial secretion of α-MSH to stimulate α-MSH-receptor responsive cells. In this study we investigated whether an NO-induced pathway can enhance the ability of the melanocyte to respond to α-MSH on melanogenesis in alpaca skin melanocytes in vitro. It is important for us to know how to enhance the coat color of alpaca. We set up three groups for experiments using the third passage number of alpaca melanocytes: the control cultures were allowed a total of 5 days growth; the UV group cultures like the control group but the melanocytes were then irradiated everyday (once) with 312 mJ/cm2 of UVB; the UV + L-NAME group is the same as group UV but has the addition of 300 μM L-NAME (every 6 h). To determine the inhibited effect of NO produce, NO produces were measured. To determine the effect of the NO to the key protein and gene of α-MSH pathway on melanogenesis, the key gene and protein of the α-MSH pathway were measured by quantitative real-time PCR and Western immunoblotting. The results provide exciting new evidence that NO can enhance α-MSH pathway in alpaca skin melanocytes by elevated MC1R. And we suggest that the NO pathway may more rapidly cause the synthesis of melanin in alpaca skin under UV, which at that time elevates the expression of MC1R and stimulates the keratinocytes to secrete α-MSH to enhance the α-MSH pathway on melanogenesis. This process will be of considerable interest in future studies. more »

The aim of this study was to determine if any correlation exists between melanocortin-1 receptor (MC1R) polymorphisms and skin and fibre colour in alpacas. Primers capable of amplifying the entire alpaca MC1R gene were designed from a comparative alignment of Bos taurus and Mus musculus MC1R gene sequences. The complete MC1R gene of 41 alpacas exhibiting a range of fibre colours, and which were sourced from farms across Australia, was sequenced from PCR products. Twenty-one single nucleotide polymorphisms were identified within MC1R. Two of these polymorphisms (A82G and C901T) have the potential to reduce eumelanin production by disrupting the activity of MC1R. No agreement was observed between fibre colour alone and MC1R genotype in the 41 animals in this study. However, when the animals were assigned to groups based on the presence or absence of eumelanin in their fibre and skin, only animals that had at least one allele with the A82/C901 combination expressed eumelanin. We propose that A82/C901 is the wild-type dominant ‘E’ MC1R allele, while alpacas with either G82/T901 or G82/Y901 are homozygous for the recessive ‘e’ MC1R allele and are therefore unable to produce eumelanin. more »