Molecular cloning and expression analysis of tyrosinase gene in the skin of Jining Gray Goat (Capra hircus)

Abstract

Tyrosinase is the key regulatory enzyme of melanogenesis and plays a major role in mammal coat color. For the first time, we have sequenced and characterized the tyrosinase (TYR) of Jining Gray Goat (Capra hircus), which is the world-famous fur-bearing animal with its special color and pattern. The full-length cDNA was cloned by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end (RACE) method. As a result, one 2131-bp nucleotide sequence representing the full-length cDNA of TYR was obtained. The entire open reading frame (ORF) of the TYR is 1593 bp and encodes for 530 amino acids, which is well conserved compared with TYR of various species with higher degree of sequence similarity with other mammalian (74-99 %) than amphibian, aves, and fishes (56-73 %). The deduced amino acids contained one signal peptide, one transmembrane domain, five N-linked glycosylation sites, and two copper binding sites. The result of real-time quantitative PCR showed that the expression level of TYR was the highest in the dark-gray goats and the lowest in the light-gray ones, while the goats of dark-gray individuals have more than 50 % black fiber and light-gray ones less than 30 %. During the whole life of Jining gray goat, TYR expression level changes with certain regularity and their coat color will change correspondingly by investigating the expression level in ten development stages. After comparing the result and the coat phenotype, we presume that it seems to have a positive relationship between the color depth of coat and the expression level of TYR.