不同品种实验兔虹膜酪氨酸酶基因序列和表达量的变化

目的从酪氨酸酶基因序列和表达量两个方面探讨酪氨酸酶与家兔虹膜颜色表型的关系。方法通过PCR扩增和测序检测4个具有不同颜色性状的家兔品种的酪氨酸酶基因外显子序列多态性;通过荧光定量PCR检测酪氨酸酶基因表达水平。结果白化品种日本大耳白兔和獭兔的TYR基因序列在第1118个碱基处都由C突变为A,并导致编码蛋白在373位,即最后一个N-糖基化位点发生由Thr到Lys的突变。白毛黑眼兔和青紫兰兔在第870个碱基处全部发生由A到T的无义突变。在白毛黑眼兔种群的所有个体和獭兔种群的部分个体中都发现TYR基因序列在第91个碱基处发生G到A的突变,导致氨基酸序列第31位处Val到Met的变异。经内参基因GAPDH的校正,TYR基因在白毛黑眼兔和青紫兰兔中表达水平显著高于在日本大耳白兔和獭兔中的表达水平（P〈0.01）。而在白毛黑眼兔和青紫兰兔之间、日本大耳白兔和獭兔之间,TYR基因的表达差异没有显著性。结论家兔TYR基因突变可能大幅度降低TYR基因表达,导致酪氨酸酶功能低下,从而影响虹膜颜色表型。

Sequence and Expression of Tyrosinase Gene Variants in the Iris of Different Rabbit Strains

Objective To compare the sequence and expression level of tyrosinase gene（TYR） among four rabbit strains covering a wide range in the extent of iris pigmentation and to verify the relationship between the tyrosinase gene and the iris colour of rabbits.Methods Exons of TYR were amplified and directly sequenced.The relative expression level of TYR in different strains of rabbits was analyzed by real-time quantitative PCR.Results The albino strains Japanese White and Rex rabbits showed a specific nucleotide exchange leading to an amino acid exchange（T373K） at the last N-glycosylation site.The silence nucleotide exchange（A→T） at nt870 of the tyrosinase coding sequence was observed in both the white hair black eyes（WHBE） and Chinchilla rabbits.A non-strain-specific amino acid exchange（V31M） was revealed in WHBE and Rex rabbits.The gene expression level of TYR in dark iris rabbits was significantly higher than that in non-pigmented ones.All results were corrected by the household gene GAPDH.Conclusions The nucleotide exchange at nt 1118（C→A） affect the function of tyrosinase,and the findings indicate that the gene expression level of TYR is related with the phenotype of iris color in rabbits.